Do I need to ask DNO if I am installing air source heat pump

[markocosic]

The engineer will specify multiple smaller pumps and run them in parallel. A 16 kw compressor would be part of a 50 kw total installation. You might use 4,4,4,2 or 8,4,4 on a lower output system. Look at the graphs of cop vs load and source temps for a given output temp and choose operating points accordingly.

 

[mpooley]

The engineer will specify multiple smaller pumps and run them in parallel. A 16 kw compressor would be part of a 50 kw total installation. You might use 4,4,4,2 or 8,4,4 on a lower output system. Look at the graphs of cop vs load and source temps for a given output temp and choose operating points accordingly.

ah! I see thanks

 

[markocosic]

I appreciate it wasn't the original question, but it is worth asking "does this make economic sense?" and "does the person I trust to answer that and specify the system have a clue?" bat some point!

Personally I'd retain the oil system regardless, in the same way I keep a fan heater in the cupboard and a bottled LPG heater in the garage for the day the gas heating packs in. It isn't expensive to "have kicking around" if you've got space, only expensive to run.

 

[ban-all-sheds]

I cant have solar hot water as my roof is full up of PV!

Really?

Generating much at the moment, is it?

 

[mpooley]

I cant have solar hot water as my roof is full up of PV!

Really?

Generating much at the moment, is it?

Yes roof is full and although not generating much at the moment that's expected in February.
Had it for three years now and overall I am getting much more generated than the producers predictions thank you

 

[ban-all-sheds]

But isn't February one of the times when you need more electricity, not less?

 

[ban-all-sheds]

Regardless of the system, there comes a point where the COP drops to the point it is cheaper to burn fossil fuel. There's also the catch that if you size the system large enough to cope with maximum demand, it'll spend more time at part-load/short cycling that a system sized for "most of the time" plus a backup heat source, and the COP will suffer. It's therefore usually more economic to size the heat pump for most of the year's heat needs, then revert to oil/bottled gas for when it's really frickin' cold outside.

But what if what you really want is air conditioning, and you call it an air source heat pump to greenwash it?

 

[markocosic]

You can, but you won't get the RHI subsidy.

Most domestic ashps are indeed just that though. An a/c system with a new mcs accredited sticker. Notice the complete absence of even manufacturer certified performance numbers on the daikin case studies, let alone independent verification...

Would it be because they're gobshite perchance?

(nothing inherently wrong with the component parts; just badly packaged and controlled)

 

[SilentDancer]

ASHPs were always good.

Domestic / light commercial UK installers are the problem: MCS accreditation means diddly squat about competency...

Most gas fitters also haven't got a clue how to design a heating system, but gas boilers are far more forgiving of bad system specification/design than heat pumps.

What are the nameplate rating of the heat pump? Type C MCB for the compressor? Outside fan won't need the full 32A unless heaters are in use, and they're a fairly friendly resistive load.

From what I have read I think you are right. Poor installations are the main culprit.

I have done a lot of research and have a friendly installer on another forum who has given lots of free advice so I'm as confident as I can be that the system will work ok. I'm not expecting COP's of 5 ! lol in fact even at COP's of 2 it is cheaper to run than Oil.

I haven't got the pump yet so can't read the faceplate but it's a Daikin Altherma single phase 16kw system that I'm thinking of fitting.
Thanks

You need a COP of at least 2.7 to be cheaper than oil.

 

[SilentDancer]

Re the original question the current draw tends to be largest at start up. Try and go for a heat pump with soft start to avoid problems.

 

[bernardgreen]

I cant have solar hot water as my roof is full up of PV

Out of interest do you own the PV panels or have you rented out your roof and the PV panels are owned by generation company who supply you with free electricity and profit from the subsidies.