Geothermal: how to specify and verify performance?
Hello,
I am looking at retrofitting my home with a GeoComfort GSHP and was wondering how to specify and verify performance. Other than simply saying the unit should be able to maintain 71F in winter without backup heat and 79 in summer. Are there any specs from a consumer stand point that can be put down on paper and then can be verified?
The home description is in this other thread (I am in zone 5A):
My current system is a 3-ton air-handler paired with a 3.5 ton exterior condenser unit. The
contractor has done a “Manual J Load” and has specified a 3-ton replacement GSHP with 4 vertical loops (doesn’t mention depth).
The analysis from the contractor:
Heating Cooling
Annual Heating Load: 59.8 MMBtu Annual Cooling Load 28.7 MMBtu
Electricity (GeoComfort): 4682 kWh Electricity (GeoComfort): 1612 kWh
Electricity (Auxiliary): 207 kWh Average Efficiency: 17.8 Btu/Watt
% by GeoComfort: 98.8 % Annual Cost: $161
Average Efficiency: 3.59 COP
Annual Cost: $489 Estimated Annual Operating Costs
Heating: $489
Hot Water Cooling: $161
Annual DHW Load: 17.8 MMBtu Hot Water: $299
Electricity: 2994 kWh Total1,2,3 $949
% by GeoComfort: 53.0 %
Average Efficiency: 1.74 COP
Annual Cost: $299
Design Heating Load: 55338 Btu/hr Design Cooling Load: 26286 Btu/hr
Indoor Design Temperature: 70 °F Indoor Design Temperature: 75 °F
Outdoor Design Temperature: -7 °F Outdoor Design Temperature: 94 °F
Heating Electric Rate: 0.10 $/kwh Cooling Electric Rate: 0.10 $/kwh
Hot Water Electric Rate (Htg): 0.10 $/kwh Hot Water Electric Rate (Clg): 0.10 $/kwh
Winter Peak Electrical Demand: 6.47 kW Summer Peak Electric Demand: 1.96 kW
GeoComfort Model GXT036C Compass Series with hot water generator
Water Heater: Electric Emergency Heat: 12.22 kW
Auxiliary Heat: 3.95 kW Balance Point 12 ° F
Loop Type / Soil: One Vertical U-Tube, Polyethylene SDR-11 3/4″ / Heavy Soil Damp
Bore Depth: 150 ft Deep Earth Temp: 54 °F
Total Bore / Pipe: 663 / 1326 ft Annual Temperature Swing: 24 °F
Minimum Loop Temp: 30 °F Phase Shift: 37 Days
Maximum Loop Temp: 83 °F Soil Conductivity: 0.8 Btu/hr-ft-F
Average Heating Loop Temp: 46.9 °F Soil Diffusivity: 0.03 ft²/hr
Average Cooling Loop Temp: 69.3 °F Pipe Conductivity: 0.226 btu/hr-ft-F
1 Total estimated annual operating costs includes heating, cooling and hot water. Base electric use (electric use other than heating,
cooling and hot water) is not included, and will vary depending upon lifestyle. Total annual utilities equals heating, cooling and hot water
costs plus base electric use.
2 The operating costs shown above are considered to be an estimate due to the variability of living habits, weather, and system
installation.
3 This software uses the latest algorithms from IGSHPA (International Ground Source Heat Pump Association) for ground loop sizing.
Operating costs are based upon IGSHPA and ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning Engineers)
algorithms. All calculations are based upon GeoComfort equipment, and may not be comparable for other manufacturer’s equipment.
The quote is for:
BASE BID: Install Total Comfort System with each unit consisting of:
GeoComfort “Compass” Two Stage Geo-Thermal Heat Pump System
This unit utilizes two stages for optimum efficiency and comfort. It also incorporates a variable speed blower.
10 Year warranty on all parts and labor, and 50 years on loop piping
LIFETIME WARRANTY ON COMPRESSOR
GXTO36 3ton
* Tear Out of Existing System
*All Loop Piping (4Vertical Loops) 50’ Maximum Distance to Header
* Inside Loop Piping
* Flushing and Charging of Loop Piping
* Hot Water Generator
* 10 KW Electric Heat
* Tying Electrical into Panel
* Honeywell Prestige Thermostat
* 50 Gallon Water Heater used as Preheat tank
* Dynamic Electric Filter
* All Custom Fabricated Ductwork
* All Taxes and Labor Complete.
Thanks,
venkat
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Replies
Venkat,
Q. "Are there any specs from a consumer standpoint that can be put down on paper and then can be verified?"
A. Unfortunately, the answer to your question is "not really." That's why HVAC engineers and energy consultants are often called out to troubleshoot problematic ground-source heat pump installations. There are a great many details that can go wrong, including loop sizing, pump specification, control problems, and distribution system problems.
