You want to run a model to ensure your loop plan will reap dividend.
There also may be a geological reason the local standard is 300 feet.

One of the well respected geothermal drillers proposed drilling three 400 foot loop wells. So I don't think there is geological reason not to go 400 feet. The other drillers proposed four 300 foot loops.

Unfortunately, I don't have the software to run a simulation. But my manifold will be simple and short. The loops will be 1 inch, and the manifolds 1 1/4 inch. All four holes will be in a row, 20 feet apart, about 10 feet from the house. I have been considering spending a few more dollars to get a 2 inch manifold, even though that would likely be over kill. Just the same, I prefer to over design the ground loops.

Posted By engineer on 28 Sep 2013 11:34 PM
I'm skeptical of EWT running anywhere near just 5 degrees either side of undisturbed deep ground temperature. That may happen during shoulder season's sporadic short cycles but not during prime time.

... EER values don't incorporate water pumping power other than the small pressure drop through the geo system's water side heat exchanger.

For my location my undisturbed soil temp is 68 degrees.  Since my structure's cooling load is substantial compared to its heating load (minimal - see 13 month history at http://www.welserver.com/perl/plot/...ansfer.png ), my EWT runs worse case -3 degrees on the cold side of undisturbed earth (down to 65 degrees at coldest point of winter, and + 13 degrees on the hot side (up to about 81 degrees at hottest point of summer) (see http://www.welserver.com/perl/plot/...ilyAvg.png ) .

Indeed, the EER algorithms used by the major geo manufacturers does not take into account pumping power.  While this enables comparison of actually measured EER to manufacturer claims (my EER measurements match WF's Envision 5 ton marketing claims), it doesn't show the whole picture of energy consumption.

(North of Dallas location, vertical loop, 8 holes, 300' deep each, 1" HDPF U-tube, clay soil, Bentonite grout, 2 units (3 and 5 ton) servicing 3400 sf single-story structure running exclusively in first stage, with 4 air zones, using 1 - 3 1/6th hp single speed water loop pumps, no aux coils.

424 kWh monthly 12 month rolling avg for heating & cooling; this is $49/month averaged over last 12 months, at my current cost per kWh.)

Best regards,

Bill

Posted By t5800512 on 27 Sep 2013 10:10 AM 
... I like your WEL page. What I have seen before were block diagrams. Your looks like pictures with the WEL monitor imposed over it. When I setup my WEL monitor, I will have to get with you to find out how you did that. Way cool.

Easy to do.  Docjenser is one of the best at doing it.

All WEL real time system screens simply display numbers on a background JPEG.  There's a place in the WEL configuration system to upload the JPEG background screen, and a separate place to specify the X,Y coordinates for any real time data to be placed on the JPEG image.

The JPEG screen is created however the customer is most comfortable.

Some, like Docjenser, start with a JPEG picture, and then, using some kind of picture editing s/w (I use Photoshop), add anything desired.  Others, like myself, start with a 'blank surface' and create the JPEG image from scratch using the picture editing s/w (my screen is at http://www.welserver.com/WEL0043 ).

Having a real time customized web page screen is one of the WEL's best features.

It's hard to imagine a better value for the hardware and s/w needed for a measurement and verification system, at $405.  Particularly noting that there's no monthly fee - i.e., the $405 cost for a WEL includes a perpetual license fee for the intellectual property built in to the WEL.  And it also includes a dedicated web site for your WEL unit.

Best regards,

Bill

Hey Bill, You are always very helpful, and I really appreciate it. Thank you for the information about the WELL setup.

I'm surprised to hear that your EWT gets up to 81 degrees in the summer. I always look at the 70 degree lines when I'm comparing the manufactures EER ratings. At 80 degrees, the EER ratings really fall off. I think they go down to the range of high efficiency air to air heat pumps. Someone correct me if I'm wrong.

Yes the manufacturers all boast numbers with ideal EWT's. The trouble is reducing your EWT 10* or from a design of 80 down to 70, might cost you thousands extra in drilling, so there is an economic balance point where you accept a little higher op cost to avoid a much much higher install cost.

Posted By t5800512 on 10 Oct 2013 06:46 PM
At 80 degrees, the EER ratings really fall off. I think they go
down to the range of high efficiency air to air heat pumps.

Air source heat pumps also lose efficiency as ambient air temp
increases. Their ratings also apply only to a particular temp --
and with air source, you have no control over EAT.

Hey Joe and Looby, you both make very good points. Thank you. Say, I have a ClimateMaster question for you. Does the Tranquility 30 (TE) require access from multiple sides (front, right and left)? My current air handler is in a closet, and there is about 32 inches of space between the wall and the hot water heater. The only real access will be from the front. I would use a right side return, and it would have to go through the wall as upflow is not an option.

side access is not required.
is this closet on a slab? you do not want a compressor on timber or it can radiate noise through out house

Since the information in this thread has moved way past the rebate expiring, I'm going to open a new thread for the current subject. I hope everyone will comment in the new thread called Geothermal Retrofit. Thank you all for your interesting feedback. I really appreciate it.

http://www.greenbuildingtalk.com/Forums/tabid/53/aff/13/aft/81837/afv/topic/Default.aspx

Posted By t5800512 on 10 Oct 2013 06:46 PM

... I'm surprised to hear that your EWT gets up to 81 degrees in the summer. I always look at the 70 degree lines when I'm comparing the manufactures EER ratings. At 80 degrees, the EER ratings really fall off. I think they go down to the range of high efficiency air to air heat pumps.

In the Dallas area, I'm fortunate that my EWT stops at a high of around 81°F annually.  It's because my borehole field is large enough such that my 3400 SF single story home doesn't ever need to run outside of first stage cooling.

Right now my EWT is about 74°, continuing to slide down toward the 68° steady state down deep earth temp I have for my location ( EWT Daily Average ).

This is because I'm extracting less heat from my structure on a daily basis (it's about 100 KBTU/day - see Heat Removal Each Day ) than what the earth can absorb.  Thus, this is the 'shoulder season' where my borehole field gets to 'relax,' with more heat moving away from the pipes than is being pumped into the pipes.

100 KBTU/day heat removal from the structure is because Degree Days each day are declining, as you'd expect for the Fall season.  Right now DD/day is averaging about 10° (Base=65°) ( Degree Days Each Day ).

If I look at the WaterFurnace supplied tables for one of my units, my 5 ton unit (ND064), running at low speed, at 1500 CFM, my EER (from the table) is 20.0 at EWT at 80° (at 14 GPM).

At 70° EWT, the table says EER is 23.6.  So yes, I have an EER swing of about 4 between the hottest of the summer (for me) and the point just before heat starts to be needed regularly.

My EWT of 80° or more comes in the July and August months after there's been many, many weeks of blistering heat.  I'd be stunned if high efficiency air to air heat pumps don't have an EER fall off too (and maybe even a more steep fall off).  This is the time of year when outside temps are over 100°.  I can't imagine air to air heap pumps being very efficient when the heat from the structure is exchanged into 100°+ air.

Best regards,

Bill

You are correct that ASHPs fare badly in 100+ degree ambient. The same extended specification tables we look to for efficiency and capacity of water source heat pumps at differing water temperatures are also available for ASHPs. In triple digit temps efficiency and capacity fall off as the compressors both move less refrigerant and use more power moving it. Liquid coming back to the evaporator heats up as well, requiring more of it to flash off to cool the remainder to coil's operating temperature.

It is there one can learn a quiet little truth - it is typical for a system ballyhooed as SEER 16,17, etc on up to 20+ to have an EER (efficiency at 95*F) of just 12-14.