Cable identification question

[ColJack]

this is a long standing and often recurring argument we have at work...

we make large commercial air-con units that are 3 phase and are wired accordingly in the proper colours..

however, we often include an RCD socket for the commissioners, and interior lighting..

these are single phase obviously and are wired from the control panel..

they are not always on the L1 ( brown ) phase.

the regulation regarding identification of colours for circuits is the cause for the argument..

one side says that the circuits should be wired in the correct phase colour.

the other side says that since they are single phase, it doesn't matter what phase they are on and should be wired in brown to indicate 240v ( obviously blue for neutral )

where we have mixed single and 3 phase into the same terminal box ( such as for the compressors and their crank case heaters ), we do identify which phase the single phase is on.. this is because there exists a potential for 415v phase to phase..

anyone got a view point on this?

 

[securespark]

If the units are 3 phase & it is possible to simultaneously access 2 different phases, then the unit should be labelled with "WARNING 400V" at least.


Can I ask a silly question? Why aren't all units wired to the same spec??

 

[ricicle]

It depends which standard you are working to.If you work to EN60204 then all control panel main lines should be black.If you are feeding this socket off the switched side of the panel then that should also be black for the phase.Neutrals must be coloured light blue.
I don't know if the control panels for air -con would fall under this standard.If you work to BS7671 then a single phase circuit must have it's phase coloured brown.The only exception to this is sub - mains in large installations.

 

[RF Lighting]

From a standard circuit point of view then brown if it is a single phase supply, and Bn / Bk / Gy for a TP supply. This is how it would be wired for example a TP dist board supplying both TP and SP sockets.

As for your scenario, then I don't think it really matters, but I would be inclined to use brown to supply the SP socket. Purely so that if a large bank of units were installed the sockets could be balanced without the need to rewire (It would just be a case of swapping a connection)

 

[JohnD]

In a telecomms installation I came across (in the early 2000's so red and black were usual on SP) there was a rack or cabinet of "things," the power came in to the top of the rack, and there was (say) a 5A MCB, the output to which was wired to (say) a dozen 5A cartridge fuseholders, each of which fed a "thing." The output of the MCB was chained to the input of the fusefolders using blue wire.

There were several sets of these MCBs with subsidiary fuseholders on the same DIN rail. IIRC the same wire fed the Supply side iof each of the MCBs (there were no Busbars) and they were all Blue.

I thought it very odd, and don't know they they seemed to wire L in Blue.

My guess was that the cartridges were intended to blow faster than the MCB, so you would not normally lose a bank of "things" from a fault in one of them. I don't know if the MCBs were supposed to have greater Fault Breaking Current capacity.

 

[ricicle]

The cartridge fuses could have been semi-conductor fuses, designed to blow if you sneeze......no seriously they are used to protect electronic equipment (very fast acting)

In modern machine control panels blue is normally the colour used for 24V DC

 

[JohnD]

would they have been special MCBs for 24v?

 

[ricicle]

would they have been special MCBs for 24v?

I've seen/used standard MCBs for protecting 24v DC circuits for overload only as they are looking for the thermal effects of cable heating only (from overcurrent).
The ac RMS current heating effect is based on the same heating effect from an equivalent dc current

 

[JohnD]

but it's more difficult to break a DC arc.

 

[plugwash]

it is but the voltage is 10 times lower, i'd expect that to be enough.

 

[ricicle]

but it's more difficult to break a DC arc.

But the short - circuit fault current is probably only in the region of a few hundred amps at the most.The lack of zero - crossover should not be a problem.

 

[Paper Spark]

All the control panels we had installed with a new machine in 2000 had the following colours for the panel wiring:

380/415V - Black

230V - Orange

110V - Red

24V dc - Blue

4-20mA, 2-10V control signals - Violet

I don't know if it's a standard or just the Italian manufacturers that did it that way.
I know it was easier when fault finding knowing what voltage to expect on any cable.

 

[JohnD]

what colour for Neutral?

 

[DESL]

what colour for Neutral?

White?

 

[Paper Spark]

Those particular panels didn't have a neutral feed, they just had 3Ph supply and then transformers for the lower voltages using the same colours for feed & return. There wasn't much 230V used, it was mostly 110V for the contactor coils & control equipment. And 24V for the PLC I/O
If 230V was needed they used a normal 230/110V transformer reverse connected ie output as input & input as output.