25mm conduit

[ukants]

From what I’ve noticed, metal surface back boxes only ever seem to have 20mm knock outs. How do you attach 25mm conduit to them? Is there a reducer to allow 25mm to enter the 20mm knock out or do you use some kind of drill bit to enlarge the hole?

I’d rather use 20mm conduit and singles to be honest, but only half the installation will be in the conduit and the rest buried in the wall, so I’m thinking 2 x 2.5mm t&e in 25mm conduit may be the better option. Any thoughts? Thanks.

 

[breezer]

no need to put t&e in conduit, as for the hole size use a 25mm hole cutter

 

[plugwash]

with some holesaws you can put two sizes on the mandrill at once which can be very usefull for enlarging holes.

as for joining 25mm conduit to a 20mm hole you could use a 25mm coupler a reducer and a 20mm bush

 

[EdwardCurrent]

Hi,

With the existing knockouts, just be sure not to give it too much 'force' when making your pilot hole, then once through it should be a walk in the park.

Ed.

 

[Belle427]

you will get two 2.5mm t&e down a 20mm conduit,its a bit tight but it does go,failing that use 2 pieces

 

[reggie perrin]

?

 

[ricicle]

?

Conecutter.I find them very useful.

 

[jimbob100_99]

2x2.5 down a 20mm conduit?????? What about leaving room in the conduit!!!! Use PVC SINGLES.....

 

[Lectrician]

There is nor problem at all using 20mm conduit with 2x2.5 - you wont get any more in though! Straight lengths obviously.

A cone cutter is useful to increase hole sizes, or get an "oops arbour" from sterret - it uses a 20mm holesaw as a 'pilot' for a 25 or larger.

if you are using oval conduit, 25mm can be used upto the box, and then a simply fit a grommet in the hole.

If you wanted to terminate 25mm conduit into the box, use atleast a 35mm box otherwise the conduit will sit too close the wall.

If you bush the conduit to the box, use a female adaptor - males take up too much space.

If you are using round, not oval, get the matt finish conduit, not glossy - plaster on glossy....?

 

[RF Lighting]

I use a Reload holesaw, which allows you to stack different sized holesaws for enlarging existing holes

 

[ukants]

Hey, thanks everyone for the input. Much appreciated. It's now going to be conduit throughout the install so 20mm conduit and singles it is! However, as always I've learnt a few things from you guys so your advice is never wasted on me. Cheers.

 

[ample]

I use a Reload holesaw, which allows you to stack different sized holesaws for enlarging existing holes

Reload, one of the best things i ever bought.

 

[RF Lighting]

Not as good as my cable rods, but a damned useful bit of kit!