Heat pumps and noise

[transam]

Ripped out an air source heat pump yesterday

2nd one we have taken out in the last 2 months

Also in the new year a land lord we do a lot of work for is considering taking out 4 in his new build rentals ????

( new build 7 years old )

 

[Rad1o]

And back to the original question after all this rant.

We have a heat pump outside our bedroom window - about 2m into the garden. We hear a faint humming noise even when it is working hard, e.g. when it was -9°C in January. The neighbours do not even know that we have a heat pump. What we do hear is the flow through the pipes as the installer did not bury them into the ground but bracketed them onto the outside walls.
Our house has 15mm pipework, but some new builds have 7 and 8mm pipes with heat pumps.

If you have an poorly insulated house, a heat pump will probably not work well as the temperature gradient / heat loss is quite steep. Insulate your walls first. This is also a bliss for the summers.

 

[robinbanks]

Genuine question. If there was a cold period with temperature at -10 for a week (it happened in 2011/12), how would the ashp system fare?

Fine. 0 degrees is not a magic number to an ASHP; the air still has useful heat energy they can extract. The lower limit is determined by the characteristics of the refrigerant, not water, and any water in the system should have antifreeze added. Any air temperature capable of warming the tefrigerant up can have heat extracted - the cycle they run is:

Compressor compresses gas, heating it
Extra heat is extracted to water
Cold compressed gas is expanded, cooling it
Air is used to warm the expanded gas, heating it, and cooling the air (extracting heat energy from the air)

If the gas is at -30 when it is cold compressed, air at -10 will warm the gas up

--

The efficiency lowers as the temperature drops and you do theoretically reach a point with very low air temperatures and high flow temperatures where a pump is little better than a resistive heater as the efficiency approaches 1 (uses 1 kw of electrical energy to produce 1kw of heat)
Some pumps have resistive heaters built in or can control an aux one

Ripped out an air source heat pump yesterday

2nd one we have taken out in the last 2 months

Also in the new year a land lord we do a lot of work for is considering taking out 4 in his new build rentals ????

( new build 7 years old )

Dare say was mis sold, the system was badly designed and the house was suboptimal.

That it's new means nothing; bad design, shoddy build and ignorant occupants are plentiful in supply and all that's required to make a low level heating system unworkable

You post doesn't contain enough useful facts to be anything more than anecdotal scaremongering/bluster but if you're ripping anything then you're just being a fool about it; remove it carefully, because someone out there willing to put the effort in to make it useful and viable will pay good money for that install second hand

 

[mitch66]

Why would anyone want to spend £12k (5k with the grant ) to save £100 per year

Cos they're mugs. Better still they buy solar, batteries and have a smart meter. Then they can up send at 6p a KWH to there neighbour who pay the grid 50p a KWH for it. They also get a chance to show their virtue to other mugs who give a crap about it.