Hope someone can help with this issue.... I am in the final stages of building a 3,000sq ft house in central NH with a Hydron Module (5ton) water to air system as the primary heat system. To keep costs down, I opted to heat the finished basement (2,000 sq ft additional to the above) using a radiant in slab system supplied by a separate propane ultra efficient wall mounted Baxi boiler (98% eff when condensing). This boiler is also my 'on demand' domestic hot water heater. The house will initially be used as a second home, used every weekend and vacations year-round, but mainly vacant during the week. Therefore, using the desuperheater for domestic hot water alone, seems a real waste, as most of the time no one will be there to use this heated water!

The idea was to use this desuperheater water for my radiant slab by supplying to a pre-heat tank, with a check valve, so that the radiant system could use it as a pre-heat for the basement radiant system when the house was not occupied. Ingenious, right?! Not so fast though. Based on this plan, we expected the Geo system, with some fine tuning of thermostats, to cope with most of the building's heating requirements even during cold weather when not occupied. Sadly, the engineer for our Geo installer (who I made the plan with!!) informed me last weekend that this boiler would not be able to use the pre-heat tank water (for very legitimate reasons I'm sure) - fyi to be fair.., the radiant part is being provided by my plumbers so the Geo guys were not entirely on top of this side but did agree the principle of the idea. But I now urgently need to find an alternative solution to use this pre-heat water for both DHW and my radiant system.  I hate the idea of having two separate heat sources for radiant and DWH in addition to the Geo system. The good news is that we haven't bought or installed the Baxi boiler yet so can go with an alternative if we can find a solution quickly. HELP very much appreciated! And here's the payback...using one wire thermostat sensors we will have all the data needed to fine-tune the system and show precisely how it is working if a solution can be found. If we can solve this issue, it could dramatically cut the cost of GEO install in a larger home (by down-sizing the system) using propane as a back-up for those coldest nights.

Thanks!