Faulty Thermostat Causes Homeowner's Power Bills To Skyrocket

[edb]

Defective Honeywell thermostat. Ed B

[hallerb]

honeywell owed him the bucks too bad customer service wasnt cooperative...

[MDT at Paragon Home Inspection]

This one may be pretty tricky. My guess, offhand, is that the thermostat might not have been "defective" in the sense of a manufacturing defect, but rather that this might have been a design defect: that it was possible to program the heat and cooling set-points such that the thermostat could call for both simultaneously.

If so, a system might operate fine as long as 'stat was in ether the "heat" or "cooling" mode (which is how it would likely be tested during installation) but if it was switched it to the "auto" mode afterwards, both might be active

I can see how an HVAC contractor or Home Inspector could easily "miss" this unless they had a prior reason to test for it - both would likely force the system directly into the 'stats "heating" and "cooling" modes as required for routine testing - and I'd have to agree that it's unreasonable to "expect" a typical homeowner to detect the problem other than in the form of a high electric bill.

Michael Thomas Paragon Home Inspection, LLC Chicago, IL mdtATparagoninspectsDOTcom

847-475-568

[Tony Hwang]

Hi, In design aspect that can't happen. In auto mode it's either cool or heat, not both. ASIC can't do both at the same time.

[JimL]

My unit can't do both at same time either.

[MDT at Paragon Home Inspection]

Well, I'm no EE, and "Don't turn on heating and cooling at the same time" would seem to be something rational beings would want to implement at a pretty fundamental level when designing thermostats, so unless somebody else comes along and says differently, I'll take your word for it

But if the the article is correct, and a properly connected thermostat was energizing both, it would be interesting to know what mechanical, electrical or electronic defect was present.

I've submitted a request to Honeywell Tech Support for additional information on this problem, if I get an answer, I'll post it.

Michael Thomas Paragon Home Inspection, LLC Chicago, IL mdtATparagoninspectsDOTcom

847-475-568