I recently posted a question about people's experiences with water to water heat pumps and radiant heat.  I see there have been several other such questions in the past.

One of the responses got me thinking about DX (thanks Clark) instead of water to water. 

It seems you could have an efficent refrig to water heat transfer, as well as refrig to air in a seperate Air Handler if desired.

So, it would be nice to hear about anybody whose using DX to radiant, or other hydronic heat.  What is the maximum usable temperature you're getting?  Anything you would have done differently...



...slowly designing the perfect system!

My dad and my uncle both have DX for their radiant heated houses. We've installed numerous DX radiant systems. Typically we don't need more than 110* water. Max is usually 120*, though with the better heat exchanger, we see a littler higher than that even at lower head pressures (125* at 295# head). Most radiant systems for geothermal are going to use embedded tubing. When using embedded tubing (in concrete or gypcrete), as long as the tubing is properly installed with a good radiant barrier underneath (foam board is recommended as the best) most any floor won't require more than 110*-115*. If much higher temps are required, it's usually because of excessive windows in a room, or excessive floor coverings (2" or wood or more, or really thick carpet with the wrong type of pad, etc).

thanks Clark,
120 - 125 would be my worst case value, for short portions of winter. Will usually need water in the 90 - 110 deg range, reset to OA and other conditions. I have an underfloor staple up radiant system, with heat transfer plates. I am going to double up on the tubes under floor to get my requirements down to these values, maybe a little lower.

I am also considering an AHU as a second stage of heat, which would again lower requirements on the radiant floor. That way we could also get the occasional cooling from AHU, really don't have much of a cooling season here in NH, but once in a while it would be nice!

Sounds like your Dad and Uncle have nice heating systems