Wiring 16 amp socket

[sumo2001]

Hi if I get a type C MCB and use normal 2.5mm twin and earth and run as a radial circuit is this the right cable to use please?got spare capacity for extra mcbs in my fuse board so would be a dedicated circuit with a switched socket also can I add a 2nd one in case I upgrade my saw to a 16 amp one? Cheers for advice

 

[Phil Pascoe]

I've just had my "shed" wired , one 16a to its own 2.5mm supply.

 

[sumo2001]

I've just had my "shed" wired , one 16a to its own 2.5mm supply.

Cheers that's what I thought

 

[Spectric]

The first mistake here is talking about a cable size but no mention of length, the current carrying capacity of a cable is not just it's CSA but also the length of the run and how it is fixed, plus you always need to take into account the voltage drop under load which should not exceed 4% of the supply voltage.

You have to look at an electrical installation as a complete system starting at the point and means of supply all the way down to the final loads because that is what gives you the circuit impedances and the basis of design. Just changing or adding something somewhere to the system might work but cannot be certified as safe or meeting standards. Think of it as a chain with maybe a weak link but you just add extra load and at some point that link fails. You need at least a basic multifunction tester in order to confirm any changes are within specification otherwise you are working in the dark and only discover something was not right when an event occurs.

 

[sumo2001]

The first mistake here is talking about a cable size but no mention of length, the current carrying capacity of a cable is not just it's CSA but also the length of the run and how it is fixed, plus you always need to take into account the voltage drop under load which should not exceed 4% of the supply voltage.

You have to look at an electrical installation as a complete system starting at the point and means of supply all the way down to the final loads because that is what gives you the circuit impedances and the basis of design. Just changing or adding something somewhere to the system might work but cannot be certified as safe or meeting standards. Think of it as a chain with maybe a weak link but you just add extra load and at some point that link fails. You need at least a basic multifunction tester in order to confirm any changes are within specification otherwise you are working in the dark and only discover something was not right when an event occurs.

Ah ok it seems to be bit more complicated than I thought gives me room for thought

 

[Spectric]

Ah ok it seems to be bit more complicated than I thought gives me room for thought

This is a problem with electrical work, it might function but could also be lethal when a fault occurs wheras with plumbing you are more likely to see the leak and very unlikely to drown.

 

[HOJ]

In my past life as a Sparky, had a call to a "garage" shop, where the guy had a CU with spare ways, did the same as this proposal jammed a 20 A breaker in, wired out to a new 16A socket, plugged in his new machine, then after a while got a whiff of burning, but carried on, the supply cable to the garage was melting in the roof which was insulated with polystyrene, melted through the insulation, but didn't blow a fuse because it was connected into the re wireable fused cooker circuit back in the house, a good cause for the start of a fire, with not only burning insulation but probably live wires to contend with...

Oh and don't forget wiring a new circuit into a CU is classed as BR notifiable work.

 

[Phil Pascoe]

In my first house the cooker was suppied by a lead sheathed 6mm spurred off the 1mm dining room light.

 

[Spectric]

In my first house the cooker was suppied by a lead sheathed 6mm spurred off the 1mm dining room light.

Sounds like that was also part of the heating system .

 

[Sapper]

Hi if I get a type C MCB and use normal 2.5mm twin and earth and run as a radial circuit is this the right cable to use please?got spare capacity for extra mcbs in my fuse board so would be a dedicated circuit with a switched socket also can I add a 2nd one in case I upgrade my saw to a 16 amp one? Cheers for advice

Just had one fitted by electrician but he made sure I had surge protection fitted he then used very thick cable for no more than a foot run from consumer unit.

 

[Skeety]

The first mistake here is talking about a cable size but no mention of length, the current carrying capacity of a cable is not just it's CSA but also the length of the run and how it is fixed, plus you always need to take into account the voltage drop under load which should not exceed 4% of the supply voltage.

You have to look at an electrical installation as a complete system starting at the point and means of supply all the way down to the final loads because that is what gives you the circuit impedances and the basis of design. Just changing or adding something somewhere to the system might work but cannot be certified as safe or meeting standards. Think of it as a chain with maybe a weak link but you just add extra load and at some point that link fails. You need at least a basic multifunction tester in order to confirm any changes are within specification otherwise you are working in the dark and only discover something was not right when an event occurs.

Exactly that!

When doing the calculations for my workshop I could have got away with 10mm2, I didn't as the cost of going up to 16mm2 was negligible and removed any concern for future upgrade. That was 60% direct clipped to brick and the other 40% buried in ducting.

You have to bear in mind where and how the cable is routed, direct clipped to timber\brick in the fabric of the wall etc.

 

[Phil Pascoe]

The OP's speaking of one 16a socket, not supplying the workshop.

 

[Skeety]

Yes, but the same applies. Voltage drop over the length of run, where and how the cable is routed etc.

In the same way that you cannot run larger loads off an extension lead, even if fully extended and not coiled. Voltage drop!

This should help for reference: https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html?ad_position=&source=adwords&ad_id=355999072784&placement=&kw=voltage drop calculator uk&network=g&matchtype=b&ad_type=&product_id=&product_partition_id=&campaign=ROAS_Cable&version=finalurl_v3&gad_source=1&gclid=Cj0KCQjw0MexBhD3ARIsAEI3WHLOcZ_8JfbCLwXccalWDrtoYu71KEr7xnKStF8kRyDGN1_zin8PtrUaAuPnEALw_wcB

 

[Spectric]

It might just be one extra socket but often it is just that extra one that causes failure especially if you have no detailed info on the rest of the system. It could be amp's, Kg's or N/m2 but once that limit has been reached then failure is imminent.

 

[Dabop]

I use the Australian wire sizing calculator for our AS 3000 standards, which is pretty good for sizing the cable sizes required (the BS standards are very similar to our Au/NZ standards)
https://www.jcalc.net/cable-sizing-calculator-as3008
It lets you play with all sorts of configurations (clipped, in conduit, buried etc) and even gives you a chart of what sizes will do what as the result (first 'all green' is the minimum required cable size needed...) along with the various test parameters you can be expected to get...

 

[trvlr]

If in doubt (any at all) generally wiser to use a higher spec cable, rather than just enough for the load anticipated and minimum cable your calculations may suggest? It may cost a bit more - but at least you'll know that the higher capacity larger (size) cable will be more than just adequate; and thus far less likely to "erm..." cook and/or blow the breaker/trip the rcd/gfr