Cable sizing

[mcgaw81]

I have a job which is to out power in an outbuilding. All that is required is 6 x double sockets and 3 x 5ft flu's.

Been today to look at it and the guy has already run in a 2.5mm 3 core armour cable, a cable run of approx 18m. Would this be big enough, My big red book is in van at my mates so can't check till tuesday.

Also the outbuilding is 13m x 2m, i thought about a 16amp radial but he tells me he is turning it in a gym, is there mush load on gym equpmient????.

Thanks

 

[Andy™]

most gym equipment is probably low powered - for built in electronics etc, although treadmills may use a little more.

using TLC volt drop calc, 2.5 should be good for 4.5KW at 18mtr (19.6A)

 

[batty]

I always use 10mm 2core swa for outbuildings as I TT them and this is big enough for most things. I would think 2.5mm swa will limit you quite a bit.

Batty

 

[binky]

I have a job which is to out power in an outbuilding. All that is required is 6 x double sockets and 3 x 5ft flu's. Been today to look at it and the guy has already run in a 2.5mm 3 core armour cable, a cable run of approx 18m. Would this be big enough, My big red book is in van at my mates so can't check till tuesday.

Also the outbuilding is 13m x 2m, i thought about a 16amp radial but he tells me he is turning it in a gym, is there mush load on gym equpmient????.

Thanks

Define MCB by cable size, and if its overloaded the MCB will trip, you can't do much else if the cable is already fitted. If its a personal gym its unlikely that more than one bit of kit will be in use at a time anyway.

 

[Evans Electric]

Cable already in place so fit a 20 amp MCB . As Binky says, if its a personal gym that should be OK .

Deke

 

[SPECIAL LOCATION]

I have a job which is to out power in an outbuilding. All that is required is 6 x double sockets and 3 x 5ft flu's. Been today to look at it and the guy has already run in a 2.5mm 3 core armour cable, a cable run of approx 18m. Would this be big enough, My big red book is in van at my mates so can't check till tuesday.

Also the outbuilding is 13m x 2m, i thought about a 16amp radial but he tells me he is turning it in a gym, is there mush load on gym equpmient????.

Thanks

Hello Mcgaw, as the others have said 2.5mm is a tad small IMHO?

but as it is already fitted best you can do is stick on a 20A MCB:|

but we can back track though a few calcs to check what max power you can draw and still be within permitted Volt drop limits.

Assuming the following facts..

SWA Cable run:

18m SWA is full run from CU to out building.

13m x 2m outbuilding has SWA enter at one end of the 13m building.

If taking 20amp up 18m of 2.5m volt drop = 6.5v

Lighting:

3 x 5ft florries, (single or doubles?) assume doubles 6x 58watt tubes 348watt, 1.5amps.

Any external security light, maybe allow 150watt small flood, 0.65amps.

Total lighting load less than 2.25amp.

13m building one light in middle 2 lights 3m in from each end, total cable run approx 12m cables, including drop down wall to connect to incoming SWA.

If wired in 1.5mm lighting in the building would drop 0.8volt.

Power

Assuming the 6xD/S are radial around side of room, say up one 13m wall around top and part way back down other wall.. around 20m.

Is there any Heating going to be plugged in?

If we need 2.25amp for our lights that leaves 17.75amps on our sockets. (4.0Kw)

If sockets wired in 2.5m, @ 17.75amp over 20m volt drop = 6.4volt

So adding our bits together.

lighting volt drop will be 6.5+0.8=7.3v 3.2% [max permissible 6.9v]

Power volt drop will be 6.5+6.4=12.9v 5.6% [max permissible 11.5v]

If running to full power on 20amp MCB then the volt drop would be a tad high?

Now saying that if the florries are just single tubes & no security light and only drawing 3.0Kw on sockets then you are going to be just under & ok!

