RCD to RCD

[bchong]

Hi all,

I was on a construction site the other day and someone had a mild electric shock using an appliance. Someone then said that you should not connect a RCD to another RCD.

The arrangement of equipment was something like this

|Generator|-|RCD|--------------------------------|RCD|---|Appliance|

I've been reading up on the issue and thought that maybe the issue would have been that the lead lengths might have exceeded what is appropriate. Anyone have any insight on the issue?

Thanks in advance for any help that you guys can give me

 

[sparkytim]

Hi working nights?

RCDs in series (RCD TO RCD) are not a problem, just fails to give discrimination in the event of a fault unless the Upstream one is Time delay type (S TYPE)

RCDs do not PREVENT shocks, they will minimise the effect of a shock by disconnecting the supply before it can harm you (i.e. cause Ventricular Fribulation), thats why the standard Tests for RCDs are Time tests, i.e. @

<300 m S and @

< 40 m Sec.

Some times a perceived shock can be actually a static discharge FROM the person TO earthed metal work, ( i.e. the sort some people get when getting out of a Car).

 

[bchong]

Thanks for the quick reply.

Nah not working nights, just working in Australia

So the RCD to RCD wasn't a problem. Might the long leads have caused the shocks? Was reading up on the standards and there are restrictions on max length for the leads. I don't think this was a static shock as this incident was serious enough to be reported up to higher management.

 

[ProDave]

What was the person touching when he got a shock?

If it was a bare exposed live terminal, then that piece of equipment needs taking out of service until repaired.

If it was just touching the case of a power tool say, then check the earthing. Is the CPC bonded to an earth stake at the generator?

 

[sparkytim]

Good Day Mate

Have the RCDs been tested?

 

[bchong]

@prodave

I think the guy was just picking up his tool when he got the shock. I'm pretty new at these electrical terms, what's a CPC? But yeah I gotta check if the generator was grounded

@sparkytim

I think that the RCDs would have been tested beforehand as it's standard safety procedure. However, will have to check up with the safety guys to see if that was indeed the case.

 

[PC Electrics]

CPC = circuit protective conductor (aka 'earth wire')

Check the earthing arrangements are sound.

You don't mention whether the RCDs tripped or not (I'm presuming not).

Test the RCDs - just because this is ssp doesn't mean it was actually done.

You don't say what the tool was and whether it's a class I or II device.

 

[a1]

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