Hello All
I have been thinking about a heating system for OTR as well as a secondary heat system while parked in my MCI 102dl3. I am going to remove the OTR HVAC except for the drivers heat and defrost. I removed the floor and have cleaned out all the ducts. The floor will be installed over the duck outlets. I drew a rough draft of the system so I can get my head around the major components. Please take a look and give me some advice on what is missing. Thanks
Your heat exchangers are arranged in parallel. The header says series?
How are you going to balance the flow to all the exchangers?
Fluid will choose the path of least resistance, so the longer and twistier will see less than shorter and straighter.
How are you going to prevent overheating the engine, if the plate exchanger doesn't remove enough heat from the coolant?
Have you budgeted a power source for all these electric fans, pumps and the boiler, for camping use? Meaning, How much power is it going to need to keep you warm for a day, or overnight?
In abandoning the duct work, don't leave any "accidental air intakes" which you cannot control, drafts, hot or cold, will screw up your underway HVAC attempts.
Happy coaching!
Buswarrior
Without some way to remove the engine from the system when, you'll struggle to ever get any heat from this when using it for interior heat when camping. The engine will just become a huge heat sink hanging out in the cold and suck all the heat away.
Why not have the Webasto main loop provide for the interior heat/defrost. If you include a surge tank in that loop, it can be run by itself. When you want to preheat the engine or tap into the engine heat to provide interior heat, you can open the engine loop and connect the two systems.
Your still not reading the original post,,,He is NOT interested in heating "the interior",,Only a few lower storage bays,, the generator,, and engine.. Even then he is only interested in eliminating the possibility of freezing in those areas.>>>Dan
I will have heat pumps in the ac system for heat when it's not that cold. I also have a 42k BTU propane furnace when boondocking. My main point of the hydronic system will be for heat while going down the road and for engine preheat, etc.
Yes, the drawing is in parallel. The heading (series) was not cropped out when I copied and pasted from the original illustration. What is the best way to balance the flow? In regards to engine overheating I need some suggestions. Would it be better to have the system in the same big loop rather than isolating the engine loop with the plate exchanger? Can someone point out where are the "air intakes" might be so I can address air infiltration. Thanks for the help with this.
Quote from: buswarrior on November 08, 2019, 09:05:24 AM
Your heat exchangers are arranged in parallel. The header says series?
How are you going to balance the flow to all the exchangers?
Fluid will choose the path of least resistance, so the longer and twistier will see less than shorter and straighter.
How are you going to prevent overheating the engine, if the plate exchanger doesn't remove enough heat from the coolant?
Have you budgeted a power source for all these electric fans, pumps and the boiler, for camping use? Meaning, How much power is it going to need to keep you warm for a day, or overnight?
In abandoning the duct work, don't leave any "accidental air intakes" which you cannot control, drafts, hot or cold, will screw up your underway HVAC attempts.
Happy coaching!
Buswarrior
Ok, so I drew another diagram this time in series. Is this a better way to do the heat? It's simpler but I was worried that it wouldn't be as efficient due to the cooling of the fluid as it goes through each exchanger. Wouldn't this produce uneven heat distribution? How much heat would be left for the engine? Is this how most of you plumb your system?
Quote from: Utahclaimjumper on November 08, 2019, 12:18:13 PM
Your still not reading the original post,,,He is NOT interested in heating "the interior",,Only a few lower storage bays,, the generator,, and engine.. Even then he is only interested in eliminating the possibility of freezing in those areas.>>>Dan
Sorry, but it appears differently in his recent posts and in the drawings being posted. Your point was valid on the earlier thread, but now it appears that the system will also be used to warm the interior, at least some of the time. The heat exchange units labeled as 'kitchen', 'bathroom', and 'bunkhouse' are certainly part of the interior.
Here's how this thread began...
Quote from: Jcparmley on November 08, 2019, 08:38:55 AM
...I have been thinking about a heating system for OTR as well as a secondary heat system while parked...
Sorry for the confusion. There is actually two of us posting on the forum asking about Webasto heating.
The other poster (not me) wants to run his for just the bay heating and engine heating.
My intention is to have interior heat while driving (OTR) and a back up system while parked. My primary heat will be mini split heat pumps when on the pole or when it's not super cold, and a 42K BTU Propane Furnace when boondocking or when it's really cold.
My drawings are very basic rough draft so I can visualize the major components and get my head around the system. I hope that makes sense now and clears up some of the confusion.
What I need to figure out is do I plum such a system in series or parallel? Do I separate engine coolant loop from the interior loop? If so how do I keep the engine from overheating when the interior is calling for heat? All your points are very much appreciated. Keep them coming.
Quote from: richard5933 on November 08, 2019, 02:40:46 PM
Sorry, but it appears differently in his recent posts and in the drawings being posted. Your point was valid on the earlier thread, but now it appears that the system will also be used to warm the interior, at least some of the time. The heat exchange units labeled as 'kitchen', 'bathroom', and 'bunkhouse' are certainly part of the interior.
Here's how this thread began...
I liked the version with all the heat exchange units parallel and run through the manifold. You will then be able to micro manage how much heat each produces by opening/limiting flow. Probably will need a safety to be sure that all of them are not able to be closed at the same time though, or your pump will be really unhappy.
If your interior heat loop and your engine loop are the same you'll lose a considerable amount of heat through the engine. That's a lot of cast iron hanging out there in the cold, and it will suck all the heat from your system and make the Webasto work really hard to keep up if it's always getting flow from the Webasto.
The Webasto on our 4106 had a loop for the interior heat. There was also the OEM loop from the engine to the defroster core and back again (chassis loop). They were usually separate, so we could easily heat the interior using the Webasto without losing heat to the engine.
When we wanted to preheat the engine, there was a third 'loop' which connected the chassis loop to the interior loop. It was really just a feed and return line between the two loops. The feed line had a 12v Bosch pump which took hot water from the Webasto system and pushed it into the chassis loop. When we flipped the switch on the control panel to 'engine heat' the Bosch pump came on and diverted the heated coolant into the chassis loop. Ours used the existing OEM coolant boost pump to circulate the heated coolant, but you could also add another Bosch coolant pump to the chassis loop to be sure that it made it to the engine.
Hope this makes sense. I tried to sketch it out but didn't have much luck doing that on the laptop. If you need, I'll break out the markers and do a paper sketch later on.
