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Discuss CHINT RCD MAIN SWITCH MALFUNCTION AFTER TEST in the Electrical Forum area at ElectriciansForums.net

South Spark

Regular EF Member
Installed a new radial circuit in a garage from an existing CHINT garage unit.

All functioning well (tests fine) until after the RCD test. Then everything, lights etc stops working.

On investigation, while I've got 244V at the incoming side of the main switch I'm getting a reading of between 85 and 166.5 on the outgoing.

Guessing it's knackered the RCDI'll swap it out tomorrow but wondered if anyone else has encountered this fault. I've never touched CHINT gear.
 

Wilko

Electrician's Arms
Hi - sorry but this sounds a bit unlikely to me - you tested an RCD but you think the main isolator has died (?). I’m not familiar with this make but is it possible the bar is not clamped and it’s just wobbled out of contact during testing?
 

Charlie_

Electrician's Arms
As above, was going to say exactly the same thing..
Clamp might be tightened up but the busbar is floating behind it
 

South Spark

Regular EF Member
Hi - sorry but this sounds a bit unlikely to me - you tested an RCD but you think the main isolator has died (?). I’m not familiar with this make but is it possible the bar is not clamped and it’s just wobbled out of contact during testing?
I'm testing directly on the outgoing terminals of the RCD main isolator. Not sure how a floating busbar would affect that?
 

happyhippydad

Member
Electrician's Arms
A recent thread identified Chint RCD 's as being prone to faults. I have just fitted one that had the opposite fault to yours. It would not operate.
I think the confusion with the replies is that it was not obvious from your first post that the RCD was in fact the main isolator as well.
 

NDG Elecs

Electrician's Arms
I've only ever had one 60947-3 main switch go bad on me. It wouldn't have been that old either at the time, probably 20 yrs max. The customer had recently upgraded to LEDs in all rooms (cheap Amazon ones) but had left all the 400W dimmers in situ. The house flickered more than a paparazzi shoot! Never thought about whether this could have been the cause..seems unlikely perhaps but nothing else was apparently wrong with the installation.

But to the OP - yep, RCDs do fail and quite often they don't like big faults going through their circuitry.
 
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LeeH

Electrician's Arms
I’ve had a 4P 125A Merlin Gerin MCB fail after an RCD test (shunt trip) on a machine. Had to get one in a taxi at a cost of 300 quid.
 

spinlondon

Forum Mentor
A little while back, there was a thread about the reliability of RCDs.
Apparently only 3% of RCDs fail.
Currently there are 3 threads about failed RCDs.
 

Charlie_

Electrician's Arms
Also bear in mind, the 3% figure will be from manufacturers tests, all done under certain conditions..
In reality that 3% figure will be higher out there in actual installations..
 
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Wilko

Electrician's Arms
All things made by man will eventually fail. With cam belts on cars the manufacturer spells out the service life and if it’s not followed at some point the engine explodes.

So perhaps X% RCD failure rate should be a reminder to regularly test. Optimistic today :) .
 
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spinlondon

Forum Mentor
Main differences between seat belts and RCDs:
Seat belts are a statutory requirement.
As is there use (with a few exceptions).
Statistics show using seat belts reduces injuries and fatalities.
Seat belts are mechanical.
The failure points of seat belts are required to be tested during MOT tests.
Mot Inspectors can refuse to allow the vehicle to be driven if they deem a defect to be life threatening.

Other than when used for gardening tools, none of the above applies to RCDs.
 

Charlie_

Electrician's Arms
Main differences between seat belts and RCDs:
Seat belts are a statutory requirement.
As is there use (with a few exceptions).
Statistics show using seat belts reduces injuries and fatalities.
Seat belts are mechanical.
The failure points of seat belts are required to be tested during MOT tests.
Mot Inspectors can refuse to allow the vehicle to be driven if they deem a defect to be life threatening.

Other than when used for gardening tools, none of the above applies to RCDs.
Think you missed the point of my comparison..
A 3% failure rate for a life saving device is unacceptable
 
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