Light Industrial Electrical Installations - how?

Asking for information only - no forseeable plans!

What is the usual configuration for a light industrial electrical installation?

Following mostly from observation & guesswork - please correct as necessary:

Incomer, 3 phases and neutral + earth (depending on local earthing arrangements) Each phase fused at 100A (or whatever, but I'm guessing this is a common setup) Single meter, but recording consumption on each phase Single (or several) consumer unit(s) each carrying all 3 phases. Distribution of 3 phase to machinery (usually hardwired) is each on a seperate MCB - no rings Same with hard wired single phase machines -all spurs, no rings. All hardwired machines must have an isolator next to them (and an NVR?) There are also single phase (16A?) "blue" sockets for non-hardwired machines What's the rating on 3 phase connectors? Regular 3-pin socket outlets, where used, are connected onto a single phase per floor - ring mains used?. Lighting may be on a different phase per parallel strip to reduce strobing problems (loop in used like domestic?) RCD's - not used on hardwired machines, may be present on single phase outlets (never on 3 phase outlets?)

What would be a typical cost for a 3 phase new connection, assuming it's available nearby? Are standing charges and per unit charges similar to domestic tariffs?

Reply to
dom
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On 5 Apr 2007 12:38:58 -0700, " snipped-for-privacy@gglz.com" mused:

Maybe, or single phase.

Could be, or 80A, or 60A, or whatever.

Maybe, or several meters. Depends on who what and when\why etc...

Maybe, or none carrying all 3 phases, or several carrying 1 phase, or

1 carrying 1 phase.

Usually.

Sometimes, sometimes not. Depends on the installation.

No, al hardwired machines should have an isolator withiun a reasonable distance, and they don't need an NVR depending on what they are.

Sometimes, sometimes there aren't. Depends on the machines and job.

Depends what the rating is, could be anything from 1A to hundreds.

Maybe, could be a phase per floor\room\area\building\anything. Could be ring main, or not. Depends.

Maybe, maybe not. Depends on the job.

Nope, could be used on single or 3 phase, or none. Depends on site.

What ratiing, wiring method, distance, works involved etc...

How long is a piece of string?

Yes, in the way they work. Often different on charges though.

If you want to ask any more vague questions feel free.

Reply to
Lurch

Thank you for your informative reply.

What I'm looking for is to understand what is different about light industrial installations, and what modern standard practices are used in them, and not domestically and vice-versa. What's different other than the obvious wiring in singles and conduit/trunking?

Ok - let me get rid of the vague and invent a specific example (but feel free to change it to illustrate an important difference not covered in this example) - lets say I'm setting up a joinery workshop. The building is 120 sq metres, single (concrete) floor, 6m ceilings, and is an old barn with no electrical installation. 3 phase is available on overhead wires within 10m of the building. There will be

6 machines requiring 3 phase with ratings between 3 and 10 KW (table saw, spindle, bandsaw, thicknesser, planer, dust extractor). There will be 1 machine requiring single phase at 3 KW (smaller planer/ thicknesser). There will be 3 machines requiring single phase at 2KW or less (grinder, pedestal drill, small bandsaw). There will be 20 power outlets required mostly on workbenches, though some are next to doors and will be used for handheld power tools outside the building (some 240V, some 110V). There will be overhead fluorescent lighting. All heating is non-electrical. There is a water supply and sinks and a toilet, but no electrical outlets in close proximity, only lighting.

Is a single CU suitable for the whole installation? What parts of the installation should be RCD protected? What types of MCB should be used (B or C)? Which machines need to be hardwired, and which can use connectors? Where should rings or spurs be used? Would it be better to have all industrial connectors (and wire new plugs onto power tools), or a mixture of industrial connectors for small machines and stick with domestic-type plugs/sockets on handheld power tools?

And finally, if all sockets that might be used outside are RCD protected, is there any need to buy 110V power tools any more?

Reply to
dom

as said, it depends. Industrial wiring is a very wide term, and could cover almost anything.

