Any Advice on tripping problem

[Bornagainsparky]

This one has really got me. I changed a Board on a TT system protected by 100mA RCD everything was fine on the old board except more ways were needed. Put the new 17th edition CU in covered by 100 amp main switch and 2 x 30mA RCD's, everything is tripping.

Carried out IR Tests everything is fine, changed RCD's again, same problem.

Re-checked all cables both visually and again with IR test, no problem up to sockets, switches, cooker outlet, showers etc but as soon as switches are made and loads is applied, both RCD's trip, very frustrating

 

[telectrix]

neutrals incorrectly cross connected or borrowed neutral on say, landing light. try putting both lighting circuits on the same rcd.

 

[woowoo]

1: Check that the Neutral conductors are connected correctly e.g Main switch to supply side of 2 x RCD's then load side to 2 seperate neutral bars for final circuits.

2: You could have earth leakage on the appliances / loads which is <100ma but >30ma hence tripping of the RCD.

Have you done a ramp test on the RCD to see where it trips?

 

[meego]

also in some cases, previously a circuit could have been sharing a neutral somewhere, so in the board u have 2 lives, one on each rcd, and only one neutral, in wich case both lives need to be on the same rcd. this will stop the tripping, however it is incorrect, this is only a possibility.
to confirm, make sure u have an equal amount of lives and neutrals.

your first replies r correct your neutrals are mixed up strip them all and start over, put them back one at a time, first switch on all lights and plug a load into all plugs

 

[Bornagainsparky]

also in some cases, previously a circuit could have been sharing a neutral somewhere, so in the board u have 2 lives, one on each rcd, and only one neutral, in wich case both lives need to be on the same rcd. this will stop the tripping, however it is incorrect, this is only a possibility.
to confirm, make sure u have an equal amount of lives and neutrals.

your first replies r correct your neutrals are mixed up strip them all and start over, put them back one at a time, first switch on all lights and plug a load into all plugs

Thanks to all who have responded, much appreciated and I agree with all points

To simplify things I disconnected everything including all earths and neutrals and tried 2 of the more easily identified, offending circuits, one at a time, this was the shower and cooker, and in both cases they tripped. Again I carried out IR Test to confirm if ok and readings above 200Mohms were obtained up to isolator.

Unfortunately I don't have ramping facility on my test equipment, one of the earlier Flukes but something to consider.

The installation was carried out new, some 4 years ago by another electrician and I have seen one or two questionable items but in general it doesn't appear too bad but what I'm experiencing appears to defy all logic

I have considered disconnecting all again and trying each circuit individually with RCBO or even just MCB which is a bit radical but may highlight something

Any advice greatly accepted

 

[telectrix]

check that the neutral connections are in the correct neutral bars . including the manufacturer's tails from main switch to RCDs to N bars.

 

[Octopus]

You say both the shower and cooker circuits tripped the RCD - are they both on the same RCD or are they on seperate RCD's? Is the rest of the house "stable" if these cicuits are not connected? Sounds like you're on the way to finding the issues.

 

[tony mc]

If you dont have a ramp test try testing the RCD with everything disconnected.

Power up the RCD and test it a 1/2 1 & 5 to see if its working at the board no load or neutral connected.

As Tel has said check the way the RCD have been wired it won't be the first time they have been mixed up at the factory.

The way I read it is that the ccts power up but when you put a load on it trips putting the trip coil out of balance.

 

[Bornagainsparky]

check that the neutral connections are in the correct neutral bars . including the manufacturer's tails from main switch to RCDs to N bars.

Not back until Monday but will do, have assumed they are correct but shouldn't take that for granted

Thanx

 

[Bornagainsparky]

You say both the shower and cooker circuits tripped the RCD - are they both on the same RCD or are they on seperate RCD's? Is the rest of the house "stable" if these cicuits are not connected? Sounds like you're on the way to finding the issues.

They are currently on the same RCD but have moved them around in different configurations to the same effect, the way it is at the mo' is that I have 2 rings working, 1 upstair and 1 downstair with another downstair tripping under load

None of the lighting, Shower and cooker circuits work, the lights are on a different RCD

 

[Bornagainsparky]

If you dont have a ramp test try testing the RCD with everything disconnected.

Power up the RCD and test it a 1/2 1 & 5 to see if its working at the board no load or neutral connected.

As Tel has said check the way the RCD have been wired it won't be the first time they have been mixed up at the factory.

The way I read it is that the ccts power up but when you put a load on it trips putting the trip coil out of balance.

I have done this with all breakers off directly on load side of RCD and they don't trip under x 1 condition but around 14.8ms at x 5 but will try as above

You are correct in the way that you see it

 

[tony mc]

I have done this with all breakers off directly on load side of RCD and they don't trip under x 1 condition but around 14.8ms at x 5 but will try as above

If the RCD is not tripping under test a 1 x then you have faulty RCD.s they should be tripping out under 300 ms.

 

[Bornagainsparky]

I have done this with all breakers off directly on load side of RCD and they don't trip under x 1 condition but around 14.8ms at x 5 but will try as above

If the RCD is not tripping under test a 1 x then you have faulty RCD.s they should be tripping out under 300 ms.

Exactly my initial thoughts so we changed them and the same problem existed so I contacted CEF and asked if they had any knowledge of a faulty batch to which they said no, however we are in the process of changing again but from the concensus of opinion, it appears to be a neutral problem which I will investigate, possibly coupled with faulty RCD's on Monday so will keep you posted in the meantime sincere thanks for all contributions

 

[Bornagainsparky]

neutrals incorrectly cross connected or borrowed neutral on say, landing light. try putting both lighting circuits on the same rcd.

Thanks to all concerned on this query, as promised I said that I would keep you all informed. It was a borrowed neutral that gave me the problem and it was actually taken from the existing lighting circuit to a new bathroom which as we all know should have had it's own supply as per 17th edition regs. However a great relief after going round in circles for a couple of days, so sincere thanks to all and a great resource in the Forum

 

[AP Electrical]

Thanks to all concerned on this query, as promised I said that I would keep you all informed. It was a borrowed neutral that gave me the problem and it was actually taken from the existing lighting circuit to a new bathroom which as we all know should have had it's own supply as per 17th edition regs. However a great relief after going round in circles for a couple of days, so sincere thanks to all and a great resource in the Forum

Its good when somebody takes the time to put the end to an interesting thread, As a novice it can be frustrating reading threads regarding issues people come across, only for them to vanish without saying whether the issue was resolved or not, this site and it's members have a wealth of knowledge and are great resource for anyone looking for a future in the electrical sector - just an observation. :goofy: