Why SWA?

[chaban48699]

Aparts from the regs requirement could somebody explain why SWA cable needs to be used over normal cable when working outdoors.

For example why not 10mm cable running in steel ducting theng buried rather than 10mm SWA buried? Just curious.
Many Thanks

 

[plugwash]

SWA is not the only option for running underground just the one most sparkies preffer to use.

undeground cables must be surrounded by earthed metalwork either as part of the cable or as a seperate item, ideally it should also resist digging through though thats not a requirement as such.

earthed steel conduit containing virtually any cable type is fine but installing conduit with proper joins in a trench is not most peoples idea of fun.

MICC is an option but more expensive than SWA, not as tough and more of a pain to terminate, its main advantages are that it is thin and fire resistant which aren't really relavent to burried runs.

screened fire resistant cables would technically comply but are expensive and very prone to damage.

split-con is a cheaper and thinner option than SWA but its prone to developing neutral-earth faults especially if pulled through ductwork. The DNOs use it when they have to run TN-S but they don't give a f*ck about neutral-earth faults.

 

[Spark123]

I think allowed to use cable in an earthed metallic conduit underground, you'd need to take into account such things as water ingress and corrosion though. SWA has this protection built in and does not need special tools to terminate.

 

[chaban48699]

Thanks for the quick reply guys. I ask because I notice the price of SWA is quite high but I suppose if you have to buy seperate ducting if not using then it works out more cost effective to use SWA from the start.
Thanks Again.