RCBO's

[Rikki Barrett]

Was wondering if there are any types of circuits that could be sensitive to RCBO's???
I need to put an RCBO on a circuit with lots of computers and the like on it, the last thing I want to happen is a nuisance. These computers have to be running and can only lose power once really.

Also can you get different types e.g B,C??

Thanks for any input. Rik

 

[DurhamSparky]

Bear in mind that a typical PC has a MA leakage of about 3mA so 10 PC or Less may trip your RCD!!

Type B & C dont worry to much about them..! lots of Manufactures only make Type C RCBO

 

[Rikki Barrett]

Hmm, could be a problem, I did think that about computers but didnt realise it was so much. Ok. Going to have to re-think this one.

 

[Rikki Barrett]

Or just suck it and see with a MCB to hand jus in case.

 

[Sintra]

Was wondering if there are any types of circuits that could be sensitive to RCBO's???
I need to put an RCBO on a circuit with lots of computers and the like on it, the last thing I want to happen is a nuisance. These computers have to be running and can only lose power once really.

Also can you get different types e.g B,C??

Thanks for any input. Rik

May i ask why you need to install RCBO to the circuit?

 

[Rikki Barrett]

The customer has had a PIR done and it has come back with no RCD protection on circuits supplied by t & e, they put there quote in for fuseboard upgrade from 8-way to 12-way TP & N with the 9 circuits on RCBO's.

 

[Sintra]

The customer has had a PIR done and it has come back with no RCD protection on circuits supplied by t & e, they put there quote in for fuseboard upgrade from 8-way to 12-way TP & N with the 9 circuits on RCBO's.

There is no requirement to install an RCBO on existing T&E circuits or socket outlets as this is only a code 4 on a PIR.

 

[Rikki Barrett]

Code 2 according to this guy. And I dont have any insurance in place to dispute that, besides, customer will say ''if thats what needs doing, do it''. I know it.

 

[Sintra]

Have a good read through this link it will explain coding for PIR's

http://www.elecsa.co.uk/downloads/public/PIR Best Practice Guide_ESC.pdf

But if it's giving you some work say nothing and carry on.

 

[davelerave]

i have a job coming up with 24 workstations- i'm going with 4 workstations per rcbo

i think i'm right in saying they should be the ' A' type

anything critical would prob go through a UPS (assuming you require rcd) i assume that will provide a level of protection against nuisance?

 

[Sintra]

Don't think there is such a thing as an "A" type well at least not in UK.

 

[davelerave]

Don't think there is such a thing as an "A" type well at least not in UK.

i should have said type A rcd(not sure if there's an rcbo)-for pulsating DC where supply is rectified

not to be confused with the B AND C protection of mcbs/rcbos


there's one here alright

5SU1 RCBOs, type A - - Siemens

 

[cornburn]

I regularly put up to about 15 PCs on a single RCBO, depending on the age of the machines and have never had a tripping problem. Strip the sheath off a kettle lead and get your clamp round the earth with one of their PCs running and see what leakage it measures. New systems with flat screens and efficient power supplies don't leak anywhere near as much from what I've seen. One RCBO for each 4 computers just seems like a massive waste of money to me. Plus it would mean some sections of dado trunking in an IT suite having 16 lengths of 2.5 running through it!!!

 

[davelerave]

i'd prob get away with 8 easily


what's the 'demand' with those 15 pc's- about 4.5 kw at 300w each?

there'd be no diversity in a classroom situation

 

[cornburn]

i'd prob get away with 8 easily


what's the 'demand' with those 15 pc's- about 4.5 kw at 300w each?

there'd be no diversity in a classroom situation

Standard PCs as you've said so 20A, would be on a 32A ring. I wouldn't normally put 15 standard PCs on one ring, have done it with thin clients in the past (around 150W each).

 

[davelerave]

2 radials instead of 1 ring -would be same no. of cables
but less nuisance risk

 

[cornburn]

2 radials instead of 1 ring -would be same no. of cables
but less nuisance risk

I suppose that would mean you could have twice as many circuits convering the same number of PCs so as you say, less chance of nuisance tripping as more RCBOs to share the leakage across. It would also mean you had no high integrity earthing in place though which is a requirement for any final circuit with a CPC current exceeding 10mA.

 

[davelerave]

interesting-dunno if that applies here in ROI -will check though

is a radial in steel conduit with separate cpc classified as high-integrity earthing? (steel conduit is a parallel fault path)

 

[cornburn]

interesting-dunno if that applies here in ROI -will check though

is a radial in steel conduit with separate cpc classified as high-integrity earthing? (steel conduit is a parallel fault path)

It's there in the BRB and onsite guide gives a detailed page on it if you work to the 17th still over there? Steel conduit as a separate CPC would be fine, as would running the CPC in a ring using an extra single core and terminating them both under their own screw.

 

[caddy]

Why exactly do you need to fit an RCBO to the computer circuit ? Are you doing it becuse they are 13a sockets or becuase cables are buried or some other reason?