When does 3 phase supply become 230V in domestic consumer unit?

[HappyHippyDad]

I went along this morning to quote for an EVCP install.

I thought it was a domestic house but it was a B@B. It has a 3 phase supply. I always pass on commercial or 3 phase as it is outside of my remit. However, I am toying with the idea of fitting this EVCP IF I can fit it from a single phase supply.

I am unsure where to take power from. Usually I would either split the meter tails or use a spare way in the CU. I could use a spare way in an existing CU at the property but it may be better to take power from somewhere in the meter room. However, I am unsure where it is 230V and where it is 400V.

You can see in the pictures there is a 3 phase cut out, to meter, to isolator, to Henly blocks, to separate meters, then to switched fuses, then off to each area. Where would I split the tails? Where is it 230V? It must be 230V coming from the switched fuse (B) going to the single phase consumer unit in the annex (because it's a single phase board). But, another switched fuse (A) goes off to the main house which has a 3 phase board. There is no difference with regards the cables leading up to either of these switched fuses, (i.e they both have a separate meter and a single Line and neutral going to them), so how is one of them 230V and the other 400v?

 

[HappyHippyDad]

Wow if you honestly don’t know how to get single phase from a 3 phase supply you shouldn’t be let loose near electrics

btw the isolator in the db is only 2 pole so my gues would be that it is a 3 phase db with a single phase conversion kit

Nice one chap, useful stuff as always.

 

[marconi]

HHD: I think you would enjoy slides 1-20 of this set - those after 21 quickly dive into technicalities I reckon you ought for now to leave for 'later':

https://www.bu.edu.eg/portal/upload...es/Cir2_Lect_8_Introduction_to_Poly_Phase.pdf

 

[Julie.]

But at which exact point does it change from 400v to 230V? How can it decrease in voltage without a transformer? I think this last question is also the answer to your question Julie ?

ps.. I'm assuming the 3 phase CU in the picture below is fed from the switched fuse (A) (single phase). How can it be a 3 phase board? Is it a 3 phase board? It looks like it only has a 2 pole isolation switch. I'm guessing it's actually single phase?

View attachment 90321

As has been said previously, the normal supply in the uk is 230/400V

Each of the three lines is 230V when measured between line and earth/neutral
BUT measure between lines you will get 400V.

This is part of your basic training, you probably ought to re-familiarise yourself with it if you are dealing with a site which has three phase.

If you have a 32A supply available, you could fit a single phase EVCP connected to any one of the three phases and neutral - this would charge at 32A or 7.4kW, obviously you would need a supply cable - either 2 or 3 core SWA usually (3c if you need the earth at the charge point).

If you use a three phase charge point this would charge at 32A per phase, so 22kW in total, in this case you would need a 4 or 5 core SWA (5c if you need the earth at the charge point). A 3ph charge point is around £100 more expensive than a single phase, but can charge up to 3x as fast.

Look in the standard charge cable connector - there are 5 main contacts and two small - the 5 main are the three phases, neutral and earth (be it from the supply or a specific TT for the EVCP).

The vehicle charger itself (in the vehicle) determines from the two small contacts what the maximum charge current is and then takes up to the limit of the charge point or the charger itself.

So some cars have a max of 6.6kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 6.6kW
• if you connect it to a 32A 3 ph EVCP it would charge at 6.6kW

Some other cars have a max of 11kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 7.4kW
• if you connect it to a 32A 3 ph EVCP it would charge at 11kW

Some other cars have a max of 22kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 7.4kW
• if you connect it to a 32A 3 ph EVCP it would charge at 22kW

I would always try for the largest I could, because more and more cars will be able to handle the larger values as time goes on.

The work is exactly the same - run the cable connect in the EVCP end and connect (Via a RCD/RCBO if specified) into the supply - usual methods be it single or three phase.

 

[ipf]

As has been said previously, the normal supply in the uk is 230/400V

Each of the three lines is 230V when measured between line and earth/neutral
BUT measure between lines you will get 400V.

This is part of your basic training, you probably ought to re-familiarise yourself with it if you are dealing with a site which has three phase.

If you have a 32A supply available, you could fit a single phase EVCP connected to any one of the three phases and neutral - this would charge at 32A or 7.4kW, obviously you would need a supply cable - either 2 or 3 core SWA usually (3c if you need the earth at the charge point).

If you use a three phase charge point this would charge at 32A per phase, so 22kW in total, in this case you would need a 4 or 5 core SWA (5c if you need the earth at the charge point). A 3ph charge point is around £100 more expensive than a single phase, but can charge up to 3x as fast.

