AquaHot While Under Way

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AquaHot While Under Way

June 20, 2014, 10:12:38 pm

We don't travel in cool climes much, but Upper Michigan is proving Spring is not over.

I've read here that AH can heat using the feature that the engine heat is used to heat hot water.

So I tried AH the other day and no heat emerged. What I understood earlier is that the AH does not have to be on. True?

best, paul

Re: AquaHot While Under Way

Reply #1 – June 20, 2014, 10:36:50 pm

Paul,

The diesel burner, electric element and engine preheat switches can be off and you will still have heat for the interior thermostats to call for while driving down the road.

When the main engine is running, hot engine coolant is being pumped through the engine preheat coil that is wrapped around your coolant tank and embedded in heat transfer mastic. The 3/4 inch coolant line from the engine will supply enough heat to warm the coach till the outside temp drops below 50 degrees F. Lower temps need the diesel burner on to supply enough BTUs to handle the demand.

If no heating occurs, especially above 50 degrees, your engine coolant loop may no longer be embedded in the heat transfer mastic. Or, there is a restriction in the flow of hot engine coolant from the engine to the heater (not real likely). The engine preheat pump does not need to be on for the engine coolant to flow normally when the engine is running.

Re: AquaHot While Under Way

Reply #2 – June 20, 2014, 10:52:51 pm

Some also have a shut off valve in the system I think

Re: AquaHot While Under Way

Reply #3 – June 20, 2014, 11:10:25 pm

Thanks, Rudy.

I'll be very careful to see if there's any heat the next time I need heat.

On this:

"The engine preheat pump does not need to be on for the engine coolant to flow normally when the engine is running."

I thot I read the AH could be damaged if preheat was on while the engine is running. The above quote does not say the preheat could be on when the engine is running, but, it does not say the preheat should not be on when the engine is running either.

I always use preheat to speedup getting engine to 150F

best, paul

Re: AquaHot While Under Way

Reply #4 – June 21, 2014, 02:50:20 am

Paul,

Having the preheat pump on when the engine is running has two pumps moving the engine coolant through the heater instead of just one. I do not think any harm will occur as both pumps run in the same direction. Just not best practice.

Re: AquaHot While Under Way

Reply #5 – June 21, 2014, 09:46:10 am

Quote from: Paul Smith – June 20, 2014, 11:10:25 pm

Thanks, Rudy.

I'll be very careful to see if there's any heat the next time I need heat.

I always use preheat to speedup getting engine to 150F

best, paul

Paul, an easy way to check that is just open a hot water spigot and see if your water is hot. If you are using the preheat to warm up the engine you have to have a working system i.e. no valve closed somewhere and your loop is working. Just a thought. Let us know what you find. David

Re: AquaHot While Under Way

Reply #6 – June 21, 2014, 10:28:46 am

I use my AH all the time in cold weather with just engine heat. It is good down to the 30s to keep the coach at 65 with the dash heat on as well. Now it does nothing to stop the snow from falling but does keep us warm in the rest stop. It is the biggest advantage AH has vs a gas heat coach. I have not had to turn on the diesel yet in cold weather driving along but do put it on when I stop for a fuel stop or a quick bite of lunch.

Re: AquaHot While Under Way

Reply #7 – June 21, 2014, 01:18:43 pm

I don't know much about the AH as I don't have one but I assumed that the engine heat would keep the coach warm down to -20 as the engine heat
is at least 180 and if the heat exchanger in the AH is any good the engine heat should be better than the diesel heater

Re: AquaHot While Under Way

Reply #8 – June 21, 2014, 07:03:49 pm

Oldguy,

See my post above regarding how low the outside temp can be for good interior heat from the engine (50). The 180 degree F engine coolant is NOT in the fan coils inside the coach.

It is in a loop surrounding Paul's tank full of boiler fluid. It is the boiler fluid heated by the engine coolant that is in the fan coils inside.

So no interior heat at 20 degrees outside from the Aqua Hot/Engine combination. The engine coolant loop just can not transfer enough BTUs to meet the demand below 50 degrees F.

Hope this helps.

Re: AquaHot While Under Way

Reply #9 – June 21, 2014, 07:49:50 pm

If the electric is 5,000 btu's and the diesel is 50k any idea what the engine loops btu is in and out?

Re: AquaHot While Under Way

Reply #10 – June 22, 2014, 06:24:07 am

John S has shared that dash heat, which is hot engine coolant, along with heat from the Aqua Hot fan coils has kept him comfy down to 38 degrees.

Thanks John.

Re: AquaHot While Under Way

Reply #11 – June 22, 2014, 06:48:13 am

Dash heat? Â Who knew?

Will Foretravel ever stop surprising us with features we never knew we had years after we get our FT?

It's too bad the PO had our FT on consignment and all docs were stolen.

So there's plumbing distinct from AH that brings heat up to the dash?

best, paul

Re: AquaHot While Under Way

Reply #12 – June 22, 2014, 09:39:01 pm

I thought I wanted and AH cause it had a heat exchanger and I thought it would put out at least as much as when it burn diesel. I guess the only thing
to do is put in a motor aid heater the same as I do with propane heat. I find it doesn't make sense burning propane or diesel when you have all that free
heat form the engine. One one of my motor home I had a motor aid hot water heater and that was great and it worked really well. Every time I stopped
I had 180 degree hot water in my tank. I ski so any motor home I have gets winterized so I can live in or drive it in at least -20

Re: AquaHot While Under Way

Reply #13 – June 22, 2014, 09:55:09 pm

Well Oldguy,

The motor loop will put 180 degree boiler fluid in the Aqua Hot too when there in no demand for interior heating. But the question is how many BTUs can the motor replace in your water heater or the Aqua Hot to meet the demand of heating a 40 to 45 foot motor home front to back and the basement too in -20 degree weather. 50,000 BTUs from the diesel burner with do the trick.

