Hydronic and Espar Heat

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

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.

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

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

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.

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.

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

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.

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

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.