thermostat cable insulation voltage rating

Mar 09, 2005 2 Replies
D

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


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S

Manufactures get to do what ever they want when the designs are submitted to the testing agencies like UL and CSA. I worked for an electrical manufacture that ran line and low voltage in the same bundle ty-wrapped together. As long as you see the acceptance sticker on it chalk it up to the way of the world.

Check out a electric waterheater. Fed with a minimum of #10 and inside the manufactures use #12.

Air conditioner condensers are the same situation

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S

I agree; appliance manufacturers get a lot of leeway from UL. Practices which wouldn't be permitted by NEC are routinely OK'd *inside* the appliance where UL feels the mfr has sufficient control to satisfy some minimal level of safety.

Jim

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