Thanks Richard. My bus came from the factory with a webasto for keeping the engine up to temp. It's all disconnected now because the webasto needs to be rebuilt. I would need to keep that feature. I like the parallel system as well. If you don't mind could you draw out how you system worked? I know it's a lot to ask but I am a visual learner. Was your loops separated from each other with a flat plate exchanger or something similar?
Quote from: Jcparmley on November 08, 2019, 04:57:45 PM
Thanks Richard. My bus came from the factory with a webasto for keeping the engine up to temp. It's all disconnected now because the webasto needs to be rebuilt. I would need to keep that feature. I like the parallel system as well. If you don't mind could you draw out how you system worked? I know it's a lot to ask but I am a visual learner. Was your loops separated from each other with a flat plate exchanger or something similar?
I'll try and sketch out something this weekend. They were separate loops, but were also connected. It'll make more sense when I get it on paper.
Ok, thanks Richard
Quote from: richard5933 on November 08, 2019, 05:30:41 PM
I'll try and sketch out something this weekend. They were separate loops, but were also connected. It'll make more sense when I get it on paper.
JC, some of the features of the original system were very good but it was designed with warmup and OTR use in mind so it needs a few mods to work well as an RV. Basically you just need to be able to restrict flow to the house loop and webasto loop only. Although you have disabled that system there are still parts and features of it that you could use.
Originally the house loop was an auxiliary loop that paralleled the engine loop and could be shut off at both ends. This allowed warmup and engine heat, or warmup, engine heat, and coach heat. There was no way to take the engine loop out of the system. Normally the manual valve on the coach loop was left open and the solenoid valve controlled the level of coach heat.
This system could be reconfigured to allow house heat exclusive of engine heat. That requires a minimum of one additional bypass line and one additional valve, either manual or solenoid type.
The best way to think of this system is as a set of interlocking loops. Always the primary loop contains the engine and the radiators, including of course the engine driven coolant pump and surge tank. The next loop contains the webasto and the circulation pump. The final loop contains the house radiators. This is the only passive loop as it needs no pump. It can be series or parallel regarding the radiators, or in fact both. The biggest problem with your serial radiators is line size and flow capacity. Usually such a system uses one or two very large radiators. A parallel system is much less expensive to build but has more complex plumbing. The original system can be thought of as a hybrid series/parallel even though the series (main) circuit only has one radiator. Flow is controlled by valves and line sizes. It's not particularly hard to understand if you have a reasonable grasp of plumbing in general.
Anyway the three loops are interconnected by no less than two points for each loop pair, one on the supply side and one on the return side. Look to the pump to see which is which. If you want to supply webasto heat, connect the webasto loop to the loop you want the heat to go to, such as the house loop. Because the circulation pump is part of the webasto loop it controls coolant flow. Similar for heat both to and from the engine, though in the first case you connect the webasto loop to the engine loop and in the second connect the engine loop to the house loop.
That's really about all there is to the theory, the rest is just details.
Jim
Here's a really basic layout of what we had in the 4106. The two basic loops are the engine/defroster loop (black in the diagram) and the interior heating loop (purple in the diagram). There is an surge tank on the interior heating loop which increases the volume of coolant in the system and allow for expansion.
The two main loops are interconnected with the two lines running between them (red in the diagram). There are two auxiliary pumps used when the system is on pre-heat: one to circulate the coolant in the engine/defroster loop, and another to exchange coolant between the interior loop and the engine/defroster loop.
When the pumps are turned on, heated coolant from the interior Webasto loop is exchanged with the engine loop. Can't remember if there was a solenoid to shut off the return between the two loops, but I don't think there was. Any exchange between the two systems when the pumps are off would be minimal.
The distance between the feed line and return line between the two loops will effect how much exchange there is between the loops.
Curiously, this is very similar to how the boiler was connected to the radiator loop at my old wood shop. There was a loop throughout the building which circulated water to all the radiators, and another very small loop between the boiler and the surge tank. There was a feed line and a return line between the two, and when the system called for heat a small pump turned on to exchange water between the two loop. That 5000 sq. ft building was heated nicely, and there was only about 6" of space between the feed line and the return line for the exchange to take place.
you can also think of it in terms of source and sink. Your sources are the webasto and the engine and your sinks are the radiators, defroster, and engine but conceptually that's a little harder to keep straight. You can make it as simple or as complex as you like. MCI went for simple I think and I like that approach but complex can work too and has some theoretical advantages. However a simple system that is well designed can be essentially invisible to the occupants and this is also an advantage. You will have to decide what you like.
But think in terms of pumps transferring heat. The circulation pump runs on demand, the engine pump runs with the engine. You can add more pumps if you like but don't have to, and every additional pump is another source of potential failure. Usually not if but when.
I would seriously question the logic behind adding additional heat exchangers. Even if potable water is part of the system. Do you drink water from the hot water heater? Few people do because of concerns about lead leaching and aluminum anions affecting long term brain health but it's an individual choice. I can't think of another justification. Also using the water heater as a heat source is perhaps not the best idea, as it doesn't put out enough heat to do much and will shorten the life of the heating element. Losses through the exchanger will diminish even that, and the exchanger adds a restriction that will reduce the efficiency of the entire system.
Jim
ok, I think I have a better understanding now. The diagram below is a hybrid system. It is three loops. One loop is the OEM engine to driver defroster/heater.
The second is what I will call the Webasto Loop. This is a bridge loop to supply heated coolant to either the engine loop or the interior loop.
The third is the interior loop.
The way I understand the diagram is the engine while running will supply hot coolant. If the coolant goes below 160 degrees the Webasto and the booster pump will turn on and push hot coolant into the engine loop. Thus keeping the big S60 engine in operating temp. I believe this process happens automatically when the Webasto senses cold coolant. I will need to set up a relay to turn on the booster pump at the same time.
When the interior loop calls for heat a relay will turn on the Webasto and the Webasto's pump will push hot coolant to the manifold and then to the exchangers. The exchangers fans will turn on when the exchanger senses the hot coolant and the thermostat is engaged. I still need to figure out how to set up the thermostats.
When the engine is off and I want to preheat the engine I will need to switch on the preheat pump in the engine loop and the Webasto and pump in the Webasto Loop.
Is this correct?
Close. Probably would work, but I'd make one tweak (or at least talk to a boiler guy to confirm which way works better).
