Technical information

CONTROL CIRCUITS
89
1.9 Control of the temperature in the panel
American and Canadian standards do not make any reference to specific over
temperature tests of the panel but they require the control of the temperature in
the panel to guarantee its full functionality.
The over-temperature can be avoided with fans, anti condense resistors and
conditioners.The components in the conditioner system are considered po
w er
components and therefore part of one of the branch circuit already described:
•fans motor branch circuit;
•anti condense resistors heater branch circuit;
•conditioners motor appliance branch circuit.
In UL508A fans may be installed inside the control circuits provided that both the
following conditions are respected:
–using approved fans: CCN GPWV2 (UL 507 “Electric Fans”). The use of these
components implies automatically low-voltage use: in fact UL507 imposes, as
maximum fan feed voltages, 30 V effective in alternating current and 42.4 V in
direct current;
–deriving the control circuit downstream from a transformer/power supply unit
that ensures electrical separation.
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