fire seal around CU cable entry

Sep 28, 2019 Last reply: 6 years ago 11 Replies
S

I have a plastic CU (installation according to regs in 2006 when plans were passed !), that I am just finishing - having changed to all RCBOs, etc.



Well if I did another CU I'd try to have cable entry in the back or bottom, but where it is that would be difficult anyway.



So I need to seal the cable entries at the top, which are cables going into square cutouts with a lot of gaps.



The best price for a smallish amount of intmescent putty I found is here (it seems to generally be quite expensive):

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I also thought of using intumenscent sealant and letting it dry a bit and using as a putty if that would work, i.e.
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I also thought of some type on intumescent foam that could be pushed in to all the gaps but I did not find anything suitable.



Any ideas ? How is this usually done ?



Thanks, Simon.


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S

Oh, the other idea of course was ... expanding foam (intumescent) ! You can get fire-rated expanding foam, it that would do (might not actually expand with heat though so not truly intumescent). The risk there is of putting in too much and wrecking the installation !

Simon.

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T

No. Just no. Use fire rated silicone. Though you're not doing it to regs anyway.

NT

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T

Seems a bit pointless considering if there is a fire the rest of the box will melt around it

Richard

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A

You still have an IP rating to meet.

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T

I am not questioning your reply Adam but if the OP installed the CU in 2006 surely it would have conformed to the IP ratings at the time? The OP stated that he has completed the installation by converting to all RCBOs by doing so is he obliged to update to an additional standard? As he has not changed the actual CU I would have thought the standards of the day would still apply even if they do not meet current standards. The only obligation I can see he may have is that if he has removed cables resulting in open entry points that they may need blocking but his post does not make that clear.

Richard

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R

The OP did state this is an installation "that I am just finishing".

And I have no problem with someone finishing now an installation started in 2006.

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S

Yes, the electrical works were described on the full plans passed in 2006. So I am doing it to 16th edition. There is of course no end date for building regs works. But I have to get electricals finished and certified to get the building regs signed off.

I get the point that to those regs the cable seal is not for fire rating (the plastic box would melt) but for IP rating and particle ingress, etc.

I have added/modified some circuits since 2006, but that does not mean the box itself has to be upgraded to latest regs metal box, etc. (I hope !) I never sealed the cable entries since 2006 ...

Simon.

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A

Think of the massive savings by using 2006 standards and not bothering with the AFDDs that do f*ck all - 19th edition regs?

An all RCBO installation in a plastic CU with all the terminals tightened up properly is OK with me.

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S

OK, I've finally sealed the cable entries. Its 2006 regs (full plans from 2006), to only ingress not fire proofing required. So I have sealed them with "oogoo" (silicone and corn flour - see web !). Cheap and does the job.

Thanks all, Simon.

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