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Topic Title: water leak
Topic Summary: 32A no trip
Created On: 10 January 2013 04:26 PM
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 10 January 2013 04:26 PM
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Avatar for zeeper.
zeeper

Posts: 1427
Joined: 11 July 2008

What is this resistance off fresh water out the tap.
 10 January 2013 05:07 PM
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monk

Posts: 18
Joined: 08 December 2012

Resistivity of tap water depends on a lot of factors, someone mightbe able to give you a ball park figure if you tell them your water supplier/location. You might be surprised how high it can be. Pure water is a rather good insulator! It's all the stuff dissolved in it that provide charge carriers

I would be surprised if a 32A breaker tripped from a wet cable. An RCD should trip if the cable is soaked enough, I've seen that often enough
 10 January 2013 05:21 PM
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rocknroll

Posts: 8907
Joined: 03 October 2005

UK tap water does have a high resistivity around the region of 2.5/3 x 10^6, depending what charge carrying ions are in the water the resistance you asked for generally equates to a ball park figure of around 80-120 ohms/metre.

regards

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"Take nothing but a picture,
leave nothing but footprints!"
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"Oh! The drama of it all."
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"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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 10 January 2013 05:23 PM
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Parsley

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 10 January 2013 05:43 PM
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daveparry1

Posts: 6381
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Probably not much help but i've seen a 13amp trailing socket drop into a bucket of water, first we knew of it was steam coming out of the bucket! Fuse was probably 30 amp 3036 although there would have been a 13 amp fuse in the plug, long before the days of rcd's everywhere,

Dave.
 10 January 2013 08:27 PM
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Jaymack

Posts: 4789
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When I was just a common electrician in the steel industry, one guy who looked after the pump room, boiled water for washing his overalls in a steel bucket, this had 2 suspended steel plates, wired with a 2 core cable plugged into a 15A power socket. Health and Safety was not known then!

Water filled, steel tank starters connected to the slip rings, were once very common for starting wound rotor motors; salts were added to the water to reduce the resistance.

Regards
 10 January 2013 11:39 PM
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gkenyon

Posts: 4489
Joined: 06 May 2002

A B32 requires a heck of a lot of energy passed before a trip.

In fact, so does a fast-acting 5 A IEC127 HBC fuse: I've seen high-temperature silione flex burning without the fuse blowing, and had to unplug myself to stop it !

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Eur Ing Graham Kenyon CEng MIET TechIOSH
 11 January 2013 07:26 AM
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Avatar for zeeper.
zeeper

Posts: 1427
Joined: 11 July 2008

I would be surprised if a 32A breaker tripped from a wet cable. An RCD should trip if the cable is soaked enough, I've seen that often enough


We had a water leak at work, which resulted in stream coming from a floor box. Im not sure how much ingression there was, because I didnt get to look at it until 2 days later. And it was all bone dry in side the floor box. The circuit was >299MOhms the lowest reading I could get was on one of the sockets of 40MOhms.

generally equates to a ball park figure of around 80-120


Thats a lot lower than I was hoping, which leads me to think that there was not as much ingression as I had be lead to believe. Although I could see evidence of arcing from the exposed line conductor.

When I turned up to work on Monday I was met with why did it trip the circuit.

But it all checks out, so I think the resistance never got low enough to trip the MCB.
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