Replies

1. 
   Dana1 | Mar 28, 2015 06:07pm | #1

   The actual performance of GSHP systems are so system-design specific that there's really very little you can tell from the heat pump specs themselves. You can put the highest-efficiency heat pump in a so-so system design and the net performance will be fair to middlin', but you can also put a lesser pump in a carefully optimized system and do extremely well.

   The system design and implementation is the biggest risk factor in going with GSHP, and it's very difficult to discern the hacks from the true professionals when it comes to optimizing the system.

2. 
   user-2890856 | Mar 28, 2015 11:05pm | #2

   Dana hit the nail on the head . GSHP have to be designed really well by someone competent . Load and source sides must be done right or you have a dog .
   Also remember that source side pumping power is not factored into the COP so don't forget to figure that . Another thing , just because someone drills wells does not mean they know GSHP field design . Have seen too many jobs now where the wells were shortchanged and performance was terrible .

3. 
   jverschu1 | Mar 29, 2015 01:11pm | #3

   Hope to help you some... We are in the process of installing a GSHP setup. Been at it for a looong time due to other delays to the house. FIRST thing is to get your heat load and when wanting cooling to get you calculations as accurate as you can get. Then make sure your groundloops are NEVER short. Our installer put in twice the amount per ton required. YES you waste circulation pump energy that way but that is security needed in an overall inaccessible system (once the ground loops or wells are drilled you are DONE!) Your comparison between two heat pumps regarding there EER and COP numbers I fear is kinda moot.. I think no matter what expert you bring in: it will always, to a point, be a guessing game. Just make sure you never can freeze you loopfield/wells. And never sit uncomfortably cold in winter or uncomfortably hot in summer with a multi thousand dollar setup. Have redundancy as that costs little in the total expenditure. The ONLY important question is how much redundancy, I think. Heatpumps efficiency shopping I fear is energy wrongly applied when going for a GSHP residential setup. Insulate insulate insulate is always the focus before anything else. (I have been staring at COP and EER numbers for a long time too, so I kinda think how you feel! Just shake it off maybe? :-*)
   Jan

4. GBA Editor
   Martin Holladay | Mar 30, 2015 09:46am | #4

   C. Maglio,
   Unlike Jan, I think that the elements of a GSHP system should be right-sized, not oversized. If you start saying "It's OK if we use a little more electricity than necessary for our pumps," you're on a slippery slope leading to a poorly designed system.

   Pump oversizing is a big problem with these systems. You need a designer who understands GSHP design -- but also one who is good at pump sizing.