If you put SWA into a 2way CU in the outbuilding & stick a 16amp on for the sockets. should do the trick but...

advise the customer if it keeps tripping he will need a bigger cable put in.

you could always run another SWA and split lights & sockets via their own SWA at a latter date if it becomes a problem of nuisance overload tripping.

 

[Apache]

LED lighting? 'buy back' some amps for the sockets?

the time is all wrong!

 

[SPECIAL LOCATION]

LED lighting? 'buy back' some amps for the sockets?the time is all wrong!

so it is?

does that mean I have more time for another beer?:^OGuiness DrinkGuiness Drink.

florries arn't high power lighting anyway! :|

 

[mcgaw81]

Hello Mcgaw, as the others have said 2.5mm is a tad small IMHO?but as it is already fitted best you can do is stick on a 20A MCB:|

but we can back track though a few calcs to check what max power you can draw and still be within permitted Volt drop limits.

Assuming the following facts..

SWA Cable run:

18m SWA is full run from CU to out building.

13m x 2m outbuilding has SWA enter at one end of the 13m building.

If taking 20amp up 18m of 2.5m volt drop = 6.5v

Lighting:

3 x 5ft florries, (single or doubles?) assume doubles 6x 58watt tubes 348watt, 1.5amps.

Any external security light, maybe allow 150watt small flood, 0.65amps.

Total lighting load less than 2.25amp.

13m building one light in middle 2 lights 3m in from each end, total cable run approx 12m cables, including drop down wall to connect to incoming SWA.

If wired in 1.5mm lighting in the building would drop 0.8volt.

Power

Assuming the 6xD/S are radial around side of room, say up one 13m wall around top and part way back down other wall.. around 20m.

Is there any Heating going to be plugged in?

If we need 2.25amp for our lights that leaves 17.75amps on our sockets. (4.0Kw)

If sockets wired in 2.5m, @ 17.75amp over 20m volt drop = 6.4volt

So adding our bits together.

lighting volt drop will be 6.5+0.8=7.3v 3.2% [max permissible 6.9v]

Power volt drop will be 6.5+6.4=12.9v 5.6% [max permissible 11.5v]

If running to full power on 20amp MCB then the volt drop would be a tad high?

Now saying that if the florries are just single tubes & no security light and only drawing 3.0Kw on sockets then you are going to be just under & ok!

If you put SWA into a 2way CU in the outbuilding & stick a 16amp on for the sockets. should do the trick but...

advise the customer if it keeps tripping he will need a bigger cable put in.

you could always run another SWA and split lights & sockets via their own SWA at a latter date if it becomes a problem of nuisance overload tripping.

Spec thanks for the above,

The SWA enters in the middle of the building with 2 x scokets at the bottom 2 x middle 2 x top, evenly spaced. total cable run for sockets is just over 25m i'd say.

Running in another cable would'nt be an answer as because of the design of the house thats why its already in.

Was wanting to use this in my NICEIC assessment but think i'll take him else where.

Thanks to all

 

[SPECIAL LOCATION]

Spec thanks for the above,The SWA enters in the middle of the building with 2 x scokets at the bottom 2 x middle 2 x top, evenly spaced. total cable run for sockets is just over 25m i'd say.

Running in another cable wouldn't be an answer as because of the design of the house thats why its already in.

Was wanting to use this in my NICEIC assessment but think i'll take him else where.

Thanks to all

Unless you can get some more specific info of the customer about max loading.. its of a bit of guess work?

If they could list the main electrical appliances they will be using..

and get a power rating off them,

do a bit of addin up allow or a bit of diversity & may be ok.

The main dodge area I can think is that I bet they will have some plug in heaters connected at some point

as 13m x 2m 26sqm floor space could be quite chilly on colder days...

maybe ok once they start pumpin the ironB-) but methinks heating will be there! :|

Electrically, if you have a 16a limit on the sockets & 6a lights off a 20a SWA will be safe & ok......

It just may no be enough power for captain treadmill?

If I had been designing this from the start I would have tended towards the batty train of thought 6mm or 10mm 2 core SWA