Cable entry into 17th edition compliant metal clad ccu

[bigsparks]

Hi All

I wanted to get an insight into how electricians were proposing to implement cable entries into metal clad ccu once it is compulsory in the new year. I have not been on the latest 17th edition update but through reading info in the IET and NICEIC member literature I have garnered that the biggest amendments are with the introduction of metal clad ccu & revised elz maximums.

We have now began installing metal clad ccu with rcbo devices, to future proof installations for our customers, and wanted to see how other electricians are carrying out cable entries into metal clad ccu.

For top/side entry into a metal clad ccu, is it suitable to use fire rated pvc glands for cable entry or can a knock out / hole big enough for all cables to enter be used as long as an intumescent sealant/foam is used thereafter to seal any spaces in that cut out?

Up until the present time, we have only had rear entry situations with metal clad ccu.

Thanks

 

[Midwest]

Can't seem to upload the pic, but have a look my thread on Wylex CU, they have some suggestions on cable entry. Nothing we not done before, except you going to need some bushes. Hager aren't using 20/32mm knockout, just larger cable entries. Why do you think you will need to use fire rated glands or sealant foam? http://www.electriciansforums.co.uk...endment-cu-tt-recommendation.html#post1106922

 

[shanky887614]

plastic trunking header then bush and lockrings into board if you cant fish behind.

 

[bigsparks]

Thanks Midwest

I would use fire foam or sealant to prevent the spread of fire/smoke out of the metal CU.
Obviously, there is a reg that states you must prevent spread of fire/smoke and as these new CU are specifically designed to prevent spread of fire, we will have to fully seal any holes, small or large, with a non combustible material.

So, I would imagine, if bushes are used, any remaining gaps around the cables will need to be filled with intumescent sealant. Or it may be easier to use fire rated stuffing glands.

I think to make the CU / entries look tidy, a trunking header with bushes, like shanky has suggested, will work.

 

[Simlec]

Only the correct IP rating needs to be maintained, same as your current plastic/metal enclosures.
I think people are over thinking what's required and metal consumer units are not new !!

 

[Midwest]

Thanks Midwest

I would use fire foam or sealant to prevent the spread of fire/smoke out of the metal CU.
Obviously, there is a reg that states you must prevent spread of fire/smoke and as these new CU are specifically designed to prevent spread of fire, we will have to fully seal any holes, small or large, with a non combustible material.

So, I would imagine, if bushes are used, any remaining gaps around the cables will need to be filled with intumescent sealant. Or it may be easier to use fire rated stuffing glands.

I think to make the CU / entries look tidy, a trunking header with bushes, like shanky has suggested, will work.

Reg. 421.1.201 only requires the CU to be non combustible. Think you are confusing yourself with reg. (don't know number) about preventing the spread of fires, when running cables through internal linings for example. If you think about, the new metal CU's aren't thermally sealed where the MCB's/RCD etc are located.

 

[bigsparks]

Ok cheers Midwest, point taken.

 

[Redvanman]

No fire stops etc needed just follow the IP ratings as normal.
if your going in through the top plastic trunking is okay slotted no need for bushes either
If you check the Hagar boards out there are designed for trunking
The idea of the metal board us to stop the fire spreading as there is no combustible material inside the metal enclosure therefore the fire can't travel through any holes made in the enclosure.
Once you read the reg and look into the fine details you relise that it's not the end of world scenario we all thought it was and the cost isn't that much more
Also as a bonus to this all the boards seem to have been made bigger therefore aiding in a better install of the cables so hopefully better terminations and less burnt out connections. Well hopefully any way.

 

[Midwest]

The idea of the metal board us to stop the fire spreading as there is no combustible material inside the metal enclosure therefore the fire can't travel through any holes made in the enclosure.

Think you have that slightly wrong. Everything inside these metal CU's is still combustible. The inference made by the instigators of this reg change, are hoping that when something inside starts burning for whatever reason, the outer casing of said metal will not catch fire, thus limiting spread of fire to whatever might be around, above or below it. I think

 

[richy3333]

All this thought and I haven't yet seen any metal blanking plates for unused ways. They appear to still be plastic?

 

[Richard Burns]

Wylex have brought out the metal blanking plates!

 

[Midwest]

All this thought and I haven't yet seen any metal blanking plates for unused ways. They appear to still be plastic?

Can't see the point, when you have plastic mcb's and a metal cover flap. But then I didn't come up with the reg!

 

[Lazlo]

Fitted new Hager metal DB the other day, I reckon I'll start fitting these as standard as they are robust and have loads of room to make a nice tidy job, also comes with grommet strip. Only annoying thing was the door to access MCBS etc didn't have a hinge that kept it open, that would make it much better in my opinion, can't see why they wouldn't add some spring clip hinges. I came into board from the back on this occasion, if I was in from top I'd either go straight over top with trunking or use a couple of 2" couplers and bushes, simples. Cost was circa £85 for a 10way split with breakers.....Quite steep but I'm not the one paying so not really an issue.....

 

[Simlec]

Fitted new Hager metal DB the other day, I reckon I'll start fitting these as standard as they are robust and have loads of room to make a nice tidy job, also comes with grommet strip. Only annoying thing was the door to access MCBS etc didn't have a hinge that kept it open, that would make it much better in my opinion, can't see why they wouldn't add some spring clip hinges. I came into board from the back on this occasion, if I was in from top I'd either go straight over top with trunking or use a couple of 2" couplers and bushes, simples. Cost was circa £85 for a 10way split with breakers.....Quite steep but I'm not the one paying so not really an issue.....

In the top would be very hard to maintain the correct IP rating in my view.

 

[Lazlo]

When I say 2" couplers and bushes I mean from the trunking to the top of the DB (metallic or plastic) sometimes the top of the DBs have a lip on the cover so you can't get the trunking directly on top of the DB housing, in that instance I run the trunking the height of the 2" coupler above the DB and couple the trunking to the DB with the couplers! IP rating is not an issue.