Radiant off HWH

Rob Holzapfel

I want to run a radiant system off a hot water heater. Has any one had problems doing this?

heatboy

Do it all the time..........

with a few conditions, of course. The water heater will have to be 65K to 75K MBH to make any heat along with your hot water demands. Also, the system must utilize a heat exchanger to seperate the fluids (heating and potable). If those two conditions are met, go for it!

hb

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kevin_5

OR...

Just use a separate water heater. Another one of those is most likely cheaper than the heat exchanger anyway and simpler to pipe eliminating some check valves etc...
Of course a boiler will be much more efficient, but I heat my own (small) home with a hot water heater (38,000 Input)which I would like to someday replace with a Rinnai tankless and a heat exchanger to do both my domestic water and radiant heating. It wouldn't be cheap either, but a great space-saver.

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Rich Lorimer

It depends on the amount of space you are trying to heat. I've had great results on sunrooms and other small additions or just doing hard surface areas of houses such as kitchens and baths. It makes a nice, much cheaper alternative to a boiler. I would definatly use seperate water heaters for domestic and hydronics.

John T_2

Water Heater/Boiler

Just make sure that it's ok to use for space heating according to the code. Here in Michigan I just recieved an update from the state that it is not allowed to make a water heater into a "closed heating appliance". I would imagine a hx would be alright though.

John

Mark Wolff

H2O Heaters for closed systems

Have the state plumbing inspector read the International Mechanical Codebook 2000 Chapter 10 Section 1002.2 (Water heaters utilized for space heating).

He might change his mind. It is a commonly accepted practice and most codes allow for it. If Michigan doesn't I'd be interested in knowing the justification for denying their use.

hr

A sweet DHW package

is a Polaris with a HX for the radiant! Plenty of horsepower for domestic and 50,000 or so radiant.

I add a setpoint control to streccccch out the differental. Polaris aquastats are real tight, maybe 2 degrees, so the 15 delta T prevents short cycles.

This was connected Wed to a 1000 square feet of concrete slab. Balancing the HX supply allowed the tank to reach 120, adequate for showers, within 20 minutes, while ramping up the 2 zone cold slab. It ran non stop for an hour before I left it on it's own.

The Goldline setpoint will run the tank to 130F which, after the HX, gives me about 120 to the slabs.

A fine way to get high efficiency 50 gallon dhw and radiant in a package requiring about 30" in diameter. I build and test fire the assembly in the shop. The homeowner installed the RTI tube, and plumbing pex himself.

Sorry about the turned pic

hot rod

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