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dave_in_delaware 10-05-2009 11:46 PM

Hydronic Heating System - anyone?
I've been doing some research on heating systems for RVs, and found the typical options: basic furnace, catalytic heaters, ceramic heaters, etc... But I also found an interesting concept:

A Hydronic Heating System. Exactly like this guy did for his travel trailer.

This is basically where water (or some sort of antifreeze) is heated and pumped through pipes, into a heating core (like a radiator in a car or in a home), and back to the heat source. It's a closed system. Behind the heating core is a variable speed fan that blows the heat into the area being heated. Sounds pretty simple. And it's supposedly more efficient, quieter, and uses fewer resources (propane and electricity) because of its size.

There are larger systems that use hydronic heat in larger RVs, like 5ers, TT's, and Class A's. And it's used in homes as baseboard heat (hot water going through pipes which have metal fins on them). But I'm wondering if a simplified, smaller system could be built into a van-sized RV. All that would be needed is a propane water heater (6 gallon), some sort of heating core (like from a car), a small pump, and a fan.

Has anyone seen this idea? Do you think it would work in a van RV? I'm guessing it could be integrated into an existing sink's hot water system (somehow one water heater serving both potable water and the heating systems at the same time)?

Hmmm.... I think it's worth some more research. What do you think?

AndrewST 10-06-2009 10:53 AM

Re: Hydronic Heating System - anyone?

I have such a system on my boat.
In my case it is a Webasto unit acting as a central heating.
Heat's up the water that is circulated in radiators all around the boat and back to the webasto.

You need to add on the line an expansion tank for the variation with the heat.

In the van I will be going with the dual top from Webasto not sure if available in the States yet.
More under:


panion 10-06-2009 11:29 AM

Re: Hydronic Heating System - anyone?
Sounds like you are on the same search I was a year ago. I went crazy researching all of the different options for a heater. I was leaning towards the hydronic since I have a propane system, but no water heater. I was planning on installing a hot water heater and the hydronic heat system. It was between that and a vented catalytic heater. I finally decided I don't really need hot water and the system was too complicated anyway. I didn't want to lose the space required for a hot water heater, heater core, fan, and lines. I also opted out of the catalytic heater fearing too much moisture build up in the van.

Finally installed a simple atwood propane fired furnace a few months ago. Simple, plumbed right into the propane, cheap, doesn't take up a lot of space. Even cycles way less than I thought.

Good luck if you go for it. It would be a really neat system that no one else has.

Don't forget pictures if you do the install.


dave_in_delaware 10-06-2009 11:30 AM

Re: Hydronic Heating System - anyone?
Thanks for the info Andrew! I'll check into it.... Actually, it looks like it's for diesel vehicles only? Is that right?

And thanks for the comments, Tom. I had considered the catalytic heater option for a while now. But the more I read, the more "uneasy" I get about it. A furnace is another option I suppose, but I'd like to install a system with minimal drain on the batteries. comparatively speaking, the furnace draws more battery than the hydronic's little pump and fan.

Scalf77 10-06-2009 07:06 PM

Re: Hydronic Heating System - anyone?
I had a thought on this a while back, I was looking into getting a Suburban or Atwood six gallon water heater that had the heat exchanger option (for attaching to the engine). The thought was to then attach a Hydronic heaters like this ... ctid=1113H along with a pump similar to the article. It does appear that it would be pretty low in battery draw. Of course I haven't really tried to calculate our how many BTUs/h you could get out of it.


dave_in_delaware 10-06-2009 08:31 PM

Re: Hydronic Heating System - anyone?
That looks interesting, Greg. That's basically what I'm looking at from the article I read. At least I assume all the Heater Craft item is, is a heater core with fan behind it and water line connections, right?

Heck, at this point, I'm also considering adding to the hydronic system, by running small baseboard-type units along the floor (like in a home), in addition to an adjustable heater/fan unit.

I wonder how having a closed loop heating system affects the regular water heater for hot water at the sink? I guess you could just add this additional loop into an existing sink's hot water supply, without it affecting the potability, right? It's still potable water running through the heating system, right?

AndrewST 10-07-2009 03:51 AM

Re: Hydronic Heating System - anyone?

Yes dualtop is diesel, sorry didn't see you where going with gas...

If you do a heating loop, I would have it antifreezed so you don't have to worry about cold temperatures. For hot potable water I would use an exchanger on the loop.

daveb 10-07-2009 07:31 PM

Re: Hydronic Heating System - anyone?
I don't know about other systems out there, but my Hydronic water heater pulls more amperage than the Airtronic and the Hydronic doesn't have a fan pushing air for cab heat. I don't know why it pulls more than the Airtronic but you'd think someone like espar would offer something like what you're after.

John Kalmbach 10-07-2009 09:42 PM

Re: Hydronic Heating System - anyone?
SMB did install a few Webasto units with a heat exchanger mounted in the cabin area. The issue is the amp draw of the pump to circulate the water. It takes less power to circulate air and that is why the Espar Airtronic is so popular. You could install a heat exchanger with the Espar Hydronic, you just have to know that you will deplete your battery power quicker than you would if you used the Airtronic. Also, remember that your battery power is reduced as the ambient temperature goes down.

John K.

WVvan 10-18-2009 01:42 PM

Re: Hydronic Heating System - anyone?
I'm also at the heater stage of planning. I wonder if it has anything to do with the recent drop in temperature :o6: . Probably just a coincidence.

Question: Does anyone use a Hydronic system just for hot water not general heating? If you have a 6 gallon water tank with a heat exchanger hooked to a Espar D5 HYDRONIC coolant heater I wonder how long it would take to heat the water in the tank to shower temperature? I'm assuming the Espar can't be used directly as a on-demand type water heater.

PS. In my research I found a foreign forum where they stated that the company is called Espar in America because we couldn't pronounce it's true German name of Eberspächer. I could probably pronounce it. But like a lot of German words I'd just accidentally get spit on you while trying. :b8:

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