how to measure existing shower cable?

reddemonic · 20 Jun 2021

Hello

the current Mira 7.5kw shower is packing up, plastics has cracks and replacement parts are hard to find and so we thought we should upgrade to a 8.5kw shower. it has 40A mcb on the fuse box.

how do i measure the existing shower cable, the prints on the cable are badly scratched so i cant read what it says. do you measure the outer grey sleeve or individual wires?

thanks guys

EFLImpudence · 20 Jun 2021

https://www.diynot.com/wiki/Electrics:flatpvccables

winston1 · 20 Jun 2021

Measure the copper core diameter with a micrometer and calculate the cross sectional area using pi times dia squared divided by 4. Multiply by the number of strands.

JohnD · 20 Jun 2021

winston1 said:
Measure the copper core diameter with a micrometer and calculate the cross sectional area using pi times dia divided by 4. Multiply by the number of strands.

hahahahaha!

I used to find it hard to identify 4mm cable by eye as I seldom saw it.

if you buy the smallest possible pack of cable clips in common sizes (1mm, 1.5mm, 2.5mm, 4mm, 6mm, 10mm) you can mark them with a stabilo pen and keep a set in your toolbox. Practice clipping them on and off and you will soon recignise the difference between "too tight" "perfect fit" and "too loose."

reddemonic · 20 Jun 2021

13.19mm x 7.02mm

does that mean it has 6mm cable?

winston1 · 20 Jun 2021

Why don’t you measure the copper core with your gauge and calculate it as I have already explained? Much better than guessing using the sheath measurements.

studentspark · 20 Jun 2021

Edit. Just noticed picture

Not a fan of using Metal calipers on Electric cable.

reddemonic · 20 Jun 2021

damn, i dumb at math.

each core has 7 copper strands and each copper strand is 1mm
no idea how to calculate the cross sectional area. i think i'll leave it and get an electrician to find out for me.

reddemonic · 20 Jun 2021

studentspark said:
Edit. Just noticed picture

Not a fan of using Metal calipers on Electric cable.

why not, if the power is off from the fuse box. i've already checked with a multimeter.

bernardgreen · 20 Jun 2021

winston1 said:
Measure the copper core diameter with a micrometer and calculate the cross sectional area using pi times dia divided by 4. Multiply by the number of strands.

You wrote " diameter" and also "dia" are these different things or just another bit of lazy writing by you when imparting low value advice.,

Suppose the OP does not have a micrometer, would you advise him to buy or hire one

SUNRAY · 20 Jun 2021

I don't know where this table originated but generally it seems to work

studentspark · 20 Jun 2021

reddemonic said:
why not, if the power is off from the fuse box. i've already checked with a multimeter.

I think its potentially dangerous.

I would want to be 100% sure I had safe isolation before using a metal caliper on an electrical cable.
A multi meter is not an 'Approved' voltage indicator
It is difficult to know if a multi meter is working, or it could be on the wrong setting.

Get an off cut of 6 and 10mm 2 cable and compare. The difference in size is quite apparent, side by side

EFLImpudence · 20 Jun 2021

SUNRAY said:
I don't know where this table originated but generally it seems to work

That - 1.04 - is the same as in the wiki link I posted, although both should actually be 1.09mm.

Edit - I am wrong. The figures are correct. Sorry

reddemonic · 20 Jun 2021

studentspark said:
I think its potentially dangerous.

I would want to be 100% sure I had safe isolation before using a metal caliper on an electrical cable.
A multi meter is not an 'Approved' voltage indicator
It is difficult to know if a multi meter is working, or it could be on the wrong setting.

Get an off cut of 6 and 10mm 2 cable and compare. The difference in size is quite apparent, side by side

after turned off from the fuse box, the shower no longer starts. my mutimeter its a fluke 115 and i use it everyday on laptops repairs. i use ac mode on the mutimeter for checking home electrical.

reddemonic · 20 Jun 2021

SUNRAY said:
I don't know where this table originated but generally it seems to work
View attachment 236919

yep, i think mine its 6mm. it has 7 copper strands and 1mm each copper strand. 13.19mm x 7.02mm grey sleeve.

so 8.5kw could be fine. but just to be safe i gonna find another 7.5kw shower to replace with as i dont want electrician to replace the cable to higher rating as it will cost a lot of money..

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how to measure existing shower cable?

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