Hi Scott, You are correct. The COP that I calculated was the refrigerant or theoretical COP. It did not include the mechanical and electrical efficiency. Each heat pump system will have ratings (SEER) that will allow you to calculate the actual energy efficiency and may list the actual COP of the system at different temperatures. The SEER on our heat pump is 18.2. Most systems drop off drastically once you drop below freezing temperatures. The easiest way to save on electricity is to turn up your thermostat after the sun comes up and warms the air.
Regards, Chuck On Mon, Feb 6, 2023 at 11:20 PM Scott Stewart <[email protected]> wrote: > Hi Chuck, > > I was under the impression, and could be wrong, that each heat pump > manufacturer will provide specified COP values for each model of > heat-pump they manufacture. The COP values vary over temperature, and > decrease as temperatures get lower. As the temperature gets lower, > eventually the heat pump yields a COP value of 1, which is essentially > similar in performance as a full electric furnace. I viewed this number > (COP ~1.0) as the point at which your heat pump is essentially running as > efficient as if it was an all electric furnace. > > I was curious what the specified COP values are for your unit, and if > they're close to the values you calculated? > > I'm a huge fan of my heat pumps and always feel good when I hear them > turn-on on cold days. However, at some point it becomes just to expensive > to run them and they're too inefficient. That's when I'm happy to have my > Propane furnace turn on and quickly heat up the house. As I said earlier, > if I could find a much more efficient heat pump that held a COP value above > even 2.5 at extreme cold temps, I'd probably find it cost effective to swap > mine out. > > Thanks for the info. > > Best, > Scott > > > > On Monday, 6 February 2023 at 10:27:45 pm GMT-5, Cj Sizer < > [email protected]> wrote: > > > 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 <[email protected]> > 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 < > [email protected]> 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 <[email protected]> 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 [email protected]. > 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 [email protected]. > 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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