Isolation

[wiefil]

Afternoon,

I was working on a machine the other day to which we had a faulty 32a socket (Phase loss). Unfortunately we did not have any sockets available for a replacement. I decided that it would suffice to fit a suitable circuit breaker behind the socket and sealing back up until another socket arrived. This obviously rendered the switch on the socket useless, but as the machine had its own means of isolation I considered it safe to do so to get the machine to run, deadlines and all that. But another shift partner said it was probably an incorrect thing to do and should not be repeated. I haven't got my wiring reg book to hand, but I was sure I read that so long as there is some form of isolation the it would be fine. Please correct me if I am wrong.

Regards

 

[JohnW2]

I decided that it would suffice to fit a suitable circuit breaker behind the socket and sealing back up until another socket arrived. This obviously rendered the switch on the socket useless ...

It's probably just me being dim, but I don't completely understand what you're saying there. Could you perhaps clarify a little?

Kind Regards, John

 

[bernardgreen]

This obviously rendered the switch on the socket useless,

NOT sensible. That switch at the socket might be the only way to shut the machine down in the event of a mechanical failure that prevents anyone reaching the isolation switch on the machine.

 

[wiefil]

Hi,

the 32a socket had a faulty non-fused switch dis-connector inside. I removed the faulty switch and put a 3 phase circuit breaker inside the socket, as it had plenty of room. screwed the cover back on and let machine run till another socket arrived couple hours later.

Kind Regards

James

 

[wiefil]

Just to clarify, the machine did have a means of isolation, it was on the machine itself.

Kind Regards

James

 

[wiefil]

also, e-stops are either side of the machine. I was under the impression that one point of isolation is required. Also, we have machines hard wired from the panels in the roof void with only an isolator on the machine itself, I just put another circuit breaker in on top of the the one the socket has up stairs in roof void. I honestly still believe this to be safe and within wiring regs.

Regards

James

 

[JohnW2]

the 32a socket had a faulty non-fused switch dis-connector inside. I removed the faulty switch and put a 3 phase circuit breaker inside the socket, as it had plenty of room. screwed the cover back on and let machine run till another socket arrived couple hours later.

OK, that's a bit clearer. If I understand correctly essentially you bypassed the faulty (non-fused) switch disconnector, but I'm still not clear as to why, given that it was not going to remain accessible after you put the cover back, you used a circuit breaker to do that - were you perhaps just using it as a 'junction box', as a matter of convenience (i.e. it was all you had to hand)?

As bernard has said, removing the 'external' means of isolation would not really a very good idea if there was any chance of the one on the machine itself not being accessible in the event of some catastrophe (e.g. 'machine in flames'!). Given that it was only going to take a couple of hours to get a replacement socket, could the machine not have been taken out of service for that short period of time?

Kind Regards, John

 

[wiefil]

Aye, I did indeed bypass the switch and for convenience I just placed a circuit breaker inside, making it a junction box. I would never have done this were I not sure that at-least one point of isolation be required either at supply or on machine.
Since the machine is not in its final resting place as of yet, it is needed to be unplugged and moved at times, hence having a socket and plug for ease of moving. Once we have a final place for the machine to rest we will then remove the socket and wire directly into the circuit breaker upstairs, as most machines are in this building.
If for a moment I thought that this was dangerous I would have of course waited a couple of hours, I am mortified at the thought of putting lives in danger, but in this case no danger is present, the worst I have done is simply put another circuit breaker on the supply.

I really need my BS7671 to quote from, but can't seem to find it anywhere.

Kind Regards

James

 

[EFLImpudence]

537.2 Isolation
537.4 Emergency switching.

Isn't pulling out the plug acceptable for both?

 

[JohnW2]

I really need my BS7671 to quote from, but can't seem to find it anywhere.

It's not really an area about which I have ever had any need to know much but, at first sight, I cannot see anything in BS7671 which says anything other than what you have suggested - that there must be at least one 'means of isolation' and 'emergency switching' (which I would imagine that the one on your machine would qualify as).

I would imagine that others will have more definitive/authoritative answers!

Kind Regards, John

 

[JohnW2]

537.2 Isolation ... 537.4 Emergency switching. ... Isn't pulling out the plug acceptable for both?

Certainly acceptable for isolation - I'm not sure about 'emergency switching'.

Kind Regards, John

 

[mfarrow]

I don't see anything inherently wrong here. The machine can still be isolated, there's emergency switching arrangements, and the socket was replaced within hours.

If need be you could have stood by the socket in case someone wanted to use it for isolating or emergency switching the machine in the interim, and act appropriately. Two hours isnt long enough to warrant a full shop floor briefing I gather?!

 

[deadshort]

I would have thought pulling the plug out of the socket would have the same effect as the switching it off ?
You need to buy your mate a life

DS

 

[stillp]

e-stops are either side of the machine. I was under the impression that one point of isolation is required.

E-stops are not means of isolation.

 

[JohnW2]

I would have thought pulling the plug out of the socket would have the same effect as the switching it off ?

As has been said, that's certainly acceptable for isolation. As for 'emergency switching', I'm not sure. We don't know about the nature/size of the machine, so don't know what current one might be breaking if one pulled to plug 'on load' in the name of 'emergency switching'.

You need to buy your mate a life

I'm inclined to agree, particularly now we know that the 'temporary fix' was only in place for a couple of hours - for once, 'temporary' really was temporary!

Kind Regards, John