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Topic Title: RCD Socket tripping
Topic Summary: Machine TRIPPING rcd?
Created On: 01 November 2017 12:33 PM
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 01 November 2017 12:33 PM
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BILLYBOY65

Posts: 86
Joined: 11 May 2011

Hi

We have installed some socket outlets in an operations room in a company. Ran a new circuit x2, and fitted RCD socket outlets rather than try and install a RCBO to an old DB which is obsolete.
All good and tested OK, client called said that the RCD sockets keep tripping!

went to investigate, and the client had a machine that tripped the RCD socket, unplugged it tried other appliances and no trip, tested the RCD trip times and all good.
Told him the machine has an earth leakage,he got it PAT tested and said all OK ?

What are my options here?

1. Change to a isolator and hard wire machine in.

??
 01 November 2017 12:48 PM
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Martynduerden

Posts: 3235
Joined: 13 July 2008

Have you measured the equipments actual leakage?

What is the kit?

-------------------------
Regards

Martyn.

Only a mediocre person is always at their best
 01 November 2017 01:11 PM
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mapj1

Posts: 9553
Joined: 22 July 2004

Do you have a clamp meter that can measure milliamps ? If so measure the L-N current if need be using a small extension lead broken into singles. If not can you make a test lead with a mA meter in series with the CPC ? - though take care with any test leads that interrupt the CPC, especially with equipment where there may be a leakage problem.
In any case you need to know how badly the RCD is tripping, and if it is by design or because there is a fault.
If it is just the one appliance, it rather suggests that it is the problem. Depending how the PAT was done, it may have only passed an insulation test at DC, and not the AC leakage- which may be higher if it contains a mains filter (as the filters usually include a triangle of capacitors between L/N/E that serve to by pass short duration transients, but of course being capacitors they pass some current at 50Hz, but are seen as insulators at DC.)

As a matter of course check L-N polarity, but I'm pretty sure it will be alright.
And as Martin says, we need more info please - what is it, is it class 1 or 2, how old is it, condition of use, does it always trip, or only when hot etc.

Can you or he contact the maker of the equipment? It may be mis-wired internally.
(L-N reversal should not matter on CE marked kit, but depending on age and country of origin it may be asymmetric- when stuff for the UK was only sold in the UK, filters with a larger capacitance NE than LE were made, and do give better interference rejection in some cases)

Other options could be just to tell him its unfit for use on a 13a socket, or help him fix it.

-------------------------
regards Mike
 01 November 2017 08:31 PM
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Dave69

Posts: 621
Joined: 16 July 2011

All sounds very sus. You say the client says the SOCKETS keep tripping but you only mention one item plugged in which you call a machine, did you bother to do an insulation test on this so called machine? Guess not or otherwise a portable appliance would not of been necessary..
 01 November 2017 08:48 PM
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MHRestorations

Posts: 40
Joined: 22 October 2017

I'd also query 'had it pat tested'. Not all people who carry out PAT are equal. Do the test yourself to be sure.
 02 November 2017 10:53 AM
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AJJewsbury

Posts: 15990
Joined: 13 August 2003

this so called machine?

That's usual parlance for IT equipment (i.e. computer/server/PC) around here - PAT would probably have only done a visual and low current earth bond on that (at best). It might even have been a group of machines (or rack even) fed via a single plug - in which case quite a few mA of leakage could well be expected. If so, think about high integrity earthing (section 543.7) and using BS EN 60309 sockets rather than BS 1363 ones.

- Andy.
 02 November 2017 03:49 PM
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BILLYBOY65

Posts: 86
Joined: 11 May 2011

We are about to get further information regarding the piece of equipment.

There is a circuit with around 4 double outlets which are 30ma RCD socket outlets, when this is plugged in to any of them the RCD socket trips where it is plugged in to.

Andy- you mention BS EN 60309 Sockets and High Integrity earthing, surely I would still need an RCD for additional protection?

Billy
 02 November 2017 06:01 PM
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AJJewsbury

Posts: 15990
Joined: 13 August 2003

Andy- you mention BS EN 60309 Sockets and High Integrity earthing, surely I would still need an RCD for additional protection?

They tend to be mutually exclusive - the natural (correct) leakage current tends to cause the RCD to nuisance trip. In theory there is a small window (between 10mA and 15mA) where equipment could fall into high protective conductor currents bracket but be safe from tripping a 30mA RCD (as it may trip anywhere above 50% of its rating) - but I don't know anyone who can estimate leakage current that accurately. High leakage current equipment tends to be stationary and in a nice clean peaceful environment so additional protection isn't particularly necessary and BS 7671 is satisfied by a simple label on the socket saying for a particular piece of equipment only (or by using a higher rated socket).
- Andy.
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