TV trips rcbo in one socket but not the next socket.

[a-z electrics]

Here's a weird one.. customer complains of sporadic rcd tripping some time ago so I do a series of tests, only thing on rcd are skts and lights... never got to the bottom of it but I noticed the quirky Square D quikline rcd trips at around 15mA on a ramp test.
So I recommend replacing the whole DB, as its quite old anyway, which Ive just done with rcbos.. no real problems apart from a N-N ring open but found this at a kitchen socket and now ok.. All tests fine, downstairs ring lowest IR was N-E 170MOhm at 500V dc. Auto rcd test trips at 29ms at both x1 and x5.

Now when the plasma screen tv is plugged in at the lounge, the ring trips after a few seconds. When tv is plugged into the next socket along, about 3m away via a reel extension, it works and doesnt trip... Its on the same cct.

when anything else is plugged into the tv socket (and there's a lot of media stuff on it too) its fine. Kettle plugged into it will go to boiling no problem.
when tv is plugged back into the original skt via the extension reel, it trips again!
replaced the socket just in case but no difference.
WTF? Any suggestions welcome.. I'm going back to do a pat test on tv this afternoon but is this weird or am I missing a trick here?

 

[buzzlightyear]

Before you start ripping a consumer unit out to replace with another rcd or other, I would be better to find the culprit for what's causing a rcd to trip.it would be better to pat test on see what causing a problem has well.

 

[a-z electrics]

Here's a weird one.. customer complains of sporadic rcd tripping some time ago so I do a series of tests, only thing on rcd are skts and lights... never got to the bottom of it but I noticed the quirky Square D quikline rcd trips at around 15mA on a ramp test.
So I recommend replacing the whole DB, as its quite old anyway, which Ive just done with rcbos.. no real problems apart from a N-N ring open but found this at a kitchen socket and now ok.. All tests fine, downstairs ring lowest IR was N-E 170MOhm at 500V dc. Auto rcd test trips at 29ms at both x1 and x5.

Now when the plasma screen tv is plugged in at the lounge, the ring trips after a few seconds. When tv is plugged into the next socket along, about 3m away via a reel extension, it works and doesnt trip... Its on the same cct.

when anything else is plugged into the tv socket (and there's a lot of media stuff on it too) its fine. Kettle plugged into it will go to boiling no problem.
when tv is plugged back into the original skt via the extension reel, it trips again!
replaced the socket just in case but no difference.
WTF? Any suggestions welcome.. I'm going back to do a pat test on tv this afternoon but is this weird or am I missing a trick here?

Before you start ripping a consumer unit out to replace with another rcd or other, I would be better to find the culprit for what's causing a rcd to trip.it would be better to pat test on see what causing a problem has well.

thought i did because of the very low trip level on the rcd. Also it was very sporadic earlier, maybe once a couple of days.

 

[pc1966]

Have you a leakage clamp ammeter to see what the current on that RCBO is before TV and after on that socket and on extension lead?

It may be close to tripping on other stuff, or it might be something bizarre relating to high frequency noise that somehow the extension and 2nd socket is reducing a touch.

 

[Lucien Nunes]

Is the TV class I or II? Not long ago someone tried the same trick with the extension lead which stopped the tripping, but it turned out that the extension lead earth was open-circuit and stopping the faulty / leaky appliance seeing earth.

 

[a-z electrics]

thought i did because of the very low trip level on the rcd. Also it was very sporadic earlier, maybe once a couple of days.

Is the TV class I or II? Not long ago someone tried the same trick with the extension lead which stopped the tripping, but it turned out that the extension lead earth was open-circuit and stopping the faulty / leaky appliance seeing earth.

its class1 and pleased to say it failed the IR test, 0.06M i think it was, except it wasnt the tv even, it was the power lead!! had a spare lead and everything fine now, altho why it failed in one skt and worked in the next one is a bit puzzling.. must have just been on the edge.
thanks for all the helpful replies, we learn something new each day
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its class1 and pleased to say it failed the IR test, 0.06M i think it was, except it wasnt the tv even, it was the power lead!! had a spare lead and everything fine now, altho why it failed in one skt and worked in the next one is a bit puzzling.. must have just been on the edge.
thanks for all the helpful replies, we learn something new each day

the original lead had two interference suppressors on, one at each end.. my new one didnt have any, dont know if thats relevant or not..

