Electricians - Single to three phase

[cheezemonkhai]

Hello to all the electricians in the room

 

Has anyone changed from single to three phase at home? I've spoken to the DNO who are going to quote for supplying the extra phases to the home, however I wanted to understand a few bits:

 

1) Can you temporarily use just a single phase from the three phases, then get all the electrical upgrade to a 3 phase panel etc done at the same time as installing the three phase equipment?

 

2) What needs changing internally/at the fuse box?

 

3) Do they do 3 phase smart meters etc?

 

4) What else do I need to worry about?

 

Thanks in advance

[@Lee]

I think I saw something about Smart Meters for 3 Phase supplies a while, perhaps four or five months, ago. Buggered if I can remember where though. Fairly new to the market stuff.
I think it's standard to have a 3 phase outlet here. 

Edit. Not the piece I saw but maybe helpful? https://www.sms-plc.com/insights/blogs-news/what-does-the-3-phase-smart-meter-mean-for-the-smart-energy-revolution/

Edited 13 October, 2021 by @Lee

[cheezemonkhai]

Aye, 3 phase is pretty common in Europe, particularly Germany.

Sadly it's not so common here, although luckily I am close to the nearest 3PH node

[gadgetman]

Is the plan to run something 3 phase? 

 

Or simply to balance loads on to different single phases? 

 

If the latter, not sure the benefits unless you have a lot of high power equipment 

[cheezemonkhai]

44 minutes ago, gadgetman said:

Is the plan to run something 3 phase? 

 

Or simply to balance loads on to different single phases? 

 

If the latter, not sure the benefits unless you have a lot of high power equipment 

 

Both...

 

We have enough load that we had to make sure we had a 100A not 80A fuse.
It's not that it is all drawn all the time, but it could be if things worked at maximum power at the wrong time together.

Adding electric car charging would push us over the limit and ditto if we were to go for a heat pump instead of the boiler.

 

When we spoke to the heat pump manufacturer we were told we'd need to go three phase or remove some existing equipment.
They also pointed out the three phase versions are more efficient to run for a given output.

Solar panel companies all said decide if you're 1 or 3 phase before hand as if you move up, then things will need changing/replacing at quite an expense.

Car charger, if we added a single 7kW, we'd again be right up against the limit nearly all the time and told us to talk to the DNO about the costs of 3 phase as it might make more sense.

An added bonus would be that the 3-phase car charger will do 22kW for 1 output or 2 outputs at 7kW simultaneously.

 

 

 

 

[john999boy]

There are chargers out there that can limit their load depending upon your house usage and also paired chargers that can either load balance or smart switch.

[cheezemonkhai]

14 hours ago, john999boy said:

There are chargers out there that can limit their load depending upon your house usage and also paired chargers that can either load balance or smart switch.

 

Subject to the cost of 3Ph upgrade they're an option, but evenwithout the charger, the heat pump is likely to push us over

Even the DNO suggested it was probably good to look at it

 

One advantage in the UK vs Europe, is a typical UK supply can be 100 Amps per phase with the standard cables

In Europe, it tend to be lower current capable cables (Thinner), but they they compensate by giving 3 phases.

 

 

[PetrolDave]

1 hour ago, cheezemonkhai said:

One advantage in the UK vs Europe, is a typical UK supply can be 100 Amps per phase with the standard cables

In Europe, it tend to be lower current capable cables (Thinner), but they they compensate by giving 3 phases.

If you run many single phase appliances their combined current returns along the neutral  (phase summed), so worth checking what the neutral current is likely to be - when I was in charge of a test lab we consumed around 200A per phase on single phase equipment and warned the installation electricians that there could be considerable neutral current, they ignored us and within a week the neutral cable to our lab was overheating and they had to come in at the weekend and install a replacement neutral cable from the lab to the switchoard.

[cheezemonkhai]

12 minutes ago, PetrolDave said:

If you run many single phase appliances their combined current returns along the neutral  (phase summed), so worth checking what the neutral current is likely to be - when I was in charge of a test lab we consumed around 200A per phase on single phase equipment and warned the installation electricians that there could be considerable neutral current, they ignored us and within a week the neutral cable to our lab was overheating and they had to come in at the weekend and install a replacement neutral cable from the lab to the switchoard.

 

After a chat with the DNO and some further research,  I'm thinking:

 

 - 3 phase supply

 - split the current items using a 3 phase panel, such that the load is split over the three phases somewhat equally.

 - Leave a few blanks for all three phases, such that things such as a car charger/heat pump can use all three phases.

