Preheat Max Override

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Is there any way to override the eQuest max limit for Preheat leaving temp? It is set at 70?F. I am trying to estimate savings for fixing a simultaneous heating/cooling AHU problem: faulty controls on the preheat coil that has an 80?F LAT, then cooling coil cools to 55?F. I could change the air flow proportionally to get closer to the heating and cooling energy consumption but then there is fan energy.....

I seem to remember some discussion on overriding min ad max limits for something but can't remember the topic or find it in a search.

Any ideas?

Ever thankful for this group!

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Melissa P. Crowe, LEED AP
Project Engineer
Engineered Solutions, Inc.
6 Union St, Natick MA 01760
508.647.9200 x225 (P) l 508.652.1936 (F)
MCrowe at

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Melissa Page Crowe's picture
Joined: 2011-09-30
Reputation: 1

I would suggest that a ground-source heat pump is not fundamentally any different than an air-source heat pump (you could just as easily say a traditional heat pump extracts free heat from the air). Both use electricity to run compressors/refrigeration cycles to accept or reject heat to the ambient environment. It just so happens that ground-source heat pumps utilize a heat sink/source that is much more moderate in temperature year-round and thus realize higher efficiencies. At least in my mind that makes the GSHP a high-efficiency options, and certainly commendable, but not inherently renewable energy.

That is my best guess at the rationale. It certainly gets a bit fuzzy, especially if you start talking about taking advantage of true geothermal energy (that is high-temperature geologic features, not just stable ground temps).

Nathan Miller, PE, LEED AP BD+C - Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100

Nathan Miller's picture
Joined: 2011-09-30
Reputation: 200

I agree with Nathan (and the USGBC) on this one. I think that if you are using a true geothermal system (i.e. - extracting heat from the earth's core), you could make a case for it being counted as a renewable energy system. However - with a traditional ground source heat pump - the ground is not a source of renewable energy, but really a heat sink that allows for you to be more efficient in your heat exchange. The system still uses energy - like any other heat pump.

Vikram Sami
Associate Partner

T 206.521.3509 E vikram.sami at
925 Fourth Avenue, Suite 2400
Seattle, WA 98104

vsami's picture
Joined: 2013-05-31
Reputation: 1

In the United States geothermal heat pumps - I'll refer it to them as "ground-coupled" here, a.k.a. geo-exchange, ground source - are specifically identified as a design strategy that is considered to be renewable energy for tax incentives in some cases. That's a specific designation in order to incentivize use of this type of system due to the extra construction cost.

When you take off your accounting hat and put your engineering hat back on...use of that type of ground-coupled system does displace cooling tower fans or other condensing unit energy by using the perhaps some percentage renewable. There is an added benefit for heat recovery if the system uses multiple heat pump units and some are in heating while others are in cooling. I don't think this affects the designation as "renewable" though, but does distinguish the system from air-cooled units.

However, there isn't an energy conversion process taking place in the ground. Think of it this way - energy is not extracted from the ground, it is stored and withdrawn. If the energy was only stored, there is potential for the ground temperature to increase over time. There might be properties of the ground and/or ground water that carry the excess heat away. This might be equated to using lake or river water in a chiller condenser, is that renewable? Your answer might depend on the impact to the river or lake. Similarly, installing phase change materials in your wall...high efficiency yes, but It's more of an issue of energy storage than energy sources.

Wind energy, solar, tidal, deep water cooling, landfill gas, and of course true geothermal heat - are a distinctly different category than ground-coupled heat pumps, and the effect of harvesting from these sources would generally be seen as negligible to the environment. This isn't true for ground-coupled systems in some cases. The GCHP system still needs to draw power from another source to run the compressors and pumps, and the use of GCHP may have varying levels of impact on the ground.

Anyway, to anser the original question about LEED - the efficiency of the ground-coupled system is modeled in EAC1 as an efficinecy measure. It would be difficult to separate a renewable component of the GCHP system energy use from those that are conventional (but high efficiency). If you compared the GCHP system to a water-loop heat pump system (with boiler and cooling tower) and showed the net savings separately from the LEED baseline, that might show the magnitude of potential "renewable" benfit from using the ground heat exchanger compared to an above-ground water loop heat pump.

