Hydronic and Espar Heat

[06ViewH]

Last year we modified our Winnebago View to be able to use the motorhome (full water, showers, dump tanks, without Propane) throughout the Wisconsin winters. I thought I'd share the writeup that I did on the Winnebago View Owners site. The following are the posts that may give someone some ideas on winter heating.

By the way - we still LOVE the hydronic heating setup and the Espar heating.

[SteveAE]

06ViewH,

Thank you for the explanation.
Since my first heater will only be located a couple feet from the water heater think I will start with the lower flow (and power) pump.
Have you have calculated the BTU output of your system yet?
(Total BTU = 500 x GPM x water temperature change)
As you can see from this equation, assuming no losses in the system (i.e.; heating plumbing....which I agree has value), using a typical hydronic heater drop of 20 degrees F, a 0.5 GPM flow would produce 5000 BTU of heat output.

Steve

[06ViewH]

SteveAE wrote:

If you are still monitoring this post, why did you choose the 3 gpm (15 watt) pump rather than the 2.2 gpm (5 watt) pump?

I first installed the 2 gpm pump and when I did my testing, the heat registers would not get to the temperature that I desired. I then switched to the 3gpm pump and that heated the registers to the desired temperature and reduced the heat loss. I wanted to get the water thru the pipes and back to the water heater with the least amount of heat loss as possible. The big factor in the whole setup is the recovery time on the water heater.

On our setup, I have two pumps installed. One pump for the hydronic heat and the other pump to circulate the water thru the water pipes if needed. That way I was able to shorten the path that the hydronic heated water took -- installed a check valve to make that loop smaller - bypassing the majority of the motorhomes water pipes. The other pump will turn on if the "other" pipes get below a certain temperature as set on the thermostatically controlled switch.

So to answer your question, I found that I needed the 3gpm to get that water thru the registers and back to the water heater faster than the 2gpm.

[SteveAE]

06ViewH,

If you are still monitoring this post, why did you choose the 3 gpm (15 watt) pump rather than the 2.2 gpm (5 watt) pump?

Thanks,
Steve

[westend]

Thanks for posting this thread, Hydronic heating seems to be the most efficient.

[toddb]

Nice job. I just tested my second version with a stand alone atwood water heater. It worked awesome, had no trouble holding 60 all night with lows of 36 degrees. I just need to insulate the tank some how. If you're a cold weather camper this type of system should be seriously considered.

[06ViewH]

SteveAE wrote:
06ViewH,

Thanks. You said that you were able to raise the temperature of the water. What temperature do you think most RV hot water heaters are pre-set to? I assume you keep you system running all the time, but if you were to turn it on in a cold coach, how long till you start getting some serious heat out?

Steve

I believe the Atwood water heaters are pre-set to turnoff at 140 degrees. You can buy an adjustable thermostat to allow that to be higher.

It will take about 20 minutes to heat the water hot enough to provide heat. If we run both the Propane and 110v on the water heater, then this will be a bit quicker.

Let me know if you have any other questions - this was a great project . Provides us with a few nice options to heat the motorhome without using propane and very quiet.

[SteveAE]

06ViewH,

Thanks. You said that you were able to raise the temperature of the water. What temperature do you think most RV hot water heaters are pre-set to? I assume you keep you system running all the time, but if you were to turn it on in a cold coach, how long till you start getting some serious heat out? Sorry for all the questions, but I am looking to build something similar to heat my bathroom that doesn't have heat....but is right next to the hot water heater. I have a new residential hydronic heater core (just a length of copper tubing with aluminum fins on the outside) that I was thinking of using for this application.

Steve

[06ViewH]

SteveAE wrote:
06ViewH,

I understand that you are using two different heat sources, one of which is a water heater. Is this water heater also your domestic hot water heater?
If it is, did you find it cooled your water off too much for domestic usage?

Steve

Yes, we are using the domestic hot water heater. In order for the hydronic heat to work correctly in very cold weather, the hot water heater needs to heat the water to around 170 degrees. So, actually the hot water does not cool off as you only need around 110 degrees for showers.

The hydronic heat uses the same pipes as the shower, sinks, etc. The registers are plumbed into the hot water lines and a check valve sends the hot water back to the water heater via the cold water pipes. This is controlled by a small solar pump that will circulate the water if the coach's thermostat calls for heat.

