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Author: Subject: And the moral of this story.......
shortie

posted on 29/1/05 at 05:15 PM Reply With Quote
And the moral of this story.......

Make sure you unwind your extension lead before you plug in your 1KW heater!!!

http://www.locostbuilders.co.uk/upload/Extension_Lead_01.jpg

http://www.locostbuilders.co.uk/upload/Extension_Lead_02.jpg

Seriously though guys I didn't even think about it and fortunately I have a circuit breaker fitted which tripped the power out.

When fully unwound it can handle something like 4000W but if you leave it wound on the reel it can only handle 720KW, given that the heater was 1KW it fried!! Could have been much more serious.

Worth mentioning so that others know, I knew it but didn't even think about it when I plugged it in.

Rich.

[Edited on 29/1/05 by shortie]

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scotlad
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posted on 29/1/05 at 06:04 PM Reply With Quote
oops
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Northy

posted on 29/1/05 at 06:10 PM Reply With Quote
I don't think "a bit of tape" will fix that one!





Graham


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Peteff

posted on 29/1/05 at 06:14 PM Reply With Quote
Ah well..

How far was the heater from the socket if you didn't need to unroll the extension?





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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Ben_Copeland

posted on 29/1/05 at 06:14 PM Reply With Quote
Health and Safety states that you should unwind all reel cables anyway

and take the knots out of cables too.

Lucky you had a trip switch





Ben

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Northy

posted on 29/1/05 at 06:15 PM Reply With Quote
quote:
Originally posted by Ben_Copeland
Health and Safety states that you should unwind all reel cables anyway



Trip hazard!





Graham


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Ben_Copeland

posted on 29/1/05 at 06:21 PM Reply With Quote
Thats what i thought... but it's better than setting fire to ya place!





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Northy

posted on 29/1/05 at 06:22 PM Reply With Quote
They'll shut ya down anyway the ba***rds!





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shortie

posted on 29/1/05 at 06:28 PM Reply With Quote
Heater was about 3 metres away but there was still loads on the reel, not sure I needed the heater anyway as the cable provided a fair amount of heat!!!!
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CairB

posted on 29/1/05 at 06:29 PM Reply With Quote
quote:

....but if you leave it wound on the reel it can only handle 720KW, ...


720KW.. thats some extension lead

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shortie

posted on 29/1/05 at 06:31 PM Reply With Quote
Oh yeah, should have said when wound on the reel it takes 720W not KW!
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chunkielad

posted on 29/1/05 at 07:45 PM Reply With Quote
It's mad when those magnetic forces create heat and fry electrical components!!!

Oh and to stop the trip hazard with fully unwound reels, you need to use cable bridging (the rubber ramp stuff that goes over the cable run).

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CairB

posted on 30/1/05 at 10:21 AM Reply With Quote
Just an observation...

I think that the phenomenon is mainly due to the fact that the current capacity of the cable is based on it's ability to keep the temperature of the insulation down to an acceptable level. The rating will be based upon the cable being in free air at moderate ambient temperature. The current capacity is derated when cables are grouped together or not in free air conditions or higher ambient temperature.
These factors also affect the rating and type of the circuit breaker / fuse due to the temperature rise that occurs due to the let through energy as the device is tripping.

When cables are on a reel there is a double effect, one due to the extra insulation and the insulation is a heat source due to resistive heating.

The magnetic affect can be interesting though. I once had a screwdriver shot out from the centre of a coil when passing current. I'd left it in the centre of the coil so that I wouldn't loose it.

Cheers,

Colin

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NS Dev

posted on 30/1/05 at 11:00 AM Reply With Quote
We recently had to run an "extension lead" to one of the main drive motors at work, as the cabling/busbars had failed in a wiring duct.

The motor in question pulls 7000 amps and is a little over 1500KW (2000hp approx) and the size of a transit van..........................................glad we didn't leave that lead rolled up!!!!

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ned

posted on 31/1/05 at 09:56 AM Reply With Quote
my dad managed tha once, think it was with a welder with the extension lead still reeled up..

Ned.





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Peteff

posted on 31/1/05 at 11:27 AM Reply With Quote
pulls 7000 amps and is a little over 1500KW

Not quite that large but we helped the sparkies to fit a machine at work once and it took 8 of us to drag the cable into place. Sounds like what you need Shortie. You'd have to be blind to trip over it as well.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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dern

posted on 31/1/05 at 11:53 AM Reply With Quote
quote:
Originally posted by CairBThe magnetic affect can be interesting though. I once had a screwdriver shot out from the centre of a coil when passing current. I'd left it in the centre of the coil so that I wouldn't loose it.
I know your intent was to warn but I just have to try that

Mark

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James

posted on 31/1/05 at 04:44 PM Reply With Quote
quote:
Originally posted by dern
quote:
Originally posted by CairBThe magnetic affect can be interesting though. I once had a screwdriver shot out from the centre of a coil when passing current. I'd left it in the centre of the coil so that I wouldn't loose it.
I know your intent was to warn but I just have to try that

Mark


Isn't it know as a Rail Gun?


James

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