Dewayne, thanks.

You only need to subtract it out (both numerator and denominator) if you want to compare actual COP performance to manufacturer claims.

I.e., WaterFurnace doesn't include pump power consumption in their COP calculation for their advertising claims of "world's first 5.0 COP" GSHP units.  You need to subtract it out for an 'apples-to-apples' comparison.

And if you have customers sophisticated enough to compute COP, wanting to verify they got their money's worth from their installation, they're probably going to compare to the manufacturer claims.

Otherwise, yes, it's certainly power that's required for the system to run!

Best regards,

Bill

I find it odd that your 5 ton is operating so much better ?

Do you know the reason

The system I was refering to in the begining was a 5 ton DX so all net BTUH measurements where on the air side .

geo fan, I'm not sure I understand your question of what is the reason my 5 ton GSHP is operating so much better.  So much better than what?

If the comparison is to a 5 ton DX, I unfortunately don't have any knowledge on DX systems.

I've been very pleased with the performance of the WaterFurnace Envision units I have.  While my measured COP and EER performance numbers don't match publish specs, they're either close (close enough to rationalize against laboratory conditions WF probably used), or, I can figure out where my measurement error is.

I just don't have any difficulty pumping out of the earth about 11 KBTU/hr with my 3 ton unit, or 35 KBTU/hr with my 5 ton unit, both in 1st stage only.  That's about 46 KBTU/hr available to be processed by the evaporator coils / air handlers and pushed into the structure.  Which even in this high 20°F temp outside conditions we have at the moment (cold for Dallas climate), in a non-set back scenario, run time is right around 10 minutes to satisfy the tstat setting (68°).

Best regards,

Bill

So much better than your 3 ton?
Regards, Masoud

I actually don't know why my 3 ton WF Envision doesn't run with as high of a COP as my 5 ton Envision does.  Here are a few things that come to mind:

1. I have a pretty signficiant air distribution challenge on the 3 ton unit, with air being zoned into 3 zones.  As a result, the zones are small, and the air velocity higher than normal.  My guess is the air distribution efficiency is not as good as with the 5 ton unit (no zoning on the 5 ton unit).

2. It's actually a little challenging to get really good, accurate temp numbers for EWT and LWT using the Dallas Semiconductor 1-wire sensors.  Getting a good mechanical bond, to a place where the pipe is copper, with good heat sink grease, and getting it all insulated well, can be a challenge.  In the case of my 3 ton unit, I don't think I did as good of a job installing the temp sensors as I did on the 5 ton unit.  Hence, I think I have some measurement error.

3. The GPM value I use to compute the HE portion of the COP formula is a constant, measured from taking pressure readings during the Summer.  It's possible I've got more than 14 gpm flowing through the unit at the moment, and I'm just not aware that it has increased.

Best regards,

Bill