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I wasn't having a go at him Shanky :) , just curious as the thinking behind it that was all :) , I must admit that I had dark thoughts of someone thinking a source/supply RCD may somehow negate possible bonding issues with PME, as I have heard this before from someone who should have known better :)
 
It's suppled from a pme system
rcbo at supply end and rcd at garage end but over the top but it's not going to give any nuss tripping.
4mm fro radial (got in in the van )

Over the top is one one thing but wasting money and having no discrimination of 2 rcd in series thus does not comply to regs is another, yes its not going to give nuisance tripping par' ce but its poor design from a professional all the same.
 
No, it won't. Or am I missing some of what you missed?
 
I have thought for a moment and I cannot see why an ordinary RCD test button would trip an upstream RCBO. Pray tell...
 
just out of interest, can anyone quote a reg. that forbids 2 30mA RCDs in series?
 
I have thought for a moment and I cannot see why an ordinary RCD test button would trip an upstream RCBO. Pray tell...

Right, I have had a thought :), and it seems maybe you are correct and I was wrong for this scenario being that the RCBO is upstream and the RCD is downstream, however if the RCBO and RCD were the other way around then it trips both devices for some reason, maybe something to do with the functional earth on the RCBO ?

I know this as a fact because I once was testing a custom built SP DB (by the firm I as working for), and all of the test rigs were in use so I used a normal socket outlet and "widow maker" lead to power this DB up to check the metering etc., anyhow I accidently caught one of the test buttons on one the many RCBOs fitted to this board and promptly tripped out the supply RCBO for this supply too, the howls of protest from a co-worker whom was using a computer powered from this supply revealed this lol :)
 
Reg 1: Use Common sense.

or it'll be something out of Chapter 3 about discrimination.

yes. i know, but was seeking a specific reg.

531.2.9 only asks for discrimination between RCDs when it is necessary to prevent danger.
 
I was always taught that the test button mechanically tests the device. I'm not sure about RCBO's.

well yes to an extent, it checks the electro-mechanical aspects out, the test button usually switches a resistor from the incoming L terminal to the outgoing N terminal so it checks the trip coil operation too.
 
he is a trainee, i wouldnt be suprised if he is a first year

it sounds like a homework question, if it is its in the wrong section


he mentions mv/a/m on basic domestic circuits so its homework, why would you need to work this out when it gives you all that info in bs7671 and onsite guide if we wanted it

Sounds like he wants to do the job because he's applying for elesca registration in another thread he started.
 
well yes to an extent, it checks the electro-mechanical aspects out, the test button usually switches a resistor from the incoming L terminal to the outgoing N terminal so it checks the trip coil operation too.

That makes sense, but wouldn't cause an upstream device to operate as it only diverts current to neutral so no imbalance would be detected on the other device.
 
That makes sense, but wouldn't cause an upstream device to operate as it only diverts current to neutral so no imbalance would be detected on the other device.

Hence my earlier reply to Lucien ;) , I am not sure why the RCBO tripped out the upstream one that I did at work though, but it did.

I might tomorrow fit my spare RCD that I keep, to a plug and lead , and see if it trips out the house RCD lol :)
 
My downstairs sockets at home are fed from a rcbo and I spurred a outside rcd socket off this circuit, now every time I use the outside socket I always push the test button and it has never tripped the upstream rcbo.
 
My downstairs sockets at home are fed from a rcbo and I spurred a outside rcd socket off this circuit, now every time I use the outside socket I always push the test button and it has never tripped the upstream rcbo.

I wonder if it only happens with an RCBO downstream ?, as I said maybe it was due to only certain types or possibly with the functional Earth when this is present.

I originally opened my mouth based on my earlier experience without thinking , then I thought about it and came around to Luciens way of thinking. :)
 

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