 

I think we'll still be below 50-70kVA, which most companies offer as the entry to 3phase without extra considerations.

It's just likely we would be above 23kVA if we add a heat pump and/or car charging in addition to the current loads.

I'm not saying three phase is the only option, but it's what everyone we've spoken to has suggested so far.

 

In terms of the combined neutrals, I assume you're talking about the neural from the main 3-phase meter/switch to your breaker panel?

I'm assuming, but know what a dumb idea that could be, that a neutral on a 3 phase supply to switchboard would be enough to handle such instances (again assuming the electrician understands 3 phase as well as having part-p).

Be really good to understand more about what sort of returns you were seeing and anyother issues.

 

[Warrior193]

Another thing to seriously consider if considering using a mix of single and 3-phase equipment is separation of portable appliances running on single phase - there is a potential hazard if 2 individual appliances (on different phases) are able to be placed within touching-distance of each other.

Edited 14 October, 2021 by Warrior193
correction

[cheezemonkhai]

5 hours ago, Warrior193 said:

Another thing to seriously consider if considering using a mix of single and 3-phase equipment is separation of portable appliances running on single phase - there is a potential hazard if 2 individual appliances (on different phases) are able to be placed within touching-distance of each other.

 

You know what, I knew that was an issue  

back when I was using multiple 3 phase PSU in racks, but having not had to do it, I’d completely forgotten about it in regard of this.
 

That does complicate things.

 

Do you know of a technical solution to this?

Is it if only mixing single and three phase devices, or just using different devices on different phases.

 

I mean as much of Europe is 3 phase and it’s pretty common is the US too, so there must be some solution.

 

This is going to require quite a bit of thought….

and a 3 phase experience home qualified electrician.

 

[lol-lol]

Robert Llewelyn loves his 3 phase he has at his small holding so he can have his 3 phase charger for his EVs and discovered that the Zoe can charge must faster than a Tesla on a home charger, 10 to 11 minutes he describes how it works on his 3 phase charger.

 

My local council I do not think would even quote for digging up the pavement to put in 3 phase so sadly a no starter, sounds like it would be cheaper to find an agricultural or industrial building that has 3 phase already than try and get it put in to most domestic properties from what I am hearing. 

 

 

[Warrior193]

19 hours ago, cheezemonkhai said:

 

You know what, I knew that was an issue  

back when I was using multiple 3 phase PSU in racks, but having not had to do it, I’d completely forgotten about it in regard of this.
 

That does complicate things.

 

Do you know of a technical solution to this?

Is it if only mixing single and three phase devices, or just using different devices on different phases.

 

I mean as much of Europe is 3 phase and it’s pretty common is the US too, so there must be some solution.

 

This is going to require quite a bit of thought….

and a 3 phase experience home qualified electrician.

 

The important thing to consider is separation, fixed appliances aren't an issue because they are already on 400 volts - technically, anything that is fitted with a plug and is capable of being moved is considered a portable appliance.

I recall the minimum separation to be >2 M (6ft) between different phases for portable appliances, although I will need to check the regs on this. It becomes an issue if two appliances, supplied on different phases, are capable of being moved to the point where they can both be touched at the same time. Remember, the length of the appliance flex. needs to be taken into account.

 

In the case of a two-story house, if the downstairs ring circuit was on phase 1 and the upstairs cuicuit was on phase 2 (or 3)  you should be able to satisfy separation - although you would need to be aware of the potential hazard of running extention leads between different areas. Ditto for different rooms on the same floor where there is more than one ring-circuit per floor.

[cheezemonkhai]

That’s the worry… plus i’d never rely on someone not being lazy and running a spur from a socket above etc.

 

In house I imagine all the plugs could go on a single phase, single phase heat pumps, on another… however that could potentially lead to imbalance, especially with a three phase heat pump/car charger in place.

 

three floors, three phases is ok, but as you say need to be super careful about plugging in on one floor and moving it to another…

 

The kitchen tome is the difficult one though as the cooker is a reasonable  load so you’d want that and say any induction hob on different phases. The you have to mind what you put the sockets on.

 That or I just stick the whole kitchen, cooker etc on a single phase.

[gadgetman]

Can you not keep the house one 1 phase, and put car charger & heat pump on the others? 

[cheezemonkhai]

22 minutes ago, gadgetman said:

Can you not keep the house one 1 phase, and put car charger & heat pump on the others? 

I could, but I thought you had to try and valence the phases. Plus heat pump for water would likely  be 3 phase.

 

Will dig more on single phase..

