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Topic Title: Using SY Steel Wire Braid Cable
Topic Summary: For AC installs
Created On: 27 November 2008 10:22 AM
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 27 November 2008 10:22 AM
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Stottie

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A friend of minr installs AC units he has used SY Steel Wire Braid Cable as the interconnecting cable between the indoor and the outdoor unit.

The sites he works on install a isolater for him by the outdoor unit.

He has been told that the SY steel wire braid cable can only be used for temporay installations as it does not have mecanical protection.


Any comments appreciated.
 27 November 2008 10:26 AM
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perspicacious

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"He has been told that the SY steel wire braid cable can only be used for temporay installations as it does not have mecanical protection."

Does SWA offer sufficient mechanical protection?

522.6.1
522.6.2
522.8.1
522.8.10

Regards

BOD
 27 November 2008 10:59 AM
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zeeper

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 27 November 2008 11:32 AM
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davezawadi

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This manufacturer is trying all the things to avoid any responsibility, he also says that it is not suitable for connection to a mains supply!! It is widely used in here and in Europe both outdoors and for mains connected cables. The clear sheath does have poor UV resistance, but this is rarely a problem in a fixed installation.

As to the mechanical protection, why is this required and why is SY any less good than T&E? Usual requirements apply to all cables including SWA.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 27 November 2008 01:10 PM
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AJJewsbury

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All the Air Con installs I've seen recently have SY between the indoor and outdoor units.

- Andy.
 27 November 2008 03:07 PM
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zeeper

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RS also says

Can be used outdoors when protected, and in dry or moist conditions indoors.
 27 November 2008 03:35 PM
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lbelectrics

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As I understand it, SY is basically CY with additional protection by way of metallic braid & outer sheath..

Obviously not as robust as SWA but perfectly suitable for use where the machanical protection of SWA is not deemed necessary. SY, like CY and other similar flexibles is rated for mains use and is often a great choice, subject to appropriate glands being used at the ends.

-------------------------
Regards

Lee
 27 November 2008 03:55 PM
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leckie

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If the braid does not offer mechanical protection what is it for?

Also, I have had to get proper glands for stock 'cause none of the wholesalers stock them in my area, and Ive never seen the correct glands fitted to sy on an air con installation. They all seem to use stuffing glands, sometimes with the braid twisted together and connected to earth or more usually not even earthed!

Im amazed SY is not suitable to outside use since I see it all the time to AC units all over the country.
 27 November 2008 04:40 PM
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AJJewsbury

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If the braid does not offer mechanical protection what is it for?

Screening? (possibly shock protection via earthing too).

As I understand it, SY is basically CY with additional protection by way of metallic braid & outer sheath..


I think CY has a tinned copper braid (rather than steel) between the cores and the sheath (and no 'inner' sheath).

YY types I think are the ones with no braid - like our ordinary flex.

- Andy.
 27 November 2008 04:42 PM
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davezawadi

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The correct glands are plastic skintop type of the appropriate diameter. The wire is considerable mechanical protection, and also gives protection against penetration to the live wires by sharp objects as they would almost certainly cause an earth fault. The wire covering should be earthed by unbraiding to make a pigtail, sleeving and fitting a crimp tag. It has a significant cross sectional area, but the cables (3 core and above) have a G/Y core anyway for the ECC.

-------------------------
David
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 27 November 2008 04:47 PM
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perspicacious

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"The wire is considerable mechanical protection, and also gives protection against penetration to the live wires by sharp objects as they would almost certainly cause an earth fault. The wire covering should be earthed by unbraiding to make a pigtail, sleeving and fitting a crimp tag. It has a significant cross sectional area, but the cables (3 core and above) have a G/Y core anyway for the ECC."

How come then SY cable is excluded from 522.6.8 (i)?