Look in the standard charge cable connector - there are 5 main contacts and two small - the 5 main are the three phases, neutral and earth (be it from the supply or a specific TT for the EVCP).

The vehicle charger itself (in the vehicle) determines from the two small contacts what the maximum charge current is and then takes up to the limit of the charge point or the charger itself.

So some cars have a max of 6.6kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 6.6kW
• if you connect it to a 32A 3 ph EVCP it would charge at 6.6kW

Some other cars have a max of 11kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 7.4kW
• if you connect it to a 32A 3 ph EVCP it would charge at 11kW

Some other cars have a max of 22kW

• if you connect it to a 16A 1 ph EVCP it would charge at 3.6kW
• if you connect it to a 32A 1 ph EVCP it would charge at 7.4kW
• if you connect it to a 32A 3 ph EVCP it would charge at 22kW

I would always try for the largest I could, because more and more cars will be able to handle the larger values as time goes on.

The work is exactly the same - run the cable connect in the EVCP end and connect (Via a RCD/RCBO if specified) into the supply - usual methods be it single or three phase.

I know what you're saying but there's no doubt, with his experience, HHD should know the vast majority of that. Let's face it, he's been a forum member for 10 years.

 

[HappyHippyDad]

I know what you're saying but there's no doubt, with his experience, HHD should know the vast majority of that. Let's face it, he's been a forum member for 10 years.

As in the first post, I have stuck rigidly to domestic electrics. I have always declined any work to do with 3 phase because, as a domestic installer, we should not be touching commercial/industrial 3 phase etc. My instinct was to immediately decline this job, however I thought I'd chat through with you guys and see if if there was a simple way to use 230V (which it seems there is). This I understand.

I may yet still walk from this one, but I'm now erring towards doing it as it seems it will all se 230V.

 

[ipf]

As in the first post, I have stuck rigidly to domestic electrics. I have always declined any work to do with 3 phase because, as a domestic installer, we should not be touching commercial/industrial 3 phase etc. My instinct was to immediately decline this job, however I thought I'd chat through with you guys and see if if there was a simple way to use 230V (which it seems there is). This I understand.

I may yet still walk from this one, but I'm now erring towards doing it as it seems it will all se 230V.

To tell you the truth, I don't see where 3 phase comes into it. You're installing single phase.
It seems the problem, from your point of view, is whether it is 'domestic' or not....the very first point you made.
It's down to you, but knowing, to some extent, the way you seem to regard your position and work, I wouldn't object in the slightest to you carrying the installation.
If you're worried, have a look at your company insurance, maybe.

 

[plugsandsparks]

As in the first post, I have stuck rigidly to domestic electrics. I have always declined any work to do with 3 phase because, as a domestic installer, we should not be touching commercial/industrial 3 phase etc. My instinct was to immediately decline this job, however I thought I'd chat through with you guys and see if if there was a simple way to use 230V (which it seems there is). This I understand.

I may yet still walk from this one, but I'm now erring towards doing it as it seems it will all se 230V.

No dont walk unless the route from that room to the charge point is full of Bramble and thistle, lol - seriously you have fallen on a gem. 3 Phase is generally 4 wires, 3 X Line, 1 X Neutral, you only get 400 (actually more like 420V if you put you tester between 2 of the lines, you get 240V between any of the lines and Neutral.
So when you come to start if not sure what is what test the voltages and polarity which you would do anyway for a Sp install. Typically the Phase lines are coloured Brown, Black, Grey. Neutral is Blue (dont ask, its a long story) or if you still cannot figure it out, follow the cables from the service head. The three on the left above the fuse carriers are the lines and the one on the right which does not have a fuse is the Neutral.
Seriously man, TP does not get easier than this install, you gotta start somewhere

 

[HappyHippyDad]

It does all sound pretty straight forward now thanks to you lot. ?

 

[Resu]

Not sure if it's been said before but the only real worry you should have with the 3 phase in this scenario is which phase to use. A quick check on the main tails (around main meter/isolator) with a clamp meter should give you an idea.

Whether to come off of one of the already metered (& seemingly unused) supplies or come direct from the henleys and possibly include your own seperately metered supply is a question you'd need to put to the client.

Yet to come across a farm electrical system as well laid out as this, with plans too!

 

[Lucien Nunes]

HHD: I'll recommend a simple exercise to consolidate your visualisation of the voltage relationships: Draw a phasor diagram for yourself.