As I've said before, ductless minisplit systems are much less likely to have commissioning problems than ground-source heat-pump installations. Good luck.
There is equipment available for the monitoring you would need to do, but you'd either have to buy it and set it up yourself, or pay a consultant to do it. At a minimum, you need an electricity monitor on each component of the heating system, including the various circulators and any backup heat source. PLUS a way to measure the amount of heat produced. The simplest form of this is going to be a setup that measures flow through the heat exchanger, plus the delta T. All of this is going to have to be collected and logged in real time and then crunched into a usable picture. Bottom line, you want to know how much heat was provided, and how much electricity was used to provide it.
Increasingly there are companies that are looking at the monitoring space for HVAC systems much like the intrusion and fire alarm monitoring companies. Benefits include lower operating costs (visualization tool to stimulate lower usage), lower maintenance costs (anticipate repair expenses before catastrophic events), optimized decision making (having having quantitative feedback and ability to question unusual anomolies), faster repairs and problem solving, and increased satisfaction (ensure results indeed occur, surprises don't happen, promised savings materialize).
Popular 'tools' to use include Web Energy Logger ( http://www.welserver.com ) and HOBO ( http://www.onsetcomp.com ).
For a residential example illustrating using the Web Energy Logger system, see http://www.neukranz.com .
Hope this helps.
VENKAT Y
Although Martin knows I appreciate the detail and patience he exhibits to date with all he has been given to know,
--- I will speak from 1976 HVAC and heat gain and heat load sizing beginnings and 1980 GeoThermal with TWO distributors helping the customers of some 1700 hands on and sales of over 70 that I installed as well directly- among the consults and engineering training to 6 engineers and over 78 contractors: (over 40 GeoThermal HVAC-HW proficient contractors)
With ECL Earth Coupled Loop GEOTHERMAL:
A common household 35 degree alarm for freezing protection at the home and bath and bed stores works quite well through an average coldest Jan 3rd week-4th week-Feb week #1 strapped to the INLET line from the Earth-Coupled GEOTHERMAL ground loop at the unit "IN" port to sound off through a 24/7 typical GT SYSTEM operation period. Or I sit by in an "overnight" while trying to know about possible air in loop and as well: Monitor with simple, or none of, temp recorders so available today.
To avoid leaving fluids below 28 deg F and freezing-heaving of runs to loops
2) PERFORMANCE GUARANTEES can be EASILY specified (as I always do since 2003, on the sales agreement that also always has a "you have threee business days to rescind/cancel this agreemnet" in duplicate to all on the household deed...
Here in our zone 5 to zone 6 , some are shocked, but so many were installed as may still be entering the system with fluids dropping below EnergyStar(tm)32f referencing, that two pumps are required below or one near 1/2hp for just a 3-ton AHRI-rated (2.1/2 Compressor-Ton) unit !!
While some have 5 ="size" ons on just one pump working so well with a 4.1./2 compressor-ton unit.
3) One CAN specify loops are headered for flushing and purging but operation shall be across the pump at averaging 3 gallons per minute per compressor-ton inside unit having not more than a 26 ft TDH water pressure drop with ALL COMPONENTS and UNIT (coil hx) pressure drop INCLUSIVE.
Hitting 19-22 these days AND COMMERCIALLY since the 21st century IS COMMON among those getting over 20 compressor tons per pump horsepower.
4) One can specify that in cooling a reasonable dehumidification CFM of blower air volume per ton shall be not over 340 cfm/Compressor-Ton(C-ton) and total highest cooling at not more than 440 CFM/C-t (fairly easy to have quicly determined if a strip-heat electric heater is in airways of the ducting for measurements.
5) One can specify Variable IQ compressors (field tested over 3 years) and variable pump FlowCenters Products that are working well.
6) ONE CAN SPECIFY IF THE HOUSE IS CLOSED AND SHADES OR GLASS OF A LIFESTYLE IS AGREED IS OR IS NOT COVERED, SYSTEM BALANCE POINT UNDER 15 OR 12 OR 10 OR 5 DEGREES...
oem:
SOME MONITORABLE SYSTEMS WIH 8 AND 9 SENSORS HAVE READ IKE THIS SINCE 2007
Jon,
As inscrutable as ever: "ONE CAN SPECIFY IF THE HOUSE IS CLOSED AND SHADES OR GLASS OF A LIFESTYLE IS AGREED IS OR IS NOT COVERED, SYSTEM BALANCE POINT UNDER 15 OR 12 OR 10 OR 5 DEGREES"
?
That reads like something a not-so-great web-translation tool would come up with. Try posting it in the native language.
Dana,
I've been puzzling over JP's style, and I think you've nailed it.