You just shut off all the ducts to the rest of the house and put a thermost at in there, connected right in parallel with the existing one. Set the oth er one all the way down. If you live in an area where is goes significantly below freezing you want that other one to be there to keep your pipes from freezing.
I mean in that one room you might have it heated up but the rest of the hou se, wherever there is plumbing, can't go much below freezing or the pipes w ill burst.
Why are you doping this ? Financial setback of some sort ? Just curious her e because I know these are tough times.
Natural gas will probably have a millivolt gas valve.
Google for "zone thermostat" (more correctly dual zone thermostat or multi zone thermostat): Google finds quite a few articles on how they work and how to convert your existing system. Hopefully, your existing ducting will support zone dampers.
For sensors, you just use a modern wall thermostat such as:
Just about everything decent includes wi-fi operation. However, you don't have to use wi-fi. You can connect to the central controller with wires.
Kinda sounds like you want to do it yourself. I suggest you discuss this with someone in the HVAC business, as there may be some things you've missed. If the system is old enough to have a mercury switch thermostat, I suspect that the ducting will need vacuuming, the furnace might need an upgrade, and the flue pipe might need cleaning.
Jeff Liebermann email@example.com
150 Felker St #D http://www.LearnByDestroying.com
All room have ducts feeding its room's louvered vent.
One thermostat in the living room (the wrong room).
I want a thermostat that will control the temperature in my one room independent of all other rooms. My room will be warmer than all other rooms.
I do not want to waste energy heating rooms I am not in.
I live in a three bedroom house. Two bedrooms have their louvers closed tight and do not need to be adjustable.
The living room and dining room are all one big area and each has one heater louvered vent. That area may seldom want to be heated.
I generally keep the living room and dining room open to the outside air except on exceptionally cold days. The two bedrooms doors are usually closed except for the occasional air out. I air out my room daily.
That means that his entire house will (tend to) seek the temperature of the warmest thermostat setting. He doesn't want to push BTU's into parts of the house that he's not using (or, that he has intentionally opened to the out-of-doors!).
Then he ends up with the *coolest* thermostat setting controlling it all.
He has to address the "supply issue"; some way of arranging for BTUs to only be distributed to the places he wants them. Then, he can deal with WHEN he wants them (in each place).
I think he's going to find retroactively try8ing to fit a multizone control to a facility/plant not initially designed with that in mind (esp when one of the zones is JUST a single room) will yield dubious results.
Put a space-heater beside your easy chair while you're watching TV... (or, wear a sweat shirt)
The *only* way to not heat the entire house is to not heat the entire house. Forced air systems require vents or dampers to be closed to cut off heat from rooms. That's a bit of a PITA if you are moving around during the day.
I have a large single living space with bedrooms and bathrooms separated. I let the large room be heated, but at a low temperature. My bedroom has two vents because it has two windows. I have the window behind my bed covered with a 3/4 inch piece of Styrofoam insulation. I close the bedroom door and leave the two doors for the bathroom ajar. That leaves a path for the air to move but minimizes cold drafts when the heat is off. This arrangement keeps the bedroom several degrees warmer than the rest of the house and saves significantly on the heating bills I expect.
I'm not at all sure what the OP is looking for exactly. Something like I have done could give him some savings. To do more would mean shutting off the air flow to the rooms he is not in. This is either awkward if done manually or complicated and expensive if automated.
OK, then he needs zone dampers that can send the heat (presumably a hot air furnace system) to the required zones. You have to be careful to never restrict the airflow too much or it can damage the furnace's heat exchanger.