Hi Scott, Your comments are very relevant. The COP calculated was the theoretical number based on the R410A refrigerant temperatures from actual measurements. It was not based on the EER taking into account the electrical and mechanical losses of energy. At the coldest time, the compressed refrigerant was 41.7 degrees Celsius and the refrigerant under vacuum was at a temperature of -30 Celsius. The COP was calculated to be about 4.4. I included these calculations in the spreadsheet so that I could compare them to the actual hourly energy usage of the heat pump (which was measured with an Emporia Energy System).
The very low temperatures that we experienced had more of an effect on the heat loss through the walls than it did on the efficiency of the heat pump. I was very skeptical of air source heat pumps initially. After this brief study, I think that they are an economical solution that is sustainable. I considered the cost of drilling two 750 feet deep geothermal wells. This is more easily offset by adding two more solar panels to make up for the reduced efficiency of air source heat pumps. Chuck Sizer On Mon, Feb 6, 2023 at 5:57 PM Scott Stewart <scott_a_stew...@yahoo.com> wrote: > Hi Collette, > Thanks for sharing this info... Do you have the model of the heat pump > you're running at your house? I find it very interesting that it can hold > a COP so steady around 5 with such a wide outdoor temperature swing. Is it > underground? > > My heat pump is ~5 years old, and not by any means the most expensive. > It's specs between 10F and -5F go from 2.06 to 1.24. > > Are you sure you're getting a COP of around 5 from 10F to -13F? > > I plug my cost for electricity and propane into a DOE calculator each year > to figure out when to set my heat-pump to turn-off and the propane furnace > to kick on. If I could get a COP of 5... I'd never need propane. :-) > > [image: Inline image] > > Just curious. > > Thanks, > Scott > > > On Monday, 6 February 2023 at 08:46:01 am GMT-5, Cj Sizer < > cjsi...@gmail.com> wrote: > > > Hi Rich, > > My husband kept data on our system through the bitter weather. He made a > ppt for CFREE (working group of the Green Energy Committee). You might find > it interesting, Our heat pump is located in a nook on the southeast side of > the house. The area warms when the sun comes up. We added insulation when > we replaced our roof last year. We also replaced many of our single-pane > windows with triple pane. These things surely helped keep our energy usage > down through the cold wave. In the coldest hours of the early morning, the > heat pump held the temperature 1° below the thermostat setting. > > Best regards, > Collette > > On Sun, Feb 5, 2023 at 11:42 AM Rich Rosenbaum <s...@bcdef.com> wrote: > > I was wondering how people with air-to-air heat exchangers managed during > our very cold night. > > Rich > > -- > The LincolnTalk mailing list. > To post, send mail to Lincoln@lincolntalk.org. > Search the archives at http://lincoln.2330058.n4.nabble.com/. > Browse the archives at https://pairlist9.pair.net/mailman/private/lincoln/ > . > Change your subscription settings at > https://pairlist9.pair.net/mailman/listinfo/lincoln. > > -- > The LincolnTalk mailing list. > To post, send mail to Lincoln@lincolntalk.org. > Browse the archives at https://pairlist9.pair.net/mailman/private/lincoln/ > . > Change your subscription settings at > https://pairlist9.pair.net/mailman/listinfo/lincoln. > >
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