Commercial premises electrics questions

[daleyd]

Ive not seen many factories where everything is on plug and sockets (obviously a ring main with some 32a sockets on would be a good idea for welders, portable equipment etc, but I'm talking about large fixed equipment), but where I have seen them is in large plants where its critical to get things swapped over quickly, and they have spares with plugs already wired in. I dont really see what your going to gain by having things on plugs/sockets as unless you have a new motor with a spare plug already attached you would have to remove the old one to fit on the new? You would perhaps gain a bit of flexibility in where you want to position your machines, but thats only if there is already a socket nearby.

Personally I dont think I'd bother, it takes minutes to unwire a 3 phase supply, and in a small unit your unlikely to require moving things around a huge amount, or to be swapping motors/ machines out regularly.

 

[knighty]

ring mains are no good, they're illegal in most of the developed world, we only started using them here because of the shortage of copper during the war

problem is you can have a bad connection or damage/break in the wire somewhere and everything will still work... problem is you're now only feeding power from one side so through half the copper. also makes it easier for any damaged wires/connections to get hot / overheat

ok, ok... I know, they're everywhere in the UK... but for a factory you're betting off running either dedicated circuits for each machine/socket

and/or use thicker cable so there's no ring needed, spur each extra socket off the last (within reason)

 

[daleyd]

If you read my post I didn't advocate a ring main for connection of fixed machinery, only to provide some power sockets for portable equipment. As long as it's properly protected by the right breaker then there's nothing wrong with a ring main, it's the most copper efficient way of distributing power throughout a house/factory whatever.

Obviously for heavier loads then you would be running dedicated supplies, the same as you would for a cooker or shower in a domestic environment.

 

[Robotstar5]

A lot of factories/industrial units I've worked in have some form of busbar system and machines, DB's etc. are just plugged in with "tap in" boxes (normally fused)

 

[knighty]

If you read my post I didn't advocate a ring main for connection of fixed machinery, only to provide some power sockets for portable equipment. As long as it's properly protected by the right breaker then there's nothing wrong with a ring main, it's the most copper efficient way of distributing power throughout a house/factory whatever.

Obviously for heavier loads then you would be running dedicated supplies, the same as you would for a cooker or shower in a domestic environment.

32amp sockets are too big for a ring main imo

you only need a couple of big loads (motors) starting up at once to trip you over 32amp


extra advantage of separate circuits / plugs/sockets is you can turn off a circuit / unplug something while you work on it / move a machine etc.. and leave everything else running... which is a big bonus when you're running a business

A lot of factories/industrial units I've worked in have some form of busbar system and machines, DB's etc. are just plugged in with "tap in" boxes (normally fused)

check out the prices of those busbar systems... even second hand they go for thousands :-(
(I thought about setting one up once, worked out to about £12,000 using second hand stuff)

 

[daleyd]

Your obviously not reading my post, I'm in no way suggesting they are to be used for plugging fixed machines in to, but for portable equipment like welders which may need to be used in different locations. As I said fixed machinery should be on separate circuits.

I'm confused as to why you can't leave other things running just because you don't have plugs and sockets? Isolate the breaker, lock it off - job done?

 

[MattH]

Guys, this is going off topic a bit. I've got a 1200sq/ft unit that will have two or three large fixed machines with ancillary support equipment (extractors, vacuum pumps etc). No moving machines around, no swapping out machines etc.
As people have suggested I will run high level trunking all around the unit and drop down to sockets or isolators. I'll run SWA out of the top of the trunking to the lights.

 

[daleyd]

Guys, this is going off topic a bit.

Surely your not surprised by this are you Matt?

 

[MattH]

LOL, not really.

 

[knighty]

I wasn't going to post because the thread has been dragged so far off topic but I guess original topic is covered and Matt has all the info he needs

Your obviously not reading my post, I'm in no way suggesting they are to be used for plugging fixed machines in to, but for portable equipment like welders which may need to be used in different locations. As I said fixed machinery should be on separate circuits.

