Bit Of A Quiz For Fun

[Tywais]

Wasn't sure about putting this in DIY or not due to being more an industrial issue. Our new 3 story research building has been completed. As chief engineer at our facility I did a walk through to check the electrics out before we sign off final approval. The below is a photo of the Mains panel for the building. Spot the problems, sorry no prizes given (I know the problems but thought this might be a bit entertaining and educational for others). One problem is not obvious so will describe the building functions.

The 2nd floor is all office space, low power requirements. The 3rd floor will be fuel cell research and moderate power requirements. The 1st floor is the machine shop which has a very large automated 3D milling machine, one large manual milling machine and two smaller ones. 1 large lathe - two smaller ones. A few drill presses (large and small) and 2 or 3 arc welders including a TIG welder.

Some hints from a couple of useful articles.

University of Western Australia

Loop impedance

[sorensen]

Nice red, yellow and blue cables, but seriously, you guys need a gf (one each) if you time and energy to analyze breaker boxes

My guess: I have no clue, but looking forward to hear the answer.......and I guess some long and complex explanation

[Tywais]

Nice red, yellow and blue cables, but seriously, you guys need a gf (one each) if you time and energy to analyze breaker boxes

I have two full time jobs, one is the above and the other is the wife.

[Crossy]

OK, I'll rise to this one and start the ball rolling.

I am assuming that each floor will have its own sub-distribution board for outlets, lights, machine tools etc. with an ELCB for outlet circuits.

Your installer seems to have a surplus of black wire, it's OK for all the lives to be black but they should be oversleeved with L1, L2 and L3 to differentiate. Neutral and Ground also black is not a good move, a transposed phase and neutral is not a pretty thing (not good for your expensive kit), a transposed phase and ground is even less pretty (not good for the poor sod who touches some metalwork)

I don't see any fixings for a cover panel.

It's not obvious if there is an insulating panel over those incomers (the one over the bus-bars is visible). There are other touchables with no covers, live conductors should not be accessible without the use of tools (scrub that if the door needs a screwdriver to open).

I would like to see a 4-pole incomer (opening the neutral too) but it's not required by the regs AFAIK.

That green wire should be on the stud that's fallen off the door.

Those outgoing lives seem more than a little skinny considering the loads you've described (I can't see the rating of the breakers though).

That main ground is woefully small, it should be at least the size of the incoming lives.

Is this installation supposed to have MEN? Where be the link?

The feed for the Hall transducers/ CTs is coming from the hot side of the incoming breaker (at least they are fused).

Does the door have a 'Danger High Voltage' notice?

That's it for now, beer o'clock

I have a wife who keeps me occumpied when I'm not analysing breaker boxes

Edited December 27, 2008 by Crossy

[longball53098]

I agree with everything that Crossy mentioned.

[neverdie]

If its anything like the meter box on my rental, it should be sparking?

[PhilHarries]

Sorry I'm a dumb meccie (mechanical engineer).

You can't see electricity and if you can't see it you can't 'it it with an 'ammer. If you can't 'it it with an 'ammer you can't fix it. If you can't fix it then it's bu66ered. Call the sparkies.

PS I'll go with everything Crossy has said, go for it son and I'll put the kettle on.

[kennkate]

Ok I am No Sparky so one look at that, and sorry mate but would not go closer than a meter.

Is the problem mesured in HENRY's ? if it is I See

[dingdongrb]

OK, I'll rise to this one and start the ball rolling.

I am assuming that each floor will have its own sub-distribution board for outlets, lights, machine tools etc. with an ELCB for outlet circuits.

Your installer seems to have a surplus of black wire, it's OK for all the lives to be black but they should be oversleeved with L1, L2 and L3 to differentiate. Neutral and Ground also black is not a good move, a transposed phase and neutral is not a pretty thing (not good for your expensive kit), a transposed phase and ground is even less pretty (not good for the poor sod who touches some metalwork)

I agree and especially the grounds should be all GREEN or GREEN/YELLOW.

I don't see any fixings for a cover panel.

Must be too many beers for Crossy as I can clearly see the panel lid is hinged and opened to the right side of the photo.

