garage electrics

[paul c]

is the 4mm swa running from house to garage?

Just wondering as i would protect that with 20A mcb, I would say 32A for 6mmsq ,45A for 10mmsq and 63A for 16mmsq.

 

[Davek0974]

Hi,
sorry, yes, i've just checked the box and it's a 20A.

Dave

 

[Davek0974]

is the 4mm swa running from house to garage?

Just wondering as i would protect that with 20A mcb, I would say 32A for 6mmsq ,45A for 10mmsq and 63A for 16mmsq.

Just been looking at the IEE book and 4mm SWA cable can take 38A enclosed or 41A open so I can easily upgrade to a 30A breaker if i need to. Its only a 10mtr run so volt drop will be 3.3V which is acceptable at 30A loading.

Dave

 

[PyroDan]

Where did you get 3.3v from? i make it out to be 6.39v at 30a @ 10m @ 230v Still well within the 4% limits, just interested in how you reached 3.3v (you may be right)

Danny

 

[Davek0974]

I've got in my table...

38A max,
11mV /A /m volt drop so for 10mtr @ 30A..
11mV x 30A = 330mV/m
10m x 330mV = 3300mV or 3.3v drop.

of course i may be up the spout but thats how i read it:-)

Dave

 

[rtbcomp]

I've got in my table...

38A max,
11mV /A /m volt drop so for 10mtr @ 30A..
11mV x 30A = 330mV/m
10m x 330mV = 3300mV or 3.3v drop.

of course i may be up the spout but thats how i read it:-)

Dave

Are those figures for a single conductor or a conductor pair? If for a single conductor you have to double the voltage drop for live & neutral.

 

[Davek0974]

They are for
"Armoured multicore pvc insulated cable to BS6346",
"One or two core cable",
"single phase AC",
"open, clipped direct or on non-metallic surface installation"

Dave

 

[rtbcomp]

They are for
"Armoured multicore pvc insulated cable to BS6346",
"One or two core cable",
"single phase AC",
"open, clipped direct or on non-metallic surface installation"

Dave

If they quote the same figure for both I reckon it's got to be voltage drop per core.

 

[Davek0974]

sorry, typo,

it states "One, two core cable"

Dave

 

[Davek0974]

Also, going by cable factor, my example has a factor of 300 (length of run x load) and 4mm SWA has a factor of 545 so is ideal.

Dave

 

[Davek0974]

Going back to the original post, he wanted 70mtrs of 16mm SWA, that would *just* about give a 30A supply to his workshop. Cant find out if it has to be buried or just clipped out of harms way will suffice.

Dave

 

[Wozzaaah]

Dave, it was my original post and I still haven't found the answer to my question about burial or fence clippage. Where did 30A come from? According to TLC's voltage drop calculator;

SWA (3 core) XLPE
Load 12 kW
Voltage 230
Length of Cabling 70 metres
Required Cable Size 16mm
Voltage Drop 9.1volts.
Percentage Drop 4%.
Load = 52.17amps.

 

[Davek0974]

I was working on 2.5% volt drop, thats if i sized using the cable factor.

My list shows 16mm has a factor of 2143, 30A over 70m gives a factor of 2100 so it just about fits, with a drop of 2.5%.

I'm still looking into the buried or surface thing.

Dave

 

[Davek0974]

Got something, dont quote me on it but...

Burying cables is a recommendation NOT a requirement. BUT where buried, MUST be at least 600mm deep with a yellow warning strip or a cable cover 150mm above the cable.

Surface cables i.e. on a fence, must be placed as to prevent risk of damage and if possible, signage affixed at regular intervals warning of it being there.

Personally, i would fix to fence.

Dave

 

[Wozzaaah]

Ah, now that's what I thought! I think the sparky who's going to do the work has read into that that cables MUST be buried 600mm deep. Where did you 'glean' that info from please?

 

[paul c]

Dave, it was my original post and I still haven't found the answer to my question about burial or fence clippage. Where did 30A come from? According to TLC's voltage drop calculator;

SWA (3 core) XLPE
Load 12 kW
Voltage 230
Length of Cabling 70 metres
Required Cable Size 16mm
Voltage Drop 9.1volts.
Percentage Drop 4%.
Load = 52.17amps.

if you have the option of underground installation then i would go for that.What type of fence and cable is it?(just read posts again,16mmsq swa)

The IEE regs is only a guide it isnt law so if you want to clip to fence then do so.Just make sur it is safe to others and your doing this by having armourings mechanically protecting the cable and this would be earthed as well.

 

[Wozzaaah]

Hi paul, the cable is 16mm 3 core swa and the fence is a normal wooden fence. I'm trying to avoid burial for 2 reasons, one is the length of trench I'd have to dig and the other is to keep the run as short as possible to minimise volt-drop.

 

[Wozzaaah]

You edited your post as I was typing mine

 

[paul c]

when i install my swa run to the garage i wil be clipping direct to outside wall so i cant see a fence being a problem.

 

[Davek0974]

Ah, now that's what I thought! I think the sparky who's going to do the work has read into that that cables MUST be buried 600mm deep. Where did you 'glean' that info from please?

I just did a quick google for "SWA surface or buried" and up it popped.

If i were running it, and i had a wood fence with arris rails, i would fix it to the underside of the bottom rail. That way the rail would help protect it as well as hide it visibly.

Common sense usually prevails. Armoured is *really* hard to cut with a standard shovel, give it a go sometime.

Dave