 

[DPG]

What sort of mains lead was it? Clover leaf?

Did the lead show low resistance between cores when a standard (ie. Non IR) resistance check was made?

Just interested to know what the fault actually was. I'd be splitting the cable until I found the fault, but that's cos I don't get out much

 

[Strima]

Those power leads break at the earliest opportunity, normally by one of the ends near the plugs where the flex tends to bend, especially in tight areas behind TVs etc. I found similar problems with laptop power leads being coiled up and thrown into bags.

 

[DPG]

Those power leads break at the earliest opportunity, normally by one of the ends near the plugs where the flex tends to bend, especially in tight areas behind TVs etc. I found similar problems with laptop power leads being coiled up and thrown into bags.

Unusual on a TV though where it would very rarely get moved.

 

[Lucien Nunes]

Yes, would be interesting to examine that lead. I wonder whether it was original to the TV or a grey import replacement? I've seen plenty of dodgy cordsets but not yet encountered one with low insulation, although there have been reports of connectors being moulded out of partially conductive plastic, where you could get a tingle from just touching the plastic body of the IEC.

 

[littlespark]

Why would a faulty lead trip on one socket, but not the next one?

could be the 2 sockets are actually on different circuits, and one rcbo more sensitive than next?

Does the “working” socket not have a cpc? (I think this was alluded to earlier)

Simply the distance between one socket and the next from the CU.
3m could make a difference, but not if they are on the same rfc. Is one maybe a spur, making it longer?

 

[Strima]

Unusual on a TV though where it would very rarely get moved.

Probably not but if the bend radius is exceeded for a period of time the damage may not show/occur until the cable is moved.

Why would a faulty lead trip on one socket, but not the next one?

Movement of the cable from one position to another. Had it where holding the cable straight will pass and IR test but bend it slightly the cable will fail.

 

[stevethesparks]

Try disconnecting the aerial, if this stops the tripping I refer you to post #5

 

[a-z electrics]

What sort of mains lead was it? Clover leaf?

Did the lead show low resistance between cores when a standard (ie. Non IR) resistance check was made?

Just interested to know what the fault actually was. I'd be splitting the cable until I found the fault, but that's cos I don't get out much

It was a standard kettle type lead, I was so relieved to find the problem I just binned it.
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Why would a faulty lead trip on one socket, but not the next one?

could be the 2 sockets are actually on different circuits, and one rcbo more sensitive than next?

Does the “working” socket not have a cpc? (I think this was alluded to earlier)

Simply the distance between one socket and the next from the CU.
3m could make a difference, but not if they are on the same rfc. Is one maybe a spur, making it longer?

It's on the same RFC but I think (from an earlier inspection I did) that the second sky was a spur..
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Why would a faulty lead trip on one socket, but not the next one?

could be the 2 sockets are actually on different circuits, and one rcbo more sensitive than next?

Does the “working” socket not have a cpc? (I think this was alluded to earlier)

Simply the distance between one socket and the next from the CU.
3m could make a difference, but not if they are on the same rfc. Is one maybe a spur, making it longer?

All cpcs are intact.. I can assure you the installation testing was thorough! The only other thing I wondered about was the ring had been extended into the conservatory but all was good..

 

[hasel5]

So you replaced a complete Db ?

 

[DPG]

So you replaced a complete Db ?

Eh? He replaced the TV power cable.

 

[hasel5]

Says he changed DB in his post

 

[DPG]

Says he changed DB in his post

Sorry, yes you're right. The original job was a DB change.