Aqua Hot, to use or not to use, that is my question.

[Peterson143]

Was wondering what thoughts were out on the forum re the use of the Aqua Hot system? Currently when we leave for the day or for extended periods we shut off the system (electric, plugged into shore power) and then turn it on when we return. Obviously do not use the diesel power except when dry camping or need the water hot much faster. So the question is generally speaking to leave the system on all the time or shut down and then turn back on when returning to the rig? I'm thinking that powering off the system saves on electrical cost, equipment overuse, and the possibility of system failure when away from the rig.

[kketterling]

When staying at an rv park leave electrical on the whole time we are there but when dry camping diesel burner only when we need hot water. Note if your staying long term at an rv site and they are charging you for electricity, then I definitely would turn it off when not needed.

[Mr_D]

Leave either one or two elements on all the time if on shore power and burner only if dry camping.

[LSBEH]

Well it depends on who is paying for the shore power, and the ambient temperature outdoors (through the day).
If we are in an area with cooler outdoor temps through the day, and especially if we have already paid for 30 or 50 amp electricity, then we'll leave the electric side of the aqua hot on.
The reason the outdoor temp is a factor is...the aqua hot if left on generates heat, which radiates up from the basement (through the floor) to the living area. The living area then gets warmer than you may like, or the air conditioners work overtime.
On the other hand if it's cooler outside you may appreciate the extra heat in the coach when you get home.
I would not worry about system over use, or safety. The electric side is an electrical block heater element that is designed to be left on for long periods of time, and has safety parameters built in. If it's warm outside and you are paying per KMP yourself then turn it off...when you return you can turn it back on. It should only take an hour or so to give you hot water.
Just my two cents....hope it makes sense
LEBEH 😎

[moisheh]

Originally Posted by LSBEH

Well it depends on who is paying for the shore power, and the ambient temperature outdoors (through the day).
If we are in an area with cooler outdoor temps through the day, and especially if we have already paid for 30 or 50 amp electricity, then we'll leave the electric side of the aqua hot on.
The reason the outdoor temp is a factor is...the aqua hot if left on generates heat, which radiates up from the basement (through the floor) to the living area. The living area then gets warmer than you may like, or the air conditioners work overtime.
On the other hand if it's cooler outside you may appreciate the extra heat in the coach when you get home.
I would not worry about system over use, or safety. The electric side is an electrical block heater element that is designed to be left on for long periods of time, and has safety parameters built in. If it's warm outside and you are paying per KMP yourself then turn it off...when you return you can turn it back on. It should only take an hour or so to give you hot water.
Just my two cents....hope it makes sense
LEBEH [emoji41]

Do you turn off the power or the water heater in your stick house when you go shopping? I can see leaving the diesel off as it heats up quickly when you turn it on.

[mecdatlanta]

Let me preface this by saying that I am only about 2 weeks into getting to know my Monaco Signature 42' and a newbie at RVing.

I just have one switch (that I could find) at the sink that says AquaHot. I have hot water when that switch is in the off position, which leaves me thinking that it is for the diesel side of things. As a matter of fact, the only reason I know it affected the diesel heater that it has is one night all three kids took showers and I noticed the next day that the exhaust pipe melted my sewer line. Unfortunately it wasn't until after I started emptying the black water. Yep, total newbie move, I know. Luckily I caught within about .5 seconds after releasing. Still, not pleasant...

Also, while we're on the subject, is there a way to regulate the water temperature (of either the electric or diesel heating)? If so, is it the same thermostat? I would rather set the temp a little higher so that I don't have to run the diesel heater (or at least run it a little less).

[Mhcorrigan]

The water temperature off the aqua hot is set by the mixing valve, located on the aqua hot itself.

[K7JV]

In our '06 Dynasty, the only time the AquaHot is turned off is when it is in storage. When it is out of storage, it is on, 100% of the time.

Electric - ALWAYS ON, when 50 amp service is available. If we are on 30 amp service, we may turn it off occasionally, but only long enough to run the convection/microwave or some other combination of high use appliances. If we are on 30 amp service and the weather is calling for air conditioning, then we leave the electric source off and just use the diesel.

Diesel - ALMOST ALWAYS OFF. We use the diesel when on a 30 amp supply and the weather is hot, so we can have A/C and will still have hot water when we want it. Otherwise, we use the electric. The two primary reasons we don't use the diesel unless necessary are: 1) it does consume fuel that has the ability to become a factor when consumption becomes large enough to impact fuel stops or available travel range, and 2) it can make us "bad neighbors", as under the best of performance conditions, there is a small but present noise factor and the unavoidable aroma of "fairly" burned diesel.