We have a thermostatic controlled shower faucet to ensure the water is not too hot while taking a shower.

[SteveAE]

06ViewH,

This is an interesting topic for me, but I got a bit confused (of course, the wine doesn't help....).
I understand that you are using two different heat sources, one of which is a water heater. Is this water heater also your domestic hot water heater?
If it is, did you find it cooled your water off too much for domestic usage?

Steve

[06ViewH]

Update:

On our 14 day trip from Wisconsin to Florida over Christmas, we did not have a need to run the Espar heating. Instead we just used the Water Heater Hydronic heat using propane to heat the water. The nice thing with the hydronic heating is that it is very quiet - while sleeping it is not noticeable at all.

At night we like the coach colder, so we set the thermostat to 55. In the morning we just set the thermostat to 70, the thermostat will kick on both the hydronic heat and the furnace until the temp is 66, then the furnace will turn off. That feature is nice to have as the furnace will bring the coach temp up much faster than the hydronic heat.

Also, having the hydronic heat use the water pipes was very reassuring as we drove the View back toward Wisconsin - no worries on freezing pipes.

So far - love it.

[06ViewH]

Update:

I did a couple tests the last few nights to see how well the Hydronic Heat (via 110v hot water heater) will work as the temps get closer to zero degrees.

Saturday night the temps were in the 15 degree range. I set the thermostat to 60 degrees and in the morning the coach was at 60 degrees and the hot water heater was at 170 degrees (around the maximum temperature). Of course, the water pipes are all good to go as the hot water circulates thru them (under the kitchen sink the pipes are normally around 115 degrees). Also, the sewer compartment is kept at 48 degrees. So, that worked great - the system was able to keep up with the cold temps with no problem.

Sunday night the temps were in the 15 degree range also. I set the thermostat to 68 degrees and in the morning the coach was at 68 degrees but the water heater was at 115 degrees. Everything still worked great as the coach was at 68 degrees, but the system was probably running close to 100% of the time to keep the heat at that level. At 115 degrees in the water heater, that probably is very close to the minimum required to keep the heat at 68.

It will be interesting to see what outside/inside temperature is the "break even" point for the system. The hot water heater's recovery ability is the limiting factor along with the btu's required to keep the heat.

At some point, I'll re-test the Espar heating. I don't see that being a problem in any temperature. Basically, if you can heat the inside of your car/truck/van in below freezing temps (which I have 48yrs experience that says "Yes you can"), then the Espar heating will work without problems.

[06ViewH]

Update:

The outdoor temperatures have been more consistently cold over the last week or so - with some days low 30's for highs and low 20's for lows. I can tell how hard the hydronic system has to work based on how low the water heater temperature gets while it is heating. At these temps, it is not having to work hard at all. When the thermostat calls for heat, it only takes a few minutes to bring in back to the set temperature. The water heater normally stays within 10 degrees of its setting.

Our planned trip to Calgary, Alberta is now a planned trip to Florida (son decided to snowboard with friends in Vancouver instead). So, I know the hydronic heating system will work down there.

I'll post more when we get temps closer to zero - probably soon.

[06ViewH]

The last few nights it has been in the low 20's and we have the View plugged into the house. I have kept the temperature in the coach to around 68 degrees and the Water Heater Hydronic's has had no troubles keeping up. It is nice and toasty in the coach. As others have stated, the cab area really lets in the cold air unless you close that off.

I added the last step yesterday (besides additional insulation here and there) - I added a "computer" fan that blows down from under the shower into the sewer compartment. I hooked up an electronic thermostat controller that will turn on the fan if that compartment is below the set temperature. The controller will also turn on one of the solar circulating pumps to keep the pipes warm and help add heat to under the shower to be blown into that compartment. Worked fine last night.

Now we'll see how it holds up in closer to zero weather - I'm guessing all will be fine based on the system not working very hard in these low 20's temps. Also, once we get snow cover - the cold is more consistent and will test the system a bit more.

[06ViewH]

Stayed in downtown Chicago last night in the McCormick Placd parking lot. Ran the Espar in low 30 degree weather with no problems. I'm glad that I added the heat register directly on the Espar loop, because the Motoraide heat exchanger would not have kept the water hot enough.

Great place to boondock in Chicago. Right next to convention center, safe, bus to Michigan ave, etc