Hooked up a bay heater thermostat today...

[gumpy]

Had a diesel leak inside my Aquahot, so I pulled it apart and found that the screws that hold the cover on the pump were a bit loose. Tightening them seemed to fix the leak. Sure made a mess! It's been leaking for some time.

While I had the bay torn apart, I decided to install a thermostat in the water bay. My Father-In-Law had given me a large industrial thermostatic switch with a stainless bulb that he had surplus. I mounted it in the bay and tie-wrapped the bulb to the water manifold. I set the thermostat to 35*. It has a 4-6* differential. I then hooked the output from the switch to the relay I have connected to my AquaHot electric element element. I also connected an output to the pump on my heating system. My bay heat exchanger fan is connected to the pump circuit so that when the pump comes on, the bay fan comes on also.

So the theory is that when the temp in the bay falls to 35*, the switch will turn on the 120v element in the Aquahot, and it will also turn on the pump and bay heater. Then when the temp rises to about 40* in the bay, it will shut everything off.  This way, I don't have to winterize the bus until we get back from our Christmas trip, and I don't have to keep the entire 15 gallon tank of coolant at 180* for 2 1/2 months.  It can heat up only when it needs to, and then only enough to warm the bay, and then shut off until the bay cools off again.  Also, since the heater pump that runs off this switch is for the interior heating system, there will be some heat going upstairs, too, which should keep the sink, shower and toilet from freezing.

If I find that it's still using too much electricity to heat the Aquahot, I may just buy a small electric heater and connect it into the thermostatic switch, instead.

[John316]

Gumpy,

That sounds very impressive. I had a little bit of a hard time following everything that you said, but I got it figured out. It sounds like you should be in good shape now.

Thanks for telling us.

God bless,

John

[Gary '79 5C]

Sounds great and minimizes the required heat to keep winterized.
Obviously your AquaHot is diesel fired (like my 2010 Webasto) but does it also have provisions for a electrical element in a coolant surge tank ??
Or put another manner, are you heating the coolant or the stored water ?
Pardon my ignorance, others have & many will in the future.

Have a great day !
Gary

[gumpy]

Sounds great and minimizes the required heat to keep winterized.
Obviously your AquaHot is diesel fired (like my 2010 Webasto) but does it also have provisions for a electrical element in a coolant surge tank ??
Or put another manner, are you heating the coolant or the stored water ?

The AquaHot is a diesel fired heater with a 15 gallon coolant reservoir. It has copper tube wrapped around the reservoir which produced domestic hot water on demand.
There is a 120v electric element in the coolant reservoir. The system is originally set up such that electric takes priority over diesel when plugged into a large shore power.
The way it does this is my having the electric snap disk switches set 10* hotter than the diesel snap disk switches. So the electric keeps the coolant at 190* when plugged in,
and the diesel never needs to run unless it drops below 180*. You can't heat the coach on electric, but it will produce enough domestic hot water without running the diesel
burner.

My thermostat simply turns on the electric element for a time when the temperature in the bay falls to 35*. It also turns on the circulation pump and heat exchanger in the bay.
When the bay temp rises above 40*, it will turn off.

We'll see. It may not work. There may be too much heat sink (radiant floor, walls, and heat exchanger) for the electric element to compensate for. If that's the case, I may hook
it up such that it fires the diesel burner for short periods. Or, since I have a second thermostat, I may hook it up to the Aquahot tank and keep it at 40* all the time. That way,
when the bay thermostat called for heat at 35*, there would be sufficient heat to warm it up.

[Jerry32]

I just used a plug in winter switch that turns on at 35 deg and off at 40 then used a heat lamp to keep the bay above freezing . Jerry

[rv_safetyman]

I used the bay heat unit from Aqua Hot.  It controls the valve for that circuit independent of any thermostats on the circuit.  Seems to work OK if you are careful where you place the temperature measuring bulb.  I got in a hurry and put it on TOP of the tank .  Of course, the bays stay reasonable warm from the inverter and Aqua hot, so the top of the tank was fairly warm.  It did not turn on the heater when it got down to about zero and the plumbing parts were exposed to the bay door that was quite cold (not insulated).  Broke a fitting.  I now have the bulb close to the critical parts.

Slightly off subject, I can't winterize my bus - at least from a practical standpoint.  Have water filters, fridge water dispenser, washing machine, etc.  I keep the interior at 50* via the Aqua Hot thermostats.  As Craig mentioned, the electrical element will not keep up with heating demands.  It is a 1650 Watt house type element.  With the price of diesel, I have been playing with what options I have to keep the bus warm enough to prevent freezing.  The bus is currently not in the shop and the nights are getting down in the 30s.  I have a cube heater that has two settings 1500/900.  I have been using that at the 900 watt setting, along with the Aqua Hot electric element (diesel turned off) and it has kept the bus interior temperature in the low 50s.

I have placed one of the sensors from my system so that it touches the boiler.  When the boiler is up to temperature it reads about 188*.  That agrees with Craig's number.

This morning I went out and the interior was about 53 degrees and the boiler was at 185*.  That would suggest the cube heater is doing most of the heating.

I tried to put some numbers to the cost of electric versus diesel.  The diesel usage according to Aqua Hot is:

Our customers tell us they typically use 1 - 3 gallons of diesel fuel per day for all of their heating needs. The diesel-burner's fuel consumption is actually rated at a half a gallon of fuel per hour when operating continuously. We always like to emphasize, however, that a customer must be in sub-zero temperatures with the hot water running non-stop for the heater to operate continuously.

So, if the boiler ran all the time, it would cost about $1.5 per hour on diesel.  I have my cube heater set on 900 Watts.  Our power cost is about $.12 per KWH.  Thus it would cost about $.12 per hour to run the cube heater and $.20 per hour for the Aqua Hot element (total $.32 per hour of usage if they were both on).

The analysis falls apart when you try to factor in how much each of the three heat sources run.  Obviously, the diesel provides much more heating capacity and runs far less than the electrical elements.  However, the combined electrical elements would have to run about 5 times longer than the diesel to cost more.

My other issue is that the Aqua Hot is fed by a separate 40 gallon tank.  Filling that tank via jugs is not a lot of fun. I had to add diesel a couple of times last winter (no cube heater). 

Sorry, just an engineer's rambling.

Jim

[Ed Hackenbruch]

No winterizing needed in Yuma in the winter.

[gumpy]

Thought I'd put an update on this thread regarding my water bay heater. 

On Thursday morning we had a hard frost. Temps down to about 25 degrees. Before heading to work, I checked the bus. The temp inside was at 28 degrees and the temp in the water bay was the same. The heater was not running. I pulled the cover off the thermostat and turned the setting up very slowly. When it hit just under 40 degrees on the dial, the pump and fan kicked on.
I left it there and went to work.

This morning it was again in the mid 20s.  I went out and checked the interior of the bus. The driver's area was about 27 degrees. The floor was showing 41 degrees and the areas under the kitchen sink and bathroom were showing about the same. I checked the bay, and it too was in the 41 degree range. The fan and pump were not running, but the heat exchanger showed 50 degrees, indicating it had been running not too long before.

I'm feeling pretty good about this heater solution for now. Hoping it will keep things from freezing until after Christmas when we return from CO. Then I can winterize it properly for the last 6 months of winter.