It's not obvious if there is an insulating panel over those incomers (the one over the bus-bars is visible). There are other touchables with no covers, live conductors should not be accessible without the use of tools (scrub that if the door needs a screwdriver to open).

I would like to see a 4-pole incomer (opening the neutral too) but it's not required by the regs AFAIK.

That green wire should be on the stud that's fallen off the door.

Those outgoing lives seem more than a little skinny considering the loads you've described (I can't see the rating of the breakers though).

I agree, I would like to see the rating of the breakers to see if they can handle the current required for the machinery described. Also it would be nice it labeling on the breakers to which floors (areas) they service but perhaps they are on the inside of the door that I cannot totally see.

That main ground is woefully small, it should be at least the size of the incoming lives.

Is this installation supposed to have MEN? Where be the link?

The feed for the Hall transducers/ CTs is coming from the hot side of the incoming breaker (at least they are fused).

Does the door have a 'Danger High Voltage' notice?

Others:

Since this appears to be a breaker/distribution box I would like to see the main breaker have separate breakers for each phase.

Hard to tell but is the guage of wire used large enough for the currents it will see?

I do believe that the GREEN ground wire Crossy is referring to only connect the main box to the lid???

Some Tywraps on those wires would be impressive.

That's it for now, beer o'clock

I have a wife who keeps me occumpied when I'm not analysing breaker boxes

By the way, I also have a Thai wife and I think that she would oppose if I had a girlfriend.

[PhilHarries]

Aw go on Tywais, power it up and post the pics of the fireworks.

[Crossy]

Must be too many beers for Crossy as I can clearly see the panel lid is hinged and opened to the right side of the photo. No, that is the door, I'm looking for a cover (which must require tools to remove) to protect the person operating the breakers from those nasty naked bitey bits. The door may have openings but it looks like the breakers are too low in the box for that. There is a token cover over the bus-bars, but it certainly wouldn't pass muster in the UK.

Others:

Since this appears to be a breaker/distribution box I would like to see the main breaker have separate breakers for each phase. Not in a 3-phase dizzy, all three phases must open together or you'll fry any 3-phase equipment, 3-phase motors for example do not like operating with a phase missing.

Hard to tell but is the guage of wire used large enough for the currents it will see? Reckon you're right, I did note this in my observations.

I do believe that the GREEN ground wire Crossy is referring to only connect the main box to the lid??? Correct and an important safety connection, if it wasn't necessary it wouldn't be there at all.

Some Tywraps on those wires would be impressive. Actually, properly laced looms would be impressive (and totally un-necessary). http://www.dairiki.org/hammond/cable-lacing-howto/

Shame it's going to have to come out, it's actually a nice job, proper crimps, neatly wired too

EDIT I suppose, assuming those lives are big enough, then appropriately coloured sleeves on those black wires could make it at least reasonably safe.

Edited December 27, 2008 by Crossy

[dotcom]

What are those 3 white things - to the right of the main breaker which are wired up with yellow wire?

Yeah that naked bus bar is kinda scary.

All Black - what was he thinking?

As for that little green wire - looks weird doing nothing. A dandle? a dongle?

[Crossy]

What are those 3 white things - to the right of the main breaker which are wired up with yellow wire? They are fuse holders in the supply to what I believe to be Hall-effect current transducers (the green things sat on the bus-bars).

As for that little green wire - looks weird doing nothing. A dandle? a dongle? It's supposed to be connected to the door for ground bonding.

Edited December 27, 2008 by Crossy

[Tywais]

One other thing during my preliminary walk through inspection. While in the machine shop (still empty room) area, had the technician flip off each breaker in the local distribution/breaker panel. When he turned them back on, after a couple of seconds - heard a "poof" and a puff of smoke come from a AC outlet I was standing next to.

Opening it up, saw the wires to the receptacles stretched a bit too tight and cutting into the edge of the conduit pipe lip. No grommets or insulation tape between the two. Now have to wonder how many more outlets are like this. Appears the conduit grounding is intact, but no breaker tripped. However one of the issues in the main panel probably is why no ELCB functioned. More work to do.

