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Post Info TOPIC: TPS/PVC cabling
marto1944


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TPS/PVC cabling
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Just recieved today thought some may be interested

 

 

TPS/PVC cables in contact with polystyrene products

TPS/PVC cable insulation can be compromised by a chemical reaction if it is in contact with polystyrene. Make you check the insulation is undamaged before installing this cable and always follow the cable manufacturers instructions.

The plasticiser in cable insulation PVC to make it flexible and tough is not chemically bonded to the PVC and will slowly leach out of the cable over time. The process of cable losing plasticisers increases when the cable is in contact with other materials, such as polystyrene and polyurethane. The leaching of the plasticiser will cause the cables PVC material to become harder, more brittle and prone to cracking. This could mean live conductors will be exposed, and possibly result in electric shock or fire.

One significant factor that affects the rate of leaching is the size of the contact area between the cable and polystyrene. The larger the contact area, the quicker the rate of plasticiser leaching out. The rate of the cables deterioration will vary with the installation conditions.

It may mean that the cable becomes unsafe to work near during maintenance, repairs or building alterations, meaning that the cable may need to be replaced sooner than expected.

Typical installations where cabling was used in conjunction with polystyrene products are:

caravans

cold rooms

transportable buildings

wall or roofing insulation material.

New installations

Select a cable with protective sheath material that the manufacturer confirms can be installed in contact with materials such as polystyrene and polyurethane. Alternatively cables should be installed so there is no direct contact between the cable and polystyrene.  

If installing cables that havent been proven suitable for direct contact with polystyrene or polyurethane, either:

install the cable in a suitable conduit

leave an air gap between the cable and the polystyrene

apply a suitable barrier between the cable and the polystyrene.

Existing installations

If you are conducting work in an area where you identify a cable in contact with materials such as polystyrene and polyurethane, check to see if the cable has become hard and brittle. If it hasnt become hard or brittle, consider actions to remove the contact. If the cable has become hard and brittle, replace it.

Electrical Safety Office

1300 362 128

 

electricalsafety.qld.gov.au



Attachments
TPS.docx (80.8 kb)
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hako


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That's a very interesting post - I know of a few such situations which I am now concerned about and will rectify - one example is under our Avan where I've run 240Vac cabling thru black irrigation hose for protection against stone damage. Also where cabling passes thru the van side walls that are made of expanded foam.
Many thanks.

Regards

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Cupie


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Something more to worry about.

My 1999 van has 240v cable running thru the walls that utilise polystyrene as insulation.

I suppose one day the Earth Leakage unit will do its job.

Bit hard to check & I haven't heard of too many vans catching fire or people being electrocuted from this problem though.

But it's good to know ... thanks for the heads up.



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dorian


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Interesting. Thanks.

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Phil C


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Gday folks,

In the light of this I am so pleased all my electrical cabling is on the floor in cable trunking. Its a different cable than TPS however I suspect a cheaper option for Jayco.

What I would like to find out is what time frame all this degradation is expected to take place, also if there are any cases of this at electricians workshops or caravan companies. Not that Im a skeptic but its the first time I have heard of this. TPS has a number of chemical resistance properties as far as I remember. May be that if the polystyrene gets wet may be the cause of chemical reaction. Very interesting food for thought though.

Cheers

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marto1944


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The RCD (Residual current Device) may do its job but we must keep in mind that it only works on active to earth faults that are usually some where between 20 to 30 milliamps and not Active to Neutral faults which are only limited by the total circuit resistance of the installation



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Cupie


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marto1944 wrote:

The RCD (Residual current Device) may do its job but we must keep in mind that it only works on active to earth faults that are usually some where between 20 to 30 milliamps and not Active to Neutral faults which are only limited by the total circuit resistance of the installation

 Perhaps you're right & I have no reason to doubt you, but I'm not about to strip off all the side sheeting of the van or to rewire it avoiding the insulation.  Just like thousands of other van owners.

Life is full of hazards & risks.

 

ps.  Last time that I looked at this, ELCBRs (Earth Leakage Core Balance Relays) were the current technology.   Goes to show how current my technical knowledge is.



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marto1944


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I think the answer to this problem could be that possibly owners say every couple of years get a safety check by an electrician or contractor who knows what they are doing which should involve an insulation resistance test being done and hopefully if the insulation is failing it will be revealed this article indicates that we who maybe affected are aware and mindful of these situations

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