Cable for garage and workshop

[Darren9571]

Hi
I have reviewed some previous posts but I am not sure of the size of SWA cable to use for a garage and workshop. I am only planning to put the cable under the floor before some laminate gets laid - I am yet to get planning permission for the garage - but thought I would save an awkward job later accessing the consumer unit.

The run from the consumer unit will be 14m with most of that under the house and approx 3m underground. The garage/workshop will be running some big tools and ultimately there may be a car charger, so I am happy to over-engineer now just in case and providing that doesn't cause any issues. I thought 6mm or 10mm? Is there anything I need to consider about the cable?

Thanks

 

[AndyPRK]

people often say there is little cost difference between 6 and 10mm ?
may as well use 10

 

[flameport]

10mm² 3 core will cover most purposes.

 

[ericmark]

As @AndyPRK says, but some car chargers need to monitor the power used by rest of house and adjust what charge goes to car so as not cause the DNO fuse to fail, I don't fit electric car chargers, so maybe some one else can advise how the charge monitors total use and if any cables required.

 

[flameport]

Power monitoring can be wired, but plenty are wireless so no additional cables required.

 

[bernardgreen]

Install two ducts, one for the SWA to be pulled through and the second one for any other cables such as data, phone, alarm and car charger control cables.

If the car charger so monitor consumption in the house and alters the charging rate then maybe a separate SWA cable supplying the car charger with the controlled charging current would make life easier.

 

[AndyPRK]

you don't need 2 swa for car charger

 

[AndyPRK]

maybe of interest

 

[bernardgreen]

Very interesting , why is an Earth conductor being switched by 3--4 in that Ktec25 contactor

 

[JohnW2]

Very interesting , why is an Earth conductor being switched by 3--4 in that Ktec25 contactor

I can think of reasons why one might want to switch an 'earth' conductor, but I don't think that BVS7671 would ever see eye-to-eye with such a practice, would it?

Kind Regards, John

 

[AndyPRK]

I think there is a worry that the electrical installation earth, isn't the same potential as the ground by the car. And under fault condtions isolates every conductor

 

[flameport]

CPC is disconnected as that device is designed to comply with 722.411.4.1.iv as above.
As installed in the video it will only work if the armour of the cable hasn't been connected to anything at the charger end. If the armour is connected at both ends, the CPC is permanently connected via the metal case of the device which will bypass the contactor.

Even if installed properly, those devices only detect some instances of open PEN conductors. They are not suitable for use as safety devices, they don't comply with the LVD, and should not be available for sale.

BS7671 should not include descriptions of such things either, whether they are suitable for use or not.

The whole of section 722 in BS7671 needs to be completely rewritten. As it is, an installation could comply with every detail of it, and yet still be unsafe.

 

[AndyPRK]

At 4 mins they mention it I think

 

[JohnW2]

CPC is disconnected as that device is designed to comply with 722.411.4.1.iv as above.

Interesting. I hadn't noticed (or remembered!) that and, in particular, not the reference to 543.3.3.101(ii), which says ...

543.3.3.101 No switching device shall be inserted in a protective conductor, except:
.....
(ii) a multipole, linked switching in which the protective conductor circuit is not interrupted before the live conductors and is re-established not later than when the live conductors are reconnected

Do I take it that a device such as the one shown in that video would satisfy that requirement?

Kind Regards, John

 

[flameport]

Do I take it that a device such as the one shown in that video would satisfy that requirement?

Very doubtful, it's an off the shelf cheapo contactor available anywhere.
Proper specifications for it could not be found, including from the 'manufacturer' of the contactor.