Advice on running electrics to shed

[Agent_zed]

I'll stand corrected (or sitting at the computer) if wrong but I was taught to never use a coiled cord as it increases the resistance creating heat in the wire coils. Either pull all the cable out of the reel or get a shorter cord instead.

Pete

Pretty much any coiled extension lead sold that I have seen in the UK has a rating marked on the side. My 25m cable for example can run 750w coiled or 3000w uncoiled. They often have a thermal overload protection switch as well.

I was at a party last year in an unheated space so someone plugged a 2kw heater into a coiled extension which already had some halogen lights in it. It was quite toasty by the time we noticed. It smelt hot.

 

[Sideways]

OK, seeing as pulling out old OSB in the new workshop is boring, and physics is interesting, I did the test.

2kW filament heater alone:
236.2 V
8.75 A
2058 W
PF: 1.00

2kW heater + 30m coiled extension lead (ten seconds only!):
236.4 V
8.53 A
2071 W
PF: 1.00

As you see, the coiled lead isn’t sucking (or pumping) any VARs. What you say about displacement PF is correct, but doesn’t apply in this case.

Work out the resistances on those two and they differ by about 0.71 Ohms.
That sounds like a reasonable number for the resistance of 2x 30m lengths of copper.