Electrical problems in the workshed

[dobbslc]

Proteus is pretty rubbish gear so I wouldn't be surprised if the RCD has failed again! It's worth unplugging everything first just in case it's a faulty appliance but remember if you have any hard wired equipment the neutral may still be in circuit, that includes switch fuse spurs that are only single pole. Lighting etc.

 

[reb78]

This can be a symptom of a neutral to earth fault within the installation as it causes the current from the test button to completely bypass the RCD.
Note that switching off the MCB's does not normally disconnect the neutral so this symptom will be the same with all MCB's off.

The test button not working can also suggest that the tripping mechanism of an RCD is faulty, but that is unlikely to be the case here as we know that the RCD is tripping.

Thanks for this.

Noting what you say and that it may not make a difference, all but five mcbs have now been turned off and it is still doing it. I will work my way to all turned off and I guess at that point i may have to get someone in to look at it as I wont have identified anything to look at!

 

[reb78]

Proteus is pretty rubbish gear so I wouldn't be surprised if the RCD has failed again! It's worth unplugging everything first just in case it's a faulty appliance but remember if you have any hard wired equipment the neutral may still be in circuit, that includes switch fuse spurs that are only single pole. Lighting etc.

Thanks. Thats what i plan to do. But I will be stuck when I get to the lights.

 

[reb78]

Something doesnt feel right about the rcd switch. Once it has tripped, if I turn it back on its almost like it doesnt latch and then if i try it again it stays on. Of course, it may be a fault meaning it wont stay on but odd that it latches on if I try it again then goes off after 15-20 mins again.

 

[brightspark]

Thanks for this.

Noting what you say and that it may not make a difference, all but five mcbs have now been turned off and it is still doing it. I will work my way to all turned off and I guess at that point i may have to get someone in to look at it as I wont have identified anything to look at!

its no use just turning a single pole mcb off you need to disconect the neutral feed of it as well if thats what you plan on doing it realy just needs testing with an insulation tester and the faulty circuit could be found in 5 minutes if there is any earth leakage

 

[reb78]

its no use just turning a single pole mcb off you need to disconect the neutral feed of it as well if thats what you plan on doing it realy just needs testing with an insulation tester and the faulty circuit could be found in 5 minutes if there is any earth leakage

Ah. Ok. I thought it would isolate a faulty appliance easier thats all but i get it, as you all say, it doesnt isolate the neutral and earth if thats where the fault is (which is what it sounds like?)

 

[dobbslc]

For the lights you can disconnect the neutral off the neutral bar but make absolutely sure you get the right one. You dont want any floating neutrals!
I'd swap the crappy Proteus RCD first though. You can fit different manufacturers RCD'S but the bus bars have to have the right spacing off the din rail and the neutral needs to be on the right (some have the neutral on the left)

 

[reb78]

For the lights you can disconnect the neutral off the neutral bar but make absolutely sure you get the right one. You dont want any floating neutrals!
I'd swap the crappy Proteus RCD first though. You can fit different manufacturers RCD'S but the bus bars have to have the right spacing off the din rail and the neutral needs to be on the right (some have the neutral on the left)

Thanks for that.

Now weirdly, the final mcb i tried was to a redundant burglar alarm on a 3amp fused spur - the fuse was taken out. Leaving that off seems to have ceased the tripping - this has been on for over an hour now. I havent taken the front panel off today but looking back at my pics on this thread it looks like that 6amp mcb has to live cables coming out of it. I have disconnected the burglar alarm beyond the spur but the trip still goes if i turn that mcb back on. I will investigate the second live and what its feeding tomorrow.

The test switch still doesnt work so i am not sure i have actually found the problem or if i have a dodgy rcd as well!

 

[dobbslc]

The test button on some RCD'S can stop working and that may have happened anytime and then you got a fault so they seem linked but possibly aren't.

 

[brightspark]

ive been to a few where the test button didnt work but it tested working with the rcd testmeter

 

[Dave-sparks]

Thanks for that.

Now weirdly, the final mcb i tried was to a redundant burglar alarm on a 3amp fused spur - the fuse was taken out. Leaving that off seems to have ceased the tripping - this has been on for over an hour now. I havent taken the front panel off today but looking back at my pics on this thread it looks like that 6amp mcb has to live cables coming out of it. I have disconnected the burglar alarm beyond the spur but the trip still goes if i turn that mcb back on. I will investigate the second live and what its feeding tomorrow.

The test switch still doesnt work so i am not sure i have actually found the problem or if i have a dodgy rcd as well!

It sounds like you are getting closer to the problem.

I wouldnt rule out a partial/high impedance fault between neutral and earth being at the bottom of all this just yet.

If you can safely do so fully disconnect the live and neutral of the circuit you have identified, you may find that the RCD test button work again after doing this.

 

[reb78]

Cool. Thanks chaps. Lets see if it's tripped by morning. If it hasnt, i guess its something on that 6amp circuit.

 

[Dave-sparks]

ive been to a few where the test button didnt work but it tested working with the rcd testmeter

Have you had one of the proteus RCDs where pressing the test button results in a buzzing noise, nasty smell and a load of smoke coming from it?

 

[reb78]

It sounds like you are getting closer to the problem.

I wouldnt rule out a partial/high impedance fault between neutral and earth being at the bottom of all this just yet.

If you can safely do so fully disconnect the live and neutral of the circuit you have identified, you may find that the RCD test button work again after doing this.

Will do. Thanks for that. I can isolate the whole thing if needed when working in there as we have a lever to isolate that line at the house.

 

[brightspark]

Have you had one of the proteus RCDs where pressing the test button results in a buzzing noise, nasty smell and a load of smoke coming from it?

not proteus but did have a new one i fitted just burn out with no load on it just changed it and the replacement worked fine

 

[dobbslc]

We get a lot of Proteus RCD'S on site and they really are unreliable, MCG are no better.

 

[brightspark]

We get a lot of Proteus RCD'S on site and they really are unreliable, MCG are no better.

sh,itty electrics rubbish

 

[reb78]

Would an electrical factor know whats interchangeable with that rcd without me taking the old one in for comparison?

 

[reb78]

So, an update... I left that 6amp MCB marked 'burglar alarm' off all night and nothing has tripped. What the marking on the DB didnt say was that this MCB also feeds the light circuit in the shed next door. Its much more consistent this morning and every time I turn this MCB on it throws the main RCD - yesterday this was very intermittent otherwise I would have got to this point sooner! The implicated lighting circuit has six double fluorescent tube units in it. I suppose its just a case of checking the wiring to each light now? I know this shed has a few leaks so it is possible that with the rain some water may have got in?

 

[dobbslc]

Check to see if Roland or Micky has been in there too.