[dingdongrb]

http://www.dairiki.org/hammond/cable-lacing-howto/[/url]

<deleted> is that all about? That was written in 1962 and it seems that it would take a mastering of skill as well as hours of time to dress wires and cabling like this. This is 2008 (nearly 2009) and a few pennies worth of tywraps and a minute or two would do the trick. Are you having flashbacks on the things your grandfather did?

[Crossy]

One other thing during my preliminary walk through inspection. While in the machine shop (still empty room) area, had the technician flip off each breaker in the local distribution/breaker panel. When he turned them back on, after a couple of seconds - heard a "poof" and a puff of smoke come from a AC outlet I was standing next to.

Opening it up, saw the wires to the receptacles stretched a bit too tight and cutting into the edge of the conduit pipe lip. No grommets or insulation tape between the two. Now have to wonder how many more outlets are like this. Appears the conduit grounding is intact, but no breaker tripped. However one of the issues in the main panel probably is why no ELCB functioned. More work to do.

Hmmm, worrying

Are your aircon outlets protected by RCBOs or regular MCBs?

If they are RCBOs I would have thought that more than enough ground current (30 or maybe 100mA as it's an industrial installation) would have flowed to drop the breaker when you had your splat.

Plain MCBs are a different kettle of fish, with no MEN link the loop impedence (via the ground stake) is likely too high to cause the breaker to open in a reasonable time and the splat blew out the short before that time.

EDIT That fat wire on the neutral bar IS the incoming neutral isn't it?

Edited December 27, 2008 by Crossy

[Crossy]

http://www.dairiki.org/hammond/cable-lacing-howto/[/url]

<deleted> is that all about? That was written in 1962 and it seems that it would take a mastering of skill as well as hours of time to dress wires and cabling like this. This is 2008 (nearly 2009) and a few pennies worth of tywraps and a minute or two would do the trick. Are you having flashbacks on the things your grandfather did?

555, not my grandfather, me I actually learnt to do that (long ago when the earth was green and tywraps weren't invented, actually as an MOD apprentice in the 1970s) doubt if I could now, age has got to the eyes and the joints. To be honest, with rigid wiring I wouldn't bother with the tywraps unless we're in a high vibration environment (ships for example), it ain't going anywhere and adding wires is less than convenient when it's all nicely dressed.

Any idea why no breakers dropped when Tywais had his splatting incident??

Edited December 27, 2008 by Crossy

[dingdongrb]

http://www.dairiki.org/hammond/cable-lacing-howto/[/url]

<deleted> is that all about? That was written in 1962 and it seems that it would take a mastering of skill as well as hours of time to dress wires and cabling like this. This is 2008 (nearly 2009) and a few pennies worth of tywraps and a minute or two would do the trick. Are you having flashbacks on the things your grandfather did?

555, not my grandfather, me I actually learnt to do that (long ago when the earth was green and tywraps weren't invented) doubt if I could now, age has got to the eyes and the joints. To be honest, with rigid wiring I wouldn't bother with the tywraps unless we're in a high vibration environment (ships for example), it ain't going anywhere and adding wires is less than convenient when it's all nicely dressed.

Any idea why no breakers dropped when Tywais had his splatting incident??

Dam_n you're much older than I perceived then..... But as I say, age is just a number, right?

I agree about the tywraps or the cable dressing as it is mostly for 'show' or anal attentive people such as me....

As why the breakers didn't trip my only guess was that the pinched/cut wires where the short occurred burnt back far enough and quick enough before max current was seen at the breaker.... (Sometimes a large amount of current will quickly melt the nicked insulation on a wire and it will isolate the bare wire.) Maybe to be sure of the breakers he could short one receptacle out to ensure the breaker indeed works... (Of course apply the short with the breaker OFF and then turn it on to see if it trips.) I would hate to have a defective breaker in a line that sees enormous loads and changes of loads (i.e. the machinery he mentioned).

[Tywais]

Are your aircon outlets protected by RCBOs or regular MCBs?

At the moment the aircon wiring are bare wires hanging out the of the ceiling and appear to be going to MCBs. The aircon installation appears to be our responsibility after the building is signed off to us.

Plain MCBs are a different kettle of fish, with no MEN link the loop impedence (via the ground stake) is likely too high to cause the breaker to open in a reasonable time and the splat blew out the short before that time.

