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Old 03-09-13, 11:05 AM   #1
Join Date: Feb 2013
Location: mendocino, california
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Default Heat pump connection to radiant floor

I have an older Etech water to water heat pump rated at 1 ton/12000 Btu, and we currently heat using a 30 gal Bock oil fired heater connected via a heat exchanger to a radiant floor (tile over 1.5" concrete over plywood over an insulated crawl space). The system is in its 26th year, self designed and installed including the heat exchanger. I'd like to substitute the heat pump, or perhaps a newer and somewhat larger one for the floor heating function of the Bock heater. Currently the water heater does both DHW and the floor.

Does it seem likely that the heat pump could be connected directly to the floor with the hot water output going directly to the hot floor manifold and the floor return going immediately back to the heat pump. The output temperature from the heat exchanger is about 120 deg modulated down to 110 by means of a tempering valve that injects some of the cooler return water into hot coming from the heat exchanger. The balance of the return water from the floor goes back to the heat exchanger, and that is typically about 78 deg. We keep the house at about 70 deg. all day and night, every day.

I don't understand enough about the nature or workings of a heat pump to know how it will react to return water in the high 70 degree range nor how to control its output to about 115 deg. Is it likely that I'll have to install a tank between the heat pump and the floor to act as a buffer with circulating pumps on both sides of the tank? Does anyone have a situation like this that can provide some suggestions. Is an appropriately sized heat pump a viable alternative in this case as we have sufficient ground area for a reasonably sized array of heat source pipes.

Michael Moreland
Mendocino, CA

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