6 cables in a backbox?

[Deleted member 112675]

Hello Everyone

Will be wanting a grid switch with 4xdp switches to control 4 spurs with a single socket on each. Ring main in and out plus 4 spurs of the switches equals 6 2.5mm cables. I've got a 4 module mk grid backbox - about 45mm depth I think.

Is it possible? I'm thinking the 4 spurs might just enter the bottom of the box and go straight into their respective switches but it might be hard to get all 6 earths terminated?

 

[Andy78]

You're right, that's gonna be a pain for second fixing.

 

[ferg]

As long as the cpc's are connected they dont all have to be in the same hole

 

[SJD]

You could add an extra earth terminal or two in strategic places, e.g.:

M4 Brass Earth Terminal For Metal Conduit Boxes (10 Pack) | METPRO | BES | eBay

Orders received after 1pm Mon - Thurs will be dispatched first thing following morning. This product undergoes rigorous inspection by our supplier in both the country of manufacture and in their UK warehouse.

www.ebay.co.uk

 

[littlespark]

Should be easier than if you used a 35mm box.
Go deeper if you can

 

[Strima]

47mm back box and:

 

[casperLennon]

Easy fit them all in

 

[westward10]

Beginning of the summer tested ten houses for a housing association on a five year old estate. Eight out of the ten had open continuity faults on at least one conductor on the kitchen ring final circuit. Back to do remedials, first house found in 30 odd minutes at the four gang control grid. All bar one of the others at the same point. Half a day I had resolved all eight. Bad design? or the whole MK grid unit totally inadequate for a ring final using 2.5 solid conductors. Admittedly the links could have been stranded 2.5 but nevertheless.

 

[Pete999]

As long as the cpc's are connected they dont all have to be in the same hole

As long as it aint the L or N hole

 

[westward10]

The cpcs are not the problem I did as suggested in #6 by @Strima just chopped the lot and put in a Wago with a link to the grid. The whole lot were so badly connected.

 

[Deleted member 112675]

Beginning of the summer tested ten houses for a housing association on a five year old estate. Eight out of the ten had open continuity faults on at least one conductor on the kitchen ring final circuit. Back to do remedials, first house found in 30 odd minutes at the four gang control grid. All bar one of the others at the same point. Half a day I had resolved all eight. Bad design? or the whole MK grid unit totally inadequate for a ring final using 2.5 solid conductors. Admittedly the links could have been stranded 2.5 but nevertheless.

I'm inclined to agree! I'm probably being naive, but wouldn't the customer have noticed if any of the conductors (apart from earth) was open ? I mean their fridge wouldn't be working....

Also, are you giving me a hint that using 2.5 stranded for the links between each switch might make it slightly easier?

 

[Andy78]

I'm inclined to agree! I'm probably being naive, but wouldn't the customer have noticed if any of the conductors (apart from earth) was open ? I mean their fridge wouldn't be working....

Also, are you giving me a hint that using 2.5 stranded for the links between each switch might make it slightly easier?

A discontinuous ring connection at one terminal would not mean any power loss to any one grid switch.

 

[westward10]

I'm inclined to agree! I'm probably being naive, but wouldn't the customer have noticed if any of the conductors (apart from earth) was open ? I mean their fridge wouldn't be working....

Also, are you giving me a hint that using 2.5 stranded for the links between each switch might make it slightly easier?

Good point, most were cpc issues and a disconnected line or neutral will still allow the others to function as the one conductor was still in place.
Stranded conductors allow that bit more flexibility but I find with the MK grid terminals are far too shallow especially for solid 2.5. I expected they just popped out when the grid was screwed back.

 

[Deleted member 112675]

A discontinuous ring connection at one terminal would not mean any power loss to any one grid switch.

Oh yes of course. Hence the ring. Thanks for your correction !

The pic in #6 is that an 8 way waygo? So could put all the earths in that with one going to the backbox?

 

[westward10]

I tend to just link to the grid but seeing as you have the eight way option no reason not to do both, the grid is the important one as it could be floating.

 

[Deleted member 112675]

...
Stranded conductors allow that bit more flexibility but I find with the MK grid terminals are far too shallow especially for solid 2.5. I expected they just popped out when the grid was screwed back.

DIYers get a bad press and many don't like all the regulation but my gosh. Surely whoever did that in a housing association must have been a professional electrician that should have had and used a multifunction tester (as I have). In fact I think you could diagnose that fault with a simple multimeter.

MAny thanks once again for all the advice and great tips.