Multiple 3 phase motors fed via a JB supplied with a 27 core SWA

jon6oy · Sep 16, 2014

Ok, agreed, the grouping factor possibly wouldn't be required. But it's not a bad thing to err on the side of caution, that's what I've always been told.

Thanks for letting me stretch my brain, been a while!

D Skelton · Sep 16, 2014

jon6oy said:
Ok, agreed, the grouping factor possibly wouldn't be required. But it's not a bad thing to err on the side of caution, that's what I've always been told.

Thanks for letting me stretch my brain, been a while!

Or you could just design it properly providing the client with exactly what is required, no more, no less, and saving them money in the meantime.

Knobhead · Sep 16, 2014

shanky887614 said:
before people think its a bit small usually .75 is enough for controls for valves etc

I wish. Before the advent of PLC’s with outstations some of the individual circuits were of ridiculous length, fault finding kept you fit if nothing else.

shanky887614 · Sep 17, 2014

Tony said:
I wish. Before the advent of PLC’s with outstations some of the individual circuits were of ridiculous length, fault finding kept you fit if nothing else.

i agree with that, we have generally been lucky that our panels are on the same floor and the longest we have really had to do was around a 300m run

jon6oy · Sep 17, 2014

D Skelton said:
Or you could just design it properly providing the client with exactly what is required, no more, no less, and saving them money in the meantime.

But this wasn't a design query, it was a validation question was it not?

D Skelton · Sep 17, 2014

jon6oy said:
But this wasn't a design query, it was a validation question was it not?

Originally by the OP yes, but you started talking about erring on the side of caution when applying grouping factors, which is normally done by an inexperienced electrician at the design stage.

If validation is all the client is after, again, erring on the side of caution could be tantamount to giving them the wrong advice, such as telling them that a suitably sized cable isn't suitably sized.

Either way, there is a time and a place for erring on the side of caution, and applying grouping factors is often not one of those times or places. Do it right.