Patress Boxes and Rubber Grommets

[mfarrow]

It is a bit rough not to have had grommets in the first place, but now that it's done it's done, and you aren't going to win many friends by filing PIRs with Code 2s for everything you find that you think is a bit rough.

It's a good job I won't be filing any PIRs then

The reason I ask is because I'm doing some wiring on my house and have been replacing all the accessories. I've tried to stuff grommets into a few but have given up on the majority of them.

The house was fully rewired by the electrician who lived there (apparantly) about 20 years ago. I can believe that actually - 10-way split load board with RCD protection on all socket circuits on an old MK 'slide-switch' unit. Oh, and a separate board for the immersion and washing machine.

I'll stop concerning myself now then - I could put shrink-wrap on some of them, where the plaster isn't uniform all the way round the hole - but I'm thinking heat-shrink will be softer than PVC anyway.

Thanks for the replies.

 

[RMS]

Failing to fit rubber grommets is not good practice.

I would not concern myself too much unless you can see evidence of damage to the cable sheath which is probably unlikely.

 

[PrenticeBoyofDerry]

GN3

Installation check lists
insulated cables, non flexible, protected against mechanical damage and abrasion 522.8.(11)

 

[ColJack]

every time you remove the faceplate of an accessory, there is the chance that the cable will be pulled / chafe against the metal of the backbox if a grommet isn't fitted.

 

[skenk]

One of the defects in the 2391 inspection is a split grommit (not even missing, just split) although i'd agree that if it's plastered in then there's not much to worry about.

 

[Monkeh]

every time you remove the faceplate of an accessory, there is the chance that the cable will be pulled / chafe against the metal of the backbox if a grommet isn't fitted.

Because you do that regularly and the sides of the box are as sharp as a stanley knife.

 

[ban-all-sheds]

every time you remove the faceplate of an accessory, there is the chance that the cable will be pulled / chafe against the metal of the backbox if a grommet isn't fitted.

Not if the cable is embedded in plaster up to and including the hole as mfarrow's is.

 

[ban-all-sheds]

T&E cable is lowest quality mains cable and there is no approved method of termination, I would imagine it will be phased out very soon.

I think you have an over-active imagination.

 

[dingbat]

You can still fit the grommets if you carefully chisel round the cable with a screwdriver. There is about a quarter of an inch of plaster around the box that gets cover.

FFS!

The regulation you are all hoping for does not exist. There is a regulation however(my regs book is at work, but I believe it's Reg 522.8.1) that says (again, I'm doing this from memory) that a wiring system should be selected and erected to avoid during installation, use or maintenance, damage to the cable sheath...

How you achieve this is up to you, but if an existing installation shows no sign of such damage, it can be taken as read that the requirement has indeed been achieved. The lack of grommets is not a valid observation on an inspection, but damaged cable, or a failure to protect against likely damage would be.

Skenk said

One of the defects in the 2391 inspection is a split grommit[sic]

No it isn't. Your college/training centre is not reading the course documentation properly.

To retrospectively install grommets by hacking away the protecting plaster and potentially damaging the cable would be a really dumb and pointless undertaking.

 

[skenk]

Wow, thats impressive getting the reg and number spot on from memory!

That was in 2006 they had a board of defects said to be ones from the 2391 practical. I still haven't sat the 2391 yet.

 

[Stoday]

Split a grommet transversly and glue it round the cable. Whatever you do it's only there to look good, it can't do anything of substance.

A bit like yesteryear when buckle clips were used to attach cables to walls. Lots of "blind" buckle clips - i.e. buckle's there but no nail.

 

[PrenticeBoyofDerry]

Seems to be two debates here.
One) already fixed installation,ie plastered.
Two) newly installed installations, pre-plaster.

On a newly installed installation grommets most be fitted to prevent damage to cable, if after plastered you then wish to remove them, that's up to you.
But I have come across installation in the past that the cable sheath and insulation can come in contact with the entry hole, even after plastering.

Guidance note 3 suggest this is a no no!

 

[mikhailfaradayski]

I take holmslaw's point, however don't forget that cables do vibrate in service.

hmm, vibrating cables into socket back boxes.....

I think you should call a structural engineer in, pronto. Sounds like the house foundations may be a bit suspect

 

[Risteard]

I take holmslaw's point, however don't forget that cables do vibrate in service.

hmm, vibrating cables into socket back boxes.....

I think you should call a structural engineer in, pronto. Sounds like the house foundations may be a bit suspect

I have already stated that adding grommets/grommet strip after the fact if they can't be damaged is pointless and possibly likely to cause damage rather than prevent it.

This doesn't change the fact that a cable vibrates in service. That doesn't imply that it will dance all around the backbox.

 

[holmslaw]

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