UK Armoured cable to garden shed

[banny07]

Hi Guys. Customer want to install some double sockets and few lights in new built garden shed which is 35 meters away from Consumer unit. I suggested 10mm 0r 16mm swa cable as customer want use it as a gym and also install washing machine and tumble dryer in the future. Only route available is through bathroom floor (behind the toilet and under shower tray), then under kitchen unit and through garden(burried) to the shed. Please advise me on this. Thanks in advance

 

[Bob Geldoff1234]

For an 8kw max load you would need 6mm 3 core swa running 35 meters.

 

[James]

Sounds feasible to me
do you have any specific concerns?

 

[banny07]

For an 8kw max load you would need 6mm 3 core swa running 35 meters.

Sounds feasible to me
do you have any specific concerns?

Yes , Running cable through bathroom it will be boxed though. I am also worried about voltage drops.

 

[Bob Geldoff1234]

Yes , Running cable through bathroom it will be boxed though. I am also worried about voltage drops.

See this web page for help with cable sizes.

Cable Calculator

Cleveland Cable Company - Cable Calculator

www.clevelandcable.com

 

[Julie.]

If there is a washing machine, then I presume water as well, this may therefore need bonding, which may then need the cable to be 10mm^2 depending upon the earthing arrangements.

The minimum size for bonding may be the controlling size rather than voltage drop, or Zs, or current capacity etc.

 

[banny07]

If there is a washing machine, then I presume water as well, this may therefore need bonding, which may then need the cable to be 10mm^2 depending upon the earthing arrangements.

The minimum size for bonding may be the controlling size rather than voltage drop, or Zs, or current capacity etc.

As cable will pass through bathroom ( on the tiled floor and under the sower tray) do I need to install rcd on the circuit?

 

[littlespark]

As cable will pass through bathroom ( on the tiled floor and under the sower tray) do I need to install rcd on the circuit?

Not if it’s getting boxed in.

Yes if you’re planning a joint box in the bathroom to convert cable from T&E to SWA for example.

 

[HappyHippyDad]

As cable will pass through bathroom ( on the tiled floor and under the sower tray) do I need to install rcd on the circuit?

You would also need some kind of RCD protection if the earthing arrangement at the house is TT. The SWA will have mechanical protection but no fault protection. I would usually fit an S type 100mA. If it's PME of TNS then you wouldn't need the RCD because of ADS.

 

[pc1966]

As cable will pass through bathroom ( on the tiled floor and under the sower tray) do I need to install rcd on the circuit?

If it is SWA then usually[1] no as it has the earthed armour so no risk of damage causing the damaging object (screw via headrail, etc) to become live.

[1] The "usually" aspect has been mentioned by @HappyHippyDad in that the above assumes that any fault that shorts out L-Armour will disconnect the power. On a TN supply system that is usually[2] the case, on a TT supply it is virtually impossible so an up-front 100mA/300mA delay RCD is the usual approach.

[2] Even on a TN system you might find a high current sub-main has an end of cable Zs that is too high to meet the 5s disconnection time on the design OCPD. If it is marginal the using 3C SWA[3] so one core is CPC and is connected at both ends of the armour is enough, but if that is not enough, or if the cable cost going that way is ridiculously high, then you might again consider an up-front RCD.

[3] As @Julie. has pointed out, if there are extraneous parts to be bonded and it is TN-C-S then your minimum bond size is 10mm copper (or equivalent). For the steel in SWA that is about 80mm which you only get to on 2C when you have 70mm conductors! Once again you might just consider TT'ing the supply at the building but then you have the issue of earth rods and the risk of driving in to the ground without hitting buried services, etc, so going 10mm 3C (or making very sure all the water pipes are plastic) is usually the simplest route and meets most folk's power demands.

 

[123]

Not if it’s getting boxed in.

Yes if you’re planning a joint box in the bathroom to convert cable from T&E to SWA for example.

Why would converting from T&E to SWA require RCD protection? I take it as an almost given that this cable isn't going to be sunk into the wall at any point.

 

[littlespark]

Why would converting from T&E to SWA require RCD protection? I take it as an almost given that this cable isn't going to be sunk into the wall at any point.

Rcd to cover anything within a bathroom.
Not serving anything in a bathroom, but a joint would introduce a possibility of a loose connection. Was just an example.
Boxing it in takes it outside the bathroom area if it’s inaccessible..

 

[123]

Rcd to cover anything within a bathroom.
Not serving anything in a bathroom, but a joint would introduce a possibility of a loose connection. Was just an example.
Boxing it in takes it outside the bathroom area if it’s inaccessible..

Even an SWA running through a bathroom would need RCD protection (oh what an eyesore that would be!). Don't see why a junction box requires RCD protection for a possible loose connection, it's not there to cover off poor workmanship.

 

[loz2754]

Even an SWA running through a bathroom would need RCD protection

Small correction, if I may.
Cables passing through zone 1 or zone 2 require RCD protection.
A cable completely enclosed in boxing-in would be regarded as being outside the zones.