Technical information

CONTROL CIRCUITS

have three different power supplies but a single 10 A feed can be used (for

example 1606-XL240E-3, three-phase power unit) with three overcurrent

protections down line (e.g. supplementary protector UL1077) graded to values of

not more than 4 A: two at 4 A (for example 1492-SP1C040) and the last one at 2

A *e.g. 1492-SP1C020).

The three circuits derived down line from the protections respect all the

conditions to be defined Low-Voltage Limited Energy.

It would have also been possible to realise Class 2 circuits, but in the is case the

intrinsic limitation of the power source would have forced three approved power

units of Class 2 to be used.To that respect however it should be remembered that

Class 2 circuits are provided for both by NEC and by CEC, while the Low-Voltage

Limited Energy circuit is only provided for by UL, even though it is commonly

accepted by North American AHJs.

1.7.3 External Wiring and Terminal

The same prescriptions adopted for the Class 1 circuits apply both for the

external wiring and for the terminal blocks.

The approved conductors of the Low-Voltage Limited Energy circuit and those of

the other circuits, inside the same raceway, should be insulated f or the maximum

v oltag e present; if one of the conductors is not insulated or it is insulated for a

lower voltage,it should be distanced (at least 6,4 mm) or isolated.The

isolation/separation is necessary in the case of non-approved conductors

The terminal block should be clearly indicated as Class 1 with a special marking.