Webasto Heating System

[Jcparmley]

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?

[richard5933]

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.

[Jcparmley]

Like This?

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.

[richard5933]

Like This?

That's how ours was.

[Jim Blackwood]

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

[richard5933]

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.

[buswarrior]

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

[Jcparmley]

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? 

[lostagain]

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

[buswarrior]

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

[sledhead]

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

[freds]

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.

[Geoff]

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.

[buswarrior]

Add the pump model to the performance numbers, there's different pumps...

Happy coaching!
Buswarrior

[lostagain]

Sorry, too late. The Webasto is mounted in the bus now.

JC