The unit is really quite efficient. Heat loss is not going to overly warm your coach, or break your bank account. If the cost of the actual heat loss is too much, then you are too close to the margin and RV'ing really may not be for you.

The AquaHot heats your living space, when you ask it to. And it provides all of your hot water for your use, unless you happen to have an electric auxiliary heater somewhere else in your coach.

If you are leaving that switch off, and still getting hot water, I'm suspecting that the switch that you are talking about is the FAN control switch for your AquaHot source in the front living area of your coach. It is extremely common to have a switch for AQUAHOT DIESEL, AQUAHOT 110V (or ELECTRIC), and a AQUAHOT L/M/H (or some other marking) for the front zone fan control. You could try turning that switch on, with your thermostat in the FURNACE mode, and then raising the heating setpoint high enough for the system to call for heat. When you hear the fans come on, turn that switch back off. If the fans stop running, then that switch is absolutely your fan switch, only, and your diesel and electric switches are located somewhere else in the coach. There is no ON/OFF switch for your AquaHot. You only switch the energy sources for electric or diesel, or you switch the fans. There is also likely an AquaHot fan switch in your bathroom. There will not likely be a fan switch for your bedroom, other than the thermostat.

From an energy standpoint, the electric source in far, far more efficient than the diesel source. The only losses using electric are the I-squared-R losses (wire heating) in the conductors from the meter to the AquaHot (extremely minimal) and the heat loss thru the walls of the unit, itself. Using diesel, you only need to stand by the exhaust to enjoy the heat loss from the combustion process, plus the heat loss thru the walls of the unit, itself. On diesel, I would expect they are in the 50% efficiency range, give or take 10 or 20 percent.

Finally, these units cool down so slowly that you will only save pennies by shutting them down when not using the hot water or actually heating any of the coach. When you turn the unit back on, you only replace the BTU's that were lost thru the walls of the unit that resulted in the cool down.

Don't neglect your AquaHot, though, when it comes to maintenance. If they are not used at least occasionally on diesel, and/or are not maintained, they will become "dirty" and more smelly, and my not work for you when you need it the most. You can do it, or there are many RV techs around that can do it for you. They are a fantastic system!

[mecdatlanta]

Thanks for the detailed response Jim! I will check out some of the things that you mention when I get back to the coach. I do know there is a switch in the bedroom that turns on a heater fan. where air is forced through the floor-level vents. I assume that if I switch from cool to heat, that hot air will start coming out of those vents. It's 90+ degrees in GA, so I didn't dare try that!

I have not been able to find a switch to turn off the AquaHot altogether. The one in the kitchen seems to be for the diesel. Without it even turned on, I am getting hot water heated by electric. I think I can get maybe one shower out of it.

It does seem to be a really cool system. Still learning. I will definitely start looking toward maintenance once I figure out the moving parts. Thanks again!

Originally Posted by K7JV

In our '06 Dynasty, the only time the AquaHot is turned off is when it is in storage. When it is out of storage, it is on, 100% of the time.

Electric - ALWAYS ON, when 50 amp service is available. If we are on 30 amp service, we may turn it off occasionally, but only long enough to run the convection/microwave or some other combination of high use appliances. If we are on 30 amp service and the weather is calling for air conditioning, then we leave the electric source off and just use the diesel.

Diesel - ALMOST ALWAYS OFF. We use the diesel when on a 30 amp supply and the weather is hot, so we can have A/C and will still have hot water when we want it. Otherwise, we use the electric. The two primary reasons we don't use the diesel unless necessary are: 1) it does consume fuel that has the ability to become a factor when consumption becomes large enough to impact fuel stops or available travel range, and 2) it can make us "bad neighbors", as under the best of performance conditions, there is a small but present noise factor and the unavoidable aroma of "fairly" burned diesel.

The unit is really quite efficient. Heat loss is not going to overly warm your coach, or break your bank account. If the cost of the actual heat loss is too much, then you are too close to the margin and RV'ing really may not be for you.

The AquaHot heats your living space, when you ask it to. And it provides all of your hot water for your use, unless you happen to have an electric auxiliary heater somewhere else in your coach.

