Hi eQuesters,

I have a problem regarding hybrid geothermal heat pump system built in a heating dominated building. From ASHRAE Handbook, it suggests that boiler be installed separately from geothermal heat exchanger loop due to high temperature of boiler.

In addition, one report says that even if there are some cases that boiler has to be installed into GHX loop, the setpoint shall be 5-10F lower than GHX setpoint( e.g. 45F). That is because if the boiler is installed in the GHX loop, it is likely to dump heat back into the ground if boiler setpoint is higher than GHX setpoint.

However, heat exchange is related to both temperature and flow rate. With smaller size of boiler, can we allow to install boiler with higher setpoint higher than GHX setpoint into the GHX loop? Thanks!

All the best,
Siliang