[Bldg-sim] Subject: How do you model minimum and high efficiency DX
Michael Shannon
mshannon at epinc.com
Tue Apr 15 07:40:54 PDT 2025
This is an interesting question, and mostly it depends on the task I'm trying to accomplish and the toolset that I'm using.
On the cooling side, the ideal solution would be detailed performance curves, or the data to create curves, similar to data that is much more available for chillers. it's helpful when units are rated with a full load and a part-load or seasonal rating as well, so I have some reference for a full load efficiency in addition to the SEER2/IEER values. This is more common recently on smaller sized equipment as some of the rating classifications and requirements have changed, where previously it was only available on large units. Air Conditioners, Air Cooled under 65,000 BTU are only required to be rated in SEER2, and as available equipment reaches 18+ SEER, any equations I have for converting SEER2 to EER break down. So in those cases, I think about the different component parts and how they're able to be controlled and what their rated conditions are - evaporator fan, supply air fan, compressor - and adjust those inputs directly whenever possible.
On the heating side, here in Minnesota, we're pretty much always including backup heat sources. As a result, we make assumptions about the capacity and COP reductions, but the temperature that backup heat takes over tends to swamp those considerations. Even though a product is rated to heat to 5 F or -5 F, or -20 F, doesn't mean that's how it will be designed and most important how it will be installed and operated.
There are some good answers on unmet hours as well: How do you model minimum and high efficiency DX cooling and heat pump equipment? - Unmet Hours<https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/>
Michael Shannon, PE, LEED AP BD+C
Senior Mechanical Engineer, Energy Modeling
Emanuelson-Podas, Inc.
7705 Bush Lake Road
Edina, MN 55439
Cell: (763) 744-6186
Direct: (952) 540-4019
Office: (952) 930-0050
www.epinc.com<https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.epinc.com&c=E,1,6xuFSnICzD0kigyCITUBWmplFKIf4XlEAlsLJDamsuDRAE3CNTWErAmFwPfSnnhaIf0ptkARCf8aNXeRD8f97WMslHXrb4j_yPYa8IUulClgG-XmpEC9CSquVw,,&typo=1>
From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> On Behalf Of Samuelson, Holly via Bldg-sim
Sent: Monday, April 14, 2025 4:10 PM
To: bldg-sim at lists.onebuilding.org; jglazer at gard.com
Subject: Re: [Bldg-sim] Subject: How do you model minimum and high efficiency DX
Hi Jason,
For #2, yes, we end up with different estimated heat pump COPs at different operating conditions. This paper shows what that might look like.
Optimizing window solar heat gain coefficient for energy and carbon performance in a changing context of electrification and decarbonization - ScienceDirect<https://www.sciencedirect.com/science/article/pii/S2352484725000125#fig0030>
Best,
Holly
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1. Re: Bldg-sim Digest, Vol 209, Issue 2 (Jason Glazer)
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Message: 1
Date: Mon, 14 Apr 2025 06:28:39 -0500
From: Jason Glazer <jglazer at gard.com<mailto:jglazer at gard.com>>
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] Bldg-sim Digest, Vol 209, Issue 2
Message-ID: <2eed702c-fc4d-4475-aa3f-0cc45d5e32e7 at gard.com<mailto:2eed702c-fc4d-4475-aa3f-0cc45d5e32e7 at gard.com>>
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Holly
Thanks for providing the background on such an interesting
approach. Do you end up with a map of COPs at different
operating conditions in your spreadsheets, especially for 2?
Is that something you could share?
Jason
On 4/11/2025 4:27 PM, Samuelson, Holly via Bldg-sim wrote:
> Hi Jason,
> Regarding modeling the efficiency of equipment...
> It depends on whether you're modeling a specific system
> for a specific building project, or if you're trying to
> model generalized performance, for example for research.
