Hacker News Reader

Comment by bluGill | Hacker News Reader

Maybe. However a heatpump sized to cool your house in summer cannot heat your house when the temperature is below about -3C. The heatpump might be able to produce heat to -25C, but it is too small to produce enough. Thus my system (in the US) that I just paid a lot of $$$ to install last fall leaves me using the backup gas heat a lot more than I wanted last winter which is disappointing. (It did get below -25C last winter for 2 days so I'd need that backup heat anyway, but I was expecting only 2 days not most of a month)

View on HN

A properly sized system will be based upon the worst of the heating or cooling conditions.

Luckily an inverter heat pump can run down to about 25% full load so even with them coupled and in an imbalanced heat/cool environment you can still see good performance year round.

Try to train the hvac profession of that.

They are required by code to do a load calculation, so you might wish to continue shopping around until you find one to do it.

British note: UK govt subsidies for some insidious reason are not available to "reversible AC" style systems, so the dominant form here is air-to-water.

I had mine fitted last year. Retrofitted to existing radiators with 8mm pipework. With natgas backup/hot water boiler. At the end of this month I intend to go back and correlate the bills against the previous year (both kWh and £), because like a lot of discussion in this thread I think the installers have made some poor decisions. There's too much poorly insulated external pipework.

If it's of any help in your battle with your installers the relevant part of the building regulations for external pipework is section 4.26 of approved document L: https://assets.publishing.service.gov.uk/government/uploads/...

The table in there assumes pretty high quality insulation and the neoprene-looking stuff doesn't meet that standard so would have to be thicker. Note that the way the performance of pipe insulation varies non-linearly with the pipe and insulation radius so it's a bit unintuitive.

How do I know? I had the same problem with my installers.

I have this outdoor unit https://cooperandhunter.us/product/ch-hyp36lcuo. This past winter the temperature dipped into -20C (-11F), had no issues maintaining temperature in the low 70s in the house. I was running them in heat pump only mode (resistive strips were not used).

In the summer our temperature regularly reaches into 90s (above 30C) and the house is very comfortable on those days as well with the same heat pumps

your heat pump is sized correctly for your house.

Hmm, that's interesting, we have fairly large temperature swings (typically -15 C in the winter to 40 C in the summer), so it'd be interesting to see if the heat pump could replace the AC unit and the gas heating.

They work okay in my area for -1C to 46C, imagine for your range maybe you just get a model that has improved heating over a basic one, whether that means ground source, more stages, or a heating element.

I'm in a similar zone and replaced (delivered) propane with a ground source heat pump 2 years ago. Constant temperature indoors (3C warmer in summer than winter) with plenty of AC capacity to spare. Breakeven is about 5 or 6 years.

What are the following specs for your unit?

SEER2

HSPF

BTU

Feel free to post the model #’s as well.

Reply on news.ycombinator.com