Some Help Please

[GForrow]

I have been suffering from random RCD trips in my house. Its a new house, with several MCB's controlling the circuits.

I have had the installatoin checked today by an electrician, the CU is fine. After unplugging everything and then slowly plugging back in, it turns out that my PC and associated bits are causing the trouble.

I am informed that the earth leakage from the PC is close to the limit of the RCD, and therefore it only takes a small nudge and the whole lot shuts down.

Short of trying to get the house re-wired to get the study on a separate circuit - Any suggestions. I was thinking possibly a UPS for the PC, to isolate the earth leakage, but not sure if this will work.

My understanding is that I need to reduce the total earth leakage getting back to the RCD, but how??

All sensible suggestions welcomed.

Gary

 

[RF Lighting]

The easiest way I can think of is to remove the circuit supplying your IT stuff from the the RCD side, and put it into the non RCD side of your CU, but replacing the MCB with an RCBO.


This will remove the earth leakage from your IT stuff from the main RCD, yet still offer full RCD / MCB protection to that circuit.


What make and model is your CU?

Is there a spare way on the non RCD side of the CU?

 

[GForrow]

Thanks for that. The make of the CU is Wylex, and yes there are 2 blank slots, to the right of the RCD with the lighting.

The only concern I have with this is that the study, along with the dining room, and all the first floor sockets are on this MCB. My 2nd floor sockets (3 storey house) have their own MCB.

So moving the MCB for the study, also moves the protection for the lounge and master bedroom, would this be a problem? Hoe easy is it to move the MCB, a couple of screws, plus a cable I would guess, but not sure. Electrics in houses doesn't bother me too much, always careful, but obviously would like to maintain as much protection as possible.

Cheers.

Gary

 

[plugwash]

personally the first thing i'd try is replacing the power supply in your PC with a modern high quality one. Leakage from a few PCs should not be enough to trip a RCD unless there is a fault in thier power supplies.

 

[GForrow]

I thought about that. The PC is only 6 months old, so I would have thought that the power supply is good. Unfortunately the PC is from DELL so is likely to not be standard.

Not sure how I can check, but its worth thinking about.

Gary

 

[jondiy]

Have you checked the plug tops etc for the equipment?

Could be a neutral strand of wire brushing across a strand of earth wire in the plug top (or extension leads used) . I have known offices with some 15+ PC's all running from a single 30mA RCD and have no trouble.

Why not replace the plug top that power the pc equiupment with a rcd plug top - try to find one with a 10mA tripping current (not 30mA).

Chances are if the pc is slightly leaky, ie >10mA , it may trip the plug rcd first before the house one - and all you'd have to do it reset it locally!

Combined with a UPS, this could be ideal!

If it actually works - and you want to make a more permanent job of it , then you could actiually fit a 10mA rcd socket to the wall in place of your existing socket.

It is imperative that you fit one with a delta n (tripping time) of 10mA and not 30mA. If you fitted a 30mA one, you can not guarantee it tripping before the house rcd!

It's only a suggestion, but its not going to cost you an arm and a leg to do it! surely worth a try.

The other option is to put 2nd floor sockets onto non-rcd side, and run a fused spur down (or extend the ring) , to provide a sockets for your pc stuff in the office.


OR!!!

Could be a faulty rcd - I know it's been checked, but some rcd's do not offer transient protection! Ask the electrician to do a ramp test to find out how much leakage current actually trips the rcd!

 

[CallEdsFirst]

Why not replace the plug top that power the pc equiupment with a rcd plug top - try to find one with a 10mA tripping current (not 30mA).

Chances are if the pc is slightly leaky, ie >10mA , it may trip the plug rcd first before the house one - and all you'd have to do it reset it locally!

Combined with a UPS, this could be ideal!

If it actually works - and you want to make a more permanent job of it , then you could actiually fit a 10mA rcd socket to the wall in place of your existing socket.

Clever

The other option is to put 2nd floor sockets onto non-rcd side, and run a fused spur down (or extend the ring) , to provide a sockets for your pc stuff in the office.

Cleverer still. Non-standard earth pin socket will prevent use for outside equipment too!

To be fair, a UPS might iron out the leaks anyway!

 

[GForrow]

Thanks for the suggestions, I'll have to think about which way to go.

I might try the UPS version, any suggestions as to the best place to get one from, and what rating. Failing that, and RCD socket, again, any suggestions for placing to look.

I guess the traditional Maplins would be good, but do you have any online type recommendations.

Sorry for all the questions, but obviously I don't want to make a mistake, I'd rather buy the right bits, from the right places first time.

Cheers.

Gary

 

[lookinn]

Always up the RCD to 100mA. Its common problem with computer power units they have capaciter filters going to earth.

 

[RF Lighting]

But 100mA does not provide adequate protection against inderect contact which is the reason the circuit is RCD protected in the first place.

It needs to be 30mA or less

 

[Joe4542]

Hi,
Quick point about your PC PSU - you say the computer is Dell? You should find that the PSU is bog standard ATX type - which you can get from almost anywhere, small pc repair places/maplins/PC world even.

Given that a PSU can be as little as £20 for a half decent one...Cheaper than a UPS.

Joe

EDIT : I've just looked and seen this at PC World...
UPS Extension type thingy

 

[CallEdsFirst]

Always up the RCD to 100mA. Its common problem with computer power units they have capaciter filters going to earth.

No matter what the situation. Even in a pool area. Just up it! Always! NOW!

People on here frighten me!

 

[Softus]

All sensible suggestions welcomed.

You have a faulty PC - that's the thing I would focus on.

As Joe4542 has said, the PSU is likely to be standard, and a high quality replacement should be no more than £40.

 

[ricicle]

But 100mA does not provide adequate protection against inderect contact which is the reason the circuit is RCD protected in the first place.

It needs to be 30mA or less

The 30mA RCD is to provide supplementary protection against direct contact, not indirect

 

[CallEdsFirst]

Direct contact - contact with exposed and intentionally live parts

MCB won't trip. RCD will.

Indirect contact - contact with component or extraneous metal parts live as a result of a fault.

MCB will trip assuming earthing is satisfactory.

100mA not all that useful in either situation!!!!