adding an airsource heat pump, supply problems

[Robertbaker63]

i am wiring a new build property for a private customer, im just on a labour only quote to do power and lighting circuits

there is an external firm doing the heating system which includes an air source heat pump and a 3.68kw solar system


they have asked me for my maximum demand so they can put their j forms in

i have a 7kw hob, 2 3kw ovens, then normal kitchen appliances, eg. fridge, tumble dryer, washing machine, dishwasher.
the rest of the house contains 76 jcc led7 downlights and 3 ring circuits

i have given them a figure of 84 amps for maximum demand


they then have sent the customer this email

[FONT=&quot][/FONT]
[FONT=&quot]Have now heard back from both Vaughan and Rob Baker on my queries.[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]I have had a set of revised full loadings from Rob Baker, giving an increased total load of 84.5 amps for his work only, this equates to 19.4kVa. [/FONT]
[FONT=&quot]Vaughan has indicated the transformer is only rated to 16KVa which means even without the heat pump the current supply would not be adequate.[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]Based on the original information supplied and submitted on the J Form of 16.2 kW the existing transformer would have been ok for connection of the heat pump.[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]In a normal series of events, the electrical contractor would submit full loadings for all of the equipment for the property – on this occasion we have incorporated Rob’s information with ours to try and push things along. [/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]We normally only provide a J form with the heat pump data which is then submitted by the customer/electrical contractor in conjunction with their loadings. As the heat pump installer we would have no prior knowledge of the buildings electrical requirements or its existing supply.[/FONT]
[FONT=&quot]




where do i stand. can i alter my maximum demand figures?

the customer has been given a figure of £6000 to upgrade the supply by the supply authority which is he refusing to pay

the job is now on halt as the customer believes the renewable energy company should of made them aware of this at an earlier stage which would of affected their decision to go with an air source heat pump over a traditional oil boiler

the details of what they are installing is as follows - Daikin Europe NV Model ERLQ014CAV3 (outdoor unit) EHBH16CA3V (indoor unit including 3 kW backup heater) EKHWSU*B3V3 (hot water cylinder including 3kW booster heater) Maximum Electrical Demand1 ERLQ014CAV3: 34.2 A EHBH16CA3V: 13 A (backup heater) EKHWSU*B3V3: 13A (booster heater) pkW/nA
[/FONT]

 

[telectrix]

what's the supply fuse rating?

 

[Robertbaker63]

what's the supply fuse rating?

at the moment there isn't a supply to the house, just a temporary site supply in a box outside. the supply used to supply a 3 bed bungalow before it was knocked down.

to reinstate the existing electrical supply to the new house is only £400 which is what the customer had budgeted for.

 

[telectrix]

so, basically, what we have is a customer who's spending maybe 150K + on a new build but is griping about paying for a supply adequate for his needs. a bit like the new 5K kitchen supplied from a 1970's 3036 fuse board.

 

[Robertbaker63]

Yes of course they are but its not a factor they budgeted for neither do they have the budget for as most self builds are done very tightly. my quote for labour only was £2400 although the materials have been £7000

my opinion is the renewable energy company should of checked the existing supply before quoting and first fixing the system

could someone back me up on my maximum demand figures, are they realistic

 

[telectrix]

i'd be a bit lower, allowing for diversity. say 65A, unless you've forgotten to mention a couple of 10kW showers. LOL.

 

[Robertbaker63]

i'd be a bit lower, allowing for diversity. say 65A, unless you've forgotten to mention a couple of 10kW showers. LOL.

how would i say i achieved that figure for maximum demand as doing it the proper way or any other rule of thumb way actually achieves higher than my 84 amps

 

[Richard Burns]

The information you have given from Rob Baker only shows 64A, your house supply will not rise above 60A in all likelihood at any time.
The air source heat pump seems murderously inefficient if it is only managing to supply about 50% of the heat from the air source they should be at about 3-5 times the power input and have a supply requirement of say 16A at max this would then (assuming all the back ups and boosters were required to run at the same time) give about 40A total

 

[Richard Burns]

Just thought a bit more and since you only have a 60A supply you could well be up against it there.

Even if you said the house was roughly (realistically) 40A and the air source was unlikely to need the back ups you would be on a total demand of about 60A and that would be pushing the limits of diversity for a formal declaration.

 

[Robertbaker63]

thank you. i shall go back to the customer with a revised maximum demand figure and see if i can obtain some more details from the customer about the size of the cutout western power can supply


in normal circumstances at what point should the renewable energy firm of submitted the proposal for an air source heat pump to the supply company. the customer is concerned that this additional cost should of been explained at the point of accepting the quotation and not at the end of the job

 

[Richard Burns]

I would expect the quotation may well have said "subject to suitable supply available", however a good company would have assessed the likely demand for their equipment in the same way as any electrician installing say a new shower would check if the supply was up to it and included this cost /caveat in their quote.
It certainly should not be discovered after first fix, but there is the consideration that there was no supply available to assess.

 

[Engineer54]

The information you have given from Rob Baker only shows 64A, your house supply will not rise above 60A in all likelihood at any time.
The air source heat pump seems murderously inefficient if it is only managing to supply about 50% of the heat from the air source they should be at about 3-5 times the power input and have a supply requirement of say 16A at max this would then (assuming all the back ups and boosters were required to run at the same time) give about 40A total

Never come across any of these fancy heating pump systems actually save money, come across plenty that have increased heating costs though!!

 

[Rockingit]

Never come across any of these fancy heating pump systems actually save money, come across plenty that have increased heating costs though!!

I've done quite a few GSHP and ASHP systems in the last couple of years, and it does all seem to be smoke and mirrors when inside the box is basically just a series of 2 & 3kW immersion elements waiting to kick in on 'back up'.

As to the OP, well the worst ones of these that I've done was a 12kW GSHP to a large property with lots of outbuildings, the DNO TX was 16KVA, incoming fuse was 80A and the official max demand calculation after all diversities had been allowed for was about 220A if I remember right. It ran, it ran fine, and at no point did I ever see my clamp meter get over about 40A's in a dry test. Ironically, however, the DNO DID have to come and replace the TX to a 22KVA one as even under a no-load situation it was suffering from brown-out badly which was very noticeable with all the LED lighting. What I mean by that, btw, is that having disconnected every circuit at the primary board except for one solitary 13A plug-top - so we're in effect tails > 13A - and then using a 1200W power tool as a test load with an analogue meter across the voltage, when you gunned the tool the meter dropped way below 215V which clearly wasn't right!!

Subsequent to all of my installation, they had a 4KW PV system added last year to no ill effect either.

 

[JD6400]

I have been involved in between 25 - 30 ASHP - GSHP installs over the last 8 years or so , and I would not touch them with a barge pole personally .
I would say that GSHP is the best of a poor choice to be honest , but still seems to need what seems to be endless maintenance and replacement parts , from what I have seen of them after around 5 years of service .

I have also seen two new upgraded supplies being needed after they have been turned on , only to blow the main fuse after a short time !

One was on a job we were not involved with and the other one was as a result of the so called mechanical / electrical engineer rather rudely and some what condescendingly questioning my ability to basically add up , and then ignoring our concerns !
That one needed nearly two and a half miles of new cable being laid at a knock down cost of I think around £70k , and to boot they paid the ----er for his flawed advise as well !?

 

[Knobhead]

If you use the forum search there’s a good thread about this. I can’t remember the outcome but it did get messy with the heat pump guys and the DNO.