EDIT That fat wire on the neutral bar IS the incoming neutral isn't it?

Right on both above counts. The ground (earth) impedance has been measured as ~4 ohms which is good. And yes, the MEN link is missing. Also, had to look closer to see if the MBJ (main bonding jumper) was in place. It's the screws from the right hand earth buss bar to the main box frame. Normal requirements are the screw has to be green. In this case they painted green lines on the bus bar.

The other problem is that the neutral line is significantly smaller then the incoming 3 phase lines. Haven't figured that one out as to what the thinking is behind it.

[Crossy]

The other problem is that the neutral line is significantly smaller then the incoming 3 phase lines. Haven't figured that one out as to what the thinking is behind it.

I suppose he could have been thinking that since most of your big kit is 3-phase there would be a relatively small imbalance between the phases leading to a smaller neutral current (for those readers who don't know, in a perfectly balanced 3-phase system there is no current in the neutral). I'd still want the neutral the same size as the phases though. More likely he ran out of fatter wire (witness the use of two thin wires for the main ground).

Sooooooo, what are you going to do about these 'small' issues?

EDIT I hope the wiring from the sub-boards uses a more conventional colour code

Edited December 27, 2008 by Crossy

[Tywais]

Sooooooo, what are you going to do about these 'small' issues?

The problem is we are 6 months behind schedule getting the building turned over to us and can't afford any more delays. Once it is turned over, probably the first thing planned is to run a separate 3 phase distribution directly to the machine shop and it's own mains panel. The machinery is a combination of 3 phase and 2 phase. We are not allowed to do anything to the building until it's signed off, which includes putting in the air conditioning systems and the networking.

My initial walk through was a cursory one while the contractor was there. Will do a more thorough one later. Will try and evaluate the 3 phase load balance also to be sure there are not "gotchas".

[Tywais]

EDIT I hope the wiring from the sub-boards uses a more conventional colour code

The sub panels they seem to have gotten right with the color coding. At least in all three of our research buildings we have true 3 wire grounded outlets everywhere. The AC outlets they used for the new building are unusual. They appear to have a safety interlock built in, that is not live until a plug is inserted.

[Crossy]

The AC outlets they used for the new building are unusual. They appear to have a safety interlock built in, that is not live until a plug is inserted.

Not just shutters?

Sounds like a recipe for reliability issues, and I'll bet they weren't cheap

Do you have a manufacturer and part number, could be really useful where there are small fingers.

Edited December 27, 2008 by Crossy

[tjo o tjim]

A 50% Neutral wouldn't be that bad for the installation you are describing, if you are over 400A, but I wouldn't undersize it for the 200A that it looks like. 25% Ground is typical in Thailand, but I prefer 50% ground.

My big curiosity is if you are using single phase or three phase power for your distribution panels on the office floor.

Also, 200A sounds pretty small for what is described. It's enough if you only have 5,000 square feet, or if the machine shop isn't conditioned. Might be easiest to add a second service for your machine shop.

[PhilHarries]

555, not my grandfather, me I actually learnt to do that (long ago when the earth was green and tywraps weren't invented, actually as an MOD apprentice in the 1970s)

Learnt my trade as an MOD apprentice 1968-72 at RAE Farnborough. Small world.

Did City & Guilds Electrical Theory and Practice and was okay up to 3 phase which proved too much for my mechanical brain.

Pass me the hammer and the 99 Tips.

Talking about quality of electrical installation I've just come off a refinery project in Viet Nam where the workers were stealing the cable as fast as it could be installed. Earth cable was the favourite target, scrap value of 1 kg of copper was more than a month's wages. They had to install the lightning conductors on the turbine hall shed twice.

[Tywais]

Once it is turned over, probably the first thing planned is to run a separate 3 phase distribution directly to the machine shop and it's own mains panel.

My big curiosity is if you are using single phase or three phase power for your distribution panels on the office floor.

If you note the drawing, 3 phases are being sent to all 3 floors to their respective sub panels. Load balancing for the 220VAC single then done there.

Might be easiest to add a second service for your machine shop.

See above.