One I was familiar with had a CU in each room (for most rooms), low voltage rails, and a big red stop switch at each entrance.

shan't write a book on this to satisfy your vague curiosity.

no

NT

Reply to
meow2222

This sounds very much as though you are pricing up for a proposed business venture. There is enough expertise in the group to answer your qustion but to do it properly will require someone who ordinarily would make a living out of just such design work to spend time and effort for nothing. I would suggest you approach a possibly suitable contractor or more the one in your locality with your brief and he/she may be prepared to give you a budget quote on the premise they will have a chance of getting the job. Don't expect to get full details at the outline stage if they have any business sense though.

Reply to
cynic

In message , " snipped-for-privacy@gglz.com" writes

I think Lurch was gently pointing up the *size* of your enquiry:-)

Any knowledge I have is 30+ years out of date so comes with a health warning.

In general industrial installations are expected to change as production needs vary and m/c locations/requirements alter. In consequence supplies, distribution fuse boards (in my day) tend to be oversized for the initial planned job. Flexibility can be achieved with overhead *bus bars* having fused plug in outlets but it sounds overkill for your proposal and in a joinery shop handling lengths of timber you may regret vertical obstructions.

Diversity in your example is tricky as you have not specified the number of operators. One man is only likely to operate one m/c plus the dust extraction and heat/light. Industrial facilities would want to maximise m/c utilisation and might arrange some *flow* where the slowest m/cs are duplicated and feed faster operations down the line leading to a high load factor.

The supply company will want to know things like maximum expected demand, size and starting method for largest motors etc.

Sounds like the ideal country cottage. I want one:-)

I'll leave the specifics to those with better knowledge. One thing I have done which might draw comment is to use 5 pin 16amp industrial connectors for a mix of single and 3ph *portable* equipment. (this is a farm with mobile elevators and grain augers) The downside is you can't borrow the shop tools for an off site job.

Surely the ought to be some literature covering this sort of installation?

regards

>
Reply to
Tim Lamb

No. I will eventually be setting up a workshop similar to the one described - but I may be looking to do the electrical work myself (and read up on all the relevant legislation). I'm MIET (was MIEE), but my professional experience was medical imaging (incl HV). Now with domestic installations there's a wealth of information available - the OSG, and lots more for the less common stuff that the OSG doesn't cover. Almost any professionally qualified and practically experienced electronics engineer could carry out and entirely safe, quality domestic installation.

Is the same true of small workshop installations? Are the practices so similar to domestic installs that not much new knowledge is required? Or are there a bunch of design practices/legal requirements that set them apart?

Reply to
dom

Yes, I forgot to specify that. Let's assume worst case 4 of the 6 of the 3 phase machines could be operating - say 25KW. Plus another 5KW for bits and pieces.

So that's an acceptable practice, 3 phase connectors wired up appropriately on the cable of single phase portable tools?

This is what I mean by practices that set small industrial/farm installations (well I know a portable tool isn't an "installation") apart.

Reply to
dom

Assuming a three-phase supply, yes.

Depends entirely upon the supply you have contracted for and the size of the feed.

Mine all have a three-phase meter, which simply has one day and one night reading.

Or not, depending upon whether there is a need for a separate single phase supply somewhere. However, I usually install a single three-phase distribution board and allocate parts of it to single phase supplies.

They should be spur wired, but you can run more than one spur from each MCB, provided that the total potentail load is within the rating of the MCB and that you use cable suitable to the MCB rating throughout.

There is a statutory requirement for local isolation. It need not be separate from the machine, but an isolator on the wall next to each machine makes it easier to check that everything is switched off when closing down for the night.

NVRs are not required, but may be advisable for some types of machine. If the machine is not one that requires to be shut down in a pre-determined sequence, I often fit a phase drop rely.

My computer rack has a 32A blue connector.

Depends on what you are connecting. 16A and 32A are common, but you can get ones that are higher rated.

Rings mains are acceptable for socket outlets. Ideally, they should be arranged so that the load is evenly distributed across the phases, which could involve more than one phase on one floor. It is not a requirement, but good practice would be to ensure that nearby sockets on different phases are marked with phase colours and kept at least 6 feet apart.

Also to distribute the load across different phases. If more than one phase is present in what might otherwise appear to be a single phase circuit, for example in a grid-switch box controlling the lights, it must be marked with

415v warning stickers.

Never found the need for one.

Ask your electricity supplier.

