but they're actually PWM controllers.

Pulse Width Modulation.

They will control via 'duty cycle' and you can actually measure it with a kill-a-watt meter using the 'power factor' setting.

A lot of people imagine that they're set up like a volume control on an old style radio, or a potentiometer from radio shack, but that's simply not the case.

http://home.howstuffworks.com/dimmer-switch.htm

That's also very similar to how proportional thermostats work, I'd imagine. Yes, their output is rough on fans and light bulbs. Any motor plugged into a pwm will emit the distinctive 'buzz'. I would imagine that heat tape wouldn't know the difference, though. I'm not sure........

[ Hide Replies ]

• Is a proportional thermostat safer? - rudykirk, Sat Oct 4 16:06:00 2008
• Absolutely!!!! - rainbowsrus, Sun Oct 5 00:30:06 2008
• RE: Absolutely!!!! - Bighurt, Sun Oct 5 12:43:25 2008
• RE: Absolutely!!!! - caz223, Mon Oct 6 01:31:08 2008
• RE: Absolutely!!!! - BobS, Mon Oct 6 11:15:29 2008
• Solid state components fail too! - caz223, Mon Oct 6 11:40:56 2008
• RE: Solid state components fail too! - BobS, Mon Oct 6 12:06:07 2008
• RE: Absolutely!!!! - caz223, Mon Oct 6 12:57:50 2008
• UPS ?......... - BobS, Mon Oct 6 13:28:40 2008
• Uninterrupted Power Supply - Bighurt, Mon Oct 6 17:28:42 2008
• Thanks np - BobS, Mon Oct 6 20:56:45 2008
• ARS racks - caz223, Mon Oct 6 22:02:53 2008
• RE: Nice responses - markg, Mon Oct 6 13:45:46 2008
• More.... - rainbowsrus, Mon Oct 6 17:34:29 2008
• RE: More.... - caz223, Mon Oct 6 22:28:52 2008
• RE: Rule of thumb - markg, Mon Oct 6 13:58:01 2008
• RE: Rule of thumb - caz223, Mon Oct 6 22:36:26 2008
• RE: Rule of thumb - caz223, Mon Oct 6 22:58:32 2008
• kill-a-watt - caz223, Mon Oct 6 23:04:46 2008
• They call them dimmer switches.... - caz223, Mon Oct 6 23:20:44 2008
• RE: They call them dimmer switches.... - markg, Tue Oct 7 12:39:07 2008