Mixed AC voltage levels in the same multi-conductor cable
Mixed AC voltage levels in the same multi-conductor cable
(OP)
Hi Folks,
A contractor is in discussion with a client stating that it is possible to run mixed AC voltage levels within one multi-conductor cable, e.g., a 5/Cx25mm²
The system in question is a supply cable feeding a step-down transformer at 460 VAC running from a panel and stepping it down to 127VAC single phase+neutral which should go back to the same panel. The load shall be HVAC units.
Is this possible and if not are there standards indicating this?
In advance thanks for any feedback.
A contractor is in discussion with a client stating that it is possible to run mixed AC voltage levels within one multi-conductor cable, e.g., a 5/Cx25mm²
The system in question is a supply cable feeding a step-down transformer at 460 VAC running from a panel and stepping it down to 127VAC single phase+neutral which should go back to the same panel. The load shall be HVAC units.
Is this possible and if not are there standards indicating this?
In advance thanks for any feedback.
RE: Mixed AC voltage levels in the same multi-conductor cable
RE: Mixed AC voltage levels in the same multi-conductor cable
Thanks for the prompt response. Indeed the project is not in the US but some NEC codes still apply here within the electrical regime.
We are mostly IEC governed. It just does not seem to be a common practice to mix two voltage level conductors in the same cable bundle. In this case, it will be an L1+L2(460VAC) "entering" the transformer and L+N+GND(220VAC) "leaving" the transformer in the same multi-conductor cable. That is why I was wondering if this is acceptable within norms and codes such as IEC/ANSI/IEEE, etc.
RE: Mixed AC voltage levels in the same multi-conductor cable
"... the project is not in the US but some NEC codes still apply... We are mostly IEC governed. It just does not seem to be a common practice to mix two voltage level conductors in the same cable bundle..... it will be an L1+L2(460VAC) "entering" the transformer and L+N+GND(220VAC) "leaving" the transformer in the same multi-conductor cable. ... I was wondering if this is acceptable within norms and codes such as IEC/ANSI/IEEE, etc..."
1. Cable insulation voltage consideration: I look at it that the (incoming L1-L2 460VAC), the (out going L+N+GND(220VAC). They are within the LOW voltage rating i.e. <1000V per IEC/ANSI/IEEE/NEC, etc... The cable rated good for 460VAC, will be also good for (220VAC). Electrical insulation-wise OK.
2. Safety-wise, (460VAC) and (220VAC) are widely used; technicians generally are aware and considered it of the same danger level.
3. Core marking-wise: IEC L1(Brn),L2(Blk),L3(Gry),N(Blu), E(YwGn) ; ANSI/NEC/IEEE with different colours.
3.1 In your case, perhaps you should use all four 1,2,3 and 4 cores with BLACK colour, with E remain (YwGn). Sleeve core 1 and 2 "460VAC", core 3 (220VAC) L[Brn], core 4 (220VAC) N[Blu]; to avoid confusion and complied with BS7671 or IEC. But NOT to US practice.
Che Kuan Yau (Singapore)
RE: Mixed AC voltage levels in the same multi-conductor cable
Keith Cress
kcress - http://www.flaminsystems.com