Air heat source pumps

[driverman]

Hi Guys, soon be wiring for an air heat source pump which is to be sited outside a detached double garage with a studio flat above. I need to determine the overall load that will be required to determine size of sub main to be installed. At this point in time I've no info from the owner about the heat source pump apart from that it may be a 12 kW model. I know nothing about these pumps...Would 12kW be the output? It is a large house. Scrolling through some older threads, it would appear that a 40amp MCB required.
Seems a very high requirement if pulling that amount of load. Thought it was to make running cost a great deal lower.
Your thoughts appreciated

 

[rapparee]

you cannot guess this, it could be 3P even that turns up. They are so many different ones. I would wait until the client has got written specs from the installer and has ordered against a specification before considering a supply. But if he only has Sp at the property you may want to at least steer him in that direction.

I pmed him the dimplex product range there is technical info on the website for each hp

 

[stimpy]

Whilst i do thoroughly recommend getting specs before installing, 95% of domestic ASHP installs are single phase and will require a 40A supply or less, then your immersion 16A, then your controls feed/booster immersion (16A) dependant on type.

Worst case throw a 10mm from the DB to an exterior isolator, and 2 x 2.5mm radials to cylinder cupboard. Then for most popular ASHP you need a 2 core max 1.5mm from controls to hp.

 

[driverman]

I pmed him the dimplex product range there is technical info on the website for each hp

thanks for info...................I'll read it properly when I get home tonight. The unit is a 16kW low temp Panasonic. Are the Imm/Htrs interlinked in any way to the ASHP? The ASHP is to be sited by detached garage, so will be wired via sub main from house. All controls /valves etc are to sited in the house.

 

[rapparee]

thanks for info...................I'll read it properly when I get home tonight. The unit is a 16kW low temp Panasonic. Are the Imm/Htrs interlinked in any way to the ASHP? The ASHP is to be sited by detached garage, so will be wired via sub main from house. All controls /valves etc are to sited in the house.

There should be a seperate 16a circuit for immersion heater fed thrpugh a contactor which is pulled in by the heat pump control panel when required, it is usually called in when it gets down to -10°c . The heat pumps are very slow it is not like oil burners where you get home at 5 stick on heating and house is roastong 2 hours later. They won't work with conventional radiators, they are more suited to underfloor heating or smart rads with inbuilt fans to throw out heat as the smart rads only get up to lukewarm

 

[Gavin A]

Well I've done 8 so far this year, across two different DNO's, and no they don't. Why would they?? There are some GSHP's that do, due to the compressors in them, but not ASHP fans - they're little more than AC units wired backwards!!

the DNO's say otherwise.

ENA - Heat Pumps

Application form A with a 5 day turnaround for domestic heat pumps.

That 16kW Panasonic heat pump would be likely to draw 5kW or so continuous for 18-24 hours in winter, and will almost certainly be on during peak morning and evening consumption, and probably a fair amount more peak start up current (though not too bad as they're inverter driven).

Multiply that by several houses on the street potentially doing the same thing, and it's not hard to see why they could easily cause problems for the local transformer and grid voltage levels at times of peak consumption. It's not like an electric shower or something, which will only be on for a short period.

Though I did think the DNO engineer was taking the **** when he tried to say we should have made an application in advance of a little 5kW unit (1.5kW electrical input)

 

[driverman]

Re DNO's. When i worked for a particular DNO doing Service alterations for customers supplies when building extensions , alterations etc, one of he questions that had to asked was, are they increasing the load and or installing ASHP / GSHP Heat pumps.
One particular job that I was involved in, an AHSP was required but an electric shower was being removed. The DNO (my bosses) refused permission. The house was over head supplied, end of line and in the middle of nowhere. Customer complained several times but was still refused due to the impact the ASHP would have on the network.
However, the DNO called WPD took over the DNO that I worked for, and granted permission straight away!

 

[Rockingit]

Given that the old school working for DNO's was a 100A cut out for a house with electric heating and 80A for one without, it's all complete piddle if you ask me.

If a DNO winges that's all it is, and just a reflection on their own lack of investment in the infrastructure. I mostly only deal with WPD, maybe that's where I've been lucky.