Why can't you plug Proportional thermostats into UPS's or generators?

[Adam Chandler]

I was wondering why you couldn't plug a Proportional thermostat into a uninterruptible power supply so I emailed Helix and Jeff Washburn was cool enough to write me back and explain. Just thought I'd share with everyone.

This is the email I sent him:
I was just wondering, would it be ok if I plugged my DBS-1000's into
uninterruptible power supplies? Would there be any problems doing
this?

Hello, yes you will not be happy using any signal conditioner, UPS, even some older or sloppy power generators, ahead of digital equipment that
electronically controls output power. The Sign-wave that these products
produce is "square-ish" and not acceptable for use with triac driven
devices. ( Including Helix DBS-1000 and any truely Proportional
thermostat.) . This Square sign-wave tends to turn on the power at a low
level when the system wants the power OFF.
On/Off thermostats ( at least most of them) should not have this
problem.

If your looking for back up incase of power outage...

You can set up a Ranco (On/Off) thermostat, 1-2 degrees lower
setpoint, and separate small fan and heat element.
Basically the Ranco is never putting out any heat , unless the
temperature drops to the lower (secondary system) set point. This saves the relay inside and makes the Ranco system last a 1000 x's longer

It could also speed "temperature" recovery after opening the incubator,
and closing it.
Thanks for thinking Helix, Jeff Washburn, Helix Controls, Inc.