Locking Isolator Switch in 'ON' position?!?!

[SjoramNFT]

Does it seem sensible to anyone here that a 63A 230V (UK) isolator switch is padlocked in its 'ON' position?! It feeds through to a MCB panel, which then goes through to dimmers. Personally, although the MCB panel can be used to isolate power, I would rather use the isolator switch as I feel happier with that as a complete isolate of power, as to my knowledge some of these MCB panels only isolate the live wires.
There are plenty of good reasons for locking the isolator when it is 'OFF' but not when it is 'ON'.
This is a school I'm talking about, but there are no kids near the dimmers when they are in operation. It wouldn't be to stop them turning them off anyway, as they could just use the MCB panel.
Personally, I refuse to use the equipment if it is locked in the 'ON' position and if I find myself in a situation where I have no time to rectify the situation, I have no hesitation in taking a pair of boltcutters to the padlock.
Any others thoughts on this??

[Bob]

Could this be considered an emergency lighting feed that can't be shut off? If the MCB is downstream, then the load side is still protecting the rack.

[SjoramNFT]

This is the situation I'm describing - isolator is padlocked on. It feeds nothing but the two dimmer racks.

[Mayhem]

We have a variety of switches here in Australia that can be padlocked in the ON position but not in the OFF position. Essentially, it is there to stop someone from cutting the power during your show. I know that it seems the wrong way around but having had somone turn off my lights during a gig because they thought it was the supply for something else, it does have its use.

[Chris15]

Basically all Clipsal Industrial switchgear down here is manufctured with the ability to lock in the off position. If you want to lock it on you drill a hole in it (and yes, that is what the manufacturer says).

Yes I can understand why you want to lock the supply on. It has a lot to do with stopping idiots from playing with things they shouldn't and turning it off. From a saftey perspective it may not make a whole lot of sense I realise (The desire to isolate the supply quickly if needed). I have seen switches that feed fire pumps etc. locked on. Side note: I believe that most circuit breakers are designed so that they will break the load even if the "handle" is held in the on position. This is so that you can put a lock dog on the breaker and lock it on. This is frequently specified for breakers which feed alarm and other security systems.

It is interesting to read the bit about the "complete isolation" rather than just cutting the live wires. This puzzles me. Firstly, there is no point in cutting the neutral assuming that the wiring is properly done as it will be at ground potential and somewhere will in fact be linked to the Earth wire. So it ain't goign to zap you.
Secondly, I doubt that the isolator actually cuts the neutral. All the switchgear I have seen down here only cuts the active and does not touch the neutral...

Let me take an example for a second. Think about a school generally. At least in my school, all the distribution boards are located in locked electical cupboards, with only a handful of people having keys. How is this any different to the locked isolator? Both prevent people from turning off the supply... In fact it surprises me that if the isolator is locked on that the circuit breakers are not behind a locked door. Consider this, what is the primary purpose of an isolator? I thought that it was to isolate power for maintainence etc as part of a lockout tagout sort of system. If it were for an emergency stop type setup then I would be expecting a large red mushroom head push button in a prominent location...

Anyway summary: I don't know the details but have to question whether you have the authority to remove the padlock. I imagine you have the obligation to report this safety concern to the appropriate person or committee, but the question is IF something goes wrong, are you the liable one? I doubt it, because if you were, then there would be no need to ask the question, the padlock would be long gone if you felt it was a problem. So, whilst I am fully aware of where you are coming from, I still think that just because the isolator is locked off is no reason to hold up the show, or get the boltcutters out...

[avkid]

If you do cut it off, put a new lock on it after you are done and tape a few keys to the lock, but keep one for yourself too!

[u_dakka]

what the hell?
this thread appeared in my live bookmarks in firefox. As it happens i used to be cheif techie at the school in question and Sjoram worked with me.
But this thread has been dead for ages - why did it appear in my live bookmark list??

Anyone explain??
andy

[avkid]

If you look, the topic was posted yesterday(Friday Dec 22nd, 2006).

[Mayhem]

Originally Posted by Chris15

It is interesting to read the bit about the "complete isolation" rather than just cutting the live wires. This puzzles me. Firstly, there is no point in cutting the neutral assuming that the wiring is properly done as it will be at ground potential and somewhere will in fact be linked to the Earth wire. So it ain't goign to zap you.

Chris15 - what would happen if there was a large amount of current on the neutral? (is this even possible?).

I know it is not the correct forum - but I have not posted a QOTD in some time.

[Van]

Is this switch not fused ? I have a half dozen 60a switches on the medium level roof above our offices. It's a really weird building and we often get homeless folks and tweakers " camping out" on the roof during the summer months. The switches all supply the HVAC units on that roof. When they kick on < the hvac units> they make noise and it disturbs the poor homeless who are trying to get a nice nights sleep on my roof. Somehow they figured out that if they turn the switches off it would stay quiet. I finally locked all of the switches in the on posistion. Each switch has a fuse for each leg in the switch so as far as protection is conerned the stuff downstrem is protected. Only authorized people have the keys so only authorized people are able to shut stuff off. I'm sure you have a similar situation with that switch in the picture. and probably the same lock is used as the lockout for your lock out - tag out program.