Is 100ma or 300ma required?

[Earlydoors]

My work mate is installing a three phase supply to a detached steel building used for charging bikes/scooters. He has used 16mm 4 core SWA, with 80a switch fuse, am I right in saying the armouring wants earthing at the supply side but then an earth rod at the detached building, (it is PME at the origin). If so then how do you NOT earth the other end of the SWA that goes into the TP&N panel? it's all metal! Metal glands fixed to a metal DB so the earth will be installed from the PME to the detached building.. It can't not be.. But also there will be earth rod installed, I didn't think you could combine 2 earths from different systems

Oh and is a 300ma RCD Incomer required on the DB in steel shed?

appreciate your advice

 

[nickblake]

is the building steel gurders embeded into the ground then if it is it doesnt need a rod as the steel will be earthing its self to the ground

 

[Richard Burns]

Gland the SWA into a plastic enclosure below the DB and take the cores into the DB.

If the system is TT in the shed then all circuits must be protected by an RCD.
The general approach would be to use a 100mA S type, to separate it from any 30mA requirements inside the shed.
If you believe you will have problems with 100mA then you can go up to 300mA , but you need to make sure that your EFLI is low enough to be safe.

 

[Earlydoors]

It does not have girders embedded into the ground. Each outgoing circuit from the DB is protected by RCBO, any idea where the reg is that states 100ma or 300ma must be used as main switch? Will this install fall under any of the special installations or locations (part 7)?

 

[Guest77]

How far from the existing premises is the metal building out of interest? don't take this the wrong way please, do you have a regs book? and if so again no offence, do you know how to navigate it? also why is your mate asking for your advice? is he competant to do the job? again no offence to you personally at all.

 

[Earlydoors]

How far from the existing premises is the metal building out of interest? don't take this the wrong way please, do you have a regs book? and if so again no offence, do you know how to navigate it? also why is your mate asking for your advice? is he competant to do the job? again no offence to you personally at all.

Its about 15m away at a guess, you've not offended me at all, I'm pretty useless at the minute with the regs book, I'm still learning how to navigate it. The person I work with is competent, I'm just trying to learn and get a step ahead of him, I want to know the answers and regs myself and the reasons why, not just have him saying "it's right...trust me".. That doesn't help me.

 

[Richard Burns]

It does not have girders embedded into the ground. Each outgoing circuit from the DB is protected by RCBO, any idea where the reg is that states 100ma or 300ma must be used as main switch? Will this install fall under any of the special installations or locations (part 7)?

If you have RCBOs for all circuits then this meets the requirements for all circuits to have protection by RCD.
If you had circuits that were not on RCBOs or RCDs then the main switch would need to be an RCD. Because a 30mA could then cause the whole board to trip out unnecessarily you would then install a 100mA (or 300mA), if you have some circuits on 30mA RCDs then to discriminate you would need a time delay device as the main switch.

If the vehicles are for use on the public roads then this would come under 722 as a special location (BS7671 AMD2 2008).

 

[LeeH]

What's the problem with exporting PME? It's not like you're running 2.5 to a shed.

 

[telectrix]

extending PME, not exporting. problem could be size of bonding conductor if required.

 

[LeeH]

extending PME, not exporting. problem could be size of bonding conductor if required.

That's what I meant tel, bad choice of words there. Thanks.

What my point is that he has a 16mm in the SWA that can be used to extend the equipontial zone. So why not use it instead of an inferior TT?

I'm not big on this but I thought this was acceptable.

 

[Fin170]

So why not use it instead of an inferior TT?

Thread derail imminent :willy_nilly:

 

[Knobhead]

I just hope the RCBO’s are DP for a TT install.

Just ----ing a pebble in the pond.

 

[davesparks]

Or SPSN

 

[dingledong]

How far from the existing premises is the metal building out of interest? don't take this the wrong way please, do you have a regs book? and if so again no offence, do you know how to navigate it? also why is your mate asking for your advice? is he competant to do the job? again no offence to you personally at all.

You ok? Bloody polite nowadays ! What's wrong?
How was that quote?