If I was doing this I'd would have both of the lines connecting the Webasto loop to the OEM loop go to the same side of the OEM loop, about 12 inches apart. As the OEM loop coolant circulates through this 12" it will mix with the heated coolant going through the Webasto loop.
The way it looks in your latest sketch, it almost looks like more of the heated coolant coming into the OEM loop will go through the defroster and then short-circuit back out of the OEM loop and back to the Webasto. Not sure how much will make it to the engine. Perhaps if you reversed the flow so that it went to the engine first, as that will be your priority and not the defroster.
If you have a boiler guy near you it might be good to ask which way to do this is best. I've seen both, but the boilers in my shop were both tied to the radiator loop with only a few inches of cross-over, and only on the feed side of the radiator loop. Surprisingly that few inches was enough to heat the water in the radiator loop quite quickly.
Like This?
Quote from: richard5933 on November 09, 2019, 05:38:24 PM
Close. Probably would work, but I'd make one tweak (or at least talk to a boiler guy to confirm which way works better).
If I was doing this I'd would have both of the lines connecting the Webasto loop to the OEM loop go to the same side of the OEM loop, about 12 inches apart. As the OEM loop coolant circulates through this 12" it will mix with the heated coolant going through the Webasto loop.
The way it looks in your latest sketch, it almost looks like more of the heated coolant coming into the OEM loop will go through the defroster and then short-circuit back out of the OEM loop and back to the Webasto. Not sure how much will make it to the engine. Perhaps if you reversed the flow so that it went to the engine first, as that will be your priority and not the defroster.
If you have a boiler guy near you it might be good to ask which way to do this is best. I've seen both, but the boilers in my shop were both tied to the radiator loop with only a few inches of cross-over, and only on the feed side of the radiator loop. Surprisingly that few inches was enough to heat the water in the radiator loop quite quickly.
I don't really understand why you need all those pumps.
To begin with, the engine coolant pump is more than adequate to circulate coolant through the defroster loop, as that would be a normal part of the engine coolant system. I will concede though that if you are going to circulate heat from the webasto to the defroster it could possibly complicate things a bit. But leaving that for a moment...
With two heat sources and a dedicated pump at each there should be no need for more pumps. The pump moves the heat downstream and it's up to the system to take it from there. Valves should be enough. The engine's pump that circulates coolant to the radiator is all you should need on that side. It normally supplies coolant to the defroster anyway. This drawing has two more extra pumps that should be completely unnecessary. As far as attempting to mix coolant flows I fail to see the need and it seems inefficient when what really needs to happen is the coolant from the heat source needs to be directed to the chosen targets (sinks or radiators) in the most direct manner. The only complication I see is a possible reversal of flow when warming up the engine prior to starting, but with the right routing that may not even be an issue.
So, starting with engine produced heat: You have a large source of surplus flow in the engine driven pump. External connections are made on the suction and the pressure sides of the pump. Usually the pressure side is taken off after circulation through the water jackets, so that the external flow parallels the flow through the engine radiator. The pressure across the radiator core is what drives the coolant through the lines and the coach and defroster heater cores. No other pump is needed but a solenoid valve is useful to control heat diverted from the engine.
Preheat: The webasto circulation pump flows heat through the engine. Because the pumps are centrifugal type, when not running they provide no resistance to flow and coolant will pass through in either direction without restriction. This should be taken into account.
House heat (webasto): The webasto pump circulates coolant through the house and defrost loops. Valves isolate this from the engine loop.
Why do you need separate loops for the house and defrost? The defrost has it's own flow control valve, is there some reason why you would want to heat the windshield and dash area only? Is there some reason why the defrost would be used during driving but not with the webasto? If so it can be turned off.
So back to the preheat. Assuming flow is the same direction from the engine and the webasto (high pressure sides hooked together and low pressure sided hooked together), when the webasto is on and the engine is off, and with house line valve(s) closed, flow will reverse through the engine water jacket and back through the pump, to the inlet and back to the webasto. It will also circulate through the radiator in the usual direction. Presumably the thermostat will shut off this flow. If the engine is running (supplemental heat) the flow will depend on the engine thermostat. I'd need to look at the diagram to see exactly what happens here but if you plumb that part of the system in accordance with the original configuration it will warm the engine. It is possible this is plumbed so that the webasto feeds the engine pump inlet, it's been awhile since I looked.
So all that is really needed is a valve to isolate flow from the webasto to the engine block, and another line and valve to allow the return flow from the house and defrost to go directly to the webasto pump inlet. That's it. That's all it takes to convert the original system to RV use.
The only difference between that and your configuration is that you have removed the single large heater core and substituted multiple smaller ones. That's fine as long as you maintain the same overall flow rates through the lines in a cumulative way. You can calculate that based on line cross sectional area. Rule of thumb: Double the diameter quadruples the flow.
Jim
Quote from: Jim Blackwood on November 09, 2019, 08:47:33 PM
I don't really understand why you need all those pumps.
To begin with, the engine coolant pump is more than adequate to circulate coolant through the defroster loop, ...
Jim
True, when the engine is running.
On our 4106, when we wanted to preheat the engine it was not running, therefore the engine water pump is not doing anything.
One of the circulating pumps moved water between the Webasto loop and the engine loop. The second moved the coolant through the engine loop when then engine was not running.
Could it be done other ways? Sure. There as many ways to do this as there are people doing it. Each install will be different, no doubt there. I'm just explaining how it was on our 4106, which worked well both for interior heat and for engine pre-heat.
Some stock coaches (MCI) only had the engine water pump to circulate the whole coach.
Some coaches (GM) had an electric water pump to help circulate the hot coolant forward to the HVAC pieces.
Different models, blah blah blah.
Confusing the picture further, when you wonder about the presence or absence of that stock pump in all these musings.
Before plumbing details, an executive summary needs to be worked out.
For instance:
The coach will have a separate/combined coolant system
The coach will have x sources to heat the coolant
The coach will have y devices to distribute/receive the heat
This design protects/endangers the chassis manufacturer's cooling system in these ways:
In order to reduce complexity, these orders of fuel efficiency are going to be purposefully ignored/abandoned.
These receiving devices are going to be grouped thusly.
These heat sources are going to be grouped thusly.
In order to be fuel efficient, these strategies are going to be employed.