Regards

BOD
 27 November 2008 05:09 PM
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AJJewsbury

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The correct glands are plastic skintop type of the appropriate diameter. The wire is considerable mechanical protection, and also gives protection against penetration to the live wires by sharp objects as they would almost certainly cause an earth fault. The wire covering should be earthed by unbraiding to make a pigtail, sleeving and fitting a crimp tag.

That's fine from a mains/earthing point of view, but might not be good enough if the screen is there for electromagnetic screening reasons - e.g. BS EN 50310 (the standard for bonding and earthing in buildings with IT equipment) asks for 360 degree connections - which I interpret as meaning a metal gland (into a metal enclosure).

- Andy.
 27 November 2008 05:15 PM
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leckie

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So what is it? Gives mechanical protection or not?

I think AJ is probably right, braid is probably for screening/emc. If it is for mechanical protection, to what degree?

The braid would give shock protection if the cable is pierced, providing it is bonded.

There is a specific gland made for SY, i dont think plastic glands and pitails are too great an idea, but cheap. The ones Ive got are basically a brass stuffing gland with two brass washers and a 20mm lock nut, with two slots cut in the 20mm thread to bring the braid through. The braid is put through the slots and sandwiched between the two washers. An earth tag is then fitted under the locknut.
 27 November 2008 05:17 PM
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perspicacious

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"The braid would give shock protection if the cable is pierced, providing it is bonded."

How come then SY cable is excluded from 522.6.8 (i)?

Regards

BOD
 27 November 2008 05:30 PM
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AJJewsbury

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"The braid would give shock protection if the cable is pierced, providing it is bonded."

They SY I've seen seems to have somewhat less that 100% 'optical coverage' - i.e. there are regular little gaps in the braid - so if the thing that pierced it was thinner than one of those gaps there is a possibility it could miss the wires of the braid and still hit a live conductor - a picture nail for instance. Probably does have some value where crushing or bigger implements are expected though.

- Andy.
 27 November 2008 05:37 PM
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leckie

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Not sure of the reason for the exclusion, probably for the same reason FP isnt?

Is it because neither are considered to have mechanical protection?

Not sure, we need some one clever to explain!
And can they hurry up because im off for a pint in 10mins!
 27 November 2008 06:04 PM
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davezawadi

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These are all interesting questions, particularly yours BOD. I'm not getting into the EMC issue at the moment. I don't know why it is excluded from 522.6.8, because in my experience the braid is quite good at blowing fuses given a penetrating object. It could be because its current carrying capacity of one strand is considered inadequate, or they just don't like the idea of burying it in a wall. The problem is definition of mechanical protection, and BODs second post tends to the idea that this cannot be provided by a sheathed cable, which makes SWA redundant! I would not recommend burying SY in a wall, but clipped tightly or in trunking it provides a convenient and robust way to connect equipment which may need more cores than T&E particularly 3 phase stuff for which the alternative SWA may be unattractive. Otherwise we are back to metal trunking or conduit everywhere, and although this may be continental practice in several countries, it cannot be said to be pretty or cheap or easy to install.
I wish I could get a real ale in 10 minutes!

David

-------------------------
David
CEng etc, don't ask, its a result not a question!
 27 November 2008 06:12 PM
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perspicacious

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"The problem is definition of mechanical protection, and BODs second post tends to the idea that this cannot be provided by a sheathed cable, which makes SWA redundant!"

The OP concerned impact and the thread diverted to penetration.

Regards

BOD
 27 November 2008 06:22 PM
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GeoffBlackwell

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How come then SY cable is excluded from 522.6.8 (i)?


Is it excluded - implying that it has been actively rejected - or is it - not included - which may imply the same, but might also mean that it has simply not been assessed.

Regards

Geoff Blackwell
 27 November 2008 06:36 PM
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perspicacious

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"Is it excluded - implying that it has been actively rejected - or is it - not included - which may imply the same, but might also mean that it has simply not been assessed."

Geoff

Well there is always 120.4 for the brave

Regards

BOD
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