Technical information

5. An electrically operated counter shall comply with the Standard for Time-

Indicating and -Recording Appliances, UL 863;

6. An audible signal appliance, including a horn, bell, or buzzer,shall comply

with the Standard for Audible Signal Appliances, UL 464; and

7. A coil or input circuit to another control circuit switching device or to a load

controller shall comply with other component requirements in this standard.

Caution: the lighting lamps and the fans for electrical panels are considered to

be control circuits. If these components are installed in the field (outside the

electrical panel) they should be considered power circuits instead.

1.3 Control circuit:

As already said, a general control circuit does not have voltage or power limits. It

can be derived directly from the power circuits without the need of a

transformer.

The powering of the control circuit can be obtained in two ways:

1. Directly from the general distribution inside the panel by installing a special

branch circuit protection;

2. Down line from a pre-existing BCP.

The main standards (NEC, CEC) in no way require the connection of the control

circuit on one side to the equipotent circuit, but it does not forbid it either.

NFPA 79 for Industrial Machinery on the other hand picks up again on the

obligation to use a transformer with separate windings and with maximum

voltage not above 120 V: one side of the circuit can be connected to the

equipotent circuit.

CONTROL CIRCUITS