And... I have chosen this heating system over others available because:
If one thought BTU was some fancy school in Massachusetts, before getting into the bus converters' equivalent of the space race...
Hydronic heating is, for almost every busnut, an unneccesary, unwieldy, complicated, large hammer, unreliable, expensive, both in hardware and fuel consumption, battery hog, way to be warm.
I say this so the rest of the crowd isn't stampeded into thinking they need hydronic heating.
Who is camping in the Arctic? vs keeping the chill off a spring or fall evening?
And once you are "done" everyone else will say you did it wrong...
The Admiral is MIGHTILLY PISSED OFF that the (profanity deleted) coach still won't work like home, further eroding her desire to spend time with the coach, or you...
And you get to do the ongoing maintenance, repair and constant tinkering to get this square peg into the round hole...
But by God, I have kept up with the Jones family...
Sometimes, just running a nice sized generator and some electric heaters might be a good path?
Prospective busnuts, be sure of your desires, designs and motivations?
Happy coaching!
Buswarrior
Jim
Do you think that the pump on the Webasto is powerful enough to push coolant through the interior loop and the engine loop when the engine is off? Would you mind drawing up a simple diagram that I could look at?
Last week I was bench testing my new to me Webasto. I had it set up to pump water in and out of a 5 gal pail. I was surprised at how powerful the flow was out of the 3/4" hose. It was like a garden hose wide open. I am a couple of days away from having my system completed. I will report on my thread. The Webasto will be pumping through two heat exchangers, the front defroster, back to the Detroit engine and through it, and back to the Webasto. I am guessing (hoping) that it will be fine.
JC
Webasto pumps are strong.
DBW300 plumbed in-line between engine and coach HVAC, pushed water round and round, up through the big heat exchanger and defroster, back through the engine, no trouble.
And the engine water pump had no trouble circulating through the dormant webasto and pump.
Do pay attention to the rated flow required to carry the heat away from the Websato when it is firing, or it will short cycle, and/or blow an overheat fuse.
Happy coaching!
Buswarrior
B W well said .
I had infloor heat on the M C I and when driving for hours it was amazing in the cold but for the camping in warnish weather it worked well but took to long to heat the floors so I installed some cozy rad fan heaters and that helped . I like the water heat in the new coach because when driving the big engine can warm the inside of the coach with out using the genny and when camping the boiler works great because of all the cozy fan heaters .
but yes sometimes the simplest system is best . genny and lots of cube heaters
dave
Quote from: buswarrior on November 10, 2019, 06:18:54 AM
The Admiral is MIGHTILLY PISSED OFF that the (profanity deleted) coach still won't work like home, further eroding her desire to spend time with the coach, or you...
But by God, I have kept up with the Jones family...
Sometimes, just running a nice sized generator and some electric heaters might be a good path?
Prospective busnuts, be sure of your desires, designs and motivations?
Happy coaching!
Buswarrior
Wow you hit the priority right on the head and how do you come to compromises that satisfy the significant other LOL?
I would add another point: "Why are we running that noisy smelly generator?" to which the answers could be:
1. Remember the solar power system I wanted to add?
2. We don't have enough house battery storage (More power!!!)
3. We don't have a big enough hydronic reservoir
Plus you have added disadvantage in that you are building/spending money on it and hey the house already had it as an ongoing sunken cost.
Quote from: lostagain on November 10, 2019, 07:57:53 AM
Last week I was bench testing my new to me Webasto. I had it set up to pump water in and out of a 5 gal pail. I was surprised at how powerful the flow was out of the 3/4" hose. It was like a garden hose wide open. I am a couple of days away from having my system completed. I will report on my thread. The Webasto will be pumping through two heat exchangers, the front defroster, back to the Detroit engine and through it, and back to the Webasto. I am guessing (hoping) that it will be fine.
JC
If you are still in testing mode, I would be interested to know how long it takes your Webasto pump to fill a 5 gallon bucket. The time divided by 5 would give us GPM which is useful to know.
Add the pump model to the performance numbers, there's different pumps...
Happy coaching!
Buswarrior
Sorry, too late. The Webasto is mounted in the bus now.
JC
All I have to go by is the '96 102DL3 and some not-the-best schematics which I haven't studied for a few months but I'll do my best. Those drawings are the ones I'm going by, the ones that can be downloaded from MCI.
Anyway based on the above, yes either pump is more than adequate for circulation through the entire system. The aux heater, in this case an Eiberspacher of over 80Kbtu is well able to heat the engine and the coach interior. Being able to remove the engine from the system would only make it heat the coach faster, a mod I will make when I have reason to get into the coolant system. Until then I will accept the reduced efficiency and performance of also heating the engine, with the entire original configuration intact and pay the surcharge of increased fuel consumption.
The aux heater did not work when I got the bus, but after removal and inspection I found the issue to be with the timer type controller. I connected a thermostat instead and plan to add to that later. My plan is to route the warm/cold air from the original HVAC ductwork into the rear of the cabinetry for distribution. For the time being at least I am retaining the original baseboard ducting which I expect to modify/remove as needed.
If I understand you correctly you still have the OEM webasto unit, but it is in questionable condition. If that is true, then despite what BW said about hydronic systems (and he is right) it is still possible that the cheapest, quickest, easiest route to abundant heat is to restore the original webasto to proper operation if that is still an option. I fully agree with the thought that the Admiral's comfort is paramount and to that end there aren't many better ways to warm the coach up quickly than the OEM webasto. It does make a little noise but it's not really objectionable, not like a generator anyway.
Just as a hypothetical, say you did restore that end of the system and put in the engine shutoff and return bypass. If I remember right, the return line from the coach has a manual shutoff valve where it exits the bodywork. From there it connects to the engine. I do not recall at the moment if there is any other connection to that line but that is the line you have to modify. Basically it means putting in a "T" on the coach side of the valve so that you can shut that valve and divert the flow back to the webasto pump inlet. However a solenoid valve would be much more convenient but costly, while a ball valve brings the option of running a shaft through the wall to a control handle in the bedroom. The important thing here is that you complete the loop from the webasto to the heaters and back, while shutting off the lines to the engine. As far as a surge/recovery tank goes, the OEM one should do the job and if it does not, a small bypass leak created at the shutoff point(s) should do the trick.
Jim
I am reminded of another design issue, capacity to warm up, vs keep warm.
If a busnut is out using the coach in cooler weather, the goal is continuous, keeping the coach warm. That is a very different capacity than warming up a cold coach.
