Coldest day of the year. #Heatpump now at a scorching flow temperature of 36.5 ˚C. Power drawn is 1500 W (a bit higher right after a defrost event). The temperature at the top of the stairwell hasn't moved by more than half a degree from 19 ˚C in the last two weeks.
Plot shows the last week - beautiful illustration of temperature/weather compensation - see the flow temperature in red and external temperature in green. Stairwell temperature is orange.
See ALT text for more detail.
@sellathechemist
Interesting, my landlord here in Luxembourg wanted to 'invest' in heat pump tecnology and several companies who offer that technology did come round, survey and prepare quotes; all emphasising very strongly the fact the government here pay most of the bill!
Only one company representaive was honest enough to say that in a house (the old village school built circe 1900) built of random stone rubble bonded with lime mortar with walls 650mm thick and a protected facade (you can do what you like to any other part of the building by you cannot alter the facade), that heat pump technology would be useless without doubling or trebling the size of the radiators throughout the house and applying substantial insulation to the exterior facing walls. As putting it on the ouside frontage of the building would not be permitted due to the preservation order and on the other parts it would ruin the look of the building as it has dressed stone surrounds to all the window and door openings which would be covered up, the insulation would have to be applied to the inside of the building so the total cost would be enormous as would the disruption.
@Paulos_the_fog But you have this information from your energy bills. That is data with no assumptions. The estimable @Protons4B has a rule of thumb for England that if you take your total annual energy use in kWh and divide by 2900 you get an estimate of what size of heat pump you need to match the typical heat loss of your building. This applies to houses rather than to buildings that have forced air ventilation. There is a very important thing to remember: 2/n
@Paulos_the_fog @Protons4B There is a huge difference between the energy flow required to heat a cold building to whatever temperature, and the energy flow (power if you will) required to hold the temperature there. Your bills, which will be dominated by winter fuel use will help you gauge the latter. It can be worth reading your meter daily in the coldest days because that will tell you what heat flow you need to keep your house from cooling. There is the upper bound on your heat pump size. 3/n
@Paulos_the_fog @Protons4B [Annoyingly I have to rush off for a couple of hours but I will try to come back to say a bit more but I would strongly recommend that you pay a visit to Michael de Podesta's website www.protonsforbreakfast.wordpress.com which goes into a loving detail about these estimates - I am very fortunate that I get to have regular cups of tea with him and we are quite overdue - Anyway - more later] 3a/n
@sellathechemist @Paulos_the_fog@qoto.org
https://protonsforbreakfast.wordpress.com/2022/04/05/what-size-heat-pump-do-i-need-a-rule-of-thumb/
Here's the rule of thumb article. It has a link to a YouTube video explaining why it works.
All the best
M
@Paulos_the_fog @sellathechemist @Protons4B
Stepping back even further gives yet another way to look at it: a key issue is the “spark gap”: the ratio between the cost of electricity and the cost of gas (or whatever heating you're using now, oil?). According to https://www.lowcarbonhub.org/p/spark-gap/ that ratio in Luxembourg is about 2.7 (much lower than the UK's).
Give or take 10% or so for relative efficiencies and things, if your heat pump has a SCOP (seasonal ratio of heat produced to electricity consumed) of greater than that you win, at least on operating costs.
A SCOP of more than 3 should be routine, I think, though perhaps bigger radiators or some re-plumbing (replacing small pipes with big pipes) would be needed for that.
While extra insulation, if practical, would of course be a good idea its only direct relevance to the use of a heat pump or not is that if insulation is to be fitted it should be done first otherwise you'll wind up with an oversized heat pump.
@Paulos_the_fog You might want think about it another way. Rather than getting lost in the detail of the construction and the radiators, you might start from the idea that whatever system you use to heat your house has to match the heat losses in order to keep the temperature steady. So you really need to get an idea of what that is.
The problem is that this requires a lot of knowledge of your building, its air change rates and how you actually use and live inside it. It's complicated. 1/n