Question about upgrading to 3 phase

[Geoff Toms]

Hi. Ordinary domestic property. Single phase supply 100A fuse. We're planning to move away from gas and to electric. First, replacing the old gas boiler with an electric one, then the gas hob with an induction one. Conversations with our supplier indicate we're going to need to upgrade to 3 phase. I can see that we arrange with our supplier and UK Power Networks so that they coordinate their work and we aren't left without power. The question that's puzzling me is whether we should also coordinate having an electrician here at the same time to do the internal work, replacing the consumer unit etc.? Is that the way it works, or do the guys doing the work outside leave you with a working system, and you can get the internal work done afterwards?

 

[monkey5]

Depends on the situation, I've done it both ways, installed all the 3 phase DB beforehand with 3 phases then linked until change over day and also done it where they have changed the service head and meter and just feeding the old board phone 1 phase before I go and did the work. I'd speak to an/the electrician and see how they prefer to do it or what their workload permits with your timescales etc. Sometimes the 3 phase meter can hold time up so you need to make sure all is available, eon I think it was ran out at one point last year for a new build I was doing!

 

[monkey5]

I'd also want to be there or available locally on change over day

 

[Geoff Toms]

Thanks very much for the swift reply! That was something I hadn't considered - that the DB could be changed over ahead of time. Do you mean that a 3 phase DB will work with a 1 phase supply? And as you said you would need to be around on the change-over day too. I bet there's some rewiring you would have to do on the day itself?
I'm just wondering how I'll be able to arrange for my local, trusted electrician and the grid people and the supply people to all be available on the same day!

 

[monkey5]

Where are you, there might be a member on here that might be available?
Yes the 3 phase DB can have a temp link between the phases so the one phase is feeding it all. Changing it all over on the same day could be a nightmare for an electrician, I like to have It prepared so I'm literally removing the temp link and connecting up to the new incoming Supply, all the testing then needed on the new bits and power is off for the minimal amount of time.
Have you had a price for a new 3 phase upgrade from the DNO. Can be a lot of money depending if there is a 3 phase supply near by, they may Need to dig roads/paths up before hand, you can always get your side ready with the ducting etc. Also bear in mind the meter cupboard you currently have will need to replaced for a larger one so you may also need a builder on the day too. Lots of things to get planned to work together and on the day will be so much easier.

 

[Geoff Toms]

Thanks again. We're in Hampshire, but I'll worry about getting someone a bit nearer the time. We are still at the start of the process. We haven't officially applied to go 3 phase yet (though we will very soon). We've been reading all about the digging involved, and the meter cupboard.
But thanks, really, for making it so clear to me. I can now see how you could set up the DB in advance, linking all 3 while it's a 1 phase, then undoing the link on the big change-over day.
I don't know whether we have 3 phase already out in our road. This house - and the whole estate - was built in the mid-90s. I'm hoping that means 3 phase is as near as the street outside, and the only digging they'll have to do is up the driveway. (I got some of those diagrams from safedigs.co.uk but it doesn't seem to answer whether the street cables are 1 phase or 3)

 

[monkey5]

It should be 3 phase in the street then being that new. If you look in your meter cupboard the colour phase maybe indicated on the service head,the neighbours should be a different colour and the next door but 1 another colour then next door but 2 the same as yours. Similar to this, or could be colours rather than L1,L2,L3

 

[Geoff Toms]

I wish our one was as clear as the one in your picture! Ours is just a black plastic box with cables running into it and no sticker with L1, L2 or L3, or colours. BUT, there is a circular red sticker beside it on the back board of the meter cupboard! If I'm optimistic, I'd say that means we were fed L1 of a 3 phase. (Or it could be someone just liked red circular sticky patches)
Thanks again for all your time. Now I really need to get my application in and find out how much they're going to ding us for this!! I'll get some heart meds at the ready.

 

[monkey5]

Red sticker a good sign, could you have a neb in the neighbours?

 

[Geoff Toms]

I'm not that cheeky (and he's got a security cam)
I'll ask them when I next see them.

 

[monkey5]

did mean with their permission.

 

[Murdoch]

Hampshire is a big county - roughly where?