For those used to air conditioning, you know the same issue from the other side, it is easier to keep the coach cold, than to cool down a hot one.
The difference between warm up and keep warm is wide enough, that aiming at one, will compromise the other.
The challenge is how to throttle a heat source that makes xxxxx BTU, when the interior only needs 5-10k to keep an evening chill off, but needs to be able to put the whole xxxxx BTU into the interior on returning to the coach in cold weather when away at some event, where leaving the coach heat on was not allowed or desired, or when Old Man Winter follows the snowbirds south.
A hint: "wasting heat" to the engine block may be VERY desirable, to tame a big coolant boiler under warmer weather conditions. Sure, open a window, make a draft, make the Admiral miserable again...
Also, on those cool evening chill type scenarios, after a day's drive, along with the whole coach already being "at temperature" there's over 2000 lbs of cast iron down the back that isn't going to be cooling off for a long time that can be tapped without burning any more fuel.
The first evening, the bedroom is lovely, the second evening, the engine has gone cold, and now the bedroom isn't lovely...
Keeping the inside temperature from varying wildly, under all these different conditions is really tricky, and as usual, the forums are skinny on reports of failures, only reports of successes...
The electrical power consumption of the heat distribution system often makes trouble. Fans, pumps, burners all consume battery power, at a time when most battery bank capacities are also challenged by colder temperatures.
Just as an example, running the stock coach HVAC fans in an MC8 via a bypass switch, a DBW300 firing and circulation pump running, and water valve cycling, draws about 11 amps of 120 VAC via a shore cord feeding a Trace 4024 inverter, supplying the 24 volts to a set of topped-up house batteries. That's somewhere around 1320 watts burning a hole in the coach's electric budget.
What is the consumption of available fan units?
Check the newer low floor transit coaches, they are running radiant heat the length of the sidewalls where the duct work used to be... That copper pipe and aluminum fin radiator has a rating per foot, at a certain water temperature... if I could find it again...
So much fun playing with the variables.
happy coaching!
buswarrior
And there's no reason for a generator to be noisy, except for a busnut to choose to have a noisy generator.
There are good reasons for a busnut to make that choice, but for those who want silence, it is achievable.
Generator noise is one of the easiest ways to attract attention and get asked to leave when "urban camping"
happy coaching!
buswarrior
"Check the newer low floor transit coaches, they are running radiant heat the length of the sidewalls where the duct work used to be... That copper pipe and aluminum fin radiator has a rating per foot, at a certain water temperature... if I could find it again..."
Buswarrier has a good point. Would it be a better system to use radiant basboard heat instead of forced air exchangers? I could install a couple exchangers for quick heat and use radiant for keeping a already warmed coach warm. Thoughts?
The thing about radiant is that it's generally designed to be on all the time or most of the time. That's fine if traveling, but brings additional challenges when parked. If you size your webasto for efficient operation full time it won't have the reserve for rapid warmup. But, this is where your water heaters could be handy.
Note, careful design can allow standard heater cores to act as passive radiators with the fan off, and it is also possible to run a passive thermosiphon loop for the coolant. That won't do with the webasto burning but with the water heaters it might be made to work. However, don't count on the coolant loop of standard water heaters, you will want the entire output, so dedicated units would be the better approach.
Jim
What I'm saying is, use a water heater to power the thermosiphon loop and run the coolant through where the water usually is. Use a dual power unit so it can be run on shore or LP. Then that's your low level "keep warm" heater and you can fire up the webasto for on-demand use. With the water heater in a storage bay and the heater cores at floor level you have enough height to do thermosiphon so the only energy cost is the burner or heating element. 6Kbtu is about the most you can expect from a water tank heating element at 220V.
Jim
Also, the thermosiphon loop does not have to be separate from the rest of the system. It can use the same radiators as the webasto.
Jim
How many ways are there to control temperature inside the coach?
On and off works, but is a bit of thuggery...
Coolant temperature doesn't need to be 160 to take a chill off...
Fans don't need to run all the time...
All the heat distributing devices don't have to be fed warm coolant all the time...
If the coach can't keep a chill off while boondocking, using only a modest battery consumption...
If the only person who can make it work is the owner...
And the Admiral rolls her eyes when someone asks if her coach stays warm...
we've not done a good job?
Aim for invisible, simple to control, repairable, serviceable, and easy to explain the operation to the next person.
And with dementia/Alzheimers running rampant, it might be yourself that will need help!!
Design engineering is great fun!
Happy coaching!
Buswarrior
Temp regulation on our 4106 was a simple as setting the temp on the thermostat and letting the system do its thing. When the system called for heat, the coolant circulated. If it wasn't warm enough, the burner kicked in. When the room came to temp, things shut down. Worked just the same as our furnace does at home.
Both circulating pumps ran off 12v. The air blower(s) were 12v as well. The Webasto was of course 12v. We could easily go through the night with outside temps in the 20s without having to worry about batteries, running the old Norcold swing motor fridge at the same time.
Read the old literature on the Webasto setups. Doesn't need to be complicated.
Jim, I had to look up what a thermosiphon was. It's very interesting. I am wondering if a small on demand propane hot water heater would work in such a system?
Quote from: Jim Blackwood on November 11, 2019, 09:46:52 AM
What I'm saying is, use a water heater to power the thermosiphon loop and run the coolant through where the water usually is. Use a dual power unit so it can be run on shore or LP. Then that's your low level "keep warm" heater and you can fire up the webasto for on-demand use. With the water heater in a storage bay and the heater cores at floor level you have enough height to do thermosiphon so the only energy cost is the burner or heating element. 6Kbtu is about the most you can expect from a water tank heating element at 220V.
Jim
I'm thinking that for make-up heat it could work. Depends on how much you need and how much you have naturally. Line sizing would be important and insulation on the hot line helpful. As there is no pump the flow is more sluggish and larger lines are helpful, up to a point where the line cools before reaching the top. So to at least some extent the larger lines used for the on-demand heat with pump flow would be sized well for convection flow. The main thing is to be sure there is still heat in the line when it gets to the radiators, but that there is also enough volume in the flow to carry all the available heat away from the boiler (hot water heater). Ideally you will retain all heat all the way to the top of the system.