In LEED the renewable energy credits have a specific purpose of reducing fossil fuel consumption. If the local electric grid is supplied from relatively clean sources, then the use of the GCHP may reduce total emissions compared to a natural gas furnce. GCHP would almost always come out ahead versus air-to-air heat pumps, electric resistance heat, or fuel oil combustion. Then similarly for cooling the efficiency of the baseline system would need to be considered. Most likely the result would be favorable against air-cooled systems, but savings may be less (or a loss) when compared against a high-efficiency water-cooled system. Then the combination of heating, cooling, and heat recovery benefit must be considered in total. Very complicated to allocate points for a GCHP compared to the other renewable energy sources that are all more or less 1:1 displacements of fossil fuel versus the baseline.

So to make a long story short, the opinion of the other posters that GCHP isn't technically a renewable energy source when used by itself and is more accurately described as an energy and cost efficiency measure seems to be supported. LEED specifically excludes GCHP as a renewable source. GCHP may qualify for financial incentive that is grouped with renewable energy sources such as solar or wind...and the whole scenario would be a lot clearer if the public didn't refer to them as "geothermal" heat pumps but instead called them ground-coupled heat pumps.


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers | Blog | Facebook | Twitter

David Eldridge's picture
Joined: 2012-05-08
Reputation: 1

IIRC, the "intent" language for LEED's on-site renewable energy credit
speaks specifically to rewarding/incentivising the generation of energy
using sources other than fossil fuels (my own paraphrasing).

Any medium of heat transfer (air, ground, evaporation...) can be coined
"free,? but if the associated systems (however efficient) are ultimately
largely powered by traditional fossil fuel sources / existing electric grid
distribution, then the energy savings associated will be isolated to EAc1

Something like an extreme geothermal system drawing core heat from the
earth would clearly pass that litmus test, as it could be directly reducing
the net energy drawn from traditional, fossil fuel powered, energy


Nicholas Caton's picture
Joined: 2014-12-09
Reputation: 0

Hi all,

This question is not about eQUEST, but since in this group a lot of people are working for LEED consultant projects, I think it is a good place to ask this question. I have been working in U.S. for a lot of years and just came back to China recently. In China ground source heat pump and water source heat pump systems are very very popular, and they are considered as renewable energy, since they use free heat from the soil and water. But in LEED rating system, heat pump is not considered as renewable energy. Why? Is it because those system has side effect to the environment?

Mo Yang

YangMo's picture
Joined: 2014-11-26
Reputation: 0

Thank you for answering my questions. That make sense.

Ya'll have a nice holiday!

Mo Yang

Date: Tue, 30 Dec 2014 14:40:47 -0800
Subject: Re: [Equest-users] Why Water Source Heat Pump is not considered as Renewable Energy in LEED rating system?

YangMo's picture
Joined: 2014-11-26
Reputation: 0

You are correct Nathan. The energy efficiencies provided by ground or air source heat pumps should definitely be included in the mandatory LEED Prerequisite and optional Credit for "Energy Performance?, but the optional Credit ?On-Site Renewable Energy? is reserved (with some qualifications) for only PV, Wind, Solar Thermal, Biofuel, Geothermal (deep earth), Hydro and Tidal.

The intent is that, as much as possible, duplicate recording of the same benefits in different Credits is avoided.

David Peterson
Blue Camas Consulting Ltd.
757 W.18th Ave. Vancouver, BC, Canada
604 417-7028

David Peterson's picture
Joined: 2015-01-04
Reputation: 0


I've always ?assumed it was because they require the use of a compressor so with a COP of 3-4 they're ?only 65-75% renewable. ?Deep earth geothermal (that doesn't use a heat pump) ?is considered renewable. ?

Looking at the reference guide, they state that ground-source heat pumps use vapor compression systems for heat transfer and they do not obtain significant quantities of deep earth heat. ?

Aaron Smith, P.Eng
M&R Engineering Ltd.

Sent from my BlackBerry 10 smartphone on the TELUS network.
? Original Message ?

Aaron Smith's picture
Joined: 2011-09-30
Reputation: 0

Thank you for reply. You made this point very clear!

Best regards,

Sent from my iPhone

YangMo's picture
Joined: 2014-11-26
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