air source heat pumps

[surreysparks]

I have a new house to wire where an air source heat pump is being installed for the heating and hot water. The builder tells me it just requires a standard outside socket by the main unit and that is all ! Has anyone wired one of these units ? Any information would be very helpfull

 

[ban-all-sheds]

Sounds very unlikely that a 3kW device could provide heating and hot water for an entire house, even with a quality high-COP one.

I wonder why, with a new build, and all the groundworks being done, they didn't go for a GSHP?

When he says "standard outside socket" maybe he means a 60309?

But in any event, why on earth would you want to have the thing plugged in, whatever current it draws?

There is an aircon guy here - b****ed if I can remember who.

Why not get the specs of the actual kit, see what the load is, and the recommended OPD (might well be a Type C), and see if you can check with the guy who'll be installing it what he will expect to be provided. The builder probably knows less about installing refrigeration systems than he does electrics....

 

[ColJack]

I used to wire the big industial ones in the factory, but that doesn't really help with installing the little ones in a house does it..

I'd wire to an external rotary isolator and fuse it properly at the board..
I suggest either installing 25mm conduit to it, or running a 6mm feed to it for when they realise / decide they want a bigger unit..

 

[1john]

I cannot directly help you sorry, but i can advise you to contact the unit manufacturer for information, and NOT the builder. An external socket is asking for trouble, kids / vandals or idiots unplugging the unit!

 

[ColJack]

I cannot directly help you sorry, but i can advise you to contact the unit manufacturer for information, and NOT the builder. An external socket is asking for trouble, kids / vandals or idiots unplugging the unit!

makes it a lot easier for the gypo's to nick it too..

 

[Corgigrouch]

As already stated, a rotary isolator of suitable capacity seems to be a reasonable means of connection and isolation... Potential headaches can arise if the heat pump is an inverter rather than a simple capacitor start motor as the inverter boards can cause RCDs to trip, so provision should be made for the cable to be run in a way that allows an RCD not to be used..

 

[Stoday]

Sounds very unlikely that a 3kW device could provide heating and hot water for an entire house, even with a quality high-COP one.

I wonder why, with a new build, and all the groundworks being done, they didn't go for a GSHP?

I think the 3kW is the input, so the output would be ~10kW, plenty for a house that complies with the current part L.

As for GSHP, there's plenty of development behind an air source heat pump since that's the basis for air conditioning. Very little behind ground source so much riskier.

 

[ban-all-sheds]

A COP of 3.3 for an ASHP in the dead of winter when they need the heating the most.

OK

 

[Corgigrouch]

It is always advisable to have a back up for any heat pump be it electric, oil or gas.... COPs are a great marketing tool. As BAS has stated, the COP stated will not apply in Winter and Air source suffers most from variations in the weather. Unfortunately not everyone has the land for ground source or pockets deep enough to drill a borehole or three.

Never fit heat pumps as your only source of heating or you could wake up very disappointed...And cold

 

[ColJack]

bear in mind that they're likely to be installing underfloor heating which requires a much lower water temp than rads to maintain a comfortable room temperature.

electric backup for water heating ( immersion ) leaves only the heating to do..

as said, the cost of an air source heat pump is pretty much the unit itself plus whatever pipes and such are needed, a ground source requires digging and sand etc so adds to the cost a lot more..

 

[Corgigrouch]

Electric back up is an expensive way to heat water... Even with the lower water temps for UFH the energy required is the same to heat any given area.. The COP can only serve as a benchmark to allow comparisons between various makes of equipment. Unfortunately far too many folk see the stated COP, look at the input and automatically draw the conclusion that the output of the equipment will be constant when the truth is that the COP can drop to the region of 1 in cold weather... In fact when the equipment goes into defrost mode, the compressor is running to deice the evaporator without heating any water.... The more humidity in the air the more often the defrost mode is required..

Having said all this, I would hazard a guess that heat pumps will do a sterling job for 90% of the year in Britain.... It can just come as a nasty shock when we have a Winter just gone so back up is always advisable..