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Does a SPD need a dedicated MCB?

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oscar21

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Does a SPD need a dedicated way?

I need an extra way in this unit for a 3 phase car charger

IMG_20240503_132821_535.jpg


As you can see its a small unit with no extra ways, the building is rented and the tenant is adamant that the board is not to be changed as he has been told no major alterations. We have already bodged it somewhat on his say so by adding a small single phase board for some extra lighting and sockets he wanted (we shuffled the circuits about so all the socket/water heater circuits were spread across the phases and its just lighting sat on the single phase board, thats was last year and everything has been fine so far. I would have fitted an aditional 3ph unit but the mains cupboard is tiny.

He now wants to do similar with the car charger but I need three ways so it would mean moving three socket circuits all onto one phase. But I was thinking, the little unit below has the SPD in it which is fed from a 32A 3 phase MCB, any reason the car charger can't share the same MCB from a regs point of view?

I know its a bodge but I'll be bodging it anyway in one way or another, I also cant say no as its the bloke's office that gives us tonnes of work.

Now for the second question, I don't normally fit car chargers, this is the unit he's bought,


Cant make head nor tail of the instructions, they have a whole paragraph dedicated to how the lead might strangle a kid but nothing that I can find on the type of connection, rating etc, main question is will it need an RCD, the supply cable wont need it as its back to back with the mains unit.

I hate getting involved in stuff like this, its always far from straightforward.
 
All SPD have an upper limit on the supply OCPD that is acceptable, but some of them have that at 125A fuses or higher so in practice they don't need a separate MCB in most situations. Here is one example that is OK for supplies to 250A

In some cases, like what appears above, your issue is going to be how to connect it if you don't have either a spare MCB way or some dedicated arrangement to attach them to the busbars. Even where they can work with fuses in the 100A-160A or so region, the smaller Type 2 SPD often can only accept cables to the 25mm/35mm size region so you can't easily use them as a junction point for the supply going to the main switch.

You do get bigger SPD that have dual terminals for this sort of "V-wiring" or Kelvin connection, but they are not cheap either. Here is an example of that type of device:
 
If it is just the charger needing SPD, and that is coming off a 32A or more MCB, then adding SPD there for the charger will be fine, though depending on cable lengths it won't provide much in the way of protection for other stuff off that TPN board.
 
I think the bottom left 3 pole 32A MCB feeds the SPD which is original to the installation.

I was going to connect the car charger to the same MCB. Seems a waste the SPD hogging 3 precious ways all to itself.
 
EV chargers need to be on a dedicated circuit. You have the Cop?
As you say it is a bodge and you shouldn't be considering it. New board is the best option.
 
After reading your first post fully I would suggest this is beyond your skill set and they should find a competent installer.
What do you think will happen if I don't bodge it? The person that gives us loads of easy well paid work will just get someone else in to do it the bodge way, but guess what, he will also get the new person to do all the easy well paid work as well and I'll end up sat at home staring at four walls.

Whether I do it or someone else does it will still end up a bodge but that's what the customer wants so as long as it isn't dangerous, and I don't think bunching the charger in with the SPD is dangerous in any way shape or form then I'm all for it. As for the RCD, I'll put one inline in an enclosure after the MCB if it need it, just waiting on confirmation from the manufacturer.
 
I take it you don't have the CoP to decide if it is dangerous and are just going to wing it with your limited knowledge because the customer wants it.
 
What do you think will happen if I don't bodge it? The person that gives us loads of easy well paid work will just get someone else in to do it the bodge way, but guess what, he will also get the new person to do all the easy well paid work as well and I'll end up sat at home staring at four walls.

Whether I do it or someone else does it will still end up a bodge but that's what the customer wants so as long as it isn't dangerous, and I don't think bunching the charger in with the SPD is dangerous in any way shape or form then I'm all for it. As for the RCD, I'll put one inline in an enclosure after the MCB if it need it, just waiting on confirmation from the manufacturer.
Is your office in the snug of the local pub :yum: :yum::yum:
 
I don't normally fit car chargers
Have you read through this, regarding the DNO side of things?


