And he’s right. When the heat pump is off, it is essentially a short circuit between flow and return temperature sensors which then measure the same temperature. Anything happening after the heat meter just increases overall temperature.
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I asked about this a little while back, and had originally added my secondary pump’s input to the output - since its within the thermal envelop, but not counted by the heat meter.
I still think we should - its electricity I’m paying for and its heat added to my home. We are trying to measure the overall system/install efficiency, not just the heatpump.
It might be fine if everyone did it, otherwise it skews the comparison between systems
The heat meters already include this for primary/integrated pumps. Not including the secondaries is skewing the results in the other direction when trying to compare systems with vs without secondaries.
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Umm… are you sure? I wouldn’t have thought so as heat meters can’t see the electrical input. Unless I’m missing something?
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Assuming the pump is also between the flow/return sensors, they include the heat directly generated in the pump and the piping up until the heat meter. Frictional losses after the heat meter are not included.
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I mean they already integrate the heat added by any upstream pumps
I think we should implement the most physically accurate performance assessment even if that does deviate from SEPEMO. Ideally we would have the option to calculate a SEPEMO compliant result as well, with a note that SEPEMO is not physically accurate if that is indeed the case…
That’s my thinking too Josh. As I understand it, the preference for reporting on the H4 System Boundary (rather than H2) is to represent the whole system installation, not just the bare heat pump unit - and that logic works both ways: if we’re including the consumption of the supplementary pumps / fans we should include their contribution to the heating too.
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We don’t all agree that the heat contribution isn’t already included.
I am fully supportive of the idea that everything should be included as we are comparing heating systems that use heat pumps, not just heat pumps.
However, unless my maths is wrong, whatever happens with the heat from secondary circulation pumps, including them is better than not including them, as including them will always result in a lower COP than ignoring them completely.
Sounds eminently sensible to me Trystan.
Do you happen to know of a definitive statement for what strict SEPEMO compliance looks like in this regard?
After searching for the official SEPEMO publications, I’ve turned up this conference paper which has a bit more detail than I’ve seen elsewhere:
http://sepemo.ehpa.org/uploads/media/D6_9_7_Zottl_HPC4_7.pdf
(I found that link via its Semantic Scholar entry: System boundaries for SPF calculation)
In particular, this diagram from the conference paper includes extra clarity I don’t recall seeing before:
Note the Primary circulation pump is shown outside of H3 (hence also H2) and only included in H4 - along with any Secondary circulation pump(s).
The “[SEPEMO D4.1, 2011]” in the figure caption is a reference to the Deliverable 4.1 report (as the original source for the figure), an output from SEPEMO-Build Work Package 4; here’s the full citation for that report:
SEPEMO D4.1, 2011: “D4.1. guideline for heat pump field measurements for hydronic systems – Version 1.0, The guideline contains information on what to measure in order to calculate SPF and about the required measurement quality”, IEE SEPEMO-Build, February 2011
The “D4.2” citation also looks interesting:
SEPEMO D4.2, 2010: “D4.2. Concept for evaluation of SPF - Version 1.0,
A defined methodology for calculation of the seasonal performance factor and a definition which devices of the system have to be included in this calculation”, deliverable in the Project IEE SEPEMO-Build, June 2010
I have however drawn a blank in finding the full text for the D4.1 & D4.2 reports. It’s clear they were originally published to the WP4 section of the www.sepemo.eu website which no longer exists but is showing up on the Internet Archive here: Work Package 4: Development of monitoring methodology and definitions for seasonal performance - SEPEMO - but looks like they only archived the website structure, not the linked media files 
If anyone happens to have a copy of those reports, or has academic or EHPA contacts that might be able to access them, it would be great to see the full detail of what SEPEMO defined.
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Nice work looking into this in more detail, my first introduction to the sepemo boundaries was from the EST report, there’s a fairly detailed treatment here: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/225825/analysis_data_second_phase_est_heat_pump_field_trials.pdf
I wish they had put the pumps in H3 and the immersion in H4 instead of the other way around…
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I’ve managed to find the two original SEPEMO documents I was looking for. It seems that the content previously on www.sepemo.eu has been archived to sepemo.ehpa.org but the content management front-end on the latter isn’t currently operational. I’ve emailed [email protected] to report the issue but not sure how responsive they will be.
In the meantime, I found some other documents which directly reference files located under sepemo.ehpa.org and those ‘deeper’ links work fine - as long as the exact filename is specified in the URL:
- D4.1. / D2.3. Guideline for heat pump field measurements for hydronic heating systems is here
- D4.2. /D 2.4. Concept for evaluation of SPF - Version 2.2 is here
There’s more discussion of Cooling and Defrost than I remember seeing in other SEPEMO-related publications but - from what I can see - no mention of how they proposed to treat the heat generated by control boards and secondary circulation pumps.
While attempting to track down these SEPEMO documents I reached out to @JennyCrawley at the UCL Energy Institute who kindly shared my request with her colleagues. Roger Hitchin commented that the SEPEMO research has been taken forward by various research projects conducted by the Technology Collaboration Programme on Heat Pumping Technologies at the International Energy Agency. Each of their research projects is referred to as an “Annex” and Roger specifically pointed me at Annex 52 which has the title “Long term performance measurement of GSHP Systems serving commercial, institutional and multi-family buildings”. It’s a lot more recent than the SEPEMO work and attempts to move that forward. Looks like they’ve added further System Boundary definitions (while retaining alignment with the SEPEMO ones) that better align Cooling with Heating - but the focus on larger-scale GSHP systems isn’t directly relevant to us.
However, I was pleased to find this statement in Subtask 3 Report – Guide for analysis and reporting of GSHP system performance – system boundaries and key performance indicators (KPI):
Worth noting is that while the system boundary 1 (in both SEPEMO and Annex 52 boundary schema) only includes the electricity used to run the compressor, it is in practice rare that the measured heat pump electricity use does not also include some small amount of electricity used for internal controls and sometimes an internal circulation pump. If this is the case, we recommend indicating this by adding a superscript asterisk (*) and an explanatory text.
This is at least recognition of the fact that measurements are typically ‘aggregated’ to some extent.
There are many other TCP HPT “Annexes”; they’re currently up to number 66. Some of them have contributions from the original SEPEMO researchers. If anyone is looking for info on e.g. the noise from heat pump units or a focus on net-zero-energy buildings there’s a lot of content available. See the pages for ongoing and completed research.
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