Replacing an old thermostat

Sometimes I have little revelations that pop into my head and recently one of these had to do with thermostats. Yeah, home ownership can really have an effect on you. Seriously though, I thought about the shoddy control over our natural gas furnace we have with our current, circa 1950s Honeywell round thermostat. It works well enough, I guess, except that it's analog and I'm just not into that sort of thing. I'm a digital boy. So, I did a little digging online and found that it's really no big deal (nor does it cost much) to replace it with a modern digital thermostat. With that, I hit the local Lowe's and picked up a new Honeywell (guess they've got quite the corner on the market) and began the installation.

Popping off the old thermostat wasn't any trouble but I did have to be careful because it has in it a vial of liquid mercury that, if broken, could cause some serious cancer. I gingerly set that aside and now had to figure out which wires went to where on the new thermostat. The new digital unit had spots for something like six or more wires but I read (and got a little pointer from Ken at work) that a simple gas furnace didn't need more than two wires. Great! Diligently reading the new unit's manual it informed me that the plate to which all the wires were connected on the old thermostat would have labels not unlike that of the proteins in DNA -- individual letters that may or may not have anything to do with the wire colors. This was not the case. I'm pretty sure our circular thermostat was pre-standards and, along with the mercury, probably had a plutonium core that would explode if jostled the wrong way. Nevertheless, no wire labels could be found.

I searched the Internets for old manuals and anything that might help. I found one place that alluded to where I should plug the old wires in the new thermostat but it was contrary to what I thought. There was one red and white striped wire that I thought should go in the "R" slot on the new one and the other in the "W" slot. Obeying my Internets overlord I tried it their way and it didn't work. Once I switched things around and turned the power to the furnace back on the warm glowing warming glow of hot air issued forth from our vents and life was good again.

Thanks for reading all this and, although boring, I hope someone searching the Internets out there will someday find this bit of advice useful -- I sure know I would've.

posted Nov 3, 2005 under home improvement, honeywell, mercury disposal, thermostat  


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