I've noticed that in many/most modern furnaces the thermostat cable
enters and connects to the control module in the same compartment
with various line-voltage wiring. In fact, much of the line-voltage
wiring terminates on the same control module. There is no partition to
keep the low-voltage and line-voltage wiring separate. This would seem
to violate the frequently quoted rule about separation of low- and line-
voltage wiring unless thermostat cable insulation is supposed to be rated
for line voltage. The thermostat cable I've seen is CL2 with a 105C
temperature rating but says nothing special about voltage. Is it 300V
or 600V rated?

Dan Lanciani
ddl@danlan.*com