Lathes shorting electricity

[porker]

OK, I guess you know this - running without an earth is dangerous practice as the metal parts could be live and you've just removed the protection. When you say you have tripped everything is this the earth leakage breaker taking out all the other circuits? If you are not sure put up a picture of your consumer unit.

Because both your lathes are taking out the circuit I think they are both giving just enough to just take the leakage over the edge as stated earlier.

I'm afraid I don't 100% agree with tdsoldgit that the lathe is definately faulty (although it might be). I would expect your lathe to leak a very small amount as these have the filters as he explained and they tend to leak to a lesser extent. Everything else I agree with. The fact that either lathe does this means it is unlikley they both have a similar fault (not impossible but unlikley).

There are various things you could try but getting an electrician is your best bet. It's too easy to make a mistake. I would put that earth back on if I were you. BTW if you are switching other circuits off to see where the cause might be, be aware that turning off a circuit at the MCB does not usually disconnect the neutral so if you have a neutral-earth fault, switching off the circuit won't stop the tripping.

 

[Penllysbach]

Hi, when you say "tripped the fuse" do you mean it tripped the circuit breaker on your fuse board?

If yes, what is the power requirement of your lathe - could it be that the start up current is exceeding the rating of the fuse? In which case you would need to change the circuit breaker to one that can handle the initial current surge. I think (you would need to confirm with an electrician) they are known as "type B".

Thanks for this. Have tried it on house mains but still cuts out. I will try with a circuit breaker

 

[OldWood]

Hi, when you say "tripped the fuse" do you mean it tripped the circuit breaker on your fuse board?

If yes, what is the power requirement of your lathe - could it be that the start up current is exceeding the rating of the fuse? In which case you would need to change the circuit breaker to one that can handle the initial current surge. I think (you would need to confirm with an electrician) they are known as "type B".

One of the problem in sorting out electrical problems remotely, particularly on forums as this, is understanding from the original post if is it the MCB (Mains Circuit Breaker) that has tripped on that one circuit which would indicate an overload, or if is an earth leakage in which the RCD / ELCB / RCCB has tripped and has resulted in the whole area going down. And don'e ask me why the earth leakage trip has collected so mant acronyms! As the Original Post clearly says 'tripped all the power' the indications are that there is an earth leakage problem, and that ii is nothing to do with the MCB and whether it should be 'type B or ' type C'
Rob

 

[guineafowl21]

why the earth leakage trip has collected so mant acronyms!

The Americans call it a GFCI... Anyway, this exchange:

Earth leak perhaps?

Ohhh, what does that mean???

... Suggests we won’t get far with remote diagnosis.

@Penllysbach please let us know what the electrician finds. Also, please make sure you’ve refitted the earth connection to the lathe that you took off. We want the electrician to find the fault, not his maker!

 

[mr rusty]

Where equipment has large motors it is quite possible that the start current is enough to knock the breaker out (not "earth leakage but over current). It isn't unusual for electric motors to draw 6x the run current for a very short period - perhaps 60A when the run current is only 10A. This is why breakers come in different ratings B, C, D. (the motor windings are essentially a dead short and until the motor is spinning there is no back-emf to counteract it)Selecting the right MCB or RCBO).

If it is the breaker and not the RCD that is tripping, it may be possible to uprate a "B" type to a "C" type or even a "D", but you do need a sparks to do this.

 

[Spectric]

Hi

Have you thought of dampness in the motors of these machines, get a sparky to perform an insulation test.

 

[Penllysbach]

Morning all
Still awaiting the arrival of the electrician but yes, re connected the earth wires and the issue has been resolved by putting the lathe on its own circuit breaker ... seems to be fine now.
Am wearing rubber soled boots ... just in case.
Really appreciate everyone's input into this, thanks

 

[guineafowl21]

the issue has been resolved by putting the lathe on its own circuit breaker

Could be a different type of breaker, insensitive to small earth leaks. As a couple of posters above have mentioned, we need to know what type is tripping. But that’s academic now as you’ve called in a sparky.

Am wearing rubber soled boots

Good idea. Just out of interest, and while we wait for the diagnosis, you can still receive a fatal shock while wearing rubber boots if it travels hand to hand. Old-fashioned TV repairmen used to work with one hand in their pocket for this reason.