testing code for ferrous consumer unit

thomasn · Sep 17, 2015

Hi we did a report today and the tails to the mk metal metal consumer unit were through two separate 20mm knockouts. We are now arguing if this should be C2 or C3. Also the main earth entered through the back of the unit. Any thoughts on this ?.

Octopus · Sep 17, 2015

It's not a C3 so c2 for me

davesparks · Sep 17, 2015

The regulations specify that L N and E may only be collectively enclosed by ferromagnetic material when entering an enclosure. And this has been a regulation for longer than MK have been making CU's so nobody can even say it complied with previous regs.
But is it potentially dangerous?
It isn't in normal use as the eddy currents from currents less than 100A are negligable. But under fault conditions there may be significantly more current flowing and much bigger eddy currents.

telectrix · Sep 17, 2015

C3 , IMO. i phoned Eddy asnd he wasn't upseyt by excessive currents. in fact, he asked for more in his cookies.

thomasn · Sep 17, 2015

davesparks said:
The regulations specify that L N and E may only be collectively enclosed by ferromagnetic material when entering an enclosure. And this has been a regulation for longer than MK have been making CU's so nobody can even say it complied with previous regs.
But is it potentially dangerous?
It isn't in normal use as the eddy currents from currents less than 100A are negligable. But under fault conditions there may be significantly more current flowing and much bigger eddy currents.

Hi davesparks,
Thanks for your reply which backed up my thoughts.Although I did opt for improvement recommended to bring the installation to comply with the regulations. The consumer unit has been this way for about 15 years so I could not see how the lead electrician thought this was potentially dangerous