Maintenance Free Junction boxes using Wagos

[Tricky Dicky]

I am soon to replace a couple of below floor junction boxes on the ring main owing to a change of floor covering meaning they will have to become maintenance free.

According to the installation notes for the original Wagobox and Wagobox SLA to qualify for BS 5733-MF I need to use connectors 773-173. No quibble about the connectors but am I obliged to use Wagoboxes since these connectors have been type approved for them or can I use Wiska boxes as I have used with Wagos in non-maintenance free situations?

Richard

[SH]

The Wago boxes have cable grips in them. Do the Wiska boxes have those too?

[Tricky Dicky]

Er no! Then again do junction boxes on fixed wiring require cable grips, I have not come across many that do.

Richard

[SH]

well, the Wago MF boxes I have have a pair of plastic cable grips that I can move up and down a slotted cone to adjust for different cable diameters.

see here:

I also have these:

As you can see these have cable grips too.

Everytime I see a junction box described as maintenance free, there has

*always* been cable grips provided.

Clearly the ability to retain a cable protects against movement of the individual wires that are pushed into the connectors.

The relevant standards are: BS EN60670-22, BS 5733-MF.

[SH]

This is required reading!

[SH]

P.S. and it does say the terminals MUST be screw-less AND cables MUST be secured by cable clamps....

[Steve Walker]

It may be mandated, but the question is why? As fixed wiring is usually cable clipped to joists and junction boxes are screwed to them, why on earth is a cable clamp a requirement, when nothing can move anyway?

[Tricky Dicky]

Thanks for that SH so it is Wagoboxes , no problem.

Richard

[Fredxx]

What's the difference between a cable clamp and a cable grip that you would find in a Wago Box?

[SH]

a cable clamp is a strip of plastic held with a screw at both ends

A cable grip is two shims of plastic gripping the cable on both opposite sides

Both are acceptable in MF boxes.

[Fredxx]

Thanks for the clarity.

IIRC the other stipulation is that a box can only contain one 20A connection. And that this acceptable for a ring. BICBW

[Tricky Dicky]

You can go up to 32A if you use the 773-173 push on connector which is rated for wire sizes from 2.5mm2 to 6mm2

On further question, since the CPC in 2.5 T&E is only 1.5mm2 and will be too small for the 773-173 connector is it acceptable to use a 222 series connector for that?

Richard

[SH]

Thats an excellent question......

our resident Sparky, Adam is probably the best & most qualified person to answer that....

but my gut instinct is that if you have a (RCD and MCB) or a RCBO on the circuit using those connectors, and that provided the 222 connector has a high enough rated current capacity suitable for 1.5mm2 cables, you're probably OK BICBW.

[Robin]

I think you only need 773-173 for 32A rating so you can use any 773 (or

222) /series/ connector that accepts 0.75-2.5mm

[ARW]

Andy Burns is the wago man. He has a link somewhere to answer that question.

[ARW]

I would consider a tightened up stuffing gland to be acceptable if using a whiska box.

[Andy Burns]

I was just about to say that I didn't think Adam was especially a Wago fan ... here's my collected info on Wagos in MF boxes ...

Wagos fitted in a suitable enclosure can be treated as "maintenance-free" but they need to be de-rated per conductor and total per enclosure.

A normal maximum current for 2.5mm^2 T&W cable if clipped-direct would be 27A, all the 222- and most of the 773- series Wagos have to be de-rated to 20A when installed as "maintenance free" also the sum of all currents within the single box must not exceed 50A

The exception is the 773-173 Wago, which is normally rated for 41A and de-rated to 32A and 64A total when "maintenance free", so is still OK for a ring circuit.

I hadn't previously noticed the minimum conductor size of 2.5mm^2 for the 773-173, so I'd either use a 773-10x or 222-41x for the CPC.

[Fredxx]

That's really useful, thanks.

[ARW]

Boxes available in 4 different colours:-)

We all need to accessorise from time to time.

[Adam Funk]

I've never seen the "designer colours" before --- when did they add those?