I know the subject of SY cables in fixed power installations pops up a lot but please bear with me.
I know that SY cable does not meet any British or harmonised standards and is 'discouraged' under BS 7671, but can be installed and noted as a departure on the installation certificate.
As it will need to be 'safe' under BS 7671, should SY cable be installed in metallic containment such as steel trunking?
The thickness of the wire in the braid is absolutely vital, the thickness of the braid wires makes the difference between the braid going off like an old fashioned camera flash bulb or carrying the fault current and allowing a fuse to disconnect the current.
Have you never set fire to wire wool?
The thickness of the wire in the braid is absolutely vital, the thickness of the braid wires makes the difference between the braid going off like an old fashioned camera flash bulb or carrying the fault current and allowing a fuse to disconnect the current.
Have you never set fire to wire wool?
The "not true" was regards "provide considerable extra protection from knocks and sharp objects" - patently not true, I have used a craft knife to easily slice through the sheath of SY with the steel braid embedded in the outer sheath ... and there is no penetration protection.
I agree there's the possibility of fire due to penetration of an SY cable, if the overcurrent protective device is not selected carefully. An RCD might well operate, though, if one were used to protect the circuit.
Overcurrent protection also depends on the braid being properly terminated (preferably in the correct gland).
Having said that, I've seen SY terminated in industrial plugs and socket-outlets, where the braid is not terminated at all !!!!
Perhaps you have not realised Graham but the braid is not usually mild steel, and the EMC aspect (perhaps it is in the standard none of us have) is somewhat dubious due to significant braid resistance and reactance, and the coverage is less than 100%. In my experience SY is much tougher than plain PVC cable, and using the braid as a CPC (not a G/Y (GNYE is not well known except to panel builders and electronics)) is very unwise as I have witnessed a fire due to exactly this, it has a high resistance and not a lot of current carrying capacity. I did point out that it is not "flexible SWA" Graham, and the braid often does not have anything like the equivalent copper cross section of the conductors. I have never seen (as far as I remember) a piece of SY without a bedding layer under the braid, and such would be very unwise.
SY cables do not have the braid embedded in the outer sheath Graham, that is something else entirely, and is some other type of screened cable, larger sizes of SY are quite difficult to cut, even with large proper cable shears, and a craft knife would stand little chance with the braid.
Whether SY is tougher than larger sizes of rubber cables which might otherwise be used is also interesting, it is probably a fairly close run thing, and just depends on the mechanical or chemical abuse.
Perhaps you have not realised Graham but the braid is not usually mild steel, and the EMC aspect (perhaps it is in the standard none of us have) is somewhat dubious due to significant braid resistance and reactance, and the coverage is less than 100%
David, I have many years' experience using the stuff in relation to Machinery and Controls.
I am fully aware that CY has a far better coverage than SY, but it really depends on the application (and budget). In fact, the coverage of SY varies, and some types wouldn't even offer, in reality, any mechanical protection, and only a little help with radiated emissions. SY is usually OK for short distances, and up to the frequencies used by inverter drives.
CY is more effective on longer runs, and where frequencies are higher (hence "coverage" is more important than "simple Faraday cage") ... also where there are high protective conductor currents and a lower inductance of the functional earthing down the cable is more important.
(GNYE is not well known except to panel builders and electronics)
Hence, its inclusion in BS 7671:2018+A2:2022 (following the example of BS EN 60445:2017 and BS EN 60445:2021) ... although "I didn't know" doesn't mean "It doesn't exist" or "It doesn't matter".
SY cables do not have the braid embedded in the outer sheath Graham, that is something else entirely, and is some other type of screened cable,
Some definitely out there. And definitely was sold as "SY" ... and there being no constructional standard for the cable, who is to know, or even argue (no standard, no argument really)?
larger sizes of SY are quite difficult to cut, even with large proper cable shears, and a craft knife would stand little chance with the braid.
Agreed. But it doesn't stop people thinking the smaller csa cables have added mechanical protection somewhat equivalent to SWA, which is absolute nonsense. What's more, I see a lot of (rusting) SY cable used outdoors, not UV stable, and certainly not suitable for the wet environment.
Whether SY is tougher than larger sizes of rubber cables which might otherwise be used is also interesting, it is probably a fairly close run thing, and just depends on the mechanical or chemical abuse.
Agreed - H05RN-F is good stuff for a rather wet environment, and with a range of other contaminating materials that might affect other cable types.
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