Insulation Resistance query

[tony mc]

With 10.5 meg on the test I cant see this being the culprip tripping the RCD bearing in mind it should hold anything at or over 7666Ohms.

I wonder if they will be back on the phone ??

 

[Amp David]

Don't know, wait and see i guess.

Yeah, the reading I was getting is fine, but just wondered why

 

[Guitarist]

Did you take the socket off and have a look. As said earlier, there may be "stuff" rattling around in there or possibly an internal fault with the socket when the pins are opened up. Worth a look.

 

[Amp David]

Yes removed and put on a temp replacement to see, but no difference.

 

[Guitarist]

Out of interest, have you clamped the cpc with the box connected and switched on? Just wondering what the actual leakage is.

 

[Amp David]

No I didn't.

 

[Guitarist]

Would be interesting to see what readings you got with a different sky box. Of course, this could be a red herring and the problem lies with another appliance somewhere, such as an immersion heater or a shower element breaking down.

 

[Tuttle]

See what you mean, but no coax there, just scart from sky to TV.

Wild guess ... if the sky box is connected to the TV via the scart then maybe the TV is connected to something else that is connected to earth, e.g. a TV aerial amp in the loft?

 

[Flyingsparks]

Once got called out to a tripping RCD fault at a house. On testing the circuits we found that the insulation resistance was quite low on the outside lights so disconnected these and thought we had cured the fault.

The next day we had another call from the lady to say the RCD had tripped again. so we went back & tested all the circuits again but could not find any problems .

The RCD did not trip when we were on site and seemed to perform ok when tested.

About two hours after leaving the job, we got a call to say that it had tripped again.

The only thing left to do was replace the RCD which we now suspected may be faulty, so we fitted a replacement and left site yet again.

We got a phone call a few days later to say that the unit had tripped again , but only once since we had fitted the new unit.

At this point I began to suspect that there may be a fault on the supply into the building and asked the customer if any work had been carried out on the distribution network locally, but she was not aware of any.

I got a call the next morning and the lady said that the RCD had tripped again. It was throwing down with rain outdoors and she said that she could see smoke coming from the bottom of a pole in the lane at the bottom of her garden!

Apparently a farmer had cut the hedge a few weeks ago using a cutter attachment on his tractor, and while doing this he had unknowingly caught the electricity cable a the bottom of the pole.

The DNO came out and fixed the cable and I assume the farmer had to foot the bill.

The RCD worked fine from then on and the customer unfortunately ended up with quite a large bill from us for all the fault finding work we had done.

 

[Guitarist]

I hope she managed to get compensation from someone.

 

[Flyingsparks]

The last time I spoke to her she muttered something about having words with the farmer :veryangry2:

 

[Guitarist]

Hope she has a large brolly....

 

[Edd]

Havent read the complete thread, but about 10 years ago had an RCD tripping every time it rained! nobody could find the fault. but I traced it to the video recorder which had a N fault to the aerial.. The aerial on the roof when it rained grounded the Neutral through the building fabric enougth to cause the RCD to trip.. may be the same thing with the dish..

 

[telectrix]

Havent read the complete thread, but about 10 years ago had an RCD tripping every time it rained! nobody could find the fault. but I traced it to the video recorder which had a N fault to the aerial.. The aerial on the roof when it rained grounded the Neutral through the building fabric enougth to cause the RCD to trip.. may be the same thing with the dish..

now that's interesting. throughout the 70's a lot of my work was repair of TVs. nearly all of them had a steel chassis which was the "common ground" of the set and was connected directly to the neutral. all were on a 2 wire flex, no cpc. had a couple of belts from a set where customer had fitted plug incorrectly. after a particularly sharp shock, i then got wise and checked plug wiring and fuse before starting. in those days, plug tops weren't fitted by manufacturers. to get to the point, the screen of the aerial was also connected directly to the chassis, so can see exactly where you are coming from.

 

[Guitarist]

Doesn't a sky box send out 50v to the dish?