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Topic Title: Heat Pump
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Created On: 01 December 2017 03:40 PM
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 01 December 2017 03:40 PM
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goldenboy1818

Posts: 816
Joined: 22 February 2011

Hi guys hope evryone is well. I have a issue which id be after some advice for please. I have been doing these new build houses, and now on a new one there is a change and something iv not covered before. They want to put in air source heat pumps. Now in the others we have standard system boilers, and underfloor heating througghout, three storey house with a manifold on each floor. Now with a heat pump what do i need to do, i heard i need bigger supplies, also how to i link this together with the underfloor heating as that will be a different circuit and will cause some tripping out if ciruits link in with each other. Really appreciate any help guys, thanks again
 01 December 2017 05:47 PM
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Fm

Posts: 1743
Joined: 24 August 2011

Get the heat pump installer to provide a diagram so you connect as per their drawing
 01 December 2017 06:45 PM
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alancapon

Posts: 6937
Joined: 27 December 2005

I agree. For a sizeable heat pump you could be into a three phase supply.

Regards,

Alan.
 01 December 2017 06:53 PM
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broadgage

Posts: 2449
Joined: 07 August 2007

A whole house heat pump usually has a loading of at least 5KW and often a lot more.
I saw one that was 18KW!
Remember that a typical gas boiler has an output of over 20KW, for a heat pump to equal that it needs an input of at least 10KW at a COP of 2.
Much of the time the COP should exceed 2, but the unit and therefore the power supply need to be sized for cold weather.

And yes, the larger ones often need a three phase supply.
 01 December 2017 07:00 PM
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broadgage

Posts: 2449
Joined: 07 August 2007

Arrangements regarding the underfloor heating need clarification.

Is the heat pump in addition to the underfloor heating ? Or is the heat pump to provide underfloor heating via warm water pipes.

Heat pumps do not always give satisfaction especially if poorly designed, improperly installed, or wrongly specified.
If I was in your position, I would try not to be involved beyond running a circuit of the required capacity to the correct place.

When the mud flinging starts, you do not want any to stick to you!
 02 December 2017 04:12 AM
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leckie

Posts: 4439
Joined: 21 November 2008

http://heating.mitsubishielect...20No%20%20233837).pdf

Obviously a bit more information is required GB. If you are talking about a small 3 bedroom house then Ecodan are quite common, see the link above, and the supply will be 25-40A single phase. So find out the make and model and let us know.

Basically you have a supply to the cylinder cupboard and a link cable to the external unit, like an AC unit. Then there are various season sorts that have to be connected into a control panel, and thermostats. The underfloor heating will have its own control panel, a heatmiser unit or similar. This will need a 230v power supply and a link cable to the ASHP control panel. You need a wiring diagram from the ASHP installer and from the UFH installer, and details of the interconnection. There will also be a booster heater, probably and immersion heater, that also links to the control panel. This is used when the ASHP cannot cope with the demand, and is usually the reason for high bills! Now, as you have underfloor heating, this makes me suspect it might be a larger property, then we might be talking 3-phase. So you need to find out.

Now a bit of advice, don't let them just give you the basic manuals and tell you to sort it out yourself, ask for a full installation wiring diagram showing all the control wiring requirements. Do not get involved in any commissioning or set up of the system! This needs doing by someone with full training for the system.

I have fitted the wiring for hundreds of these systems and the main problem is when they are set up wrong or when the householder alters the programming. An ASHP cannot deliver really hot water like a gas boiler can. I can't remember the temperature now, but let's say it is 45 degrees. The heating system will use larger than standard radiators to compensate for the lower surface temperature. In the case of UFH, the whole floor is a heater so it only requires a low temperature. For the hot water, the design is for a larger than standard cylinder to store a greater amount of hot water. Because it is at a lower temperature and doesn't get mixed with as much cold water - so you need more of it!

The problems are often when people set the cylinder thermostat too high, say 55 degrees. The control panel knows this temperature is not being met by the ASHP via a sensor, so it demands additional power from the back-up heater, an electric immersion heater. This might be a standard 3kW immersion heater, or something much bigger in a larger system. That cost big bucks, so the system needs designing and setting up so that this only occurs in exceptional circumstances. Often the occupants do not understand that the surface temperature of radiators, or water coming out of a tap is supposed to be lower than with other systems, and try fiddling with thermostats an the set up gets ruined. Then there are complaints of high bills.