At the radiator you want the hot line to go to the top and the return to come out the bottom. Avoid dips and traps in the lines of course and put an air bleed at a handy location at the very top of the loop. Any air in the line will defeat the effect. Often thermosiphon systems place a reservoir at the high point for that reason and that's not a bad idea, however just a large tube section with a bleed valve can suffice. The size of this chamber will determine how often bleeding is necessary. A small bleed line back to the main reservoir up by the engine radiator can eliminate this need.
The passive radiators need enough area to dissipate all the heat without a fan so they need to have an unobstructed airflow that will allow the heat to carry the air up and away from the radiator. If they have enough area for the on-demand heat they should be plenty big enough for passive.
The fluid can be interconnected to the on-demand system. More fluid mass can degrade performance but the real question is how much and in what ways? Operation may still be quite acceptable. As long as connection to the main coach distribution lines does not create any air traps or use up your heat before it gets to the top it should still work. However, because the coach loop already has one solenoid valve on the supply side for heat control and you need a valve on the return side to isolate the engine, you could consider an additional solenoid valve to isolate the passive system that opens when the webasto lights off. These valves are expensive however, average cost is probably about $350 from what I've seen, though you might find one for less if you look. A passive check valve here could work as well but does create a restriction. The thermosiphon flow would never create enough force to open it so it would remain closed during passive heating and block off the rest of the system. That would work on both sides, be much less expensive than solenoid valves and function automatically. Perhaps a flapper type check valve with the spring removed to work by gravity alone would do.
You'd have to check the btu rating of the water heater on both gas and electric. Just knowing it gets hot isn't enough. If the element only puts out 3000 watts that's the equivalent of two small ceramic plug in heaters. Is that going to keep your house warm? Better to err on the side of excess here.
Jim
This is one of those times when you've got to look around and see what's being commonly installed, both in bus conversions and in commercial motor homes, and ask if maybe they're on to something.
I'm not knocking the thermosiphon idea in principle, just in application. I enjoy doing something just to see if it works as much as the next guy, but in this situation there already will be in place a few redundant systems - heat generated by the engine, the Webasto, electric heat pumps, and an LP furnace. Is there need for yet another? is there enough advantage to thermosiphon to add yet another?
Suggestion:
For those wanting a cheap diesel heater look on ebay for Nissan Leaf auxiliary heater as they generally don't know what they are selling and price it lower than if it was sold as a truck version. The seller is more in likely looking to make their salvage nut on selling batteries out of the battery pack.
Note this is not a high power heater!!! However for the price you might want to buy two or three for added capacity and fault tolerance.
I think this is actually an Espar 5KW/13500 BTU unit.
This thread and others like it kind of ricochet back and forth between a lot of sub subjects, when what we really want in the long run is a DIY Hydronic system that we do not want to spend thousands of dollars for.
As Busnuts we are basically frugal (OK cheap) in that we will trade labor/skull sweat for verses spending lots of money on a prepackaged system.
To quote our hero member BusWarrior; our basic mission statement is:
"The Admiral (significant other) is MIGHTILLY PISSED OFF that the (profanity deleted) coach still won't work like home, further eroding her desire to spend time with the coach, or you..."
How about we divide this complex subject up into separate subject area's starting with the Subject Tag "DIY Hydronic"? That way we can pool our collective knowledge.
As an example:
DIY Hydronic boilers
DIY Hydronic Additional heat sources
DIY Hydronic Storage
DIY Hydronic Engine/Generator preheating
DIY Hydronic pumps, valves, heat exchangers
DIY Hydronic plumbing and heat distribution
DIY Hydronic Automation or Manual controls
DIY Hydronic Weather protection of house systems
Your thoughts?
Quote from: richard5933 on November 12, 2019, 10:04:14 AM
This is one of those times when you've got to look around and see what's being commonly installed, both in bus conversions and in commercial motor homes, and ask if maybe they're on to something.
I'm not knocking the thermosiphon idea in principle, just in application. I enjoy doing something just to see if it works as much as the next guy, but in this situation there already will be in place a few redundant systems - heat generated by the engine, the Webasto, electric heat pumps, and an LP furnace. Is there need for yet another? is there enough advantage to thermosiphon to add yet another?
You know, somebody has to ask that kind of question. Otherwise we might be into all sorts of messes. In this particular case it may or may not be a good idea. Are all of those other systems already installed and working? Because I thought what we have been discussing was installation.
Convection heating has been proven to work. To find if it will work here really isn't so hard during the installation stage of the game. Plumb a water heater to a heater core about 2-3ft above it, burp out all the air, fire it up and see if you get heat. The results would tell us a lot and might determine if the method has any future here.
Jim
Model T Fords used it. No water pump but I think that was the last time.
I know it has been a while but I am still tweaking my proposed heating system. Richard, is this similar to your old setup? I know I added a Flat Plate Exchanger because I wanted to keep the engine coolant separate from the house system just in case I have a failure I don't want both systems down. Let me know if you think this will work?
I also eliminated the extra pumps as it sounds like the engine pump and the Webasto pumps are large enough to circulate the coolant. However, if I do need to add a pump I would do it probably before the distribution manifold. Let me know what you all think.
Quote from: richard5933 on November 09, 2019, 10:19:15 AM
Here's a really basic layout of what we had in the 4106. The two basic loops are the engine/defroster loop (black in the diagram) and the interior heating loop (purple in the diagram). There is an surge tank on the interior heating loop which increases the volume of coolant in the system and allow for expansion.
The two main loops are interconnected with the two lines running between them (red in the diagram). There are two auxiliary pumps used when the system is on pre-heat: one to circulate the coolant in the engine/defroster loop, and another to exchange coolant between the interior loop and the engine/defroster loop.
When the pumps are turned on, heated coolant from the interior Webasto loop is exchanged with the engine loop. Can't remember if there was a solenoid to shut off the return between the two loops, but I don't think there was. Any exchange between the two systems when the pumps are off would be minimal.
The distance between the feed line and return line between the two loops will effect how much exchange there is between the loops.
Curiously, this is very similar to how the boiler was connected to the radiator loop at my old wood shop. There was a loop throughout the building which circulated water to all the radiators, and another very small loop between the boiler and the surge tank. There was a feed line and a return line between the two, and when the system called for heat a small pump turned on to exchange water between the two loop. That 5000 sq. ft building was heated nicely, and there was only about 6" of space between the feed line and the return line for the exchange to take place.
