Circuit breaker that keeps tripping - who knows about electrics?

[Bill Edwards]

I've an issue with a circuit breaker or RCD that keeps tripping. This happens mainly when a faulty item is plugged in with a dead short.
However, this is a major problem as I'm not able to access it to reset it, so I took some advice and included one of these RCD's that is designed to protect you if you cut the cable on a power tool.
So far, it's never actually tripped, it's still always the inaccessible trip that goes.

So, I installed a B10 circuit breaker into the live wire hoping that this would be the one to trip. The devices that cause the problem are protected by a 10A fuse, which sometimes blows when something goes wrong.
This still hasn't done it. The B10 circuit breaker trips, but along with the one I can't have trip. Very annoying.
Unfortunately I have no way of finding out what the problem one is rated to, but it will be more than 10a.

What do I need to do in order to stop it tripping? I'm not worried by having one that is too sensitive and causes annoyance, as that is less of an issue than the current setup.

 

[500e]

Bill it would be better to isolate the problem rather than fit a bodge, presumably the inaccessible one is in another building someone else's part of.
Does the trip go on start up, while something is running, or intermittently, you should be able to isolate the problem, is it on the circuit you think ? or is it a bigger problem that is masked by the second trip.
May be time to get Sparks in & run a test on all circuits

 

[rtbcomp]

I'm assuming you are operating some sort of test bench?

I suppose you could check for a dead short before you plug a faulty item in.

If its the RCD tripping get a 1:1 ratio transformer rated at the voltage & current you require, this will prevent the path to earth from the mains. Earth one of the secondary connections and fit an RCD (& MCB) to the output.

 

[Robotstar5]

If its the RCD tripping get a 1:1 ratio transformer rated at the voltage & current you require, this will prevent the path to earth from the mains.

Look for isolation transformer we used a lot to protect PLC's (industrial computers) where there are a lot of spot welders as they cause a lot of "noise" on the mains.

 

[BrokenBiker]

MCB blow because of over current, RCD blow because of current leaking to earth.

what are you doing when it trips? my father had issues for ages with an rcd tripping 'randomly', but after he got rid of his tumble dryer as id suggested hundereds of times it stopped

 

[Parm]

I had issues with RCDs tripping out all the time. After much head scratching it turned out that rats had chewed though the cables behind the wall cavities in the barn. Holes all blocked up and rewired the barn and ultrasonics gadgets installed to keep the rats away.

You wanted to see some of the cables, outer grey all gone and both red and black fully exposed. Im surprised the whole thing didn't burn down !

 

[rtbcomp]

A friend of mine wire a new light in and every time he switched it on the RCD tripped. He'd only connected the neutral to the power neutral instead of the lighting in the comnsumer unit!

 

[Bill Edwards]

Sorry, I didn't say. Yes, essentially a repair/test bench.
I don't know whether manually testing for continuity would work, but it wouldn't really be practical - 99% of the time there isn't any problem, it's quite rare but extremely annoying and problematic.

So, this is what I need:
http://www.ebay.co.uk/itm/SAFETY-IS...al_Components_Supplies_ET&hash=item3390e6b432

OK 'til I look at the price of them!

 

[brightspark]

A friend of mine wire a new light in and every time he switched it on the RCD tripped. He'd only connected the neutral to the power neutral instead of the lighting in the comnsumer unit!

i presume u mean he conected the neutral to the incomer supply to rcd and the live conected on the outgoing on the mcb causing current imbalance or if it was a split twin rcd board conected the neutral to one rcd and the live to the other rcd

 

[Robotstar5]

A friend of mine wire a new light in and every time he switched it on the RCD tripped. He'd only connected the neutral to the power neutral instead of the lighting in the comnsumer unit!

Quite often happens when fitting a new dual RCD board to an old installation where there is 2 way lighting on stairs and you feed the up and down lights off separate RCD's.

 

[brightspark]

Quite often happens when fitting a new dual RCD board to an old installation where there is 2 way lighting on stairs and you feed the up and down lights off separate RCD's.

tell me about it a bloody borrowed neutral typically councill electricians used to do it or cheapskates

 

[Robotstar5]

tell me about it a bloody borrowed neutral typically councill electricians used to do it or cheapskates

Got the T-shirt

 

[rtbcomp]

IIRC it was a single RCD, the power circuits were protected the lighting circuits weren't. Moving the light's neutral to the other neutral block fixed it, after we'd changed the light fitting!

 

[Cyberprog]

You can get automatic resetting RCD's by the way.

 

[Robotstar5]

You can get automatic resetting RCD's by the way.

Wouldn't like to be on the receiving end

 

[Cyberprog]

Wouldn't like to be on the receiving end

They only reset once the fault has been cleared.

 

[Bill Edwards]

OK, before parting with money is this what I need?

http://uk.rs-online.com/web/p/products/4368805/

Also, if I plug this in then connect a breaker designed to protect you if you chop a power cable would this provide the necessary protection from electric shocks?
It would also have the B10 breaker that I have which should protect the transformer from being overloaded?

 

[rtbcomp]

That's the thing, but RS do tend to be the most expensice. Try CPC or Farnell's before buying.

 

[Bill Edwards]

Thanks, but they seem to be the same and neither seem to have the 230 to 230 ones. Any other suggestions before going with RS?

 

[rtbcomp]

@ Striker I have moved your topic to its own thread to avoid hi-jacking this one

http://www.mig-welding.co.uk/forum/threads/plasma-cutter-trips-rcbo.48218/