Extension lead wired into 63A TP+N MCB/Main Switch

[MaintenanceSpark]

Hi guys,

We’ve had a new CNC Machine from China arrive this week. It came with a monitor and a tower to run the software. The monitor and tower were already plugged in to an extension lead that was wired through the slotted trunking, I took all the lids off and traced the extension lead cable to find it being fed from the 63A TP+N MCB/Main Switch. No CPC, just live and neutral. Please see attached photos.

My plan is to reroute a socket that's on a radial circuit at the back of the machine on the wall into the control panel for the monitor and tower to utilise. The radial circuit is on a 20A RCBO.

So I suppose my questions are; how dangerous is what the Chinese have done and why would they do that? Could the extension lead have drawn the full 63A?

Thanks very much.

 

[westward10]

Doesn't look good as those plugs appear to have a sliding earth contact and aren't suitable for that socket the IT equipment will almost definitely need an earth. Fit a four way extension and use 13A plugs.
I would also be contacting the supplier.

 

[MaintenanceSpark]

Doesn't look good as those plugs appear to have a sliding earth contact and aren't suitable for that socket the IT equipment will almost definitely need an earth. Fit a four way extension and use 13A plugs.
I would also be contacting the supplier.

Thanks for the advice Westward. Will definitely be fitting fused plugs with a CPC present for the IT equipment.

 

[pc1966]

The answer is dangerous. Those EU/USA style plugs and sockets have no fuse and are expected to be fed from, at most, a 20A C-curve MCB.

If they only feed internal equipment then you probably don't need RCD protection, but if they are feeding stuff that is separate like a monitor, etc, I would say they should have protection. If you can fit a single module 16A RCBO in there after the 63A D MCB to feed your sockets that would be far better.

As @westward10 has already mentioned it must be earthed as well, and you should be using sockets that are approved for UK usage so either 13A plugs/sockets or 10A IEC style (in which case fit a 10A RCBO, etc).

If you want good quality power blocks and any custom options such as a mix of socket types, etc, then contact Olson Direct (London based, good stuff as we have blocks from them that are 30 years old and perfectly good - other than dead neon indicator).

 

[MaintenanceSpark]

The answer is dangerous. Those EU/USA style plugs and sockets have no fuse and are expected to be fed from, at most, a 20A C-curve MCB.

If they only feed internal equipment then you probably don't need RCD protection, but if they are feeding stuff that is separate like a monitor, etc, I would say they should have protection. If you can fit a single module 16A RCBO in there after the 63A D MCB to feed your sockets that would be far better.

As @westward10 has already mentioned it must be earthed as well, and you should be using sockets that are approved for UK usage so either 13A plugs/sockets or 10A IEC style (in which case fit a 10A RCBO, etc).

If you want good quality power blocks and any custom options such as a mix of socket types, etc, then contact Olson Direct (London based, good stuff as we have blocks from them that are 30 years old and perfectly good - other than dead neon indicator).

Brilliant. Many thanks for the help. This forum is great.

 

[Simon47]

We’ve had a new CNC Machine from China arrive this week.

So I was already expecting something bad

It came with a monitor and a tower to run the software. The monitor and tower were already plugged in to an extension lead that was wired through the slotted trunking, I took all the lids off and traced the extension lead cable to find it being fed from the 63A TP+N MCB/Main Switch. No CPC, just live and neutral. Please see attached photos.
...
So I suppose my questions are; how dangerous is what the Chinese have done

Very

and why would they do that?

Because a) they don't know better, partly due to b) they don't care, with a good dose of c) it was the quick and cheap way to do it.

Could the extension lead have drawn the full 63A?

For a while yes, and depending on cable lengths together with Zs, it's possible it could have taken a very significant fault current for ... a long time to indefinite without tripping the supply. Of course, the extension lead would get very hot, melting it's own insulation and creating smoke - but the bigger issue is that it would also damage all the wiring it shares a trunking with which would very quickly turn into a significant repair job.

As others have mentioned, that combination of plug and socket is not earthed, and the IT equipment (at least the PC, the monitor may be Class II) must be earthed.

Is there no spare DIN rail you could squeeze an extra MCB (or RCBO) onto for a suitably protected supply ? Ideally you don't want multiple unrelated supplies going into one machine - creates scope for someone to miss isolating something.

I would suggest that you need to look over the rest of the machine. If they did this, what else have they done that might not be safe ?
At a previous employer, we got a new machine (head end for filling tins/jars with candle wax, followed by a long conveyor chain passing through cooling and reheat tunnels) which was designed by the chief engineer of our parent company in the USA, and built for us by one of their US suppliers. It was an accident looking for someone to maim.
Considering it was built specifically for us, you'd think it could have been designed for our 415V supplies, but no, we had to buy in a transformer for it. It had a load of heaters that were all 240V, so could have been wired L-N instead of L-L. All the motors were on VSDs, so we didn't need to worry about frequency, just voltage. It didn't take much looking at to realise that by the time we'd ripped out and replaced all the wiring, motors, VSDs, PSUs, etc, it would be cheaper and easier to buy in a transformer.
And our maintenance guy spent a fair bit of time making and fitting guards over all the moving bits - some of which just seemed to invite "put your hand in here so I can take some fingers off".
And after a while, we got a local engineering firm in to jack the whole thing up and stuff bits of RSJ under it's legs. The said engineer was a bit of a short a**e, so he'd designed it at a convenient height for him to lean over - but our lanky guys were having serious back problems leaning over it (manual operations, such as dropping a wick in for most of the products we did on it).

So given this came from the USA which isn't totally without worker safety and product liability laws, the mind boggles what you may find hidden in something from a country with "something of a reputation".

 

[freddo]

Those 3 phase outgoing wires look really thin to be connected to a D63 MCB!

 

[pc1966]

Those 3 phase outgoing wires look really thin to be connected to a D63 MCB!

Good point, they do look a bit 6mm-ish when you mention it, and that is not going to last long enough for a D63 to trip!

It might, on a good day and with a fine Zs behind it, trip on a short/fault, but not for overload!