I'm confused as to why you can't leave other things running just because you don't have plugs and sockets? Isolate the breaker, lock it off - job done?

it's nice to be able to unplug a machine when you're working on it and know you're 100% safe / that you don't have to give it any more thought, you know no-one else is going to make a mistake and turn it on again etc. etc. etc.

a little small fix is no problem, but something bigger than that, when you have half a dozen wires disconnected and you're wrist deep in a control panel, or when you've climbed inside the gearbox of a machine and you're sitting on a chain as thick as your leg while you grease bearings etc. then it's nice to know the machine is unplugged

if there's a problem with a machine and you want to make sure no-one tries to use it, it's nice to be able to unplug it and go do something else / go get spares etc. it's easy for someone working in a production environment to turn on a machine without thinking about it if it's something they've been doing daily for days/weeks/years

for the relatively marginal cost of cable I don't think it's worth bothering with a ring main or spurring sockets off each other, might as well run individual cables/sockets... ok, size of the unit comes into play, if the unit was massive then I could understand only running one cable, or installing a remote fuse box in something like a compressor room... run one bigger cable to the room, then fuse bot their for the compressor/dryer/extractor fan/lights and a couple of 240v sockets etc.



I helped a friend setup a cnc router and later a (low power) lazer cutter, my welding is ok but far from professional... I'm sure Matt and many other people here know more about those things than me

but I do know production environments, and wiring/plumbing them up, I've been in those kind of environments since I was a kid and I've been running my own factory since I wasn't much more than a kid

what I'm trying to say is I'm not trying to argue with you, I strongly believe I'm right and I'm just trying to help anyone who needs to setup something like this themselves. and I'm not taking this lightly, I even checked with a friend how his factory is wired up incase I'd made a mistake somewhere - he has a socket for each machine, and when I asked if any of them were on a ring main he replied "are you f***** thick?) (he assumed I was going to wire something in like that)

 

[daleyd]

OK, clearly you have either got the wrong end of the stick or are just not listening, but I did not suggest anywhere that the machines should be on a ring main, that was an idea touted for portable equipment, but as Matt says he doesn't want that so no point going over that again.

With reference to safely working on machines with no plugs/sockets - this is something that is done perfectly safely all the time with lock offs, tag outs, permit to work etc. I assume you use all these methods (If your a factory owner you should be!), as simply unplugging a machine in the hope that no one will plug it in is asking for an accident. Having a plug and socket makes it no safer than turning the switch off and hoping that no one will turn it on again.

I don't want it to be weeing competition but I've worked in some of the biggest plants (I'm currently working on one of the largest furnaces in the country at Port Talbot) and most heavily regulated industries for the past 20 odd years, I do this for a living.

If having plugs and sockets works for you, then all well and good. If I had equipment I needed to swap out regularly or needed to be moveable, I would use them too. If I had fixed equipment that was unlikely to need moving, I wouldn't.

 

[WorkshopChris]

I don't want an argument as we are already off topic and its of no help to Matt but for the benefit of anyone reading this with less awareness,

or when you've climbed inside the gearbox of a machine and you're sitting on a chain as thick as your leg while you grease bearings etc. then it's nice to know the machine is unplugged

That's exactly the biggest problem with plugs, mr or mrs machine operator comes back on shift and thinks they will plug there machine back in, where does that leave your leg?

Would much rather have a locked off isolator or disconnect wires. it alerts all to the potential danger. If you are using plugs you can get lock boxes to seal them in during maintenance.

 

[Robotstar5]

it's nice to be able to unplug a machine when you're working on it and know you're 100% safe / that you don't have to give it any more thought, you know no-one else is going to make a mistake and turn it on again etc. etc. etc.

if there's a problem with a machine and you want to make sure no-one tries to use it, it's nice to be able to unplug it and go do something else / go get spares etc. it's easy for someone working in a production environment to turn on a machine without thinking about it if it's something they've been doing daily for days/weeks/years

Simply unplugging a piece of equipment is NOT safe isolation, what stops someone else plugging it back in while you're working on it, I think you need to invest in some lock-out kits and training on safe isolation.

My qualifications to make that statement - time served industrial maintenance sparky for 40 years.

