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Problem: Could a weak thermostat battery destroy my home?


Problem: Could a weak or failed thermostat battery destroy my home? We just had a new gas furnace installed and they installed the Honeywell Pro 3000 Non-Programmable thermostat. Everything works fine. But in our area, people leave their houses for a few months and retreat to the city, or head to Florida. And we keep an eye on the thermometers that they leave in their windows to make sure the heating systems are OK. I noticed one house went down to 30, called the owner, he was here in 2 hours drive.
He troubleshooted his new furnace, nothing wrong, the power had not gone off on our street. Somewhat perplexed, he came upstairs and took the front panel off the new thermostat, saw that it was not hard wired but had batteries. He replaced them, and the heating system came on immediately. He was totally astonished that the company who installed his new heating system, had not told him that the entire house heating system was dependent on 2 little batteries, and without them, the house could have frozen up and made a horrid mess. I looked at our new system, and same thing, I was not given a choice to have my thermostat wired properly either.
And then another house on the same street with people in FL was cold, a friend who had a key went in and replaced those 2 batteries and on came the heat. Saved it.
I am astonished that the people who install these lovely new gas systems, do not inform the home-owner that the thermostats have NOT been wired into the electrical system of the house, and if you are away and nobody sees the batteries going down, then here comes real trouble.
I spoke to a local insurance company and they said many of their recent clients have had claims due to these new thermostats, and have had to have extensive repairs to their houses due to freezeups.
What gives?
Should I call the company who installed our new system and have them come back and wire ours properly?
Im rather shocked at this issue and found this website.
Reason that I contacted you, as I got your site by Google, and you could give me an unbiased answer.
Thank you,
of Cape Cod where we had a record breaking cold winter
Hoping you have time to answer me, and from your website, I can see that I will value your opinion.


Hi Jane!
Thanks so much for your informational email. I will list this on our HVAC blog post to give others information about this dreadful problem! I did not realize this was such a prominent problem! We have a battery power thermostat in our home since 1995 and I can only remember replacing the batteries twice. The batteries on our White-Rodgers thermostat have a long life I guess. Our stat even has a button on the top with a light so we can read the setting at night. We are not gone very long during the winter only for short trips to see our son play baseball during the summer. If it were me and if I was gone for long periods of time during the winter I would definitely see about running a fifth wire so the thermostat could be powered by the furnace transformer and then the batteries could be used for a back up of the thermostat memory. Most thermostats with gas heat and cooling use four wires. The Red (R) is the power wire from the hot side of the low voltage transformer, white (W) controls the heat or the gas valve, (G) green controls the fan and yellow (Y) controls the air conditioner out door unit contactor. You would need a fifth wire (C) Com to power the thermostat. I would recommend making sure that your thermostat has an option to be powered by the furnace transformer. Some can only be power by the battery. If you are asking about the Honeywell Pro 3000 non-programmable stat then yes, it does have a “C” connection for the common wire. Here is a link to the installation instructions: Yes, I would suggest getting a company to run 5 wire thermostat cable so you can get the thermostat powered by the furnace transformer. I hope that I have answered your question. If you have any other questions please email us anytime. Our email address is: Hope you have a blessed day!
Steve Arnold,

1 thought on “Problem: Could a weak thermostat battery destroy my home?

  1. Thank you for the information! We will be wiring ours very soon. And I will be warning more of our neighbors who have installed new heating systems.

    You sure can see that we here on Cape Cod had a very harsh winter, for 3 months in a row, we had record cold and record snowfall. Our dog loves it, but we are sick of it.

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