insulation test

[Nige F]

And the mechanism or process by which damp "corrodes" PVC is......?? H2Opvcu jimmy De ye wanna Glasgae Kiss

 

[Spark123]

Just imagine the fun, all the underground PVC cables

 

[pdcelec]

Sounds to me that damp has corroded the insulation on the cables in the cavitys.Have you had the walls done because of damp?

OH MY, Better contact all of the electricity suppliers around the world and get them to replace the underground infrastructure!

 

[plugwash]

not that recs seem to give a **** about insulation resistance anyway.

 

[TheStirrer]

These remarks sound like they have come from people who don't really know much about the trade they are in.Do people not know that damp conditions can have an adverse affect on electrical cables.Why do you think that you cannot have grey T+E cables outside without addequate protection not only from mechanical damage but also from the elements.The insulation will become hardened leading to brittle and cracked cables which, after time, will have an affect on the overall insulation resistance readings.So sarcastic comments from people about all underground cables needing attention really is nothing short of playground talk.

 

[ban-all-sheds]

Why do you think that you cannot have grey T+E cables outside without addequate protection not only from mechanical damage but also from the elements.

Because of the effect of prolonged exposure to UV radiation.

I don't know what would happen to T/E cable if it were kept underwater, but I'm sure that the sort of damp air that you might find under a floor or behind panelling would not damage the insulation. Not before it had destroyed the structure of the house, anyway.

And is there any difference between the PVC uses on SWA cables and the PVC used on T/E?

I hope your user name is not indicative of the sort of posts you plan to make...

 

[TheStirrer]

but I'm sure that the sort of damp air that you might find under a floor or behind panelling would not damage the insulation.

• Have you ever seen cables affected by damp conditions in the cellars of older larger houses.These are the cables that suffer as a result of the conditions.I have tested cables that show 50M ohms and then pulled them out from below because the outer sheath has rotted away.So unless you have seen said cables with your own two eyes like I have then your opinion as to wether damp can or cannot cause pvc cables to rot will differ from mine.

I hope your user name is not indicative of the sort of posts you plan to make...

• Can I expect to see you placarding outside your local B+Q every weekend trying to influence people not to buy sheds?

 

[ban-all-sheds]

Wrong sort of shed ban.

I mean

NOT

So if I did picket B&Q, I'd get moved on pretty sharpish...

 

[andy]

And is there any difference between the PVC uses on SWA cables and the PVC used on T/E?

i think SWA PVC is more resistive to UV

 

[plugwash]

yes its mixed with a substance that stops the UV penatrating. i belive this is usually active carbon which is why SWA sheath is usuallly black although other chemicals can be used for a white sheath.

shouldn't make any difference to how water effects it though

 

[ban-all-sheds]

You mean it won't rot if buried in the ground?

 

[plugwash]

i can't see burried T&E rotting, you shouldn't bury it though because it doesn't have an earthed layer round the current carrying cores.

 

[kendor]

Sounds to me that damp has corroded the insulation on the cables in the cavitys.

And the mechanism or process by which damp "corrodes" PVC is......??

aha could have been bare pyro leading to the insulation getting damp?

 

[kendor]

internally, ie not in sunlight PVC cable insulation can become hardened and brittle either through ageing(older PVC cables didn't last as long as their modern counterparts) or heat whether through overloading the cable or merely high ambient temperatures.

 

[sparkybird]

Poor ol' fencer - he only asked a simple question and look what it threw up (sic)

In case you're interested/it would help, fencer, the insulation test checks the insulation between the three conductors (ie the coloured pvc wrapped around the phase, neutral, earth). If the insulation is as it should be, the conductors will not be touching and you will get an infinity (ie vvv high) resistance reading. The poorer the insulation, the lower the resistance reading (although it might still be in Mega Ohms)

SB