I posted this in the Radiant Forum, Lots of views, no replies perhaps someone here can help answer my question.

Can any brand of geothermal heat pump with a desuperheater connected to an indirect water heater serve as the only hot water source for in slab radiant heat?
or will it only heat water while the forced air blower is on?
 I read in Radiant Living about a dual system that ran without the blower to heat water but was over ridden if the system called for forced air heat.
 I am looking at McQuay and FHP equipment now is there a specific brand of equipment targeted at dual use?
Total BTU load on the radiant is less than 20,000. Not for heating entire house just warming tile floors.

Thanks
Ed

Waterfurnace Synergy 3D units are capable of forced air heating and cooling, radiant floor slab heating, and desuperheater option. Not sure if this is what you are looking for but it may be a start.
Dan

DSH offers loosley 10% of the equipment btu capacity and only when there is a demand for the forced air cycle.
Joe

No.

in theroy yes , most DX system offer priority hot water
issues are maney , benifits are few
find a cheaper experiement or go with time tested geo radiant

Clarification: Yes, it can be done from a DX system for forced air and radiant; NO, you can't just use a desuperheater.

Geo fan,

Where are you located. Curious on the issues with priority hot water in your area.

Tuffluck, you're correct and I should have stated it in the first response. The desuperheater produces such a small amount of heat that it cannot heat water for radiant floors, but does a fair job at reducing the cost of heating hot water for domestic purposes only.
Dan

CT.
I only work with DX systems ( for now )
Have had 1 issue with high pressure , resolved by lowering water temp below manufacturer spec
we have a few systems getting 100% geo hot water all year
I would not do a passive set up with DX

Ed:

I visited an HVAC research company that had a HVAC system connected to a water storage tank and to a traditional air condensing unit. In AC mode it would run and heat the water until it reached design temp then the air fan would kick on.

So the answer is yes, it can be done, but I don't know of any unit that does it via desuper heater. Nor do I know of any company making a similar system for sale to the general public.

Alex,

yes, the desuperheater can eventually heat a storage tank, however, the BTUh, notice the "h", is usually far too low for the load of radiant heat.

As Joe noted above, desuper transfers only about 10% of a unit's total btuh capacity - useful for offseting some or all of domestic hot water cost but unlikely to meet a radiant floor load.

Thanks for the info everyone, I will probably just go with a dedicated heat source for the radiant and just the DSH on the domestic tank as indicated above.

Thanks
Ed