Tingling feeling from woodworking machinery

[petewood]

I recently bought a new 3-phase saw for my workshop. Before the saw arrived I had an electrician install some new cable and an isolator, and he left a length of cable from the isolator ready for the saw.
He could not get a suitable wylex triple breaker in time so he used 3 singles (each at 20 amp).
While he was fitting the breakers there was a loud bang, sparks flew and the lights went out. This happened again 10 minutes later but he eventually got it sorted and then he left.
The plan was for him to come back to connect to the saw.

The saw was delivered a couple of days later and the mechanic who was commissioning it wanted to wire it in so that he could run it and check it was cutting square etc. He said the electrician should check out his connections to sign it off.
He told me two things: one was that the cable was in the 'new' colours and the electrician should have put on some kind of a sticker explaining which colour was going where. The second was that he couldn't earth the machine as the electrician had used 4 core cable and had used the metal wires in the sheathing to connect to the earth at the isolator, but the box on the machine is made of plastic so it couldn't be earthed using a gland. It seems it will need an earth wire running alongside the cable to wire into the earth terminal in the machine.

I hope this is all clear, there's more to come.

Once the machine was up and running we both noticed a slight tingling feeling from the aluminium sliding carriage, which stopped when we isolated the machine.

I have several questions for anyone who is interested or feeling helpful.

1. Should the electrician have placed a sticker because of new coloured wiring?

2. Is it ok to use 3 single breakers instead of a triple one (if it trips will they all go or just one or two)?

3. Is it normal to create loud bangs and sparks flying?

4. Should the electrician have used a 5 core cable (is there such a thing?) so that there would have been an earth wire?

5. Why is my machine tingling and will earthing it stop this? If this is the case, then does it mean that there will be a constant loss of voltage to earth?

Questions 2 and 5 are the ones that concern me the most, the electrician is coming back on Tuesday to finish off and I would like to know what is right or wrong before he returns.

Any help will be much appreciated.

Pete

 

[il78]

1)Sticker is required for guidence only as two sets of colours have been used from two version of the wiring regulations.

2)Not recommended, but common in older installations.

3)Only for a laugh

4)Because of the plastic accessories a seperate CPC (earth) is required, but the armouring can be used if metal accessories are used.

5)Sorry I dont do machines, but if the earth is connected the fuse will probably blow....Something is wrong, my best advise is not to use it till its earthed...

 

[plugwash]

1 yes the sticker should be present

2 the regs say its acceptable to use 3 SP devices but use of a TP is preffered

3 NO my guess is he tried to fit the breakers live and didn't take enough care whilst doing so. Was there a good reason the board had to stay on?

4 it is normal to use 4 core with the armour as earth. Im surprised the machine wasn't designed for this (maybe the mechanic was just incompetent) 5 core SWA exists but is quite rare.

5 some designs of equipment naturally have fairly high earth leakage. I would not use this equipment until it is earthed.

 

[petewood]

Thanks for the prompt replies.

I was using a pillar drill in the same workshop when he fitted the breakers, but he never asked me about turning the power off for a while.

If the mechanic had left some of the armour as long as the core wires I suppose it could then have been fed up to the earth terminal on the saw, would this be acceptable? And how many strands should be used?

The box containing the terminals is definately made from plastic, it is a German machine but I don't know if this is common over there.

I don't intend to use the machine without earth, it makes me feel uncomfortable just to be near it at the moment!

One thing I forgot to mention, the electrician told me there was a 10 volt difference between the 3 live feeds, from 241v to 251v. Should I do anything about this? What effect on the machinery will this have?

_____________________________
Moderator

please note 10a

 

[2scoops0406]

Err, stop using it, call the sparky back.

 

[petewood]

Eddie, yes he's coming back, but can you explain what effect the different voltages will have.

 

[Panjandrum]

Can't imagine that small % difference having any impact on performance of the motor.
Idle speculation, but could this have anything at all to do with the tingle - either the tingle is caused by the difference or there is some quirky fault somewhere causing both?

 

[dw3101]

Why cant he fit a erm..a Lug (the bit that comes with the gland) To the gland then using a crimped lug run some 6mm earth cable and run that to the terminal on the machine??

Leaving the armour exposed and putting it into the terminal isnt acceptable.

I would rather have a three way breaker! - Get him to swap it out as your paying.

The voltages are most likely out due to phases not being balanced properly.. Nothing to worry about imho.

David

 

[securespark]

1 yes the sticker should be present

But only if there are two wiring colours present in the install. There are no stickers telling you what the new colours are or how they equate to the old ones. People dealing with the wiring are expected to know. If the machinery installation "engineer" does not know the new colours, then he's up s h 1 t creek without a paddle, and should hot-foot it back to college to find out.