[Warrior193]

Hi, I have done a quick check of the IET wiring regs (BS 7671, 2018) and it seems that requirements for separation were removed after the 16th edition - it looks as if the reliance is now on RCCBO devices for protection. Consult a registered electrician and the current in main neutral conductor will need to be calculated, but it would now look as if you can do what you propose.   

[Warrior193]

On 13/10/2021 at 15:01, cheezemonkhai said:

Hello to all the electricians in the room

 

Has anyone changed from single to three phase at home? I've spoken to the DNO who are going to quote for supplying the extra phases to the home, however I wanted to understand a few bits:

 

1) Can you temporarily use just a single phase from the three phases, then get all the electrical upgrade to a 3 phase panel etc done at the same time as installing the three phase equipment?

 

2) What needs changing internally/at the fuse box?

 

3) Do they do 3 phase smart meters etc?

 

4) What else do I need to worry about?

 

Thanks in advance

1 - Yes, would be the same as temporary builders supply.

2 - Will require complete new DB (3 phase).

3 - Yes, believe so.

4 - As already discussed, but see my latest reply re. 18th edition.

 

[cheezemonkhai]

Thanks, really appreciate that.

 

I expected a new DB but was hoping to get the three phases in then change the rest over once it was planned. 
 

Sounds like you can 👍

 

On the keeping loads apart, much as an rcbo is good, belt and braces seems more sensible.

 

Can I do as gadgetman suggests and keep the house on a single phase or is it better to split floors /load over phases ?

I’m assuming you’re a qualified electrician… if so what areas do you cover?

 

[Warrior193]

On 16/10/2021 at 15:44, cheezemonkhai said:

Thanks, really appreciate that.

 

I expected a new DB but was hoping to get the three phases in then change the rest over once it was planned. 
 

Sounds like you can 👍

 

On the keeping loads apart, much as an rcbo is good, belt and braces seems more sensible.

 

Can I do as gadgetman suggests and keep the house on a single phase or is it better to split floors /load over phases ?

I’m assuming you’re a qualified electrician… if so what areas do you cover?

 

Used to be, but no longer work directly in the trade. I was more on the industrial side - then television spark. Now work part-time in building services looking after a NHS health centre.   

[fabdavrav]

415Volt? in a House & all the industrial plugs & sockets?...won't be allowed...you'd have to go for a split distribution board & phasing down to single core 230v...

 

Your best option is to get additional single cores supplied to the house, one for the car only & one for the heat pump...

 

For example the cable down the street is three core (red, yellow, blue) & neutral. You existing house is supplied with say the red & neutral giving you 230volt, & is limited to 100A. What you need is the yellow core & neutral supplied at 100A for the car & the blue core & neutral supplied at 100A for heat pump....all at 230v single phase.

 

BTW the cables down the street cannot cope with supplying all the 100A to even one third or half of the houses that are on that branch due to the derating of the cables.....This is why the additional loads of electric cars & heat pumps will overload the existing infrastructure & substations....more cables will have to be put in down the streets, or they have to cut/ramp down peoples demands...why do you think they want to fit newer smart meters so they can ramp your demand down??

 

Edited 4 November, 2021 by fabdavrav
spelling

[john999boy]

1 hour ago, fabdavrav said:why do you think they want to fit newer smart meters so they can ramp your demand down??

why do you think they want to fit newer smart meters so they can ramp your demand down??

I thought they’d only got the ability to turn the electricity on or off - not to lower the demand?

[J.R.]

Have to go out so dont have time for a full explanation, Google Délesteur or load shedding relay, very common & cheap as chips here.

[fabdavrav]

11 hours ago, john999boy said:

I thought they’d only got the ability to turn the electricity on or off - not to lower the demand?

 

Pages 62 & 63 here

 

Smart Metering Implementation Programme: a report on progress of the realisation of smart meter consumer benefits (publishing.service.gov.uk)

 

 

give you an idea of how the Gov want the meters to work..most is "time" based load control at your end, but I have seen stuff to indicate that they will be able to ramp it down....especially for the bigger loads eg cars & heat pumps...to allow your fridge to work basically...This usually can be via the electronic controllers for the heat pump & car charging....so in the dead of winter on a windless day your car charger & heat pump may be ramped down...

 

Like I say its well known within the industry the existing infrastructure cannot supply or distribute these increased loads to every home..

Edited 4 November, 2021 by fabdavrav
web link

[KenONeill]

10 hours ago, john999boy said:

I thought they’d only got the ability to turn the electricity on or off - not to lower the demand?

And just how much lower does your supply get than "off"?