Hi, i have pick up some 3 phase armoured cable. But it only has 3 wires inside the amour. Is this correct? I guess a neutral, 2 lives and the outside of the cable is earth? Should there not be 4 wires inside it?
3 phase cable
- Thread starter mattysupra
- Start date
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Hope it wasn't live!!!
Thats because it is three-phase cable propper, just the 3 phases and an earthed armour, 4 core is generally for TP&N and 5 core generally gets used when you want to suppliment the earthed steel with copper.
so you mean the cable is the correct one for a 3 phase motor then?
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Probably, as long as the load is equal across all three phases. One would hope you're not planning on installing it yourself, though!
Well, probably, it depends on how large the load is, how far the motor is from the origin of supply and if the motor is going to be fixed or movable.
Do you know how to test for phase rotation.
If you answer No to the above question you shouldn't be doing it yourself!
If you have a spark lined up and thought you'd supply him with the cable you came across, ask him.
Do you know how to test for phase rotation.
If you answer No to the above question you shouldn't be doing it yourself!
If you have a spark lined up and thought you'd supply him with the cable you came across, ask him.
no im not installing. I just want to make sure i picked up the correct cable for the sparky before he has a wasted visit.
Im not installing myself. Thats a sparks job. The run is 25 meters, the motor is fixed, the plate on the motor says 9amp - 240v and 6 amp- 420v. The cable i have is 4mm.
Without getting the calculator etc out- that sounds about fine to me, but, obviously its down to the installing sparks.
Then ringing your electrician, and asking him directly, would be better than messing about posting on a forum, surely?
in reply to above, well i like to make sure things are done correct as i have had a very bad expearence with a so called sparky that resulted in my house having to be rewired twice!
This is also a forum so people can learn, plus i like to understand what is going on. What is the point in having a forum otherwise?
ANYWAY.. Im a bit confused and did not want to confront the spark that has come out to quote when i dont know what im talking about but i was under the impression that the outer core of the cable was the earth? He has stated that the cable is fine but will need to run a seperate earth? This dont seem correct to me, does the earth not need to be located in the cable?
This is also a forum so people can learn, plus i like to understand what is going on. What is the point in having a forum otherwise?
ANYWAY.. Im a bit confused and did not want to confront the spark that has come out to quote when i dont know what im talking about but i was under the impression that the outer core of the cable was the earth? He has stated that the cable is fine but will need to run a seperate earth? This dont seem correct to me, does the earth not need to be located in the cable?
A seperate earth cable made from copper is a far better earth than the wire armour.The armour cable will have to be glanded which will mean a joint/connection making it less reliable the seperate cable will have less conections.Go with the spark,all the installations I have worked on we have ran seperate earths with armours.
great stuff. Sounds like his an o.k spark then! Thank you.
The armour has a much larger csa - it's usually better than the cores.
Surely if you don't trust your ability to terminate the cable properly you should use one with enough cores to use one for the cpc?
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