Hello everyone,

I am trying to model a HVAC system that is composed of a central
geothermal system that uses a heater/chiller with back up boilers to
provide hot and chilled water to AHU for a VAV air-side system.
Following the advice I found on the archives from the Loop to Loop
Heatpump in eQuest discussion I modeled a system with a L2LHP that uses
a lake/well loop (see screen shot). I made sure to zero out the static
head for the GLHX and changed the max hot water temp in the hot water
loop to 130F to be compatible with a heatpump. I compared this system to
a basic chiller/boiler VAV system to see if it showed any signs of
improvement and the results have been very puzzling. The geothermal
system is using slightly less energy to cool but isn't providing any
heating to the system. Instead the boilers are providing all of the
heating. When I remove the boilers to make the L2LHP provide all of the
heating it is performing terribly using an enormous amount of
electricity to heat. Also, I assumed that there would be a pumping power
increase but the L2LHP is using about 3X the electricity as the
boiler/chiller system and this seems way too large.

Has anyone had any luck modeling a system like this or has any ideas why
my L2LHP model is using more energy than a standard chiller/boiler
system?

Taylor Roberts, EIT