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

[mpooley]

Hi
I have been asked to supply a 40amp and a 32 amp connection
for an air source heat pump. Both these supplies will run motors
32amp is outside fan and 40 for the Heat Pump.

I have a 100 amp single phase supply to my house will I have a problem when the motors start ? and do I need to ask my network supplier for permission to this please?

Thanks for any advice

Mike

 

[westie101]

Yes it is best to as the starting current could interfere with other supplies

 

[JohnD]

a 32Amp fan?

what does that do?

 

[bernardgreen]

The fan moves the source air ( outside air ) over the evaporator ( cold ) coils and in damp weather these coils can become iced up. Some systems have heaters to melt that ice so some of the 32 amps will be for these heaters.

 

[bhm1712]

according to the energy savings trust and reading between the lines, air source heat pumps are about the biggest waste of money possible in terms of trying to go green and cut costs.

However, the EST's recent trials of over 5000 systems found only 13% of air source heat pumps tested reached the level of a 'well-performing' system, with many systems appearing to be installed incorrectly, and by a competent installer.

 

[mpooley]

according to the energy savings trust and reading between the lines, air source heat pumps are about the biggest waste of money possible in terms of trying to go green and cut costs.

However, the EST's recent trials of over 5000 systems found only 13% of air source heat pumps tested reached the level of a 'well-performing' system, with many systems appearing to be installed incorrectly, and by a competent installer.

I have heard of this report but think it's out of date there are others who think that an ASHP's have improved a lot.
can you give me a link to that report please I have googled it but can't find it

westie101 thanks I will give them a ring

 

[markocosic]

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.

 

[mpooley]

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

 

[markocosic]

You will achieve a COP of 4.5 (seasonally adjusted) with a best-practice space heating installation in a UK climate using 2010 technology.

COP 3.5 seasonally adjusted is "ok" for space heating, but much less than that and the specifier/installer is a moron.

Hot water provision is more problematic, as the higher temperatures required (flow >65C to meet legionella control requirements) murder the efficiency of the heat pump. I'd consider using solar thermal and retaining oil or LPG for your hot water as it'll be cheaper to specify/install/maintain/run. (ie, heat pump for space heat only, with a standalone hot water system)

The EST report on heat pumps was written by AEA Technology IIRC (bunch of consultants who know nothing of heat pumps) and failed to investigate or hypothesise as to why almost all the installations they looked at were rubbish.

 

[JohnD]

was that the report on alternative energy sources that was done by the Nuclear industry, and carried the message "nuclear is good, everything else, bad?"

coincidence.

 

[markocosic]

No. The EST report wasn't particularly biased, just not particularly useful. Stated the results of the field trials without attempting to explain them.

If you think a little more rationally about it, the nuclear industry ought to be *pro* heat pumps.

AEA Consultancy was split (made redundant) years ago to jettison the pension liability, and (effectively) went bankrupt/sold itself to Ricardo late last year.

 

[mpooley]

You will achieve a COP of 4.5 (seasonally adjusted) with a best-practice space heating installation in a UK climate using 2010 technology.

COP 3.5 seasonally adjusted is "ok" for space heating, but much less than that and the specifier/installer is a moron.

Hot water provision is more problematic, as the higher temperatures required (flow >65C to meet legionella control requirements) murder the efficiency of the heat pump. I'd consider using solar thermal and retaining oil or LPG for your hot water as it'll be cheaper to specify/install/maintain/run. (ie, heat pump for space heat only, with a standalone hot water system)

The EST report on heat pumps was written by AEA Technology IIRC (bunch of consultants who know nothing of heat pumps) and failed to investigate or hypothesise as to why almost all the installations they looked at were rubbish.

I have never heard that argument for keeping my oil boiler.
I was thinking of keeping it anyway and switching over to it at below zero temps ie. a bivalent system.
But thinking about it your idea sounds good. I could even keep my old HW cylinder! ah but would the heat pump be more efficient for just Hot water in the summer than the oil?

Mike

 

[bernardgreen]

Subject to approval from building regs you could pull the exhaust from the boiler flue through the evaporator of the heat pump to recover all the otherwise wasted heat from the oil. Though contamination of the evaporator surfaces with carbon from the flue could be a big negative to this idea.

 

[markocosic]

In the summer the solar thermal will supply 100% of the hot water anyhow.

Heat pumps are a little like car engines - good efficiency at say 70% load, but rubbish efficiency at 20% load and at 100% load.

Cheap and nasty systems use single compressors and throttle them for modulation. The efficiency of the throttled compressors is pretty awful.

Good systems use multiple compressors and step-modulate, running X of them at maximum efficiency loading. (short cycling where required)

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.

A heat pump won't be more efficient than oil if you're using it for hot water. The output temperature is too high - you need an output temperature of 35C or less for the heat pump to really shine.

A competent engineer will advise you about all of this and more though. Most aren't, and oil is cheaper than a heat pump fitted by a moron.

 

[mpooley]

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

when you say 'Good systems use multiple compressors and step-modulate, running X of them at maximum efficiency loading.

could you point me in the direction of one please? I have not seen any like that except the HT daikin with a 2 step compressor that produces high temps and is said to be inefficient.

thanks