 

[knighty]

power is isolated / locked off before the machine is unplugged, plug is just an extra level of protection

re: ring main, I think 3 phase is a bad idea for a ring main, and you think it's ok as long as it's just for portable stuff... I understand what you're saying, I just disagree, install all sockets the same, keep it all universal, and most of all keep it simple


a vast array or safety procedures and paperwork are fine for a massive factory employing hundreds pf people, but in a small business (sub 30 employees) and in real world conditions shortcuts will be taken

I'm sure everyone here has run a long extension lead to where they're working where people could trip over it, or we've all plugged an extension lead into another to extend it further than you really should etc. etc. etc.

when you're working long hours and have a backlog of work, if the bearings in one of your machines starts to rumble and you want/need to grease them right then and there, you get on with it

when a machine packs up and you have half a dozen guys standing waiting for it to be fixed, you don't do paperwork, you drag it out of the way and push another into it's place

or if a machine needs repairing/maintenance you don't want to have to waste time disconnecting cables, removing control boxes from walls etc. etc. you unplug it, moved it, fix it and plug it back on


in real world conditions simplicity wins every time

 

[daleyd]

I'm not sure where you inferred "Vast array of safety procedures or paperwork" from any of the above posts, but as a minimum you should be providing a safe level of isolation for every intervention, no matter how small.

You are talking about what are in effect "portable" machines in your above post (Can be wheeled in/out etc) - in which case sockets are probably a good idea. Where I would disagree with them is where you have a large fixed machine that's unlikely to move.

I'm not actually saying plugs and sockets are wrong, they of course have their place but it's just not something I would do myself if they were not needed. They don't add anything safety wise, and if anything you are adding to the number of potential failure points in the circuit. If your happy with them, then carry on.

As an example we had 24 "Top hat" kilns in a factory, with removable lids for casting windows for nuclear reactors, each lid was on a plug as it needed to be removable to crane the castings in. Over the space of 4 years working there I must have replaced 4 or 5 plugs which had burned out connections in due to loose pins, loose wires within the plug etc. For that reason alone I wouldn't advocate plugs where they are not needed.

 

[MattH]

Well to bring this thread back to topic:

I was going to put a new isolator and socket on the end of the only existing 3ph run in the unit. It was singles in 1" round conduit feed from a 32a C curve breaker and used to supply the last occupants two twin post ramps. I needed to replace the last section of conduit as it was hanging from the wall.
When I tried to pull the cables out I couldn't. Turns out the cables had melted into the conduit!

Suffice to say I have ripped it all out back to the CU and I am going to replace it tomorrow with another dedicated run of SWA.

 

[daleyd]

Well to bring this thread back to topic:

I was going to put a new isolator and socket on the end of the only existing 3ph run in the unit. It was singles in 1" round conduit feed from a 32a C curve breaker and used to supply the last occupants two twin post ramps. I needed to replace the last section of conduit as it was hanging from the wall.
When I tried to pull the cables out I couldn't. Turns out the cables had melted into the conduit!

Suffice to say I have ripped it all out back to the CU and I am going to replace it tomorrow with another dedicated run of SWA.

Sounds like fun!! At least you'll know it's done right.

 

[desmo11225]

Hello Every One
I have tried to ask this question elsewhere , We have been given some very nice large lamp shades, they are 460 mm in diameter and the bulbs are 250 mm long and 120 mm in diameter, so there is plenty of room inside, we would like to fit LED lights in them, we need bulbs and holders to go with them, LED Lighting seems to be coming very popular just now, would some one give us some up to date advice please.
Our workshop is an old coal yard, similar in size to yours MattH, there are chains supplied with the shades, so we could hang them as low as we wanted. Hope you can help, Thank You desmo11225

 

[MattH]

Sounds like fun!! At least you'll know it's done right.

Indeed, just makes me want to rip it all out now even more. The only problem is there's only 7 days in each week.

 

[daleyd]

Indeed, just makes me want to rip it all out now even more. The only problem is there's only 7 days in each week.

I can't offer much advice other than pick either the worst or the one you need first and work from there. (Actually that's not even advice just common sense so I might as well shut up lol). Good luck, looking forward to seeing the end result with the machines in place - keep thinking of that I'm sure it will spur you on!