RCD Tripping Problem

[dan86]

Hi Guys,

I wonder if someone can give me some advice if possible? I have a uk domestic setup with a standard rcd and 32amp breaker on my ring main sockets. I've got few pc's running however when you plug too many machines in the rcd trips itself and has to be reset. Is there anyway to prevent this from happening or a solution to this problem? I have heard about running the machines earthing seperate from the ring mains earthing but I don't know if that makes any difference.

Daniel

 

[Spark123]

PCs can have a highish earth leakage current hence when you plug a few in the total earth leakage exceeds the 16+mA required to trip the RCD.
Running the PCs from separate RCDs can eliviate the problem however if you are using a lot of PCs then high integrity earthing might also need to be deployed.
How many PCs are you talking of?

 

[ericmark]

We cured the problem by using UPS on the PC's which seemed to stop the tripping.

However since then there has been a lot of talk over the use of UPS and it's removal of safety systems and in hind sight I wonder if the UPS route was dangerous.

The best would be to split the supply to a number of RCD devices.

But in university we had around 10 PC's on one RCD without a problem and one must raise the question are the PC's faulty. To be used without special earth arrangements there is a limit to the leakage. I think 10ma so no single computer should cause a problem.

 

[Monkeh]

But in university we had around 10 PC's on one RCD without a problem and one must raise the question are the PC's faulty.

No, they simply contain different components. The earth in an ATX supply is only used for the chassis. Bonded to that are USB screens (sometimes bonded to/used as the negative line in USB devices), audio shielding/ground, firewire shielding (possibly suffering from the same issue as USB), etc. A small amount of leakage is not unusual in the least, but how much very much depends on the components, case, and often peripherals.

One of these days I'll daisy-chain my way into running everything in here off a 30mA RCD and see what happens. It could be interesting.

 

[dan86]

Thanks for both of your replies.

Spark123:

I think its around twelve machines however atleast 5 of them are servers for various things like cctv domain etc. The rcd says 30mA on it. I've been told by a sparky that we can't have a seperate rcd because its a domestic property, I'd prefer to have the server machines on a seperate rcd and the rest of the house would be on the ring main which would further reduce the event of a trip.

ericmark:

I have a apc 1500va ups which is big enough todo the job however when plugged into the mains and then the machines plugged into the ups I still get the nusience trip problem.

 

[Johnmelad502]

Thanks for both of your replies.

Spark123:

I've been told by a sparky that we can't have a seperate rcd because its a domestic property,

 

[Adam_151]

I've been told by a sparky that we can't have a seperate rcd because its a domestic property,

That is incorrect, whether it is incorrect because he is mistaken or incorrect because you may have miss understood him I cannot comment upon!

If you post pics of your fuseboard and supply/metering arrangement we can advise on how big a job it would be to separate your computer room onto a separate RCD

 

[dan86]

I've been told by a sparky that we can't have a seperate rcd because its a domestic property,

That is incorrect, whether it is incorrect because he is mistaken or incorrect because you may have miss understood him I cannot comment upon!

If you post pics of your fuseboard and supply/metering arrangement we can advise on how big a job it would be to separate your computer room onto a separate RCD

Adam,

He told me that because its domestic is has to have the rcd protection before the breaker, and if you were in a ict suite at a school for example you don't need a rcd only a breaker because its being monitored. I am not a qualified electrician so would NOT carry out anywork myself especially in the consumer unit/mains incoming area however I could easily wire up a seperate breaker on its on circuit for my needs but we have electrical inspections every few years so it would be awkward explaining that and also they would remove the breaker/cirucit I had put in.

Do you mean photos of inside the consumer unit as photos outside showing the breakers/incoming power wouldn't show that much really? I might be wrong.

 

[Steve]

Do you mean photos of inside the consumer unit as photos outside showing the breakers/incoming power wouldn't show that much really? I might be wrong.

Both if you feel confident - remember, even with the CU mainswitch off, its incoming cables are still LIVE. And when you pull off the CU cover the busbar may be very exposed and 100% live if the mainswitch is on.

 

[Steve]

You got a UPS? Your other post implies so. Does it not give you enough cover to go and flick the RCD back on?

 

[Monkeh]

You got a UPS? Your other post implies so. Does it not give you enough cover to go and flick the RCD back on?

The RCD which will immediately go off when all the equipment powers on again?

 

[dan86]

You got a UPS? Your other post implies so. Does it not give you enough cover to go and flick the RCD back on?

I will get a picture of the consumer for you. I might be able to get away with plugging the ups in but sometimes with few machines running it does trip the breaker, in regards to run time yes I have a good 10-15 mins which gives time for the rcd to be turned back on. However as I said it does sometimes just trip the rcd even when i plug the ups in.

Monkeh:

Yes sometimes if all the machines boot up the rcd does trip so a couple have to be unplugged for 20-30 seconds and then plugged in again and its fine.

 

[Steve]

If it were me, I'd run a non-RCD circuit for the IT equipment. IT stuff will always have a high earth leakage.

 

[tonylec]

Your sparky is mistaken, schools are not exempt from the 17th edition! (most of our work is in schools), if its a new or modified install they have to have 30mA RCD protection, unless the school has a qualified spark on its staff it ain't under supervision (some factories claim supervision because they have electricians permanently on staff)

What you do is this, you break up the computers so as they run off separate RCBo's, say no more than 4 points from one RCBo, the board containing the RCBo's can either have a simple mains switch if it is within tails length of the meter or have a feed from a 100mA type S RCD if it's remote, this gives fire protection if the cable is damaged, but gives trip diferentiation.

 

[Steve]

Your sparky is mistaken, schools are not exempt from the 17th edition! (most of our work is in schools), if its a new or modified install they have to have 30mA RCD protection, unless the school has a qualified spark on its staff it ain't under supervision (some factories claim supervision because they have electricians permanently on staff)

1. He's not in a school. He used a school IT suite as an example of a larger scale IT installation.
2. Now, I'm not sure here, but why would a school IT suite need RCD protection? Almost always the wiring is run in compartment trunking. There are no hidden cables.