Elec install Q

[Rick Hughes]

My neighbour ... again.

He has a 3ph supply, meter feeding a TPN switch fuse.

1ph feeding house, from this he wants to allow for fact that he will be connecting a 3ph lathe in the future. I have recommended a further TPN switch fuse downstream from his existing one, fused to suit Lathe.

He asked me is there a requirement to have RCD protection for a lathe ....... the last time I worked on lathe installs, there was no such requirement - that was on an Engineering workshop in early 80's

60+ machines, none on any RCCD (or ELCB at that time)

Is there a requirement for RCCD protection on a fixed 3ph machine ? Interested to know if there is a requirement for earth fault protection.

He also had in his hand a 3ph RCCB .... asking if he could fit that ... my understanding is, 'yes' downstream of TPN switch fuse it will provide earth trip protection, but no overload protection (fuses in TPN switch fuse supply that)

[John Rumm]

Any requirement for RCD protection would apply to the cable rather than the machine as such. So if surface wired, or in trunking, or one of the approved shielded cable types (SWA etc) then there would be no specific requirement for a RCD to protect the cable.

I would expect a lather to be a class I device (i.e. must be earthed)

However fixed equipment of that nature is less of a shock risk than portable kit you drag about trailing a flex. Keep in mind it might have cooling / cutting lubricant pumps etc, so you have water and electricity in close proximity.

Yup.

[Rick Hughes]

Thanks ... confirms my thoughts