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How about an electric immersion element as a heat source for in-floor radiant?

I called on a potential client today in climate zone 5 (Northern Ohio). He built his home 20+ years ago with double studded walls, fiberglass insulation and a passive solar design. The home is approximately 1800 sq ft on two floors. The main heat source is an in-floor radiant system installed in the floor of the lower level. There is no heat on the second floor. What struck me was the beautiful simplicity of the radiant system. There are four loops of 3/8" pex installed in aluminum covered plywood panels with additional plywood and a hardwood floor on top. One small Grundfos pump circulates the closed loop liquid which is heated by an 4500W immersion element housed in-line with the water flow. No storage tank.

I was struck by how simple and elegant this solution appeared but heating is not my field and I would love to see any comments that the experts out there can provide. What, if anything am I missing? The owner says that the system is able to keep up with demand and that it operates very efficiently. I asked for consumption data but that was not immediately available.

Asked by Torsten Hansen
Posted Dec 5, 2011 7:57 PM ET
Edited Dec 6, 2011 8:39 AM ET


4 Answers

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I assumed his house is insulated like mine (also double stud, FG, built in '80) and factored his/her house size and HDD to compare to my numbers, and said client should be burning 280 gallons of oil. I don't know what electricity costs there, but if the client can pay for a mod/con boiler in a reasonable number of years with his simpler system, then it is hard to beat the joy of simplicity. I grew up SE of Cleveland, and it would be interesting to know what his upstairs temps are in Dec and January w/ no localized heat up there. Post his electrical consumption if you get it, too. It is always good to hear of someone who went off-bubble and succeeded.

Answered by John Klingel
Posted Dec 6, 2011 2:48 AM ET


The house is being heated by electric resistance heat. I'm sure it works. You call the system "simple and elegant," but there are simpler ways to do it -- most obviously, with electric resistance baseboard units, or, alternatively, with electric resistance wires embedded in the floor.

So (a) it's not the simplest way to use electric resistance heat, and (b) it's certainly not the cheapest fuel. But of course it works.

Answered by Martin Holladay
Posted Dec 6, 2011 5:00 AM ET


Of course you are right. I liked that the heat source is simple and cheap. Especially compared to the $3500 Polaris that is powering my radiant floor. I just spent $600 on a new blower so $200 for the whole heating unit sounds mighty attractive. I know that the resistance heater doesn't have the BTUs of the Polaris but then again my house isn't nearly as efficient as it should be.

Answered by Torsten Hansen
Posted Dec 6, 2011 10:05 AM ET


Keep in mind that the cat needs something else to heat his water, which your Polaris is doing.

Answered by John Klingel
Posted Dec 6, 2011 2:31 PM ET

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