Singles in conduit underground - Any reason why not ?

[vwes59]

I've been called in to complete a job started by someone else and I just wanted to ask the following:

Basically it's to provide power to a garage and then on to provide power to a Summer House. What has been done already is a PVC conduit has been buried under the patio between the main house and the garage (Distance approx 1m). This conduit continues under the kitchen floor and then up about a metre inside a wall to the consumer unit. Total distance is about 6-7m. A 2.5mm T&E cable has then been threaded through the conduit to the garage. However this cable isn't good enough for the total power requirement that the client now requires. I've calculated out that I need to put in a 4mm cable. Now I think I've got a few options. I don't like the idea of trying to feed a 4mm T&E through 7m of conduit, SWA just won't be flexible enough, so I'm left with TUFF cable or singles (2 x 4mm + 1 x 1.5mm).

Given the distance, and the fact the conduit is only outdoors under a patio, is there any reason why I couldn't feed singles to the garage ? I know I have to protect these conductors where they come out of the wall and into the consumer unit, but that's no biggy. Any regs that could stop be from doing that ? The conduit that's been used is 20mm.

 

[telectrix]

I've been called in to complete a job started by someone else and I just wanted to ask the following:

Basically it's to provide power to a garage and then on to provide power to a Summer House. What has been done already is a PVC conduit has been buried under the patio between the main house and the garage (Distance approx 1m). This conduit continues under the kitchen floor and then up about a metre inside a wall to the consumer unit. Total distance is about 6-7m. A 2.5mm T&E cable has then been threaded through the conduit to the garage. However this cable isn't good enough for the total power requirement that the client now requires. I've calculated out that I need to put in a 4mm cable. Now I think I've got a few options. I don't like the idea of trying to feed a 4mm T&E through 7m of conduit, SWA just won't be flexible enough, so I'm left with TUFF cable or singles (2 x 4mm + 1 x 1.5mm).

Given the distance, and the fact the conduit is only outdoors under a patio, is there any reason why I couldn't feed singles to the garage ? I know I have to protect these conductors where they come out of the wall and into the consumer unit, but that's no biggy. Any regs that could stop be from doing that ? The conduit that's been used is 20mm.

I would install 6.0mm singles. easily enough to pull in.

 

[Lister1987]

Would have thought steel con/ducting would have been better for underground myself.

Be sure to check conduit fill so ensure you're not exceeding, I can't see it but it pays to be diligent

 

[telectrix]

Would have thought steel con/ducting would have been better for underground myself.

Be sure to check conduit fill so ensure you're not exceeding, I can't see it but it pays to be diligent

RUST FILLED PATIO?

 

[Mikegh]

Steel is ok

Never heard of plastic being used underground, there'd be the risk of going through it

 

[telectrix]

Steel is ok

Never heard of plastic being used underground, there'd be the risk of going through it

i have 20ft. of kopex under the patio with 5 singles in it. been there 10 years no problems.

 

[Resu]

Good tie on, plenty of lube and you should be able to pull a 4mm T&E through using the existing 2.5mm as a draw surely? Least that way it's got an extra layer of protection.

 

[James]

PVC singles and twin and earth are not suitable for being immersed in water for long periods.
Can you with any certainty confirm that the conduit will remain dry and not filled with water?

It's a poor job that you are trying to fix, i understand that, but make sure it wont become a pain in your backside.

 

[timhoward]

What kind of decorative order is the kitchen in? I'm wondering if it is remotely conceivable to excavate a very small section of floor to alter the conduit so it rises inside the house, go through the wall, joint box, gland on SWA and and use catenary for the 1m span to garage....

 

[brianmoooore]

Considered 6mm2 split concentric? It's about 11mm in diameter.

 

[timhoward]

Considered 6mm2 split concentric? It's about 11mm in diameter.

Great idea - that seems the ideal solution.