Hi All, first post...

We're building a new home. It's a large home 3 storey home with 4-1/2 baths. We live in northern Canada where the water supply from the street can be close to freezing.

I would like to run tankless propane hotwater for domestic supply. However I would like to use this heat source as my primary heating to supply a hi-velocity fan coil unit. My inital research tells me I would be running two units like the Rheem 95 series linked with the EZ-Link.

1. Is the required rise the temperature differential at the tap (ie. 32F to 105F = 73F) or the temperature the tankless heater is set to (ie. 32F to 140F = 108F)?

2. Is supplying a fancoil from a tankless a good idea? If so should I run a heat exchanger or open loop to the fan coil?

3. How does the water get returned to the fresh supply prior to the tankless heaters for reheating? Would a valve on the fancoil open on call for heat and the water would move from tankless -> fancoil -> fresh supply line -> tankless on pressure alone or would it need to be pumped?

4. Considering the heat requirement of this return water to be reheated should be minimal on call for heat alone, should the unit I choose be able to fire at low or multi-stage BTU rate to meet this requirement?

Couple points...

We can run 4 months a year without the call for heat, this would be an efficient time for the home on this system.

However the house will be properly designed so that the fancoil will provide the required BTU's for the home to maintain 68F on a -43.6F day. I will need to supply the fan coil at 140F to obtain the required BTUs. If I supply the fancoil in the 130F range, we would be borderline on the deisng requirements for BTU's. We will be using the largest fancoil this company uses.