t & e in 20mm conduit

[crow11]

hi all first time i have posted, great site and lots of info cheers
putting in for my assesment shortly with elecsa doing a c/u change and putting sockets and lights into attached garage,my preffered method would of been to use 20mm conduit its a pretty big garage but they only want 2 double sockets on the same wall and 2 fluorecent lights and a feed to the electric door ive been looking at the job and it is big run in conduit probably about 17meters and 3 inspection bends and 3 inspection tee's,there would have to be about 8 meters of the conduit with 2.5 t&e and 1.5 t&e in it which would be tight and the remainder with 1 of each,cant find anything in the regs about t&e in conduit and osg only lists for singles and upto conduit length of 10 meters,i know having the 2.5 and 1.5 t&e together wont be allowed was just wondering why in the osg it only lists you can have 2 bends in a 10m run of conduit or am i being thick and reading it wrong and would comply if i did it in singles cheers

 

[Welchyboy]

t & e in 20mm conduit

T&e in conduit is fine as long as your sensible about how much you put in, I have used 2x2.5 t&e many times with no issues

If in doubt why not wire it in singles?

It's stated on the regs as singles as its based on a system of primary cable insulation then mechanical protection (conduit) the skin on the t&e is classed as the mechanical protection for the cable, but with conduit as the exterior protection this then cancels out the twin and earth sheath as its a higher standard

The only draw back to using twin in conduit is the restriction on the amount of it you can fit inside

There are limits to the amounts of cables you can wire inside the tube but your well below

As for your assessment, i think the inspector will probably be impressed your using conduit and not just clipping cable to the wall!!

 

[Marvo]

A 2.5 and a 1.5 flat twin cable should be fine in a 20mm conduit as long as you pull them in without twists and kinks. I'm guessing the 2 bends limitation is because you can't pull cables through a conduit with more than 2 bends because it gets too tight and you might stretch the cable which could damage it.

 

[somersetsparks]

hi all first time i have posted, great site and lots of info cheers
putting in for my assesment shortly with elecsa doing a c/u change and putting sockets and lights into attached garage,my preffered method would of been to use 20mm conduit its a pretty big garage but they only want 2 double sockets on the same wall and 2 fluorecent lights and a feed to the electric door ive been looking at the job and it is big run in conduit probably about 17meters and 3 inspection bends and 3 inspection tee's,there would have to be about 8 meters of the conduit with 2.5 t&e and 1.5 t&e in it which would be tight and the remainder with 1 of each,cant find anything in the regs about t&e in conduit and osg only lists for singles and upto conduit length of 10 meters,i know having the 2.5 and 1.5 t&e together wont be allowed was just wondering why in the osg it only lists you can have 2 bends in a 10m run of conduit or am i being thick and reading it wrong and would comply if i did it in singles cheers

I would go for BESA boxes as opposed to inspection bends and tees' You will never get 2x2.5 T+E through them. Better off using singles IMO, If you do use T+E though I would go for 25mm tube.

 

[crow11]

thanks for the replies, my only concern is that i want to use it for the assesment, according to osg even if i did it in singles the cable factor comes to 142, and just for a 10meter run with 2 bends the max allowed is 141 obviously the longer the length and more bends the cable factor becomes even lower 25mm would allow more cable factor but there is no cable factor for the length of 18 meters with the amount of bends i will have so i dont know if 25mm would still be over the limit, just dont want the fail the assesment over something daft like this lol cheers

 

[Welchyboy]

Yeah good comment, missed the inspection bend part, use straight lengths and besa boxes rather than inspection bends......infact don't ever use inspection bends unless around a tight corner they are a ball ache

 

[nick611]

not sure why you wouldn,t do this in singles. surely a 2.5 radial and a 1.5 radial would not be over your cable factor ?

 

[HandySparks]

In a garage, I'll often use T&E clipped direct to the ceiling timbers, then a short length of thick wall 20mm PVC conduit for the drops to the metal clad accessories. It's not a Rolls Royce job (which would be galv conduit all the way) but it provides protection where it's needed and keeps the drops looking tidier than if clipped to brick or blockwork.

 

[drew35]

Just don't put all the conduit on the wall and expect to push two pieces of twin and earth through. You'll have to thread the cable through each piece as you fit it.

 

[Rockingit]

Buy a bottle of cable lube as well!

 

[crow11]

cheers for the advice, sounds like hadysparks might be my best option just wanted it to look good for assesment, nick11 the cable factor for a 10m length with 2 bends comes to 142 and the regs state max 141 cheers

 

[somersetsparks]

Controversial, but I would probably use 20mm and sod the extra '1' on cable factor. However maybe the best solution is 25mm for the main run with drops in 20mm? Avoids the ball-ache of trying to mill out a 25mm hole from a 25mm box!

 

[johnboy6083]

Controversial, but I would probably use 20mm and sod the extra '1' on cable factor. However maybe the best solution is 25mm for the main run with drops in 20mm? Avoids the ball-ache of trying to mill out a 25mm hole from a 25mm box!

If he put a box in the middle of the 10m run, then it would then be 2x 5m runs with 1 bend, and as such have a higher allowance on the cable factors.

Practically though, pulling twin out of a box, and then putting it through the next will be a pain. Stop being tight and run singles. If you really want to, then strip the cable, and use the 2 cores without the sheath, and use conduit as CPC.

 

[Welchyboy]

cheers for the advice, sounds like hadysparks might be my best option just wanted it to look good for assesment, nick11 the cable factor for a 10m length with 2 bends comes to 142 and the regs state max 141 cheers

I can guarantee the assessor gives it nothing but a quick glance and at most just asks you to plug your loop tester into the closest socket!

However its good that your actually taking time using and understanding the tables in the regs book and applying them to your installations - well done!

 

[somersetsparks]

If he put a box in the middle of the 10m run, then it would then be 2x 5m runs with 1 bend, and as such have a higher allowance on the cable factors.

Practically though, pulling twin out of a box, and then putting it through the next will be a pain. Stop being tight and run singles. If you really want to, then strip the cable, and use the 2 cores without the sheath, and use conduit as CPC.

I think hes on about placcy conduit john! not the real deal!