At first glance, I'd assume your scenario to be an "apply to connect" not a "connect and notify".
Plan for CT clamps on each phase. Plan for upstream RCD protection that disconnects all live conductors. Plan for wired ethernet or reliable wifi.

Also at first glance that job looks and sounds like a PITA and I'd either want enough money for time and materials to do it right, or I'd simply pass ('I haven't done the training').

Finally that charger only has a 1m hard wired supply lead which would instantly put me off it as it's almost bound to need a joint box in the supply cable.
 
Last edited:
Have you read through this, regarding the DNO side of things?


At first glance, I'd assume your scenario to be an "apply to connect" not a "connect and notify".
Plan for CT clamps on each phase. Plan for upstream RCD protection that disconnects all live conductors. Plan for wired ethernet or reliable wifi.

Also at first glance that job looks and sounds like a PITA and I'd either want enough money for time and materials to do it right, or I'd simply pass ('I haven't done the training').

Finally that charger only has a 1m hard wired supply lead which would instantly put me off it as it's almost bound to need a joint box in the supply cable.
This is more like the helpful advice I needed, it does sound utterly complicated though, I thought the future was electric but it seems its nothing but a ball ache. If an electrician cant fit a simple car charger without reams of red tape then who can? Lets be honest its no harder to connect up than the roller shutter we did last year for him.

As for the massively complicated flow chart, apart from the "iON" name not seeming to be on the database everything else seems to comply but I'll bet there are hundreds if not thousands of chargers connect to the grid without any sort of paperwork whatsoever.

As for connecting it to the SPD MCB unless it presents some sort of danger then I'm nit really interested in any technical breach and I cant see how any sort of danger can arise from doing it that was to be honest. Also the lead length, I was going to put an enclosure/small CU back to back with the charger big enough for a 4 pole RCD to fit in and do the connection there. If it doesn't need an RCD it can have a 4 pole main switch in it.

PS: What on earth is CoP, more corporate blue sky office speak?
 
This is more like the helpful advice I needed, it does sound utterly complicated though, I thought the future was electric but it seems its nothing but a ball ache. If an electrician cant fit a simple car charger without reams of red tape then who can? Lets be honest its no harder to connect up than the roller shutter we did last year for him.

As for the massively complicated flow chart, apart from the "iON" name not seeming to be on the database everything else seems to comply but I'll bet there are hundreds if not thousands of chargers connect to the grid without any sort of paperwork whatsoever.

As for connecting it to the SPD MCB unless it presents some sort of danger then I'm nit really interested in any technical breach and I cant see how any sort of danger can arise from doing it that was to be honest. Also the lead length, I was going to put an enclosure/small CU back to back with the charger big enough for a 4 pole RCD to fit in and do the connection there. If it doesn't need an RCD it can have a 4 pole main switch in it.

PS: What on earth is CoP, more corporate blue sky office speak?

Code of practice. You really don't like theory/'office boys' do you.
 
This is more like the helpful advice I needed, it does sound utterly complicated though, I thought the future was electric but it seems its nothing but a ball ache. If an electrician cant fit a simple car charger without reams of red tape then who can? Lets be honest its no harder to connect up than the roller shutter we did last year for him.

As for the massively complicated flow chart, apart from the "iON" name not seeming to be on the database everything else seems to comply but I'll bet there are hundreds if not thousands of chargers connect to the grid without any sort of paperwork whatsoever.

As for connecting it to the SPD MCB unless it presents some sort of danger then I'm nit really interested in any technical breach and I cant see how any sort of danger can arise from doing it that was to be honest. Also the lead length, I was going to put an enclosure/small CU back to back with the charger big enough for a 4 pole RCD to fit in and do the connection there. If it doesn't need an RCD it can have a 4 pole main switch in it.

PS: What on earth is CoP, more corporate blue sky office speak?
You are a chancer I am afraid to say and quite frankly I don't care what you do just carry on being ignorant to what you don't understand just another person out there winging it. Do you actually understand RCD requirements for EVSE?
 
Code of practice. You really don't like theory/'office boys' do you.
Their sole purpose in the construction industry is to leach off the hard working tradesman whilst making his or her job intolerably harder. that goes for most industries also.

You can clearly see this when a site manager slopes off for the day and everyone is left to their own devices, the site always runs so much better.
 

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