If you can do that with motor coolant heat and a water heater in -20 degree weather, you are a better man than I.

Re: AquaHot While Under Way

Reply #14 – June 22, 2014, 11:24:41 pm

I travel a bunch in the winter and down to below zero. The dash heat supplementing the AH in the motor aid heat that it produces will heat up the coach to about 60 degrees down to the 30s. Any lower you need the Diesel burner to keep the heat up. I have had examples to do it both ways. Now, I also had a 270 and it meant turning on the furnace when it was cold all the time. I love the AH and it is what makes the winter travel we do more fun. In fact I rather travel in the winter then the summer.

Re: AquaHot While Under Way

Reply #15 – June 23, 2014, 11:51:29 am

Not aquahot but I have in floor heat and when we are driving the 180 * off the eng. is lots of heat it just takes a little longer to heat up the floor . Not sure how many heat rads you have but you will not cool down the 180* off the eng. ( I have driven in -30 cel. with no problems )

hope this helps
dave

Re: AquaHot While Under Way

Reply #16 – June 23, 2014, 12:50:28 pm

Thought on this over night and I may not be understanding his comments the way he does.

I do believe if you have fan coils in the living and basement areas of the coach that are fed hot engine coolant, you can heat to very low temps while traveling and you will have hot water via motor aid when you stop.

This means there is a second set of fan coils and thermostats in addition to the Aqua Hot fan coils. If one is using this second set when traveling and the Aqua Hot thermostats are off, the hot coolant in the Aqua Hot will have hot water ready when you stop since no heat was removed from the heater while traveling. Of course, with no Aqua Hot some other way would be needed to have heat when stopped such as noisy propane slurping furnaces.

If you have a floor heating zone and thermostat fed by hot engine coolant, you need a second loop fed by the Aqua Hot, or some other way if no Aqua Hot, to have floor heating when stopped.

If you only have the Aqua Hot, the heat removed in very cold conditions in heating the interior is more than the engine can supply to the Aqua Hot to keep the coach at 72 degrees. Instead of moving the Aqua Hot coolant through the very hot engine, it is being heated by the engine preheat copper pipe loop.

But there is heat being transferred and most likely the coach will be above freezing but not comfortable to us humans. In those conditions, the diesel burned by the burner supplements the heat supplied by the engine to meet the demand for 72 degrees inside and 40+ degrees in the basement.

The diesel burner would not run 100% of the time. It would bring the tank to set point, 190 degrees, shut down till the engine loop could not keep up and cycle again.

A coach built to your specs by any number of manufactures can be any way you wish. It is only money you can not take with you. But money not spent by the folks making coaches for the retail market. Bling sells, not stellar infrastructure.

Re: AquaHot While Under Way

Reply #17 – June 23, 2014, 02:42:45 pm

I have been saying that you can run with just the engine heating the coach but Rudy hit on Something here. I could not get the temp up to 72 only 60 as a max and many times it might be a few degrees cooler still.

Re: AquaHot While Under Way

Reply #18 – June 23, 2014, 03:19:23 pm

18 degrees below zero when we left for Florida in March. I had the AH on diesel the night before we left and for most of the next two days. We were warm enough, probably mid 60's. Two long days till it was warm enough to flush the winter juice from the water system and flush it again and then add water. We really like the AquaHot!

This winter we are thinking November.

Roger

Re: AquaHot While Under Way

Reply #19 – June 23, 2014, 08:58:42 pm

From what I get from everyone is the heat exchanger in the AH is not that big or efficient enough to do as good enough job as the diesel burner. The engine has enough heat to heat any size motor home. We have school buses with no insulation and other buses that drive in -40 and maybe colder that keep nice and warm.

Re: AquaHot While Under Way

Reply #20 – June 23, 2014, 09:19:55 pm

Your school buses have engine coolant flowing through heat exchangers with fans behind them. The AquaHot has to take heat from the engine coolant to heat the AquaHot coolant which then flows to the AquaHot heat exchangers and fans in the coach and the basement. Rudy will correct this if it is not quite right. The 110v electrical heater is only about 3Kw and will provide enough heat for the coach down into the low 40's. Engine heat does about the same. The amount of heat available from the diesel burner is several times what the electrical element provides.

We have had RVs with LP gas furnaces and now an AquaHot. No going back for us.

Roger

Re: AquaHot While Under Way

Reply #21 – June 23, 2014, 09:36:26 pm

Quote from: oldguy – June 23, 2014, 08:58:42 pm

From what I get from everyone is the heat exchanger in the AH is not that big or efficient enough to do as good enough job as the diesel burner. The engine has enough heat to heat any size motor home. We have school buses with no insulation and other buses that drive in -40 and maybe colder that keep nice and warm.

If the system had a coolant leak the engines could suffer damage or shut down.

The separate heat exchanger loop for the engine is probably for reliability. Especially as throwing a switch adds enough btu's to heat the entire coach.

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