Radiant Only Return Temps

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virvis

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Nov 27, 2007
37
central PA
Can anyone share what your return temps are from your radiant zones? My system will initially only be used for radiant and I'm a little concerned about return temps. If I'm thinking correctly, the storage will be warmer (160 give or take) than anything that will need to draw on it. My concern is where I'm going to get cold water to bring the storage down to 120 for the radiant zones. I'm thinking a mixing valve will be fed cooler water from the return headers but I'm not sure how cool this will actually be.

Any thoughts?

I'm installing my eko40 with 1000 gallons of storage and about 2500 lf of 1/2 pex. Headers will be made of 1" pex.

thanks,
Jim
 
Ideally, Your return temps will be 10* lower than supply from what I've been told. And yes, use a mixing valve to mix return water back into your 160* supply water to get your desired supply temp at supply manifold.
 
Also the rule of thumb is no loop longer than 300' for 1/2". So you may want to break that 2500' of 1/2" pex into 8-9 loops.
 
The supply temperature to the radiant depends on how many btus you need and also the floor coverings. Bare concrete perhaps 90- 100F, carpet or wood over the radiant raises the temperature required. Rarely does radiant run over 140F supply. Temperture drop 10- 20F use the lower number for residential.

The 180F mixes down by blending with the return from the radiant with the higher 180F. A thermostatic valve can do this without a problem.

Bob
 
I have staple up under wood, I run it at 130*. The return temp is dependant on how long it has been running, ussually in the 10-20* range. Check out Pex Supply for valve.
 
I guess I was having a brain fade this morning.

I was concerned about not being able to get the supply cool enough for the radiant but given that the water in the pex will be cool, that will provide enough cool water to get my supply to 120 and then continue to use that to regulate the supply as it's returned from the zones.

Thanks guys.
 
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