Chris, last year I replaced the same kind of round mercury thermostat
with a battery powered digital one. I am a total home-repair newbie,
and it was a very simple job.

I just bought one that said on the box it worked with my type of
furnace (gas forced air) and followed the directions. It's a Honeywell
model and came with little stickers for labeling each wire as I
disconnected each from the old thermostat, so there was no problem
getting them matched to the right terminal in the new one. The
directions even had handy hints, like wrapping the wires around a
pencil so they wouldn't accidentally fall back into the wall. The
hardest part of the job was screwing in the teensy screws on the new
terminals.

Jo Ann

DrMega wrote:
Hello group. I had a typical round mercury wall thermostat until a
drunk guy (no, not me :-) shoulder-planted into it and busted off the
dial. I'm thinking of replacing it with a battery-powered digital model
and a preliminary Internet search indicated it should be a pretty
simple two-wire job. But after reading some posts in here I'm a little
more concerned (I'm a fairly new homeowner and not super handy).
Questions a

- Do I need to cut the power to the gas boiler, the hallway, or both?
- I'm totally lost with voltage compatability issues - how do I
determine this?
- If I totally screw this up, how will I know (other than the
thermostat not working at all)?

Any help and advice will be greatly appreciated. Thanks in advance.

- Chris, home repair newbie