These cables have there uses but we tend to find during periodic inspection that the majority of faults lie with the installer. The outer PVC cover of SY is not UV stabilised so is of no use outside where it just cracks in sunlight and fills with water rusting the braid a much found defect with AC units.
I carry out inspection and testing on domestic premises mainly, so have not come across this cable. I have seen it in use on A. C both inside and outside. Good discussion on the whole- an excellent point to raise by Bill Allan.
The cable insulation has been known to break down when you use sy cables on inverter controlled motors. I believe that these types of cables can be used in fixed air conditioning installations, but only as the control cables. The air conditioners are powered by SWA cables.
Clear sheath on these cables as opposed to black sheath means these cables are prone to damage by UV light. Once the sheath splits due to exposure to UV, water ingress into the braid is inevitable with obvious consequences to follow. As the article suggests these cables are not manufactured to a harmonized standard or to an IEC standard, with only a passing reference to part of a VDE German standard - begs the question how are these cables CE marked and what action are relevant Govt Depts taking to remove them from sale and why are installers even contemplating using them?
Interesting article. We had instances in the past where motors operating from Variable Speed Drives cause noise interference problems on underground cross-site analogue signal SWA cables, even with recommended cable band segregation. This was rectified with a concession to use SY cabling as the steel braiding afforded better protection than standard armouring. Some manufacturers publish cable rating info online, but it's not always easy to find.
As you say SY cables non-standard cables and the general industry guidance is to discourage their use. Why do they form part of the AM2 test, encouraging their use in my opinion? I work in the automotive industry, if you removed the CY, SY and YY cabling, you'd remove most of the cabling from most sites.
Most inverters are wired in either CY or SY cabling. Unfortunately the iet and bs is more interested in changing regs unnecessarily to justify self rather than moving forward. Lets face it none of the so called standards bodies picked up that the consumer unit plastic was actually flammable, 20 years? Well said. At the end of the day it is FLEX.
Used as a medium to connect motors the final couple of metres its an excellent product and bridges the gap between conduit and unscreened flex. Used wholesale in a large installation, is not best practice in my book. Surly it would be in the interests of the manufactures to get together and write one, drawing on existing standards where appropriate, and get it published.
My only issue with SY cable is its clear sheath, with poor UV performance. Why not make it black?? Eland cables, for example, celebrate the fact that their cables have recently received the BS Kite Mark for quality While I know all too well why these cables shouldn't be used outdoors or underground, I don't exactly understand why they can't be used for fixed wiring However, if BS says they shouldn't be used and the manufacturer says they're not suitable then it would be a brave person who ignores this advice.
Does anyone Earth the sheathing on SY cable? Never seen anyone else do that though. Wouldn't use it, who could under BS could claim it provides equal or better protection than cables recognised by BS?
Unless you have the ability to test or pay for tests to demonstrate matched or superior performance no one. I always comment to anyone I see buying the stuff that if they are using it in fixed wiring or connecting from fixed wiring to appliances that they are not complying with BS Surely this is standard good practice and needed for regulation compliance to avoid induction.
You may know that CX cable glands, similar to armored glands are made for the braided types of cable to earth the braiding. Just a thought. Not many people know that. Robert,you can purchase CX glands to earth the braiding on the cable between the washers on the gland,they are specifically made for this cable,and you should always earth the braiding as it has the potential to become live if the cable is damaged,it also will increase your earth loop readings too along with the main cpc.
There is an earthing gland available. Would i be correct in thinking that this type of cable has a rated voltage of V so should we be using it on 3 phase? YY cables flexible?? Bill Alan obviously has never used this stuff.
The use of CYY or SYY is a must for fixed wiring where audio quality reproduction from expensive hi fi can be affected by clicks from connected AC equipment even some distance away. Ground the sheath at one end only to avoid inductive intrusion. This cable has been used in industrial premises and extreme environments for years without problems.
Does that meet BS? Its all very well for Mr Allen to talk about the YY range of cables, and no doubt a lot of what he says is true, but to preach to the electrician in the street on items they have no knowledge of is to say the least a bit much. He may say its their responsibility and to a certain extent that is true.
Answer: Gary Parker Most manufacturers state that the galvanised steel wire braid is used to prevent interference i. If it is connected to earth, then you will always screen the cable. Comments I was under the impression that general industry advice is to discourage the use of SY and CY cables as they do not meet British Standards.
