Technical information

Supply can be provided through:

•transformers with separate winding down line from the main disconnect of

the machine; the secondary must be protected;

•transformers with separate winding up line from the main disconnect of

the machine; the secondary must be sectioned;

•one 120 V control circuit with its own protection against over currents.

b) the CEC makes a difference between the maximum size/calibration of the

BCP on the basis of the power supply voltage:20 A for voltages up to 347

phases higher than 347 V, 15 A for higher voltages.

The command of a lighting circuit requires contactors that are specifically

approved for this purpose: the “lighting contactor”: The sizing must be done on

the basis of the current. One example of these contactors:

•100L series for the IEC/UL/CSA contactors: there is one size and it is 20 A;

•500L series for NEMA contactors: every size has a different current value, from

10 A to over 2000 A.

The maintenance lighting inside the panel is only dealt with in UL508A (as it is a

regulation specifically for panels) and, or Industrial Machinery, in NFPA 79

(because of the “origins” in IEC 60204-1).

a) UL508A:

•the lighting equipment must be approved in accordance to UL496 in the

CCN OMTT or ONHR, or in accordance to UL1570 in the CCN IEUZ.

•the voltage between conductors must be lower than 150 V.

•

the circuit must be considered as a power circuit and protected as already

defined. One exception is permitted: if the power supply occurs at 120 V and

it is derived downline from a control conformer with separate windings,

then the circuit can be considered as a control circuit and managed as such.

b) NFPA 79 (and relative section of UL508A):

•the lighting equipment must be approved (the previous UL approval classes

of course apply);

•less than 150 V; less than 15 A (as for all lighting circuits)

•in addition to the cases already described, the maintenance supply circuit

inside the panel can be derived from the secondary of a transformer with

separate windings upline of the machine's main disconnect (and must not

be sectioned or protected) or from the lighting circuit of the plant.

1.11 Appliance branch circuit

Any electrical user equipment mass produced to carry out a particular function is

called an appliance. In general they are non industr

ial devices (for example

household appliances).

Very often appliances are connected to a socket by means of a lead meaning that

for sizing the rules already seen for the receptacles are applied.

In cases where the ’appliance is directly connected it is necessary to provide for a

branch circuit, chosen with the following criteria (taken from UL508A):

BRANCH CIRCUIT