Geothermal with mod/con?

J Matthers_2

That is the same basic setup I have however I use the Knight to provide primary heat to three zones and then use a Flatplate exchanger as a separate zone to preheat the return water for the geo as back up. the geo runs 5 zones of heating. This preheat zone works on an aquastat with the setpoint set below the low end on the buffer tank primary aquastat. This way, if it is cold enough that the Geo can't keep up and the buffer tank falls below the limit the Knight starts the preheat and brings the buffer back up to temp. I haven't worked out a "lockout" yet for the cooling season when the buffer is at 35*. As far as efficancy, this system is in a new "sip" house with Warmboard throughout. When compaired on a SF basis with the old house and Oil FA, it was 8 Cents better per SF. That was 3 years ago when I was at 14.5 KW. I am up to 20.5 KW now. Good old LIPA on LI.

Nick S

I have a customer interested in a water to water geothermal system for a new construction home with radiant floor heat. I realize low water temps are key with these systems, but the floors should run at some pretty low temps on anthing but a design day of -5. I will be using a Knight 80,000btu mod/con with a Climate Master 5 ton unit. The boiler will handle an inderect and the additional heat needed to meet the load (53,000 BTU).

My main question is, how in the world do I control a high tech mod/con boiler with a low tech on/off heat pump and control the heat pump for cooling?

Is the heat pump really going to be that much more efficient than the boiler? (Nat. gas 1.35/therm, Electric .10/KW) I have the computer program that compares these systems, however I have read on the Wall many times that you cannot compare a mod/con boiler by AFUE, wich is exactly what this program does.

I have installed forced air geothermal units with success, but I am not quite sold on the water to water units. I guess what I'm after is some real world data that can help justify the added expense of the geothmal unit, loop field, buffer tank, chilled water coil, etc. Thanks, Nick.