If it's a one off, ask what supplies are required and insist the final control wiring is done by others, if it's a whole site then insist on full support for the system wiring, and commissioning by others.
 03 December 2017 11:30 PM
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stateit

Posts: 2682
Joined: 15 April 2005

You should be given the full wiring schematic by the designer.

Remember that the design fee also includes support. They know people have to start somewhere and are used to getting questions from both the plumbers and sparks.

If you've not done many factor in a bit of time for it. I've done a few smaller (3, 4 manifold systems) but just spent two days doing all the wiring in the outside plant room for a 7 manifold one, what with getting the SWA feeds in as well . Relays needed for each different circuit used, lots of isolation switches. That two days didn't include the time for the wiring of the 17 thermostats back to the manifolds.

Make sure you know what stats have been specified as well. Some want 4/5-core & E back to the manifold, others just 3-C & E (plus the LNE in).

I wish I had the spare ackers to install a solar loop and ASHP in my home. Having said that I wish I had the spare ackers to buy a big enough home to warrant it.

-------------------------
S George
http://www.sg-electrical.com
 06 December 2017 05:29 PM
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goldenboy1818

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Joined: 22 February 2011

Hi Guys thanks for all replies. Seems i need to provide some more information.

Been assured its definitely not powerful enough to warrant three phase. It runs alongside a U/H heating system which is hot water pipe system. Three storey house with a manifold on each floor.

In all the houses so far iv just run a heating circuit from the fuseboard to cover all three manifolds, boiler and wiring center etc. These houses dont have a heat pump, however this new one does and is confusing me as iv never done one before.

How will i tie in the power for the u/h with the heat pumps, do all the circuits from the heat pumps have to go on the same rcd ? as obviously il have dual rcd board, with a few different circuits for the heat pump ???

Thanks all
 06 December 2017 06:13 PM
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Weirdbeard2

Posts: 33
Joined: 29 November 2017

Originally posted by: goldenboy1818

Hi Guys thanks for all replies. Seems i need to provide some more information.

Been assured its definitely not powerful enough to warrant three phase.



Any further info available? The make and model of the proposed Air source heat pump might be helpful? There are probably wiring diagrams on their website for us to look up for you?
 06 December 2017 08:16 PM
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aligarjon

Posts: 3874
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Originally posted by: goldenboy1818

Hi Guys thanks for all replies. Seems i need to provide some more information.



Been assured its definitely not powerful enough to warrant three phase. It runs alongside a U/H heating system which is hot water pipe system. Three storey house with a manifold on each floor.



In all the houses so far iv just run a heating circuit from the fuseboard to cover all three manifolds, boiler and wiring center etc. These houses dont have a heat pump, however this new one does and is confusing me as iv never done one before.



How will i tie in the power for the u/h with the heat pumps, do all the circuits from the heat pumps have to go on the same rcd ? as obviously il have dual rcd board, with a few different circuits for the heat pump ???



Thanks all


Its a long time since i have done one but the recommendation on the one i did was to not use a 30m/a rcd.

Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 07 December 2017 10:13 AM
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AJJewsbury

Posts: 16095
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How will i tie in the power for the u/h with the heat pumps, do all the circuits from the heat pumps have to go on the same rcd ? as obviously il have dual rcd board, with a few different circuits for the heat pump ???

You need to ensure that each and every circuit is completely separate from every other one - regardless of whether it's on the same RCD or not (reg 314.4) - there's a very significant safety issue if there's any cross-connection, even just a shared N.

The UFH wiring centres I've used (heatmiser) have a volt-free contact for the 'boiler' call - so you just wire all of them together on the boiler (or in your case heatpump) control circuit without having any galvanic connection with the UFH control circuit. You just then need a warning label on the wiring centre saying that two separate circuits are present in the same box.

- Andy.
 07 December 2017 06:16 PM
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goldenboy1818

Posts: 816
Joined: 22 February 2011

Hi guys the Pump etc being fitted is the Alpha InnoTec LWD70ASX + HMD1

I have a basic diagram if anyone is happy for me to send them the picture
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