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Aqua-Hot heating on electric question!


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Dear Fellow Monacoan’s;

I have a 2000 Monaco Signature Series with an Aqua-Hot and have a quick question.  I have always used my Aqua-Hot on the Diesel setting since I have owned it and it works great. In fact just had it fully serviced in August  

Can I set this to the “Electric Setting” and use it to keep my coach warm (and baggage compartments) during cold weather when stored inside a huge metal storage facility? Temps dipping down to freezing overnight outdoors  

It has 50amp power continuously hooked up to it, so power is a non-issue. I only need to use this for 1 month until I can get some repairs done and winterize her for the season.

Thank you for any help you can offer me.

Monaco Bob from Tulsa

 

 

 

 

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Bob, I only use the diesel for showers. The rest of the time the AH is on electric which provides enough hot water for everything else so the AH electric is on all the time. I've not had any issues with it and, like you have it serviced with my annual service. I see no reason why leaving it on for heat would present a problem, but I don't think it heats the underbelly........Dennis

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Bob, that is exactly what I do when it gets cold. Electric on and dial thermostat in the basement set to ~40. Yours, just like our 2000 should have a Aquahot register with a fan right above the holding tanks and the thermostat on a wall just in front of the AH.

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 Bob,  That is sharp coach and trailer combo.

 I believe on the older model AquaHot the elect and diesel are on different thermostats, not the thermostat on the wall but those inside the unit.

 The idea is the elect element will come on before the diesel  That way in many cases the diesel will not need to fire if the elect can keep up with demand.

 Except when indoor ( carbon monoxide )  I usually leave both on.  That way the diesel can act as a backup.  

 Many people have gotten by with a drop light below and a space heater above .

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The electric heats the heat transfer fluid in the unit.  That is then distributed to all radiators (including the one in the water bay).  So, any of the three ways to heat the fluid also heats the wet bay.  ie: Engine heat, diesel or electric element heat.

At least that's how my HydroHot / Newmar system works.  I would be surprised if it's any different in yours.

My wetbay has it's own thermostat.  That just tells the main unit to heat up that zone.  No different than the interior thermostats do the same for their respective zones.  The heat source keeps the fluid hot and ready for any zone's heating need (including domestic hot water).

The reason to turn the diesel on is it provides max BTUs to keep the transfer fluid hot like when using the shower.

The reason to turn the electric on is it doesn't then require you to refill the Diesel tank, and the cost of energy is very likely less via electric than diesel.  And certainly less than running the coach engine to provide the heat.

The reason to run the heat off of engine while driving is it's "free" heat that the engine radiator would normally dissipate to the air.  The Aquahot is pulling that heat off and heating the transfer fluid for "free".

The problem with using electric for storage is that the transfer fluid will cool down and require electric power to keep it hot to it's set point.  Even if the storage unit is above freezing even if it's 60 degrees out.  One of the features of my automation system (that gets weather data) is to keep the HydroHot OFF unless the ambient temp is forecasted to drop below 35F.  Then, the automation system turns on the Hydrohot on Electric to keep the wetbay above freezing.  That's the best usage of energy I can figure.  It's also possible to turn on the diesel if the electric isn't keeping up with the BTU load.  But the problem with that is if the RV is in a storage unit, the Diesel exhaust would soon fill the storage unit....this could be controlled by the automation system by having a "storage" mode of operation that turns OFF the possibility of Diesel use.  But haven't done that since my RV doesn't have a nice enclosed storage barn (yet).

The automation system relays are wired in series with the existing manual switches.  So the manual switches act as an override if the slim chance the automation controller goes beserk that the Diesel won't turn on when it shouldn't.

Edited by DavidL
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Beautiful coach and trailer!

The early Aqua Hot systems only have a single element electric heater.   It is 1650 watts and produces about 5000 btu of heat.  If the incoming water is fairly warm, it works well for a short duration of hot water.  However, if the incoming water is very cold, it is not sufficient.  It will not heat the interior of the coach when the temperature is low.  