> I'll comment on the latter scenario.? For generalized
> research purposes, where we don't know the exact heat pump
> system and configuration, my team has found that energy
> simulation results are too sensitive to many of the heat
> pump details in the energy model.? Therefore, to avoid our
> results being overly-specific to one heat pump model and
> configuration we've done one of the following two things.
>
> 1.
> We've output the annual heating and cooling demands
> from tour energy model, then applied the heat pump
> heating or cooling COPs ?in a spreadsheet.? We've
> found the COPs from a published study with realized,
> weather-dependent, COPs (from representative climates
> and buildings)
>
> 2.
> We've also done this with hourly performance, based on
> realized, weather-dependent COPs at different
> temperatures from representative field studies. For
> interpolation, we've calculated the maximum possible
> COP (based on the Carnot Cycle) for each time step,
> then scaled those values down to something more
> realistic, based on the results from the published
> field studies.
>
> Hope this helps.
> Best,
> Holly
>
>
> A black and white letter h Description automatically generated
>
>
>
> *Holly Samuelson*
>
> Associate Professor of Architecture
>
> Harvard University | Graduate?School of?Design
>
> www.hollysamuelson.com<http://www.hollysamuelson.com> <http://www.hollysamuelson.com/<http://www.hollysamuelson.com/>>
>
> /Unless otherwise noted, I do not expect a reply outside
> your normal working hours. /
>
>
>
> ------------------------------------------------------------
> *From:*?Bldg-sim <bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>>
> on behalf of bldg-sim-request at lists.onebuilding.org<mailto:bldg-sim-request at lists.onebuilding.org>
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> *Sent:*?Thursday, April 10, 2025 4:00 PM
> *To:* bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
> <bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>>
> *Subject:*?Bldg-sim Digest, Vol 209, Issue 2
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>
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> Today's Topics:
>
> ?? 1. How do you model minimum and high efficiency DX
> cooling and
> ????? heat pump equipment? (Jason Glazer)
> ?? 2. Re: How do you model minimum and high efficiency DX
> cooling
> ????? and heat pump equipment? (chris.malcolm.yates at gmail.com<mailto:chris.malcolm.yates at gmail.com>)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 10 Apr 2025 08:28:44 -0500
> From: Jason Glazer <jglazer at gard.com<mailto:jglazer at gard.com>>
> To: bldg-sim at onebuilding.org<mailto:bldg-sim at onebuilding.org>
> Subject: [Bldg-sim] How do you model minimum and high
> efficiency DX
> ??????? cooling and heat pump equipment?
> Message-ID: <bf88e843-c541-47e9-9462-0ff92a23c74a at gard.com<mailto:bf88e843-c541-47e9-9462-0ff92a23c74a at gard.com>>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> I just posted a question on unmet hours:
>
> https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/<https://url.us.m.mimecastprotect.com/s/O3SNCYEX3pHL864XfVs0cxbEal/>
> <https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/<https://url.us.m.mimecastprotect.com/s/O3SNCYEX3pHL864XfVs0cxbEal/>>
>
> "I?m trying to get an understanding of the practice of
> modelers when comparing minimum efficiency and
> high-efficiency DX equipment and heat pumps for different
> applications. I know that detailed performance data is
> sometimes difficult to get. How successful have you been in
> trying to get detailed performance data from vendors? If you
> can?t get data like that, how do you model the equipment?
> How do you model the indoor fan? If you know it is
> multispeed, how do you figure out those details? What if all
> you have is the AHRI data (EER/EER2, SEER2/IEER, COP at
> 17/47, capacities, full load/intermediate/minimum airflows)
> what assumptions do you have to make? What performance
> curves do you use? If you can get data from the
> manufacturer, what assumptions do you still need to make? Is
> it different for residential size equipment than commercial?"
>
> If you can respond to this email or post a response on
> unmethours, I would appreciate it.
