Main switch SPD pen fault wiring

[ppelec100]

Hi all,

Customer is buying a Tesla ev and he was thinking of getting a Tesla charger but he said to give him 1 quote without a charger (him buying Tesla charger) and 1 quote with me supplying a charger…

The Tesla charger hasn’t got pen fault detection and I’ll need to fit one. The existing CU is split RCD and there is also no SPD or DP isolator.

My plan is to snip the tails from the meter to the split Rcd board and fit a DP isolator with SPD to provide isolation as well as upfront SPD for both EV pen unit and the existing RCD board. From the DP ISO SPD unit take tails to Henley blocks and pick up the split board with its tails. This part is where I’m a little bit stuck…

The pen fault detection device has a 2 module RCBO as the “main switch”. Let’s say the main supply fuse was 100a (couldn’t see markings British Gas tape stuck over it… the tails were 25mm). From the Henley’s do the tails to the RCBO need to be 25mm to be protected by the main 100a fuse? Feels overkill if I’m being honest just to supply a 40a RCBO. I was wondering if I can get away with 6mm tails but then it won’t be protected by the main fuse but I can’t imagine it drawing more than it needs to? What’s your thoughts?

Pen fault detection device I’m looking to fit:

PME / PEN Fault Detection Unit 6 Mod c/w C40 RCBO /4P63A contactor & PME Relays

Stay safe while charging your EV with our PME/PEN Fault Detection Unit. Designed for PME systems, it detects and alerts you to PEN faults.

www.electrical4less.co.uk

DP ISO SPD:

WCED WEC440SP Meter Supply Isolator with Surge Protection

Protect your electrical system with our Meter Supply Isolator with Surge Protection. This reliable two-in-one unit is perfect for upgrades. Order now!

www.electrical4less.co.uk

 

[Pretty Mouth]

For overload? Check 433.2 and 433.3. I think 433.2.2 (i) applies in this case.

 

[ppelec100]

For overload? Check 433.2 and 433.3. I think 433.2.2 (i) applies in this case.

Thanksss mate. They all seems to say that a protective device is needed for a reduction in cable.

The only one that says it can be omitted is 433.3.1(ii) because of the characteristics of the load or supply is not likely to carry overload current…

But then the big boss mr 433.3 kills him with this reg shall not be applied to installs situated in locations presenting a fire risk (it is under the stairs where I need to install these devices).

So I think it would need to stay 25mm tails unless I can reduce it with a fuse but it’s going to get a bit much in there.

 

[westward10]

I would personally use 10.0mm² it is only marginally larger than 6.0mm². A barn full of hay maybe a location presenting a fire risk but under the stairs, not to me.

 

[Pretty Mouth]

They all seems to say that a protective device is needed for a reduction in cable.

I read 433.2.2 (i) as saying the protective device for overload can be at the far downstream end of the reduced CSA cable, which this would be. There is no opportunity to overload that cable, as all loads on it are downstream of (and so limited by) the 40A RCBO.

The cable would need to comply with 434, in this case I believe specifically 434.5.2. i.e. a fault occurring between L and N, or L and E, will not cause an excessive temperature rise of the conductors, in the time it takes for the main supply fuse to blow.

I agree with Westward, I wouldn't consider an understairs cupboard as being a fire risk.

 

[ppelec100]

Thanks for the replies. I’m going to have a look again at the regs to try understand properly from what you replied pretty mouth.

And true I might aswell get a 10mm in for what it’s worth.