You'll like this....

[dannyboi2003]

Hi Guys,

Was showing a contractor where we want some additional network data points installed yesterday, i work for a college btw. An office is being created out of one of the student training pods in the plumbing centre. All of the pods have a single power socket and a light fed from a small CU with an emergency stop button to cut the power.

As we passed the emergency stop button the contractor pressed it and chuckled to himself when the trip popped and then told me how it was wired up. The CU has a 80amp RCD main switch and has a 32amp mcb for the sockets and a 6amp mcb for the lights, the emergency stop switch is connected between the neutral and earth on the outgoing side of the RCD so when its pressed the RCD trips and cuts the power!

The contractor i was with did not install this setup but has carried out some maintenance (changing damaged sockets/lights) which is how he knows the way its wired. It should be wired through a contactor he said but its not against the regs the way its been wired.

Anyway just thought id share that with you guys and see what your reaction is

All the best
Dan

 

[Adam_151]

I don't like it

Shouldn't be directly shorting any live conductor to earth even if is only neutral and is only a momentry connection

There are situations (or faults which would not be detected immediatly) where it could fail to work

Just gives the impression that its generally cobbled together

Perhaps my feelings are not properly justified, but I'm certainly not keen on it

The proper way to do it is of course with a contactor, and if its something where there is a danger to warrant an em stop, then you want something thats going to drop out on power failure as well!

 

[ricicle]

A stupid way of doing the safety for two reasons that I can think of:-

1)An emergency stop circuit should be wired with normally closed contacts at the mushroom pushbuttons.The circuit is wired in series so wire breaks are detected with a safety relay kept 'energised'.In this case the contacts will be normally open and therefore not 'fail-safe'.

2)A Neutral to Earth short will not always cause an RCD to trip.

 

[dannyboi2003]

I didn't like it either but as i'm just the IT guy its nowt to do with me and if its already been noticed by a contractor then its on his head (and the original installers) not mine. Plus i know that wing had a full electrical inspection and test over the summer holidays so someone passed it as safe

All the best
Dan

 

[ricicle]

. Plus i know that wing had a full electrical inspection and test over the summer holidays so someone passed it as safe

All the best
Dan

The Man With No Name who did it For A Few Dollars More, I expect...

 

[DESL]

Plus i know that wing had a full electrical inspection and test over the summer holidays so someone passed it as safe

But I bet the emergency stop was only given a functional test!!

TBH when inspection and testing how far would one go open up every single accessory to check correct wiring - in the real world clients wouldn't pay for it.

 

[JohnD]

RCDs often stick and fail to trip, especially when they have not been tested at least once a month. I think we saw a research paper not long ago with some stats.

It would be sad if some unfortunate got his finger stuck in some live connections; the RCD was stuck and failed to trip, and the quick-witted rescuer punched the EPO button expecting it to cut power

 

[Steve3948]

100% incorrect.

What if the neutral or earth connection was lost through the stop button due to a break or loose connection.

As already stated should be through a contactor with lock off stop button.

 

[Spark123]

It is daft and illegal to do this, it is a violation of the ESQCR 2002: 8 (4) A consumer shall not combine the neutral and protective functions in a single conductor in his consumer's installation.

 

[aptsys]

It is daft and illegal to do this, it is a violation of the ESQCR 2002: 8 (4) A consumer shall not combine the neutral and protective functions in a single conductor in his consumer's installation.

Doesn't apply if women do it then

 

[Spark123]

As with most of this type of law, I don't think they are gender specific. The word him being used to apply to any person as opposed to just a male.