sub main feed

[telectrix]

job came in today. granny flat already has 32A ring and 6A lighting. cust. has had a shower room built on. will have a 9.5kW shower and 5 downlighters. no problems there, and room on house CU to fit MCB and RCD. problem is, the sub main is fed with 6mm SWA. obviously inadequate. cust is OK with upgrading SWA.
BRB says 10mmSWA buried and in free air can carry 60A. this is ( taking diversity into account ) just about enough. 16mm would be ideal, but a pain to install due to bend radius and glanding. anyone think 10mm will do? or should i go for 16mm

 

[WayneL]

not that familiar with uk rules but

i think the swa sub-main means no rcd required on it -so it should be avoided as it could create a hazard in the bathroom esp. for elderly

What does this mean?

 

[Mark_Burgess]

I too would go with 16mm and be the XPLE not PVC as it carries more current and is quite flexible.

 

[davelerave]

What does this mean?

i do get a bit twisted with the uk rules(not too familiar)

anyhow in principle when fitting rcd's avoid causing a nuisance or hazard-so here in this granny flat job

sub-main is swa so no rcd required
if lights require 30ma protection rcbo them so a fault on the ring main doesn't knock out the lights when an elderly person is showering for example-that is the way i would do it anyhow

not much extra cost involved

unless i'm mistaken(could well be!)

 

[WayneL]

With you now, Dave - wasn't put clearly.

 

[Janjua]

exactly my thoughts. the only high load is the shower. no heating, no appliances, just will be TV, kettle, lights etc. i think 10mm is adequate as shower is only occassional use for 5 - 10 mins.

Why not run a separate 10mm SWA for the shower circuit alone?

 

[robsparky1975]

just wondering does the existing consumer unit have printed a maximum outgoing single circuit ie 50 amps.i think some manufacturers of 1ph units do.

 

[telectrix]

i do get a bit twisted with the uk rules(not too familiar)

anyhow in principle when fitting rcd's avoid causing a nuisance or hazard-so here in this granny flat job

sub-main is swa so no rcd required
if lights require 30ma protection rcbo them so a fault on the ring main doesn't knock out the lights when an elderly person is showering for example-that is the way i would do it anyhow

not much extra cost involved

unless i'm mistaken(could well be!)

would mean 3 RCBOs. ring, lights, shower.but good idea if cust. can stand the cost