Quote from: Jcparmley on February 22, 2021, 02:42:15 PM
I know it has been a while but I am still tweaking my proposed heating system. Richard, is this similar to your old setup? I know I added a Flat Plate Exchanger because I wanted to keep the engine coolant separate from the house system just in case I have a failure I don't want both systems down. Let me know if you think this will work?
I also eliminated the extra pumps as it sounds like the engine pump and the Webasto pumps are large enough to circulate the coolant. However, if I do need to add a pump I would do it probably before the distribution manifold. Let me know what you all think.
Couple of thoughts...
The pump on the engine loop will be necessary if you every want to use the Webasto to pre-heat the engine. And you probably will want to do this at some point.
Not sure about the house side loop. Hard to tell what's going where as your arrows seems to push against each other in a few places. Also not sure what the two connection points between the hot/cold side of the manifold are for.
Could you run the engine plate exchanger as another point in the manifold? Not sure if you are going to use electric solenoids to open/close the various loops in the manifold, but it seems like having the plate exchange unit work off the same manifold will make it really easy to turn that on or off as needed and will eliminate the need for the check valves.
So I changed it up a little. Here's how I have it drawn up:
1: When the engine is running the engine water pump will heat the engine loop as well as the plate heat exchanger on the house manifold heating the house loop. (Is the engine pump strong enough to do this, or do I need to add a pump?)
2: When the engine is off and cold I will pre-heat the engine by turning on the Webasto with a switch, which will heat the plate exchanger and push coolant through the engine loop. (Is the Webasto pump strong enough to do this or do I need to add a pump)
3: When the house loop needs heat the thermostat will turn on the Webasto and heat the house loop. I will need to use a solenoid or some kind of valve that will close off the plate heat exchanger so the cold engine doesn't pull out all the heat in the house loop.
4: When the bus is on the road and the Series 60 engine calls for more heat the OEM controller will turn on the Webasto, which will heat the plate exchanger and thus the engine will be brought up to temp. (How will the OEM controller know that the coolant is below 160 Degrees?)
5: The house loop system will have a reservoir tank at the highest point for fill and air bleeding.
Does that all make sense. I still need to wrap my head around how the OEM Webasto controller will know when the Series 60 needs heat if the Webasto is not plumbed inline with the engine.
Quote from: richard5933 on February 22, 2021, 03:18:05 PM
Couple of thoughts...
The pump on the engine loop will be necessary if you every want to use the Webasto to pre-heat the engine. And you probably will want to do this at some point.
Not sure about the house side loop. Hard to tell what's going where as your arrows seems to push against each other in a few places. Also not sure what the two connection points between the hot/cold side of the manifold are for.
Could you run the engine plate exchanger as another point in the manifold? Not sure if you are going to use electric solenoids to open/close the various loops in the manifold, but it seems like having the plate exchange unit work off the same manifold will make it really easy to turn that on or off as needed and will eliminate the need for the check valves.
You're out of my league with the OEM engine Webasto questions.
My thoughts on the engine loop is that you'll need the extra pump. There's a reason you see them in system. Even a stock bus will oftentimes have an extra pump to bring the coolant up front to heat the heater core, so I wouldn't put much confidence in the engine pump to do the work, especially at idle speed.
Ok, here is the most recent version of my layout. Perhaps Jim or Buswarrier could chime in and advise on some of the other questions.
That one makes sense to me. Now if you can get the 160 degree question answered it sounds like you're set.
JC, I really hate to say this after you have put in so much effort on this system, but it strikes me as needlessly complex. My bus is also a '96 DL with the aux heater and I have to think we must have similar goals here which would be:
Maintaining adequate engine heat and cabin heat OTR
Providing cabin heat only when parked
Preheating the engine for starting
I'm not sure anything else is required aside from defrost.
I will attempt to do this while keeping most of the OTR system intact where you are adding a supplemental system. I do understand that you feel it is best to keep the systems separate but there has to be some inefficiency involved in transferring heat across a heat exchanger. Even under the very best conditions it cannot avoid at least slowing things down some. I think you will discover this as additional delay in getting heat out of the registers. That may not bother you, but you might want to trigger your fans with a temp sensor at the radiator to avoid blowing cold air when the webasto kicks on.
Will you need more pumps? Maybe. Take a good look at the existing plumbing. Are your lines going to be the same size and go the same distance? Probably not. Your dash heat lines may be the same. Your pumps are rated for a specific flow rate AT a specific pressure (or "head") Changing the lines will change either the pressure or the flow. You can get by with some of that, and some you can't. Think of it as delivering coal. You have a specific volume of heat that you are trying to deliver to the radiator. The flow affects that but so does the temperature. You want the flow to be slow enough to pick up a lot of heat but not so slow that the boiler overheats. Then the quicker that gets to the radiator, the more of the heat can go where you want it. So you want the lines small enough for high velocity flow but big enough to allow adequate flow through the boiler, and a well designed system will do this seamlessly.
So Ideally you would take pressure and temperature readings at all key points in a properly operating OEM system before changing anything, and endeavor to match those readings in your new design. (Those heat exchangers could make that interesting.) Pay particular attention to the cross sectional area of your piping as well as the length of the runs. The area will affect flow quite a lot more than the length but the length should not be ignored. The pumps in the OEM system were perfectly sized for the job they were asked to do. If you can ask them to do a similar enough job you will be happy with them. If not, you may want to make changes.
Jim
Jim, thanks for your insight. I was planing on using 3/4 pex to the manifold and 1/2 pex for the runs. I guess I never thought of it in terms of pressure and flow. So if I remove the plate exchanger out of the system it would simplify the design. However, if I have a failure then both engine and house loop will be down. Perhaps that's not that important.
I have also considered not having hydronic heat at all. I have a large generator that is more than enough power to have some electric heaters. I also have a propane heater for those occasions where I need that. I'm not going to be full time in the bus so for what it's worth it may not even be necessary.
Quote from: Jcparmley on February 23, 2021, 09:22:58 AM
I have also considered not having hydronic heat at all. I have a large generator that is more than enough power to have some electric heaters. I also have a propane heater for those occasions where I need that. I'm not going to be full time in the bus so for what it's worth it may not even be necessary.
