Dangerous Wylex Mcb

[davetheglitz]

give up then!

Don't give up - what you say is right - but completely misplaced in the context of this forum! We've all C***** up by compacency etc at some time. You will at some time! Point out what should have been done by all means - but the tone of what you posted was out of order!

Just grow up and contribute to shared experience!

 

[Barx]

Ok, seems though this hasn't been deleted yet, I will voice my defense. Nobody, in or out of college has ever told me to check across the top of MCB's. It was never pointed out in testing at college, I have seen anyone do it AND after asking round the few electricians I know, none of them have ever done it either. So, it appears it's not just me 'breaking the law'. It's me, everyone I know and I would hazard a guess at quite a few on here too...

The prisons are going to fill up quick if this one gets out.

so, I guess I could say. Don't blame me, blame my education!

IF it is 'The Law' then it should be explained more thoroughly,

 

[Barx]

For  curiosity sake, The MCB when tested for continuity shown >1999,

Insulation resistance @ 230v, 2.71MOhm. Higher than I expected, but hey...

 

[ProDave]

Have you cycles it on / off between your mate getting a shock, and you taking that measurement?

2.71 M hms would only allow 85 microamps to flow. I doubt that would be noticable, or just a faint tingle rather than a "shock"

 

[Barx]

Yes unfortunately, it has been cycled a few times so the reading is pretty useless.

 

[Sidewinder]

As an aside, I had a 2 pole pressure switch last week, brand new out of the box, unfortunately a cheap one as the compressor is a cheap one and it was all that would fit.

So, fitted it all up, plugged in turned on, nothing!

Checked fuse in plug top, OK.

Tried it again no power to motor.

Checked for phase at the switch fine, checked phase on output of switch fine.

Checked Neutral on incoming cable fine.

Checked Neutral pressure switch motor side fine.

Checked N coming back from motor 230V.

Checked again & messed around, no contact between the moving & fixed contact tips in the switch breaking the N.

Flicked the contact closed under load, motor ran, fine after that as it had flashed the contaminants off.

I have known this before from a customer who has had similar with production materials being left coating the contact tips on switching devices.

Perhaps you had the converse where there was something conducting across the switch assembly in the breaker.

I bet if you try it again now it will be fine.

 

[davetheglitz]

I had a thing today with a Hamilton 45A isolator - switch on and you could hear arcing within the switch. Quality control is not what it should be - but on the other hand accessories are comparatively cheap compared to years ago.

Thinking about MCBs - we never test the tripping of these - it's taken as read without further testing. It's therefore reasonable to assume that off is off with the beasties!

 

[ProDave]

good point Dave

Can you imagine how often the DNO's fuse would blow if were actually did test the trip times of MCB's under real overload conditions?

 

[Evans Electric]

So according to that particular Reg .  we are expected to carry out a functional test on all MCBs   although most of us assume that they are type tested to the relevent BS  EU  standards .   They tell us not to use a rogue breaker in a board these days so we stick with all Wylex breakers and what happens , they don't break the circuit properly .  Whats happened to the 3mm min gap ?  

To properly test the function we would need to apply a load in excess of the tripping current to every breaker ...how many of us have the capability of doing this ? 

If we buy a car do  we not expect the tyres to be of the correct standard and the brakes to work in the proper manner? 

If we buy and fit a light fitting we don't expect it to burst into flames and burn the building down.    Others have designed & built the thing to the relevant standards.  

Edit :-    Barx was right in posting this thread and highlighting the problem .......I for one have never tested the tripping or isolation properties of an MCB ...I have to trust the manufacturer that it meets with BS 60898 or whatever .   My job is to choose the correct device for the circuit ,and fit it properly .  By fitting  breakers  of the same make as the board , we are told , results in a proper type tested unit .

 

[ProDave]

It is a bit strange that we are not expected to test the trip characteristics of an MCB, we just have to trust that it will work.

But we ARE expected to test the trip characteristics of an RCD, we are not allowed just to trust that they will work.

It's a strange old world.

 

[Evans Electric]

I'm guessing you meant RCD  there Dave.?    

 

[adammid]

If you are going to be self righteous, then please get your grammar right.

It's should HAVE been,  and not should OF been.

Just a pet hate of mine. they obviously don't teach English correctly any more. Okay I'll get my :coat

It could be worse...he could have said 'should OFF been'. That really gets on my wick!