Colin Bignell

Reply to
nightjar

Isolation can be remote, providing it includes provision for an electrician to lock it in the off position with his own padlock. All commercial MCBs include holes for lockout device attachment, but you do need all poles switched (for isolation).

Switching everything off for the night, emergency poweroff buttons, and NVR can all be handled in a single PDU to supply everything except the lighting (and possibly heating/frost protection controls).

Reply to
Andrew Gabriel

The Provison and Use of Work Equipment Regulations 1998 require the isolation to be 'readily accessible', which IME Factory Inspectors interpret as being local to the machine.

...

Normally I get involved with adapting an existing installation and local isolators are easier.

Colin Bignell

Reply to
nightjar

nightjar > Lighting may be on a different phase per parallel strip to reduce

Don't think 415v (sic) warning stickers are a requirement any more (and haven't been for years). I may be wrong. If so, you never see them on new office installs. Can you cite your source?

Cheers,

Rumble

Reply to
Rumble

In message , " snipped-for-privacy@gglz.com" writes

No! I mislead you. The 16 amp connector is not fused so unless you have close circuit protection the portable m/c and its supply cable are at risk. My 5 pin socket outlets are individually supplied via 15 amp HRC fuses and the machinery has local starters (usually electrically latched contactors with thermal overload/single phase protection)

Sorry. I was trying to be funny. I tremble to think what the group might say about bonding on steel frame buildings. The last new supply here was going to be PME until I persuaded them to give us an earth.

regards

>
Reply to
Tim Lamb

not at all. Electronic engineer training and experience does not usually include addressing safety of domestic installs. Wiring may seem simple, and the basics are, but there are many little safety gotchas, and these are not the same issues as encountered in typical tron eng situations..

NT

Reply to
meow2222

On Fri, 06 Apr 2007 18:02:17 +0100, Rumble mused:

That's because people can't be arsed to fit them, not because they're not required.

Reply to
Lurch

In a TN-earthed industrial installation fed from the public mains the means of isolation need only switch all phase conductors [see reg.

460-01-04]. The neutral does not have to be switched, provided it can be disconnected, e.g. by means of a bolted link [460-01-06]. Accordingly 3-ph disconnector switches and switch-fuses usually have 3-pole switching and a separate removable neutral link.

All-pole isolation is required if the supply earthing is TT.

(Also the main switch of a domestic single-phase installation must be double-pole, whatever the type of earthing.) [476-01-03]

Reply to
Andy Wade

Debatable - a warning is needed where the nominal voltage exceeds 230 _and_ "where the presence of such a voltage would not normally be expected" [Reg. 514-10-01]. In a 3-ph installation with the lighting load split between phases I would _expect_ to find 400 V in a multi-gang switch assembly and therefore ISTM that no voltage warning label is required in this case.

Reply to
Andy Wade

I think the debate would consider the "quality" of the staff likely to open a "simple - its only lighting control" bit of equipment as compared to a starter or switchgear enclosure where 3 phase would be expected.

Reply to
cynic

SFAIK, nobody sells 400v warning stickers, although you can get 440v ones.

Not on an Easter holiday weekend, when all my manuals are at work. I would, however, be surprised if anyone were able to do a risk assessment that satisfied a Factory Inspector and that did not require such a warning.

Colin Bignell

Reply to
nightjar

Since a consumer unit is a single-phase assembly intended for domestic use, then no. It's possible that a single 'Type-B board' might be suitable, using a mixture of 1-ph and 3-ph outgoing circuits, but this would depend very much on the size and layout of the unit, and the location of the supply intake. Voltage drop and other circuit length considerations for the various final circuits might mean that you'll need a number of distribution boards dotted around - e.g. 'offices' and 'works' in this case. An advantage of using multiple final DBs is that it's easier to isolate one part of the installation for alteration and maintenance, whilst keeping supplies on elsewhere.

If it's TN-earthed, then quite possibly none (until the 17th edition comes into force next year).

Probably both, and possibly some Type D too. Each final circuit should be considered separately.

"Maintenance" is the buzzword these days, in the context of complying with the EAW regulations. Whatever your electrical installation is like, you should be able to demonstrate that you have an active programme of maintenance to keep it safe.

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Reply to
Andy Wade

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