3-Phase installation

[Rad1o]

We are considering to replace our ancient gas boiler with a air-to-water heat pump. They sound good and reliable whereever you read, BUT some and in parrticular the one I have got my eye on, requires 3-phase power supply.
Our house is an old house with standard domestic supply and a split load fuse board. How much hassle and what cost would I be looking at - if there is anything like a standard figure - if I wanted to have 3-phase electrics installed?

 

[Taylortwocities]

I hope you have deep pockets.

Call your DNO, and ask.
It will probably mean a new cable to your house, a few thousand pounds would sort it out.

Better to find a single phase heat pump?

 

[flameport]

Get a new gas boiler.

3 phase will be expensive to install, assuming it is actually available at all.

 

[Steve]

As a very rough cost, BLOODY EXPENSIVE. More details required for anyone to say anywhere near. The DNO side of things is a monopoly unfortunately so their price is their price and it could be anything. How close to the road? Where does your supply come from now and what does it look like? Any businesses on the road likely to have 3 phase?

You can probably dig holes etc yourself to save money.

Don't forget you will need your main consumer unit replacing to handle the 3 phase supply. This might also cost up to £1000 including wiring your new heat pump.

 

[knowall]

I have been in a few properties which had a 3 phase cable head installed but only a single phase in use. Have you checked the supply before the meter.

Regards,

KA

 

[ringi]

If you got mains gas, then I would not touch a heat pump.

If you are on a private gas tank, then a heat pump may make sense, but you will need new radiators or UFH to get the best out of it.

When my parents had their supply upgraded to two phase, the DNO did not charge them, however that was a long time ago, and it just needed a overhead cable adding to the existing post.

 

[JohnW2]

We are considering to replace our ancient gas boiler with a air-to-water heat pump. They sound good and reliable whereever you read, BUT some and in parrticular the one I have got my eye on, requires 3-phase power supply.

Something here doesn't seem to add up - can't you move your eyes to one which doesn't require a 3-phase supply (which, as others have pointed out, would cost you dearly!)? I see no conceptual reason why such a pump should require a 3-phase supply and, indeed, it would basically be daft to try to sell one for domestic use which did require a 3-phase supply (since virtually no domestic customers would buy it). If the reason for 'needing' a 3-phase supply is because the power consumption is greater than what is usually available from a domestic single-phase supply, then I would very seriously doubt that you would get more energy out of the pump than you put into it!

Kind Regards, John

 

[Rad1o]

Thank you for the replies.
The 3-phase is for heat pumps that do heating in the winter and cooling in the summer - very nice idea - on a current radiator system.
Other pumps with lower KwH rating run on 1-phase.
Our radiators would be sufficient for heat pumps with 60° heat output.

... But I get the picture.

 

[JohnW2]

The 3-phase is for heat pumps that do heating in the winter and cooling in the summer - very nice idea - on a current radiator system. Other pumps with lower KwH rating run on 1-phase.

Yes, the pumps are in concept probably a good idea but, as I said, if you're talking about one which needs more electricity than can be supplied by a standard single-phase domestic supply, then I really can't see how the efficiency/cost sums are going to work!

Kind Regards, John

 

[ericmark]

It is possible to get 3 phase from a single phase supply the question is it three phase because of the type of motors used or because of the kW requirement.

In the main we have between a 60 and 100 amp supply 13.8kW to 23kW out consumer units are only rated at 100A so if we want more then we need two or more supply fuses these could be yours so a 160A supply into a fuse box and two 100A fuses feeding to consumer units could give you more power without going to three phase. In some areas we have split phase 230 - 0 - 230 volt inverters can convert this to three phase but as others have said likely it would cost that much that it will never pay for it's self.

Cooling in summer sounds good but for the radiators to adsorb the heat the air would need force circulating with something like the Myson radiator floor mounted radiators would not work as heat rises so cooling devices at ceiling hight heating devices at floor height so fan is required.

For cooling main thing is not to heat the house so all LED lighting and induction hob for cooking fridge and freezer on outside wall with vents top and bottom so heat removed from food goes outside not inside. Thermostatic fans which ventilate when outside is cooler but stop once day heats up and with that likely you would not need an AC in UK.

No one has a crystal ball to tell us what fuel prices will be in the future but if you have gas than heat pumps are really a non starter.

 

[bernardgreen]

Cooling by circulating cold water round central heating radiators will cause the radiators to become wet with condensation and possibly puddles underneath them.

Use a SMALL heat pump to cool in summer with air drawn through heat exchangers that will collect the condensing water vapour. It can dump the recovered heat into the bottom of the hot water tank ( bottom as that is where the coldest water is ) or a pre-heat tank that feeds the hot water tank.

Best option is to stay with gas for heating ( avoid combi boilers and use a heat only with hot water tank ) Combi's are easy to install but a pain to service and when in the shower be ready for a cold spell when a hot water tap is turned on.

 

[ericmark]

bernardgreen makes a good point all AC output units have little pumps to pump away the condensate I remember a ceiling collapse due to one of the pipes coming off the condensate pump which gives one an idea of how much water is pumped out. Clearly all feed pipes to radiators will need lagging or these will also have condensate problems.

My Myson does not have a condensate tray or pump clearly would need to be a special model for use as AC with these extras installed.

So it would mean ripping out all old radiators and pipe work and fitting all new clearly rather an expensive undertaking.

 

[Rad1o]

And there goes another not fully thought through idea. I did think about the circulating problem but not about the fact that the warm air can take up so much more moisture which will then condensate on cold surfaces.

I am only at the quoting stage, so do not have a plan yet re. which heat pump I would want to use. The 3-phase is not for the sheer power consumption but for the motor.

 

[Taylortwocities]

Quoting, or costing?
This is a DIY forum.
If you are doing this job for somebody else, maybe you should be asking the help desk of your scheme provider?

 

[JohnW2]

Quoting, or costing? This is a DIY forum. If you are doing this job for somebody else, maybe you should be asking the help desk of your scheme provider?

We are considering to replace our ancient gas boiler with a air-to-water heat pump. ... Our house is an old house with standard domestic supply and a split load fuse board.

I know one shouldn't assume, but that language seems reasonably clear.

Kind Regards, John