>
> Thanks
>
> Jsaon
>
>
> --
> Jason Glazer, P.E., BEMP, GARD Analytics, ASHRAE 209 chair
> Admin for onebuilding.org building performance mailing lists
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 10 Apr 2025 15:47:12 +0100
> From: <chris.malcolm.yates at gmail.com<mailto:chris.malcolm.yates at gmail.com>>
> To: "'Jason Glazer'" <jglazer at gard.com<mailto:jglazer at gard.com>>,
> <bldg-sim at onebuilding.org<mailto:bldg-sim at onebuilding.org>>
> Subject: Re: [Bldg-sim] How do you model minimum and high
> efficiency
> ??????? DX cooling and heat pump equipment?
> Message-ID: <000801dbaa27$72659cf0$5730d6d0$@gmail.com<mailto:000801dbaa27$72659cf0$5730d6d0$@gmail.com>>
> Content-Type: text/plain;?????? charset="UTF-8"
>
> Hi Jason,
>
> I asked this question over a decade ago to a couple of
> different suppliers in the UK. What intrigued me was the
> very high efficiency that suppliers (e.g., Mitsubishi,
> Daikin) quoted - figures that we just plugged into
> building code calculations. Based on these figures it
> seemed like a no-brainer to just rip out centrifugal
> chillers and replace them with acres of DX systems! My
> enquiries came to little. The only interesting thing that
> I got (from a Danish academic) was that the market was
> very Germany-centric which resulted in SEER & COP being
> established at what seemed like, for the UK at least,
> quite extreme temperature bins.
>
> The impression I got is that, locally, there is some
> design experience within the sales teams but it's limited
> to sizing. The best I got back in terms of energy was
> something along the lines of "we've got some boffins over
> in Japan, we can try asking them."
>
> I don't doubt that they have some very clever people. Are
> they clever enough to get centrifugal-like performance out
> of a scroll compressor? I don't know. Reading your
> message, it's interesting to see that maybe the US market
> is subject to the same "black box" issues!
>
> Good luck. I'll keep an eye on this thread and Unmet hours.
>
> Cheers
>
> Chris
>
> -----Original Message-----
> From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>> On
> Behalf Of Jason Glazer via Bldg-sim
> Sent: 10 April 2025 14:29
> To: bldg-sim at onebuilding.org<mailto:bldg-sim at onebuilding.org>
> Subject: [Bldg-sim] How do you model minimum and high
> efficiency DX cooling and heat pump equipment?
>
> I just posted a question on unmet hours:
>
> https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/<https://url.us.m.mimecastprotect.com/s/O3SNCYEX3pHL864XfVs0cxbEal/>
> <https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/<https://url.us.m.mimecastprotect.com/s/O3SNCYEX3pHL864XfVs0cxbEal/>>
>
> "I?m trying to get an understanding of the practice of
> modelers when comparing minimum efficiency and
> high-efficiency DX equipment and heat pumps for different
> applications. I know that detailed performance data is
> sometimes difficult to get. How successful have you been
> in trying to get detailed performance data from vendors?
> If you can?t get data like that, how do you model the
> equipment?
> How do you model the indoor fan? If you know it is
> multispeed, how do you figure out those details? What if
> all you have is the AHRI data (EER/EER2, SEER2/IEER, COP
> at 17/47, capacities, full load/intermediate/minimum
> airflows) what assumptions do you have to make? What
> performance curves do you use? If you can get data from
> the manufacturer, what assumptions do you still need to
> make? Is it different for residential size equipment than
> commercial?"
>
> If you can respond to this email or post a response on
> unmethours, I would appreciate it.
>
> Thanks
>
> Jsaon
>
>
> --
> Jason Glazer, P.E., BEMP, GARD Analytics, ASHRAE 209 chair
> Admin for onebuilding.org building performance mailing lists
>
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Jason Glazer, P.E., BEMP, GARD Analytics, ASHRAE 209 chair
Admin for onebuilding.org building performance mailing lists
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