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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.
 
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Wilko

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Arms
Esteemed
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_

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

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Arms
Esteemed
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.
 

Wilko

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Arms
Esteemed
I'm testing directly on the outgoing terminals of the RCD main isolator. Not sure how a floating busbar would affect that?
Hi - got it, I didn’t realise the rcd was the isolator :) .
 

NDG Elecs

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Arms
Esteemed
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

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Arms
Esteemed
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.
 
D

Deleted member 26818

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_

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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..
 

Charlie_

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Arms
Wonder what the public opinion would be if say; at least 3% of all seatbelts fail.
 

Wilko

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Arms
Esteemed
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 :) .
 
D

Deleted member 26818

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_

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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
 
D

Deleted member 26818

Think you missed the point of my comparison..
A 3% failure rate for a life saving device is unacceptable
No not really.
The failure rate of seat belts is offset by the fact that they are tested annually (after the first 3 years), and if they fail the test, they must be fixed or replaced.

Biggest problem with seatbelts is the lap belt type often used for the centre seat in the rear of cars which in the event of an accident can cause severe internal injuries which would not occur with 3 point seatbelts.
Such belts can still be used effectively with many child car seats.
 

Charlie_

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Arms
Sorry, not interested in seatbelts..
Only the 3% failure rate of a life saving device...
There are statutory requirements in place for earthing.. The use of RCDs in many instances are required to satisfy those statutory requirements..
Do you have any statistics for the failure rates of MCBs?
 
D

Deleted member 26818

To start with any safety device can fail.
The failure rate according to a report from Electrical Safety First conducted in 2006, was in fact 7.1% falling to 2.8% with regular use of the test switch.

As far as I am aware, there are no statistics for failure of MCBs.
 

NDG Elecs

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Arms
Esteemed
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.
I thought the failure rate was higher than that. I vaguely recall reading so in the Beama RCD handbook. Will have to find it again
 
B

Bobster

Think you missed the point of my comparison..
A 3% failure rate for a life saving device is unacceptable
Now you're right, but not completely right.

50% failure rate would be entirely acceptable if you had diagnostics to warn if it had failed. A seat belt for example, might not buckle one day.

Or if these failures failed safe. RCD trips and goes open circuit.

The real numbers you need to look at are the mean time to dangerous failing.

Anyone designing safety circuits or machine design will know all about this.
 
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