Mark a point in the middle of a piece of paper. That will be the neutral point.

Draw three lines radiating from it in a Y, 120 degrees from each other (the angles need to be fairly accurate.) These are the phasors that stand for the voltages of the three supply lines - L1, L2 and L3 - relative to the common neutral point.

The 120 degree angles represent the phase angles between the sine waves of the three phases. In essence, how far through a cycle of the sine wave L1 has got, by the time L2 starts, and so on. Because it is a 3-phase system, three times the phase angle makes one complete circle of 360 degrees, i.e. the phases are 120 degrees apart.

The length of each phasor represents the voltage from line to neutral. so make them represent 230V using some convenient scale such as 100V per inch, (which would make the phasors 2.3 inches long.)

Now measure the distance between the ends of any two phasors, representing the voltage between any two line conductors of the 3-phase system. Convert the length back to volts using the same scale.

That's where the 400V comes from.

 

[Gavin John Hyde]

I know you say 3 phase is iut of your remit but all new supplies from WPD are going to be 3 phase as standard from now on.
Could be a chance grow your skillset.
Assuming there is capacity on the supply (check with dno) even if offered 22kw few cars charge above 7kw on ac anyway
Then fit a few.henley blocks after the isolation switch by the meter and run a small consumer unit for the ev.
Main switch plus mcb will do a 22kw zappi. Can fit 3 ct clamps to monitor the load.
Depending in cable route you may need to factor in rcd protection.

 

[Julie.]

I know you say 3 phase is iut of your remit but all new supplies from WPD are going to be 3 phase as standard from now on.
Could be a chance grow your skillset.
Assuming there is capacity on the supply (check with dno) even if offered 22kw few cars charge above 7kw on ac anyway
Then fit a few.henley blocks after the isolation switch by the meter and run a small consumer unit for the ev.
Main switch plus mcb will do a 22kw zappi. Can fit 3 ct clamps to monitor the load.
Depending in cable route you may need to factor in rcd protection.

Agree, however we are getting more and more cars able to take in excess of 7.4kW, just a year ago there were very very few, but within the last year alone Renault, BMW, telsa and BYD have all introduced 11 or 22kW chargers within their cars.

Over the short time EVs have developed they have gone as standard from 2.3kW through 3.6kW, 7.4kW, and now 22kW.

I would expect within the next year or so pretty much every new EV will have the capability of greater than 7.4kW.

They have to really, because as smart control starts operating, it will shut down for periods, so EVs won't be able to rely on low rates for long times.

 

[brianmoooore]

I know you say 3 phase is iut of your remit but all new supplies from WPD are going to be 3 phase as standard from now on.
Could be a chance grow your skillset.

In spite of having been in the business for over half a century, working on mainly farm and rural domestic, I can count the number of clients I've had with three phase supplies on the fingers of my hands, possibly one hand. Until a few years ago, when the main 11kV trunk had a third wire added to it, I lived in the middle of about a hundred square miles of three phase desert. To this day, most of the branches off of the trunk, including my own, are only two wire.

With regards to the multiple meters in the property in question, I suspect this is similar to what I have with my own holiday cottages. Under normal operation, with 'tenancies' in the various properties being either one or two weeks, the sub meters aren't read, with the landlord picking up the tab for the whole supply, but occasionally you get a longer tenancy, such as a winter let, or, as I had once, someone moving to the area for three months to search for and buy a property, and then the sub meters are read (or card meters programmed 'on', in my case).
I also have sub meters around the place for the hot tubs, industrial tumble drier and the EV point, just so I can keep tabs on what these things cost to run.
For these reasons, I'd ensure that the EV charger goes onto its own meter,whether single or three phase.

 

[Zerax]

However, it does sound as though a 3 phase EVCP would be a better option for the owner.

That partly depends on if the intended vehicle has a 3P charger on-board... mine doesn't But then I guess there's no harm in making it "future proof".

 

[Mikegh]

What do you mean? What's crude about it? You've got to split somewhere.
All single phase supplies originate from 3 phase.
How do you connect a 3ph load when only single is required.
Any block of flats, for instance, is fed similarly, with single phase to each property. Balancing phases is a job for the designer.
Obviously, millions of single phase circuits come from 3 phase boards.
What's wrong with a single phase board in a factory, say, where required?

I was probably generalizing and I take your points

In the factory situation you generally distribute in 3P

The concern where you split at the origin is that the loads are unbalanced .That board in the pic looks well loaded.