water heater for infloor heat

Helgy_3

Say anybody have any input, when using a water heater as you heat source for an infloor job. Do you need a tempering valve on the supply and then do primary secondary pumping. Something about keeping the water temp up in the water heater so that it does not have to run so often. I guess I don't know why you would need one. But maybe I'm not looking at the whole picture.
Thanks, Helgy

Wayco Wayne

Helgy

If you are using a water heater for your heat source that is also being used for domestic hot water there should be some sort of heat exchanger separating the potable water from the heating water. There is a lot of discussion about this on The Wall. Some believe that there is a danger of bateria and other nasties (can you say legionella) getting into the potable water because when the system is not running for long periods of time the water in the radiant floor tubing can get stagnant and nasty. When the cold weather comes, and the Radiant heat circulator comes on it will bring all the stagnant water into your bathing and drinking potable water. It's similar to the situation when you go to a vacation cabin that has'nt been lived in a while, they say to open all the water taps and let it run for 10 or 15 minutes to flush out stagnant water. I use a flat plate heat exchanger or a separate water heater when I don't have a boiler to hook to. Better safe than sick. :P WW

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Ragu

Helgy

I've come close several times, and still get tempted once in awhile, but I personally have stayed with boilers.

hr

It is a common heat source

for radiant. Some Whs do not have the listings your AHJ might like to see.

Gas or oil powered tanks are not very efficient.

Yes, if you want a temperature below 140° it is best to run the tank at or above 140 and mix down the radiant. Running a tank below 140 will cause them to sweat, and corrode quickly.

This can lead to plugged burners and CO issues if not watched carefully.

I have used small electric tanks for little radiant jobs. same issue with code listings, however.

hot rod

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harvey

I don't understand

How can using a WH with a 120 degree supply temp and a 110 degree return temp cause any more condensation than a WH used for DHW with a 125 degree supply and a 50 degree incoming water temp?

hr

A WH used for DHW

will generally catch up, warm up, and shut down within 20- 30 minutes. This is usually enough time, and heat to warm and dry the flue pipe and HX surfaces.

In a radiant application, the tank may run 24/7 at design, or below, days at temperatures below condensing. You will hear them drip and sizzle when used this way

hot rod

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