Using earth as a neutral.

[conny]

Got asked to look at fixing a spotlight on one of the machines at work today. Its a 'Dynamic Balancer' used for balancing armatures/rotors and the guy said the spotlight has started blowing the bulbs more often. The light is one of these 'security' lights without the PIR. Anyway as one of the end prongs was badly burnt I decided to look for a loose connection when I discovered the earth from the lamp in the back of the fitting was connected to the neutral of the incoming supply (240v)and vice versa.
Looking further into it I discovered the 240v supply had been picked up from one of the 415v phase supplies and the main incoming earth as there was no neutral.
Now I'm not the hottest on industrial wiring, (I'm an armature winder/electrical fitter), so to me this is totally wrong. Is this a common method though as it was done by the people who installed the safety covers around the machine.

 

[RF Lighting]

Absoloutly not!!

It is very dangerous, completely against BS7671, and must be disconnected immediately.

If for any reason the earth to the machine, or worse still, the whole building were to fail, ALL the metalwork upto the point of failure will instantly become live

You need to either get a neutral to the machine, or install a stepdown transformer and run the light on two of the phases.

 

[ban-all-sheds]

Whoever did that has broken the law.

You need to speak to the duty holder and/or other persons in charge and tell them that they've got a serious breach of the EAWR on their hands.

 

[Spark123]

If there is no neutral present then use a 415v to 240v single phase transformer, not rocket science.
Like BAS says it is illegal (ESQCR) for a consumer to combine the neutral and earth in a single conductor.

 

[ColJack]

would you then earth one side of the transformer secondary to reference the "neutral" to earth?

 

[RF Lighting]

It's not a neutral

(here we go again)

 

[Spark123]

You can reference it to earth or you can leave it floating if you wish - normal design procedures apply of course.

 

[conny]

Sorry to take so long to get back to you guys, had a busy day.
Thanks very much for the info, I suspected it was illegal but wanted to make sure before I told the supervisor to shut it down till it is rectified. We had some company come in and build a 'Wendy House' affair around the machine to stop anyone getting hurt if bits flew off a rotor when it was being balanced and these are the people who wired up the light. They also wired in various interlocks so the enclosure had to be closed before the machine would start. Frightening to think how they may be wired up!

Once again, thank you and I'll get onto the supervisor first thing Monday morning.

 

[bernardgreen]

The "Wendy House" is a useful safety device but the machine itself should detect any dangerous un-balance when the shaft is rotating at slow speed and then prevent itself from increasing speed to a point where the item being tested has any risk of shattering.

 

[conny]

Good point Bernard, trouble is it is a second hand machine and quite old, (70's or 80's maybe)so although calibrated and checked regularly it is analogue meters etc so doesn't have the modern sophisticated safety features, its upto the operator to stop it if he thinks something is too far out of balance.

 

[ban-all-sheds]

I can hear the HSE lawyers licking their lips and counting their bonuses from here...

 

[Stoday]

I can remember wiring a whole farm up with no neutral anywhere — neither on three nor single phase circuits. All in pyro, the earth and neutral being common.

This was allowed for pme installations at the time - 1965 I think. Moreover, when the NICEIC inspector came around for his visit he made a beeline for my farm. Passed 100%.

 

[conny]

Just to bring you up to date.
Mentioned this to manager this morning, supervisor wasn't interested, and his immediate reaction was, "Do what ever it takes to make it safe and legal, don't give a **** about the cost."
So contacted 'Wendy House' installers and asked them to come and have a look immediately, can't get here till Friday at earliest.
I told them I would take pictures before disconnecting as proof of fault, they didn't seem too bothered. Got a feeling I will be chasing them to come out and investigate.
In the meantime I have run a length of 4mm SY cable through some 25mm conduit from a local dis board to supply a 2 gang metalclad socket fixed to the structure and plugged a new light into this. It is protected by a b16 mcb in the board and a 3A fuse in the plug. Is this acceptable for a temporary supply? If not I'll tell the manager we need to get someone in in the meantime to fix it properly.
Thanks in advance.

 

[Spark123]

It is fine as a temp supply however some labels making it clear that the socket is fed from a separate source wouldn't go amiss.

 

[conny]

Thanks Spark123, I have put signs at both ends and also one stating that the installation is to be removed no later than 26/01/2010.
This information has also been entered into the branch safety log.
Once again thank you.