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Topic Title: micc cables
Topic Summary: how do you know if they are Live
Created On: 03 December 2012 04:29 PM
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 03 December 2012 04:29 PM
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keithredpath

Posts: 423
Joined: 30 March 2002

Is there any way of confirming whether an exposed Micc cable is powered up.

There appears to be no access above or below a rising main cupboard so all we have is a group of micc cables.

We need to know if they are Live or Dead. Is there an easy answer without disturbing the cables.

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keithredpath
 03 December 2012 04:43 PM
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johno12345

Posts: 169
Joined: 22 October 2005

not that i know of, the copper sheath stops the voltsticks from working, so you have to have access to one end where its terminated.
 03 December 2012 04:48 PM
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AJJewsbury

Posts: 11472
Joined: 13 August 2003

without disturbing the cables

oh, so spiking them isn't acceptable then?

If they're carrying significant current (not exactly the same as being live of course!) - they would be a little warmer than ambient - a couple of thermometers and a bit of thermal insulation might give an indication.

On the other hand - what would you do if you knew for certain they were live? If the plan is just to leave them alone, then is there any harm is just presuming that they're live?

If the ends aren't accessible - would there be a question over the ownership of the cable?

- Andy.
 03 December 2012 09:01 PM
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Ricicle

Posts: 841
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CAT Scanner perhaps might give you an all or nothing idea ?

-------------------------
Empty barrels make the most noise.
 03 December 2012 09:31 PM
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slittle

Posts: 3515
Joined: 22 November 2007

Originally posted by: Ricicle

CAT Scanner perhaps might give you an all or nothing idea ?


Not sure it would CAT scanner would need to see the 50hz field to indicate and that's enclosed in an earthed metallic screen.

Stu
 03 December 2012 09:36 PM
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daveparry1

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But the screen being copper might not block the electromagnetic field Stu? Just a thought, don't know if that's correct thought,

Dave.
 03 December 2012 09:39 PM
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slittle

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With my radio hat on, MICC is no different to Coax (well ok, impedance etc is but...) and good coax lets nothing out.


Stu
 03 December 2012 09:52 PM
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daveparry1

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That's RF though Stu, a bit different to 50Hz I would guess? (interesting thoughts though, you with your radio hat on and me with my ex TV engineer hat on!)

Dave.
 03 December 2012 09:57 PM
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slittle

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Very true.

Going to have to play now, well actually tomorrow as I've got a 100m run of LDF450 (proper coax) to install for the fire service.

Once I've got connectors on it and before I connect the antenna, I'll introduce some 50 hz and see what happens with both the voltstick and the CAT.

I know where there is some MICC as well so if no one manages to play before I pass the site I'll play the same game there.


Stu
 03 December 2012 10:00 PM
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daveparry1

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Be sure to let us know the outcome Stu, just for curiosity's sake!

Dave.
 03 December 2012 10:27 PM
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AncientMariner

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Hi Stu

Proper coax indeed!

That's a long run to an aerial, do they not mind about the attenuation? I'm assuming there that it is for UHF comms and not AM band radio...

Cheers!

Clive

-------------------------
Clive S Carver GCGI IEng MIET
 04 December 2012 07:19 AM
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Fm

Posts: 675
Joined: 24 August 2011

If you dont know if they are live or not, you treat them as live.
Arrange withthe client for thevrequired access etc totrace the cables and identifybaccordingly
 04 December 2012 10:50 PM
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DOUGIE1000

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intresting CAT will pick up old lead cables underground though

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 04 December 2012 10:59 PM
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peteTLM

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Originally posted by: Ricicle

CAT Scanner perhaps might give you an all or nothing idea ?


i think you mean CAT as in 'cable avoidance tool' not CAT scan as in computed axial tomography which is a million pound tool as compared with 400 quid????

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Every man has to know his limitations- Dirty Harry
 04 December 2012 10:59 PM
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DOUGIE1000

Posts: 4165
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yes cheapo CAT, ill maybe get the £1m tool from Santa though

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 04 December 2012 11:01 PM
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spinlondon

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My Fluke volt stick has CAT II printed on it.
 04 December 2012 11:01 PM
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AJJewsbury

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intresting CAT will pick up old lead cables underground though

Is it detecting that it's live, or just that it's metallic?
- Andy.
 04 December 2012 11:02 PM
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DOUGIE1000

Posts: 4165
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and i have 2 CAT (brother and sisters) since they were kittens. Just shows you there is many different types of pussy out there

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 04 December 2012 11:25 PM
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impvan

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Kittens do make excellent voltage indicators.
 04 December 2012 11:56 PM
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alancapon

Posts: 5770
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Originally posted by: AJJewsbury
intresting CAT will pick up old lead cables underground though

Is it detecting that it's live, or just that it's metallic?

Sufficient inteference will get onto the outer sheath for it to be picked up by a CAT. A 50Hz signal is very good at getting on to anything metallic and there will be sufficient to pick up from a cable sheath whether it is live or dead. The only way to positively identify a cable is using signal injection, but that usually involves access to both ends of the cable as well as making it dead.

Regards,

Alan.
IET » Wiring and the regulations » micc cables

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