JC -My coach has hydronic heat available from the cantankerous AquaHot unit, plus Cadet "Perfectoe" 1000w 120vac undercounter ("toe-kick") electric heaters. Each system has four registers scattered thru out the coach: bedroom, bath, galley and front salon. There are also hydronic registers and small electric heaters in three of the four bays (none in the generator compartment.) There is no propane on board - didn't want a coach with that fuel source.
Just the four Cadets kept the coach at 68º inside when it was 10º outside a couple weeks ago, so they work, each cycling on and off as their individual thermostats controlled them. I did not fire up the AH unit because I didn't want the exhaust blowing into the rig of the neighbor parked behind me.
I do not know if there's a supplemental water pump on the engine's defroster core loop (no OEM HVAC on this coach), but then again, I haven't gone searching for one, either. There is a small pump in the AH unit for the engine coolant loop, in addition to one for the cabin heating loop, but that only runs when the AH is on for pre-heating the engine.
Anyway, that's the way Vantarè did it on my conversion, perhaps that will help you with your design.
FWIW & HTH. . .
;)
Thanks RJ, that is helpful. Do you plug into the pole or use your generator mostly?
Quote from: RJ on February 23, 2021, 10:57:53 AM
JC -
My coach has hydronic heat available from the cantankerous AquaHot unit, plus Cadet "Perfectoe" 1000w 120vac undercounter ("toe-kick") electric heaters. Each system has four registers scattered thru out the coach: bedroom, bath, galley and front salon. There are also hydronic registers and small electric heaters in three of the four bays (none in the generator compartment.) There is no propane on board - didn't want a coach with that fuel source.
Just the four Cadets kept the coach at 68º inside when it was 10º outside a couple weeks ago, so they work, each cycling on and off as their individual thermostats controlled them. I did not fire up the AH unit because I didn't want the exhaust blowing into the rig of the neighbor parked behind me.
I do not know if there's a supplemental water pump on the engine's defroster core loop (no OEM HVAC on this coach), but then again, I haven't gone searching for one, either. There is a small pump in the AH unit for the engine coolant loop, in addition to one for the cabin heating loop, but that only runs when the AH is on for pre-heating the engine.
Anyway, that's the way Vantarè did it on my conversion, perhaps that will help you with your design.
FWIW & HTH. . .
;)
Careful with the pump volume to much flow the system will not transfer the heat not enough flow the Webasto will over heat and shut down ,check the temperature rating on the Pex if tied to the engine some PEX don't like anything over 140*,if using the toe kick heaters clean those puppies a lot of Prevost and other brands have had fires because of the lint build up associated with those
I'd definitely use the aux heater. I will in fact be using it on mine which will require me to drain down the system and add at least one solenoid valve.
Now something to consider is that the engine driven system without the aux loop is quite capable of running fine with the cabin heat either on or off. But I'd have to go back and look to check the conditions. Some relevant questions need to be answered.
Does the coolant still flow through the cabin loop when the AC runs? (Not sure about this one but I suspect not, or perhaps throttled back by the main solenoid valve on that line.)
Is the dash heat an extension of the main line to the cabin heat? (I think it is, easily checked.)
I'm pretty sure the dash heat has a manual control valve. Should be a T handle on the left.
The point is, you can shut off cabin heat by turning off coolant flow I'm pretty sure. That means effectively restricting the flow from the water pump when the heat is turned off, which does several things, but mainly it causes a small increase in pressure on the outflow side to the radiator, and should increase that flow somewhat. But since that side is a good bit larger the proportional increase won't be that great. Conversely flow through the engine block will decrease somewhat as the outflow is restricted by removing the cabin path. So flow through the block (and pump) goes down while flow through the radiator goes up, which could but not necessarily will cause an increase in engine temp. A completely different effect from removing the heater cores as radiators.
But what about the aux heater then? That really depends on how it is plumbed and controlled. As is, we understand the engine preheat function and we get some cabin heat while doing that but the flow may give preference to the engine and probably does. This was probably the primary function engineering-wise and it seems likely it was optimized for that mode. So it can circulate coolant to the cabin, but may not do it particularly well.
OTR it is designed to supplement engine heat when needed. Again that means it only needs to add heat to the engine loop and the pump is sized to prevent overheating the boiler. This is a more demanding application due to the engine's heat output so pump size would be determined here.
But what happens if you take the engine out of the loop? That is the question we need to ask and answer. Is the flow through the main cabin loop then sufficient to prevent boiler overtemp? (We can disregard the dash loop since it will not always be used.)
Seems to me those lines are at least 1" and maybe 1-1/4" diameter, which I think is the same as the lines to the webasto pump. So ideally your coolant lines to the cabin radiators would add up to the same area. Keep in mind that doubling the diameter quadruples the flow, so it takes four 1/2" lines to equal a single 1" line.
Jim
Quote from: richard5933 on February 22, 2021, 05:35:50 PM
You're out of my league with the OEM engine Webasto questions.
My thoughts on the engine loop is that you'll need the extra pump. There's a reason you see them in system. Even a stock bus will oftentimes have an extra pump to bring the coolant up front to heat the heater core, so I wouldn't put much confidence in the engine pump to do the work, especially at idle speed.
If the bus has the extra pump for the front heater core; I would simply add a relay to turn it on for engine preheating. My bus has such a pump and it is of a fairly hefty size. Going to remove the extra pump I added for my system and go with this approach.
Quote from: Jcparmley on February 23, 2021, 12:55:31 PM
Thanks RJ, that is helpful. Do you plug into the pole or use your generator mostly?
JC-Both. On the pole for extended stays, genset when on the road or boondocking. If/when solar gets installed, there will be less genset usage while boondocking. But that's currently a low-priority project at this point.
Clifford - Thanks for the reminder tip to clean the toe-kicks! I will move that to the top of my "to do" list!
;)
People never realize how much dust accumulates in them. There was quite a bit of news about fires in the 90's. Guess it was forgotten. This is a good idea for all space heaters. I blow mine out every season.
Correct on annual cleaning of toe kick heaters. He have three electric ones and they gather all sorts of crud in them. I found that a slim (3/8" or so) clear vinyl hose stuck onto the nozzle of a vacuum great for getting deep inside the units to suck out the dust bunnies. I modified an extra crevice tool to accept the vinyl hose with a small vent to keep the hose shop vac hose from sucking itself closed.
Any forced air product heat or A/C needs periodic cleaning. Especially heaters including elaborate RV furnaces as dust accumulation not only effects performance will also catch fire!