AquaHot Question

[pickpaul]

I understand that the electrical heating element in the AquaHot is only for supplemental heat and/or mild weather. If you plumbed in the hot coolant from the generator in addition to the engine coolant, could you provide enough heat in freezing weather via generator without burning diesel in the furnace? I ask because I plan on converting my (as yet not purchased) bus engine and generator on veggie oil and that would allow for free heat rather than burning diesel (I know I couldn't run an AquaHot on veggie). So any thoughts or experience?

Cheers, Paul.

[rv_safetyman]

Paul, interesting question.  We are sitting in OH and it is 43*.  We are using an electrical heater and it is not keeping us warm.  We have the AquaHot on AC only right now and it is kicking on perhaps every 10 minutes.  I have one of my fire detection sensors in the area inside the housing - close to the boiler.  When the unit is at cut-off temperature the reading is about 188*.  Right now the electrical can't keep up with the heat required (currently at 163 degrees and not going higher very fast - or not at all).

That is background and does not answer your question, so lets try this:

I have one AquaHot circuit plumbed into my dash AC/Heater (RedDot R-5045 - AC 33K BTU/hr and Heater 46K BTU/Hr).  Going down the highway in 40* weather, the engine heat will not keep the coolant in the AH heat exchanger at an acceptable level (Series 60 running 185*-195*).  We have to run the Diesel side of the AH.  The water flow is via the engine WP.  I have not tried running the AH engine circulation pump.

Our bus has pretty good insulation in the lower walls, but ceiling is stock bus.  We probably have more air leaks than some buses.  However, there is no way that we could warm the bus with just the engine heat providing energy to the AH given the conditions above.

We could probably put a circulation pump (or use the AH unit) and do better.  Our system is probably not optimized to use engine heat.  We all know that our buses were heated by engine heat, but I don't know what to do to get that heat to the AH and exchange it properly.  

As I think about it, the exchange is probably the problem.  The engine coolant has to exchange the heat to the AH boiler and that is probably not all that efficient (in the OEM bus heat system, the intermediate exchange does not take place).  I doubt that this cold weather will hold for a week (next time we will be driving - heading towards BCM Rally), but if it does, I will check the engine cooling inlet and outlet temperatures at the AH unit.  My guess is that the delta temperature will not be impressive.

Given the about discussion, I really doubt that the generator coolant will provide much BTU to the AH coolant system so that you can do useful heating.

Jim

[gus]

As someone recently posted, portable electric heaters make more sense when plugged in - no LP use and no cost to operate when at an RV park.

I hadn't thought of this but it is what I will do from now on since I already have the heaters, cost all of about $20 each. Be sure to get ones with thermostats.

I used two in my 4104 which leaked air like crazy, the 4107 it pretty tight so one will probably do it. No CO to worry about either.

[luvrbus]

I never could get the generator to make enough heat to do any good on mine with a pump, the electric backup is good for nothing IMO

My AH came with a 1650W heater I changed to a 2000W if my math was right I was only producing somewhere around 6500 btu I forget the exact number but it wasn't enough to keep you warm at 50 degrees

good luck

[rv_safetyman]

Gus, the electric heater sounds good until you consider that the 1500 Watts is over 30% of the 30 amp supply that we have here.  If you add the electric heater for the AH, you are up to 60%.  Not all 30 amp breakers trip at 30 amps - as they age, their trip level can be lower.  Doesn't leave much margin for other power consumption.

I made a bit of a design error when I wired the bus.  All of my interior outlets are powered through the inverter.  No problem as long as you have power from the pole (pass through).  However, if you loose the power at night, the  would drain the batteries in no time.

I will wire an outlet that does not go through the inverter.  That way if the power goes out, the inverter only has to handle the normal loads.

One further option is to wire an outlet that has a connection directly to the power post.  That way, I could run a separate cord to the 15/20 amp plug on the pole and not run the heater through the 30 amp supply.  Probably not a good thing if the CG catches you, but not much different from the dog bone adapter that some folks use.

BTW, I just looked at the weather here in Greenfield, OH and the low tonight is going to be 34*!!!  Forecast has frost warnings!!

Jim

[Jeremy]

Going back to the premise of the original question...why can't you run an AquaHot on veg oil? Aquahots are based around a Webasto or Eberspacher-type heater aren't they?


Jeremy

[pickpaul]

I've just read enough about the difficulty of modifying home heating oil furnaces to not want to attempt that. It's a whole different world than heating the fuel supply to a diesel engine.

I just thought that the hot coolant and electrical together would be enough. It's basically a bus/rv implementation of cogeneration...

http://en.wikipedia.org/wiki/Cogeneration

cheers, Paul.

[Jeremy]

Ok. I don't really know what's inside an AquaHot so I can't comment on that. I did do a quick Google before my earlier post and people seem to be running Webastos on veg oil without problem - which is relevant to me because I've got a Webasto, but probably isn't relevant to your question about AquaHots.

Jeremy

[gus]

Jim,

1500 W is the max setting, all mine have a middle setting of 900 W which is the only one I ever use since it provides all the heat we ever need and we usually need only one heater at a time.

[Gary W]

Paul

I use mine on electric down to 40 degrees at night if we are in a campground , not real hot in the coach but warm enough to sleep. Going down the road we get enough heat off the engine loop to heat the coach and supply hot water.  Works great  to preheat the 6V92 when in as cold climate.

Gary

[rv_safetyman]

Gus, we must be wimps.  The low setting on our electric heater will not keep the coach all that warm at 40*.  As noted, our insulation in the roof area is stock bus.  The windows are all double pane and that helps.  The past couple of nights we have put insulation covers (looks like aluminum cover on both sides) on the windshields and our make-shift vinyl window covers up and it makes a heck of a difference. 

When we got back to the coach tonight the AquaHot temperature was at 120* and after an hour on electric only heat it is now at 137*.  The electric heater in the AquaHot is pretty puny.

Jim

[gus]

Jim,

We only used the electric heaters in the 4104, there was no other source when parked except the LP cat heaters. To say that the 4104 is not well insulated is an understatement! I haven't tried them in the 4107 yet but they are bound to be better since the insulation is loads better.

We always moved the little elect heaters around wherever we were, under the table when eating and etc. They definitely will not heat the whole bus but are excellent for small areas. We like it cold for sleeping and turned them down at night.

The LP portable heaters are even hotter but use up those small LP bottles at a fast rate.

My 4107 water coil is too good, it probably heats to something like 180*, the engine coolant loop is even hotter - not surprisingly. Your electric loop may be coated with lime. I don't think these things are adjustable, if they are mine is going to be lowered.