The diesel burner is 50,000 btu.  It will produce sufficient heat for heating the inside of the coach, the basement, and even pre-heat the engine.  It will also produce hot water regardless of the incoming water temperature.  

The newer Aqua Hot systems have dual electric heating elements and will function much better on electric only.  However, if you are paying for electric the diesel burner is more efficient.  

Edited by vito.a
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Depends how high you set the temperature but while just stored, ours has no problem keeping it well above freezing temp. Seeing that Bob is based in Tulsa, I don't think it would be so much colder than where we are in north TX. Yes, a nice rig!

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Look at Vito's comments above.  The electric element is rated at 1,650 watts.  Many of your common "space heaters" that you bring home from Best Buy or Bed Bath and Beyond are rated up to about 1,500 watts.  That is also about how much heat energy your AquaHot is going to be able to deliver using only the electric source.  Think of the heating capability of your AquaHot as being about the same as that little space heater.  It may do what you need it to do, but often it may fall short.  Just recognize that it will only keep it as warm as it can.

Quick lesson in basic heat transfer.  Your coach interior is at some temperature.  The outside is at some colder temperature.  The rate of heat loss from inside the to the outside of your coach is directly proportional to the difference in those two temperatures.  That heat loss can be measured in BUT per hour.  (If you want to play with the math, there are 3412 BTU in one kilowatt-hour.  Also, watts is a measure of power.  BTU is a measure of energy, which is power multiplied by time.)

If the temperature difference between the outside and the inside results in more BTU per hour of heat transfer out of the coach than what the AquaHot heating element can supply, two things absolutely will happen.  One, the temperature inside the coach will gradually go down until the resulting difference in temperature equals what the heating element can supply.  That will be the best it can do.  Two, the AquaHot zone will be running 100% of the time until the outside temperature finally warms to the point that the heating element can supply enough energy to keep up with satisfying your thermostat setpoint.

Put simply, if that little space heater would be strong enough to keep your coach from freezing up anywhere (assuming you can get the heat where is needed), your AquaHot will be able to do that same job using just the electric element.

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9 minutes ago, k7jv said:

...

Put simply, if that little space heater would be strong enough to keep your coach from freezing up anywhere (assuming you can get the heat where is needed), your AquaHot will be able to do that same job using just the electric element.

Just a detail, the Aquahot system sprawls across the whole RV.  There are heat losses mostly from the boiler unit (that is always hot) that don't contribute heat directly to the wet bay.  So not all the energy goes towards heating the wetbay.  The space heater could put all of it's heat right in the wetbay.  I'll predict there is 70% of the Aquahot energy can be directed to any one zone.  That's just a guess.  But for most purposes, that's good enough if the wetbay is well insulated and the ambient temp isn't really cold.

Edited by DavidL
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You are right, David.  I was just using the space heater as an energy comparison, not necessarily suggesting the use of one to do what the OP is trying to accomplish.  In our coach, fortunately, the AquaHot is in the same space as the three tanks so virtually all of the heat loss from the AquaHot unit is "used and useful" for protecting them from freezing.  Not so much the above the floor, inside the coach plumbing, though.  For that, like you said, the other zones would become involved and the electric heating element source alone would really fall short if the outside temperatures get very low.

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22 hours ago, vito.a said:

  

The newer Aqua Hot systems have dual electric heating elements and will function much better on electric only.  However, if you are paying for electric the diesel burner is more efficient.  

Only the larger 600 series AH's have more than one electric element.

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To my Monaco family. Thank you to each of you who responded with answers to my question along with a huge thank you to those of you who commented so nicely on my coach. 
 

I feel strongly I now know the proper way to utilize my AquaHot in my storage situation.  

Please have a wonderful Thanksgiving Holiday and know that y’all are truly living the spirit of the Holiday by helping others. 
 

Bob Dresser

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