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Topic Title: Chasing
Topic Summary: Foam filler
Created On: 02 January 2007 09:25 PM
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 02 January 2007 09:25 PM
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Jez937

Posts: 504
Joined: 02 January 2006

Hi all

A friend of mine is doing some work on his home, its a flat and all the rooms are stud partition walls. The electrics are all surface run and he wants to chase them out and bury the cables in the walls. He's done the chasing out and being a plasterer of 35 years he knows a little about the building game and I was happy to see all the chases in the right place.

Now he's proposing to fill the chases with expanding foam trim off and plaster over, this is a new one by me but actually seems a good idea, its an excellent base for the plaster takes no time at all and no mess.

My thought is with the degradation of cables due to some compound reacting with the pvc.

The foam filler is polyurethane which is the ingrediant use in coiled cables.

At the moment I can not see a problem, I'm sure their is though?



Regards


Jez937
 02 January 2007 09:34 PM
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breaker

Posts: 280
Joined: 05 October 2006

Jez

I think there was a simialr post about this, possibly cavity wall insulation.

I seem to remember that pvc cables and polyurethane foam are not good bedfellows.

Perhaps someone else can remember the thread.

breaker.
 02 January 2007 09:45 PM
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Jez937

Posts: 504
Joined: 02 January 2006

Thanks Breaker


Are you sure its not polystyrene reacting with pvc?

Polyurethane is what they use in coiled cables like the flex to a hairdryer.


Regards
 03 January 2007 09:50 PM
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breaker

Posts: 280
Joined: 05 October 2006

Jez

Yes your probably right polystyrene, got my polys mixed up.

I would think that as long as the cables are sheathed there wouldn't be a problem.

Foam just seems an expensive way to fill chases.

breaker.
 03 January 2007 09:55 PM
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peteTLM

Posts: 3137
Joined: 31 March 2005

Same goes for spray foam as well, its no good.
Id use bonding coat instead, much better and dosent affect cables.

Just as an instance, thames water hate the stuff so much they wont connect you as it will leach through a water main- if its used around plastic pipes.

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 03 January 2007 10:12 PM
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pullen

Posts: 122
Joined: 08 March 2005

Apparently polystyrene must not be in contact with PVC cable as it draws the plasticiser from the cable. This is the oil within the PVC that keeps it flexible.

I would also guess that a derating factor of 0.5 would have to be applied if the cable is embedded in thermally insulating material.

These would be the two concerns on my mind
 15 February 2013 06:31 PM
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AlanKay

Posts: 232
Joined: 09 July 2002

Sorry to drag this up again, but six years later I've just seen this "fill the chase with expanding foam and plaster over" technique in use.
Thermal derating presumably applies, but is the formulation of modern expanding foam less damaging to PVC insulation?

Alan

-------------------------
Alan Kay, CEng MIEE
 15 February 2013 06:37 PM
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rocknroll

Posts: 8835
Joined: 03 October 2005

If it is expanding polyurethane foam it does not affect cables unlike its previous counterpart expanding polystyrene.

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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 15 February 2013 07:31 PM
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mikejumper

Posts: 1702
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Originally posted by: peteTLM
Id use bonding coat instead, much better and dosent affect cables.

My thought too.
Unibond the chases then fill with bonding or browning.
 15 February 2013 09:04 PM
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ebee

Posts: 5672
Joined: 02 December 2004

"One coat plaster" can give a better finish than some existing plaster walls of great age

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 15 February 2013 09:11 PM
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daveparry1

Posts: 6151
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I've just started using one coat plaster with satisfactory results although it doesn't go off quite as quickly as bonding,

Dave.
 15 February 2013 10:14 PM
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stateit

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'One Coat' for us sparkies at the end of a day on a small job does fine.

I'd rather not revisit on a second occasion to just finish coat over bonding plaster.

With an 'ongoing' job I'd rather bond & finish coat.

But... not wanting to wait for me a builder/plasterer PU foamed my chases/holes on a job last week (bungaroosh & flint wall)

It was a bu*ger trying to get a rawlplug fixing in for the 4" vent fan I tell you!

-------------------------
S George
http://www.sg-electrical.com
 16 February 2013 09:15 AM
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ebee

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I previously used bonding then finishing in preference to browning then finishing but for years now it`s been one coat for several reasons .

Dave - To make it go off quick use some old stuff or add warm rather than cold water or ,as some plasters do, get a bit of muck in it (spit in it , pee in it, bit of old plaster, most impurities seem to work - apparently)

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 16 February 2013 09:35 AM
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daveparry1

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Thanks Ebee, I have heard that, i'll give it a go next week!

Dave.
 16 February 2013 09:41 AM
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stateit

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Blimey! I hope the customers aren't watching when you use certain additives

-------------------------
S George
http://www.sg-electrical.com
 18 February 2013 07:41 AM
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SherlockOhms

Posts: 320
Joined: 05 April 2011

I picked up a tub of "One Strike" filler from Neweys a while ago.

Odd stuff but really quite impressive. Looks and feels a bit like shaving foam. One advantage is it doesn't appear to go off once the tub is opened.

http://www.my-tool-shed.co.uk/...fOsv7UCFczHtAodzhAA1g

S.
 18 February 2013 07:48 AM
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ebee

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Originally posted by: stateit

Blimey! I hope the customers aren't watching when you use certain additives


I did not say that I did that!

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
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