Aqua hot issue

[Loren Rice]

I am starting to trouble shoot a problem (at least I think it is) in my aqua hot seems to be circulating hot water any time it's on to the engine. I thought that It should only be on when its freezing outside. I've looked every where for a switch but so far see none. My original owners manual is quite vague but gives me the impression that when the switch for the aqua hot up by the driver seat should be what brings it on but it's not working that way.

This is on my 94 Monaco signature. the heat everywhere else is controlled by two thermostats on the wall in separate locations and they work perfectly.

Any one experience in older mh's maybe you can help me. I should add that I have wiring prints that don't show these circuits.

So guess my question to any aqua hot users how, 1 Automaticity? or 2. by some control? when is warm water circulated to your engine?
Thanks in advance for your help.

Loren

[RamiDav]

On my 03 Windsor I have a switch panel in the kitchen for my aqua hot .
The panel has 3 switches , they are labeled

1 Diesel

2 Elect

3 Engine Heat ( turns on a pump inside the aqua hot )

I have a sw up by my drivers seat that controls an elect heater in the engine block .


Ray

[HJLowell]

Aqua hot
3 zones controlled by 2 thermostats

1 pump, a 4th. that turns on and off
With a switch by the drivers seat.
When on, This circulates heated aqua hot liquid, mine uses coolant
Through the engine block to warm it up when its very cold out.

This is SEPARATE FROM THE 120AC BLOCK HEATERS. My block heater switch is also close to my drivers seat. NO CIRCULATION PUMP NOR THERMOSTAT USED..

Now when you run your engine and travel. A small amount of hot engine coolant 180 to 205 maybe ?circulates through the aqua hot water heater system so that you have hot water for a shower when you arrive at your destination.

Regardless of how cold or hot it is outside when traveling. Your engine is heating your water without running your oil burner.

Your electric side will only work if you run your generator.

Download an rv aqua hot manual to study.

[K7JV]

On our '06 Dynasty, we have two switches in the group to the left of the gage cluster for engine heat. One is labeled "AQUA-HOT ENGINE PREHEAT", and the other is "BLOCK HEATER". The first controls that AquaHot pump, and the other switches a 110v outlet in the engine bay, and there is a male cord plug right there that can be left plugged in, or not, for the block heater.

See if you can find the nameplate on your AquaHot and get the model number, then go to the AquaHot website and see if they might have a service manual there for it, that would include a schematic. They do for ours, and it is a great resource!

The truth is, if you can't find an engine heat switch, you could probably find the connection on the control board for the power to that pump, and add a switch either at the AH or in your cabin to power it off. We actually very rarely turn our AH engine heat on. But we also try to avoid temperatures much below freezing, too. Our Cummins has always started very easily, even into the low teens a time or two, and when we are going to travel, we always run it on 1000 RPM idle until it is above 170 degrees before we give it any significant throttle.

It is true that then engine loop does circulate while going down the road, as the engine will ensure you have hot water in your AquaHot when you arrive at your destination, even if you don't power on the electric or the diesel input to your unit. I have never researched how that works, though. There could be a pump at the engine end, though it would surprise me for that to be the case. Or it may be that there is an ignition input to the AH control board to tell it the engine is running so that pump will run. I don't think that is the case, either, though, so I'm not sure how that loop is made to circulate, but it definitely does. I just haven't had a need to check it out, because it just works. That's not like me. Now I'll probably look into it. Dang!
Let us know what you find.

[HJLowell]

On my airstream motorhome and on my 1999 signature the engine coolant pump is always circulating the loop to the aqua hot and the dash heater as I understand it.

[Outbound]

My Exec has a switch on dash by gauge cluster.

[Loren Rice]

Thanks for all your inputs I will look more closely at the switches I do have and see if I have overlooked a control for engine heat.

It really helps to hear how in other rigs, the system are set up to operate. As I have said in the documentation I have is on the vague side. I looked at how the panels on newer rigs display information., I have just a silver box that the circulation motors, boiler and tank are contained. No marking or tell tell lights as in more recent units. Still it's not broke down -- exactly, just not as efficient as it might be.

When my rig was constructed I think they were learning and refining Monaco's. Still this unit even though is old has many of the nice things seen even in today new rigs,

So thanks for all your inputs, Today I'll go out there and identify the engine preheat heat pump and then try to find it's power source. And as suggested perhaps add a switch if no other control is found.

I'm kind of hoping there is an extra set of contacts on the front heat control by drivers seat that isn't working cause my manual now, as I reread it, may be indicating that is where the circulation motor for preheat should be controlled, possibly on this unit.

[Mike Tomas]

Just FYI about the Engine Pre-Heat Switch:

Not only is it designed to pre-heat the engine on cold days using the Aquahot to heat the engine, it can do two other things as a by-product of it's design:

A- When switched on, (aquahot off) it can pre heat your water tank while driving to your destination using the heat from your engine.

B- When switched on, (aquahot off) it can provide cabin heat to your registers while driving to your destination using the heat from the engine.

All that switch does is open a valve and turns on the aquahot pump to move the aquahot coolant around the heating system and through your heat exchanger. The heat exchanger allowas the aquahot coolant and the engine coolant to exchange heat while keeping the two systems seperated. It was designed to heat the engine using the aquahot heater.

But in milder climates, and the aquahot off, you can still utilize the pre-heat switch to take advantage of the transfer of heat from one system to the other. The effects are not immediate, but I suggest you try it one day when you know your hot water tank is cold. Turn on the pre-heat switch when you start your drive. If both of your aquahot and electric water heaters are off (assuming you drive with generator on) then the only way your hot water tank is getting hot is by engine heat!

I'm a weekender, and I've done this a few times, and it's quite nice!

[luckyd]

My 02 Windsor manual says to turn off the engine preheat
after starting engine. My preheat switch is by the drivers seat.

[HJLowell]

Originally Posted by luckyd

My 02 Windsor manual says to turn off the engine preheat
after starting engine. My preheat switch is by the drivers seat.

Correct
The engine coolant pump circulates heated engine coolant to and through the aqua heat.
Turn the engine heat switch off.

It is NOT NECESSARY TO RUN THE AQUA HOT ENGINEOOP PUMP.

Its all automatic for you.

Only turn the loop pump switch ON before you start engine to warm it up.
I turn it on the eve ing before I amd going to fire the rig up.

Then turn the switch OFF.

[96 Wideglide]

Originally Posted by Mike Tomas

B- When switched on, (aquahot off) it can provide cabin heat to your registers while driving to your destination using the heat from the engine.

You shouldn't need to turn on the AH 'engine pre-heat' switch for your engine to heat your boiler tank. Just turn on a hot water faucet, you'll have hot water. Turn on your thermostat to furnace, you will have coach heat.
From a cold AH, this will likely take 20 or so miles of driving though !

[Mike Tomas]

Originally Posted by 96 Wideglide

You shouldn't need to turn on the AH 'engine pre-heat' switch for your engine to heat your boiler tank. Just turn on a hot water faucet, you'll have hot water. Turn on your thermostat to furnace, you will have coach heat.
From a cold AH, this will likely take 20 or so miles of driving though !

Maybe not in your coach.

[96 Wideglide]

Originally Posted by Mike Tomas

Maybe not in your coach.

Do what you like !

Three of us have just posted there is no need to run the engine pre-heat pump, while the engine is running!

[Topman]

Our Aqua hot manual specifically states to only use the engine pre-heat with the engine not running. The engine water pump will distribute coolant through the aqua hot as well as the dash heat exchanger up front when the engine is running.
I would think that having the aqua hot preheat pump running while the engine is also running might disturb the coolant flow.
JMHO...