 

[Geoff Toms]

Andover, but don't worry about trying to set us up with an electrician. We can manage. But thanks (if that's what you were doing)

 

[binky]

an electric boiler and hob wouldn't justify a 3 phase supply, unless you have a six bed mansion, what are your loads? Most DNOs can offer a single phase upgrade to 125 Amp

 

[Geoff Toms]

an electric boiler and hob wouldn't justify a 3 phase supply, unless you have a six bed mansion, what are your loads? Most DNOs can offer a single phase upgrade to 125 Amp

Well, this would certainly be great and would save us spending a few grand. I've never seen this kind of upgrade to 125 mentioned anywhere, and I've been reading up on this for weeks. Our DNO is SSEN, and they certainly never mentioned it when I was talking to them.
I haven't got anyone to work out our loads yet, but for reference our MCBs in our current DB add up to 98 A (I don't know if that's relevant or just worthless info) We are a fairly heavy user, with 5 adults mostly working from home on their PCs, but also adding to dishwasher - washer - tumble - fridges - freezer - cooker usage more than you'd expect in a small-ish house.
When I said to SSEN that our current fuses totalled 98, and we were going to be adding a gas boiler and an induction hob, they said we were now talking about going 3 phase, and they didn't need to do a load check.
If they've been leading me up the garden path to get a nice fat upgrade job ..... !

 

[Murdoch]

Andover, but don't worry about trying to set us up with an electrician. We can manage. But thanks (if that's what you were doing)

not trying to set up anything , it’s just a county never gives anybody the idea exactly where you are.

I am in Woking and rarely travel more than 10 miles

 

[johnb2713]

Hi. Ordinary domestic property. Single phase supply 100A fuse. We're planning to move away from gas and to electric. First, replacing the old gas boiler with an electric one, then the gas hob with an induction one. Conversations with our supplier indicate we're going to need to upgrade to 3 phase. I can see that we arrange with our supplier and UK Power Networks so that they coordinate their work and we aren't left without power. The question that's puzzling me is whether we should also coordinate having an electrician here at the same time to do the internal work, replacing the consumer unit etc.? Is that the way it works, or do the guys doing the work outside leave you with a working system, and you can get the internal work done afterwards?

I'm not convinced you need a 3 phase supply. We have 13 heatpumps, 2 x House batteries, 2 x EV, Immersion heater, dishwasher, washing machine and tumble drier, induction hob, 2 x oven, microwave oven and a small storage heater. If we really try, we can max out our 100 amp supply but it takes a lot of doing. Induction hob is a relatively small load. The electric boiler will hopefully be one like Tepeo, phase change type boiler that will heat up overnight, they can be circa 7 to 10kW I believe but that still leaves you plenty of headroom.

 

[binky]

Well, this would certainly be great and would save us spending a few grand. I've never seen this kind of upgrade to 125 mentioned anywhere, and I've been reading up on this for weeks. Our DNO is SSEN, and they certainly never mentioned it when I was talking to them.
I haven't got anyone to work out our loads yet, but for reference our MCBs in our current DB add up to 98 A (I don't know if that's relevant or just worthless info) We are a fairly heavy user, with 5 adults mostly working from home on their PCs, but also adding to dishwasher - washer - tumble - fridges - freezer - cooker usage more than you'd expect in a small-ish house.
When I said to SSEN that our current fuses totalled 98, and we were going to be adding a gas boiler and an induction hob, they said we were now talking about going 3 phase, and they didn't need to do a load check.
If they've been leading me up the garden path to get a nice fat upgrade job ..... !

Adding up MCBs means nothing, that's just circuit protection.

The electric boiler I installed for mum was 10kw, sufficient for about 6 radiators, and I assume you will be using the shower off that, it shuts down the heating side if drawing hot water. PCs usually around 500w for a powerful unit, so say 2 kw. Tumble drier 2.5kw, cooker usual runs at around 2kw max, because once it's warmed up, it draws less. Fridge TV etc around 1 kw max , kettle 2.5 kw but only for 10 mins, so rough numbers 16kw max, plus a few lights. 100 amp main fuse will cope with 20 kw ( it's roughly 4amps per kWh) so that leaves 4 kw to play with. I would be very surprised if you really needed an upgrade, and certainly not 3 phase.

 

[Geoff Toms]

What you're all saying is very heartening, but I do want to be safe too. I certainly don't want to fall into the trap of having a system where it all works but the cables get warm and plastic starts to melt. I'll get someone to work out our loads, and they'll hopefully agree with you that it either doesn't need an upgrade - or if it does, it'll be limited to a single phase increase from 100 to 125.
A question about fuses / MCBs: Our DB has printed on it (I'm sure they all do) "Do not exceed 100A total load". Does that mean I shouldn't have all my MCBs/RCCDs adding up to more than 100A - or is that irrelevant and it's just talking about the calculated total load? (I hope it's the latter, cos we're going to be well over 100A on fuses/MCBs/RCCDs)

 

[truffle pig]

I would suggest its worth getting an electrician on board who has experience in electric boilers. Get him to do a max load calculation with and without an electric boiler. You could well get away with not having to upgrade to 3 phase (which in my experience can very quickly rack up many £k!!). Without knowing the size of property, hot water storage, insulation, etc it is difficult to know what size boiler you will need and that's what ultimately determines if you will need single or 3 phase. Most properties don't draw as much power as you would think,