Hi sorry for this waffly post!!
Any ideas welcome! Me and my certified brother-in-law are stumped. Unfortunately he is away and I am waiting for another electrician to come and review the instalation. So in the mean time thought I would try here.

Ok had my house re-wired 5 years ago so everything fairly new. Just knocked down an old utility room and built a new extension. Ring main from utility was reused in extension. So have existing downstairs ring, kitchen ring, and "new" extension ring.

Just bought new TV (class 1) and plugged in aerial lead and as soon as I went to plug power into wall the moment the earth pin connects the RCD trips (socket off).

My aerial system is a single mast with an amp in the loft that sends the signal to 5 aerials in various rooms. I already have other TVs working on this system in other rooms. Interestingly 1 tv is class 1 and 1 tv is class 2.

So I have done lots of checks and this is my conclusion so far.

The problem is not introduced by the amp as I have removed it and connected the aerials with a passive splitter. The same rcd trips.

The problem is not in the extension aerial because I have extended the dining room aerial temporarily and the same rcd trips.

This is the interesting bit. I think the fault (if there is one) may be in extension ring as when I power the new tv from either the kitchen or downstairs ring I can connect to the extension aerial and no problems.

However the extension ring was signed off and works fine for every other appliance. (I can use the type 2 tv in the same aerial and power sockets no problem.)

So because of the above and trying different combinations of aerials, tvs and ring mains I think I have concluded that:

When 2 class 1 tv is connected to any existing ring main (not extension one) and any aerial socket all is well. However the moment I try to plug the power of either class 1 tv into the new extension ring the rcd trips.

My guessing is that effectively having 2 class 1 TVs means that they are both putting some minor leakage current on the aerial lead which is connected and therefore effectively connecting the two ring mains together. But what I can't explain is why it only occurs when one of those ring mains is the new extension one?

Any ideas greatly received.

Thanks

years ago when AM cb radio was common we used to make a filter out of 2 loops of tv coax which effectivly split the feed coax so there was no direct link between the aireal and the tv, supprisingly the tv picture was still good.

In can't remember exactly how it was wired just that a loop from the aireal was taped to a loop from the tv, no direct electrical connection, the loops were about 6" Dia. not sure if this will work in the digital age.

sorry i don't have an electrical solution for the RCD's tripping.

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Vince

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You need an "isolated" co-ax aerial socket, most do have isolation capacitors in them but not all. Best put one of these at each aerial outlet,

Dave.

What happens if you disconnect all other tvs from the aerial and then plug in the tv using the supply in the extension?



That was my next suggestion.

Do a ramp test on rcd to check for correct operation and find out how many mA's its tripping at. Dont forget to disconnect the out going circuit first.
Do a earth leakage current test on the two tv's.
Insulation test between all socket circuit conductors.
Check polarity at sockets. Dont rely on documentation, for installation being correctly installed.

Thanks all but solved!

Turned out that one of the faceplate screws in the extension had nicked the neutral wire. Probably happened when decorating...:-(.
Wasn't enough to trip RCD on its own needed the aerial leakage to take it over!

Cable corrected and all TVs now work.

Thanks

That should:
A Have been picked up during dead testing.
B The RCD should continuously refuse to reset if a N-E fault exists.

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Those who make no mistakes do very little work!!......

He did say 'happened during decorating'. Plus it won't always trip. Somtimes load is required on the cucuit before it will trip.

Broke number 1 rule . Always check the basic stuff first, before breaking out the capacitors and taped loops.



Would be interesting to know what the ZS is at the socket. (with all loads disconnected)Could still be a polarity issue

FYI the fault was on the switch socket for a fused spur. That fused spur has never been used (waiting for appliance). Also the neutral cable was only nicked I.e the outer was damaged but very difficult with naked eye to see if core breached!

Come to think about it he when electrician started investigation he was able to get RCD to trip - I actually now think the earth was faulty on that ring which he sorted first which then hilighted the E to N fault in that ring.... I.e untill he started that ring wasn't earthed..properly.?

Basically the aerial leads because we're class 1 tv was providing the earth by connecting earth from extension ring to main tv ring.

Does make me wonder what results will be on the original cert.....

Yes.
I wonder if the certificates are worth the paper they are printed on.