As above, is it an easy DIY job to do this safely?

In my research into the above it has become apparant that I should consider replacing the old thermostat with a programmable one for energy savings. How does a programmable thermostat produce savings? I assumed the whole point of the thermostat in the first place was that the heating wouldn't be on if it was below the desired level anyway.

  • It is pretty simple. Likely you have only one or two low voltage wires in there. If you are not connecting AC, etc then all you need to do is follow simple instructions hooking it up. Likely installing the new one is easier than learning how to program it.
    – Tim
    Oct 16 '10 at 23:52

To answer the first question:

Replacing the thermostat is equivalent to changing a light switch.

You need to turn the power to the central heating off before you start work.

Unscrew the old thermostat, disconnect and then reconnect the new one. What you will need to make sure before you do this is that the new thermostat has the same terminals as the old.

Do you have a particular thermostat in mind? If so can you provide a link, then we'll be able answer the second question more easily.

  • Thanks for the response. I don't - but I think it would make sense for it to be the same brand as the old one, which is a Honeywell. I was just going to check eBay for the cheapest to be honest.
    – bcmcfc
    Sep 16 '10 at 8:56
  • @bcmcfc - it doesn't have to be the same brand, sorry I gave that impression.
    – ChrisF
    Sep 16 '10 at 8:59
  • To be fair you didn't really give that impression, I was just (wrongly) assuming that the same brand would help with compatability.
    – bcmcfc
    Sep 16 '10 at 10:05
  • Isn't a thermostat low-voltage? Why would you need to kill the power to the furnace? (I certainly didn't when I replaced my thermostat...)
    – Hank
    Dec 20 '12 at 16:22

Replacing a thermostat is trivial, and similar to changing a light switch. Disconnect the two wires coming from the furnace/boiler, then reconnect them to the new thermostat. Turn off power to the furnace/boiler first.

A programmable thermostat saves fuel and money because it can be programmed to lower the temperature when you sleep or are at work.

It doesn't matter which brand you pick, but most of them have horrible user interfaces, worse than old VCRs and clock radios.

  • 1
    LOL +1 for the comparison to old VCR's ... but you're right ... unless you're willing to shell out big money for the "Mercedes" of thermostats you have to slug your way through programming it. It won't kill you but it leaves you shaking your head for a while asking "why did they do it this way?".
    – user45
    Sep 16 '10 at 11:17
  • I've found the programming to be so horrible on the new thermostats that I recommend people keep the old dial ones and just manually turn it up/down to achieve the same energy savings. Actually works better because the programmable models are schedule based, not occupancy based... Unless you always leave the house/sleep/whatever at exactly the same time, you end up having to override on a regular basis anyways. Sep 16 '10 at 12:46
  • And right on cue: iPod Godfather Tony Fadell just announced his new startup Nest, which aims to bring Apple-level design and coolness to thermostats. Oct 25 '11 at 12:26

To lend support to ChrisF ... it's very easy to change your thermostat. Every place I've lived in has had the old mercury trip thermostat, wildly inaccurate. I just went to my local home depot and for about $25 I picked up a nice programmable digital thermostat. Was a snap to replace and works prefectly !!


Like other answers indicate, this is pretty simple, and a great idea if you're going from a manual to programmable thermostat. I can't comment yet, but thought it important to point out that there are (at least) two different types of thermostats. Some work for forced-air furnaces, and others work for radiators. Make sure you get the right kind.

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