If you are leaving that switch off, and still getting hot water, I'm suspecting that the switch that you are talking about is the FAN control switch for your AquaHot source in the front living area of your coach. It is extremely common to have a switch for AQUAHOT DIESEL, AQUAHOT 110V (or ELECTRIC), and a AQUAHOT L/M/H (or some other marking) for the front zone fan control. You could try turning that switch on, with your thermostat in the FURNACE mode, and then raising the heating setpoint high enough for the system to call for heat. When you hear the fans come on, turn that switch back off. If the fans stop running, then that switch is absolutely your fan switch, only, and your diesel and electric switches are located somewhere else in the coach. There is no ON/OFF switch for your AquaHot. You only switch the energy sources for electric or diesel, or you switch the fans. There is also likely an AquaHot fan switch in your bathroom. There will not likely be a fan switch for your bedroom, other than the thermostat.

From an energy standpoint, the electric source in far, far more efficient than the diesel source. The only losses using electric are the I-squared-R losses (wire heating) in the conductors from the meter to the AquaHot (extremely minimal) and the heat loss thru the walls of the unit, itself. Using diesel, you only need to stand by the exhaust to enjoy the heat loss from the combustion process, plus the heat loss thru the walls of the unit, itself. On diesel, I would expect they are in the 50% efficiency range, give or take 10 or 20 percent.

Finally, these units cool down so slowly that you will only save pennies by shutting them down when not using the hot water or actually heating any of the coach. When you turn the unit back on, you only replace the BTU's that were lost thru the walls of the unit that resulted in the cool down.

Don't neglect your AquaHot, though, when it comes to maintenance. If they are not used at least occasionally on diesel, and/or are not maintained, they will become "dirty" and more smelly, and my not work for you when you need it the most. You can do it, or there are many RV techs around that can do it for you. They are a fantastic system!

[bobcovey]

About the only time I turn off the diesel is to be neighborly, if we are parked really close to another rig. If smell were a constant problem, I'd rig a genturi. Aside from that, both diesel and electric stay on all the time and I let the AH sort out which heat source to use for hot water. The exception to that is if we are plugged into weak 30 amp like we recently had in PEI. We ran exclusively on the diesel side there.
If we are plugged in, the diesel only comes on when showering, and not always then. We have plenty of hot water in the tank to easily take a shower without it, it's just the recovery time is longer on electric. It never comes for washing dishes.
Heating the coach is another issue. The diesel is always required to heat the coach. If we are on 50 amp and not paying separately for power we use electric space heaters and the coach heat rarely comes on unless the temp is in the 30's.
If we are paying for power we use the coach heat exclusively because diesel at ~$2.85 a gallon is about half the price of electricity, at least in AZ last winter. Aside from the winter months when we aren't moving I can't measure AH diesel consumption in our overall fuel use, it is just too low. These units are really efficient.

To the poster that asked about setting water temperature: You control the delivered water temp by adjusting the mixing valve. You have no control over how hot the AH heats water (or boiler fluid actually). The thermostats that control that are fixed ranges.

Cheers,

[RobRoy]

Originally Posted by bobcovey

About the only time I turn off the diesel is to be neighborly, if we are parked really close to another rig. If smell were a constant problem, I'd rig a genturi. Aside from that, both diesel and electric stay on all the time and I let the AH sort out which heat source to use for hot water. The exception to that is if we are plugged into weak 30 amp like we recently had in PEI. We ran exclusively on the diesel side there.
If we are plugged in, the diesel only comes on when showering, and not always then. We have plenty of hot water in the tank to easily take a shower without it, it's just the recovery time is longer on electric. It never comes for washing dishes.
Heating the coach is another issue. The diesel is always required to heat the coach. If we are on 50 amp and not paying separately for power we use electric space heaters and the coach heat rarely comes on unless the temp is in the 30's.
If we are paying for power we use the coach heat exclusively because diesel at ~$2.85 a gallon is about half the price of electricity, at least in AZ last winter. Aside from the winter months when we aren't moving I can't measure AH diesel consumption in our overall fuel use, it is just too low. These units are really efficient.

To the poster that asked about setting water temperature: You control the delivered water temp by adjusting the mixing valve. You have no control over how hot the AH heats water (or boiler fluid actually). The thermostats that control that are fixed ranges.

Cheers,

Bingo!...... same as above^^^^^^^^^^

[mecdatlanta]

Thanks Bob! Where is the "mixing valve", out of curiousty?

[Mr_D]

I have a 600D AquaHot unit.
There are four switches to control it.
One turns on the burner.
One turns on the pump to preheat the engine.
One turns on the electric elements.
The last one is low or high. Low turns on one electric heating element, high turns on both elements.
Heat exchanger fans are controlled by the central thermostat.

[rpasetto]

After a significant drive, with engine coolant circulating through the aquahot system there'll be hot water, even if the aquahot diesel and electric are off.

Also, it's recommended to exercise the aquahot system on diesel about once each month, just as is done for the genset.