The quoted EER figures for geo units do not take into consideration the fact that you also need to run some kind of pump, either a well pump for open loop or a pump on your loop. How much does this add to the amount of power used and what would that bring your real power usage EER to?

Good question - can't be answered without the specifics of the particular application. Shooting from the hip, pump power can range from 0 to 25% of compressor power, sometimes more.

I am looking at an open loop system with a 1/2 HP Gould pump. It seems this is going to put a big dent in a supposed EER of 27.

Yes it will.
We've often talked about COP which regardless of perfect lab rat scenarios, average near 3.5 in the real world, but I've not thought much about EER as it matters so little to overall op costs in MI (my AO).
As all things are relative, stated SEER from air source systems only see max if systems are mated with such and such a furnace and ambient temperatures are --. If it's really hot out geo pulls away pretty quick from air source.

Fractional horsepower well pumps are relatively inefficient - that pump could well use 600+ Watts.

How much system tonnage?

Have you investigated a variable speed pump drive?

How deep is the standing water?

Know that a geo operates on 5 or fewer psi of water across its heat exchanger - it is a huge waste to deliver water at typical domestic pressures of 50+

Can you get by with 1/3 hp?

It would be a 3 ton system using 9 gallons per minute. Standing water is at 20 feet. A 1/2 HP gould submersible 10SB would give me 15.7 gallons per minute at 30 PSI. I think that pump uses about 900 watts at full load. This pump can handle the sand in FL. A 1/3 hp pump would probally work .I usually use Gould but I can look around.

If your entering water temp (EWT) is above 50* 1.5 GPM/ton is needed. If the EWT is below 50* 2 GPM/ton is needed.
That could be a 180-270 gallon difference in water flow every hour!

Bergy

entering water temp is 72 degrees.

As written above it seems like you could get by with less flow. 

I have a 3 ton 2 stage unit and run it at ~4 GPM at part load and around 6 at full load.  Winter EWT is ~50.   Well guy said I'm lifting water about ~40 feet, I have a Franklin electric constant pressure system (VFD speed controlled off pressure).  I measured power at ~840 Watts at part load and just over 1kW at full full (6 GPM), at this flow my pump is horribly inefficient as it is capable of pushing closer to 40 gpm when using domestic water, running AC, and running sprinkling all at the same time.     

Ideally, if I was doing it again I would, look hard at a (2) pump system, as right now I'm burning alot of pump energy going from almost 70 psi down to zero (atmospheric pressure) as it goes through my unit and into the recharge drainfield   A two-pipe system... with a primary low pressure pump upstream that feeds the geo unit and a boost pump downstream that feeds everything else - domestic, sprinkling, etc, would save quite a bit.  To minimize footprint and size, I'm guessing both could still be constant pressure systems with only a small expansion tank for each pump.  

Yes, quoted EER numbers from many GSHP manufacturers do not include pumping power.

WaterFurnace uses this calculation for EER: ((EAT - LAT) * CFM * 1.08) / S/T / KW
where EAT is Entering Air Temp in °F, LAT is Leaving Air Temp, CFM is airflow in cubic-ft/min, S/T is Sensible to Total Cooling Ratio, and KW is unit power in KW

Here's an example:

((76.1° - 55.0°) * 1500 cfm * 1.08) / 0.663 S/T / 2.58 KW = 20.0 EER

Now, to include pumping power into the discussion:

In my case, my pumps for this example are 2 at 385 W (1/6 hp) each = 770 W just for pumping power.  If you want to include pump power in the EER calculation, then the EER is 15.4.  Thus, the pumping required power drops the EER by almost 25%.

Hope this helps.

Best regards,

Bill

Posted By joe.ami on 13 Feb 2012 07:14 AM
... If it's really hot out geo pulls away pretty quick from air source.

If the heat rejection needed from the structure is high enough (large and/or 'leaky' structure), here in the Dallas area geo is a 'no brainer.'  When hot summer days require upwards of 700 - 800 KBTU/day removal from the home, versus a heat load during cold winter days between 100 - 250 KBTU/day being added to the home, it's hard to beat the cost effectiveness of geo.

See Daily Building Structure Heat Gain/Loss Chart for illustration.

If the home is in Virginia Beach where weather temps are very moderate, house is small and/or energy efficient, then the heat rejection peaks during the summer will be much lower, and the heating required during the winter equivalently lower.  Now the cost of the borehole field cannot be recovered nearly as quickly in terms of utility savings with geo, and other technology heat pumps thus end up with much better ROI.

With the onset of mini-splits, other true variable capacity compressor systems, and advanced conventional air-to-air heat pump systems, a Virginia Beach location is going to require some 'number crunching' to figure out which technology type of heating/cooling has best ROI.

Best regards,

Bill

This is the first reference I not to location

If it is Va Beach, I'm skeptical of 72*F deep ground water. I'd expect more like 60, based on national table and map I have on file.

Great info by previous posters as to pump Wattage - hangs some numbers on what I mentioned earlier.

It is a really bad idea to pump water to 50 psig and then drop it through a heat exchanger needing just 5 - kills COP and EER.