Fused connection unit mounted on metal backbox

[Gary Tollison]

greetings

I’m taking a spur from a ring final.
A fused connection unit will be controlling the spur.
FCU will be mounted on a metal backbox flush in a brick wall.
I’m planning on using a junction box to break into the RFC, and taking the spur cable to the FCU.
My question is, do both cables going to and from the FCU have to be in the same hole in the back-box, or can I have each cable in a different hole?
Thanks,
Gary

 

[Andy78]

Whichever is best for the physical constraints of installation. What's your thinking behind this question ?

 

[telectrix]

why not just install 1 cable from JB to the FCU?

 

[Gary Tollison]

As there isn’t much room for both cables to go through the one hole, and putting a rubber grommet in there for both is a right pain in the proverbial, so I decided that one cable in each would easier

Telectrix, apologies for my not being very clear, I wasn’t quite awake when I typed it There will be one cable coming from the junction box to the FCU, and another coming from the FCU to supply the spur dependants



Thanks for the replies!

 

[telectrix]

i never have any trouble fitting 2 x 2.5mm cables through a 20mm hole with grommet. but no problem in using separate holes if that's your preference. ( cost you an extra grommet though. ).

 

[Octopus]

What type of junction box do you have in mind?

 

[telectrix]

are there any other types?

 

[telectrix]

ah, found one:

 

[Wilko]

I thought I got a sniff of an eddy current debate there for a moment .

 

[Deleted member 26818]

are there any other types?

Yes, they do one with four terminals.

 

[Gary Tollison]

This one I’ll be using

 

[SparkyChick]

That will need to be accessible to testing in the future. You would be better off using a maintenance free junction box, such as a Wagobox with appropriately sized and rated Wago connectors.

Or Hager do some nice maintenance free boxes.

Basically anything with a screw terminal needs to be accessible for test and inspection as over time, thermal cycling can cause the termination to loosen. Loose terminals = fire risk.

 

[Gary Tollison]

Yup, I’ve made a section of the floorboards liftable where the junction box is located nice and easy to get to

 

[SparkyChick]

Yup, I’ve made a section of the floorboards liftable where the junction box is located nice and easy to get to

Why complicate your life (and more importantly the next owners of the property). Do it properly in the first place and use a maintenance free junction box.

 

[Andy78]

I agree with SC. Although the definition of accessible is open to interpretation, I use MF connections when concealed in the fabric of a building, including under floors.