I think the idea was that they should be discouraged from use in general power applications where BS applies. They are widely used for control and field wiring purposes where the screen would in fact be very useful. Having worked in the water industry, I was always instructed to use SWA cables with internal screening made from a complete foil wrap, in contact with the braid, for termination.
I would have thought that the gaps in the SY screen would mean the cable isn't completely screened from electromagnetic interference though my grasp of the physics behind this is perhaps not as complete as it should be.
Their use should continue to be discouraged due to this. IF you use CY or SY, or any other type of cable not bearing a recognised BS number, the "Designer" of the electrical work being carried out must clearly state on the electrical certificate that they deem it to be compliant and thereby they are responsible for its use and ultimately thwy will bear responsibility should the worst happen.
If CY or SY is used in a fixed electrical installation and the designer does not make a declaration along the lines of the above, then the installation is non-compliant, imho. And surely the cable manufacturers has determined the sizing and made the braiding big enough to suit. If not. Karl is absolutely correct. However in control applications the control supply should always have one leg bonded to PE or chassis - EN - s8.
Purely from a safety perspective putting aside the does and don'ts of usage. I think these cables will always be used in power situations. The braid must be earthed one end at least.
If the sheathing was penetrated and one of the live conductors came into contact with the unearthed braid then a situation could exist whereby the braid becomes live and is awaiting some unsuspecting person or animal to touch the braid to complete the circuit thus inducing an electric shock. I would have thought that there is a risk that the fault current would melt the braid around the penetrating object, due to the very fine diameter of the individual strands that make up the braid, before the protective device had a chance to operate.
I have seen a situation where the flexible armouring of an SY cable was not earthed either end and an operator received an electric shock from the cable. On further inspection and testing there was damage to the cable in several places and one of the live conductors had been exposed. In certain positions as the cable was moved around it came into contact with the unearthed screening.
Not only do these cables not comply with BS , I wonder if they are CE marked - there's no harmonized standard that covers these types of cables so how are they tested? Without CE marking should these cables even be on the market?
Can Voltimum confirm this please? Similarly its often used with the higher conductor counts for control applications, such as button boxes, etc. The alternative I've seen used is a flexible steel duct containing per-phase wires, but for smaller motors this leads to a very clunky installation, and for button boxes you end up with a considerably less flexible result.
Earthing both ends encourages earth fault currents to flow through the braid. Earthing one end the live or sending end directs the fault currents in the appropriate direction. Use SWA instead. Whilst taking on board all of the above comments regarding the fact that SY cables do not comply with British Standards they are manufactured alongside compliant flexible cable so it is likely that the centre core under the braid would meet appropriate Standards.
Where used in parts of fixed installations where flexibility is required SY cable is potentially safer than the spiral wound flexible conduit which often gets stretched and breached exposing the basic insulation of the conductors within it often with sharp edges exposed.
A hazardous situation I have observed in a huge number of installations. Glands are available for these cables which allow the earthing of the braid which gives a degree of protection and screening. Perhaps the manufacturers of these cables should consider approaching the appropriate Standard committee to develop or amend Standards to bring them in line. I know the industry discourage the use of SY cables,but have the actually been causing issues within the industry?
Any defect in the outer sheath that allows moisture to gain access to the braid, causes the braid to rust. There is no galvanizing on the braid steel.
All, some interesting scenarios listed above, I've also dealt with this in the past, please see below an email received from the rep at LAPP cables They confirmed to me that they are not telling electricians not to use it - but they are warning them that the specifier is liable for any associated costs should there be a fault with the cable.
However; the specifier is not liable if the manufacturer of the SY cable has their own quality guarantees. Please pass me their details and I will gladly take them to task over this. It is behoped that the cable has a longer-term life than 18 months.
A deliberate decision not to fully comply with the requirements of the Wiring Regulations, such as in the use of control cables in fixed installation, must be noted as a departure.
Any use of a custom, non-standard, or partially compliant cable must be declared and assessed, and it must be ensured that the degree of safety is not compromised. Some manufacturers claim that YY, SY and CY cables comply with the general requirements of the BS EN series, but these designs differ from the requirements of the mentioned standards.
For example:. In , it was reported that the insulation and sheath thicknesses of cables designated YY, SY and CY often have lower insulation and sheath thicknesses in comparison with the BS EN flexible cables.
There is a definite need within the industry for specifications for YY, SY and CY cables because they are currently unspecified though popular, and they fulfil a practical need. BASEC will be launching its new scheme very soon, which will enable the end-user to be clear on the design and performance of these cables. It is also important to note that these cables will have to meet the requirements of construction product regulations CPR.
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