Have an old Honeywell thermostat (house is 17 years old). Wondering if I can replace it with a newer Digital or Programmable one?

Here are some pictures of it.

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  • But first, why? The vague fear that the nicely contained and protected mercury is going to leak out and poison you is far-fetched unless you adjust it with a hammer. The propaganda machine is in full swing, but there's very little substance there. Short of deliberate effort those capsules stay sealed. Unless you stick to simple programmables that uses batteries, you often need a wire upgrade between the thermostat and the Furnace or Boiler (and/or Air Conditioner) – Ecnerwal Feb 14 '18 at 3:24
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    @Ecnerwal I don't see fear of mercury leakage anywhere in this question. I see OP stating what he has a wanting digital programmable instead. Pretty reasonable. OP should maybe go one step further even ... to smart or internet connected – Tyson Feb 14 '18 at 3:30
  • They start to become inaccurate after awhile. Also it's kinda difficult to actually see what i've set the temp to. Im not worried about the mercury, nor does it even need to be programmable (even a digital one would be fine) – msmith1114 Feb 14 '18 at 3:31
  • yes, you can replace it would just about anything. The third wire is for the fan; it can be skipped if needed, (guaranteed compat w/ any thermostat) but most newer models support them out of the box. – dandavis Feb 14 '18 at 19:56
  • What type of equipment is the thermostat controlling (make and model)? – Tester101 Feb 15 '18 at 1:38

What your options for replacement are (easily) depends on what your wiring is.

I find it odd that you claim it's getting inaccurate, but perhaps they built them better 50 years ago than 20 - all the 50-60 year old ones I have work as good as new, but those are the "classic round" version. They actually are subtly adjustable if needed, though non-subtle attempts can screw them up. They are sidelined at the moment, but in reserve in case of need.

Anyway, for a two wire setup the easy digital/programmable solution is to get a digital/programmable that uses batteries - I have a couple of examples of these in my view between home and work, and the older one eats batteries a lot slower than the newer one.

The fancy/expensive/prone to becoming obsolete so you need a new expensive - "Smart" thermostats (or hacking portals into your house) generally require a wire upgrade to supply the power they want. I'm obviously not a fan, but many people do seem to love them. Some of those people are not living in your house...

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  • From the picture it looks like I have 3 wires? does that make things easier for me? – msmith1114 Feb 14 '18 at 4:24
  • If it's heat/cool, no, if it's heat only, probably. I could not tell if you had 2 or 3 wires in the wall, even though I can see three colors in the thermostat. – Ecnerwal Feb 14 '18 at 4:48
  • it controls heat and cooling. – msmith1114 Feb 14 '18 at 4:57

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