UK Zappa charging point on tt install

[Thrashman]

Hi everyone, firstly hope you all had a great New Year.
Wanted to get everyone’s thoughts on best design for Zappy EV charging point install.
Charging point is going to be installed at the bottom of a long driveway approximately 35 m from property meter and consumer unit.
The Earthing arrangement of the property is TT, .
Will be installing a 10mm SWA Cable from consumer unit location along brick wall down to the charging point location.
The charger point being Zappi has built-in type a 30ma RCD protection and 6ma d.c. protection .
Being TT, The armoured cable won’t comply to Ads If directly off a 40 amp MCB as Eli won’t be low enough so RCD required at 30ma for supply armoured 10mm cable .
Problem with this is now the discrimination (selectivity), this will now leave me with 2 30mA RCD’s in series, Which is definitely not best practice and doesn’t comply.
Ideal scenario would be to not have the 30 mA RCD at the charger point , But this is part of the printed circuit board in this particular charger.
Any advice on best practice to make sure all protection has been put in place but without having both our RCDs in series.
Thanks in advance

 

[westward10]

Why does the source rcd need to be 30ma.

 

[Thrashman]

Why does the source rcd need to be 30ma.

Hi Westwood , for additional protection being TT. (. Please correct me if I’m wrong)
?

 

[westward10]

Doesn't require additional rcd protection assuming swa throughout with the armour correctly earthed. It requires fault protection by way of an rcd.

 

[Wilko]

My 20p - The RCD for SWA earth fault could be 100mA time delay and that will give selectivity allowing the downstream RCD to trip first. And the 100mA S type probably also needs to be A rather than AC due to the downstream load.

 

[Strima]

100mA S type for the SWA to provide earth fault protection, the 30mA in the Zappi will provide additional protection for shock risk. As mentioned A type for DC interference.

 

[Thrashman]

My 20p - The RCD for SWA earth fault could be 100mA time delay and that will give selectivity allowing the downstream RCD to trip first. And the 100mA S type probably also needs to be A rather than AC due to the downstream load.

100mA S type for the SWA to provide earth fault protection, the 30mA in the Zappi will provide additional protection for shock risk. As mentioned A type for DC interference.

Thanks for your responses , that’s seems like a logical route to go , had Considered a 300ma / s type , but 100ma will work as you both mentioned , for selectivity .
May look at charging units that don’t have the 30 mA protection within the unit next time and just the 6ma dc monitor / contactor.
Would then be able to just use a type A rcbo at circuit origin .
as will save on seperate encloser for 100ma rcd and 40amp mcb.
thanks

 

[eddieb1974]

I have installed a Zappi in almost the same circumstances as the OP outlines. 100ma time delay type A RCD, I used a Lewden 100/100/2SA, and it has worked perfectly. Fault protection for the cable satisfied without a selectivity clash with Zappi's inbuilt 30ma.

 

[Risteard]

The last couple of TT EVSE installations I did I installed a 4 pole 300mA S-type Type A RCCB in one, and a 2 pole 300mA S-type Type A RCCB in the other. (The first was a three-phase installation with a 22kW chargepoint being installed, and the second a single phase with a 7kW chargepoint. Both were commercial installations.) Both had existing Type AC S-type RCCBs which I informed them had to be replaced due to the risk of blinding the devices.

But a 100mA would be fine. It absolutely MUST be Type A though. (Assuming Type B protection isn't required - but you mentioned 6mA DC leakage protection, so Type A is adequate.)

Then I had a 4 pole 30mA Type A RCCB fed from the DB for the 22kW charger, and a double pole switching Type A RCBO for the 7kW. (These EVSEs don't include RCD protection on board.)