Honeywell RTH6360 JUST INSTALLED. Heat won't turn off when reach temp or when set to off.

SOURCE: honeywell round mercury thermostat - heat not coming on

If you tip the mercury switch so that it makes contact and the furnace doesn't start, it isn't the t-stat. Check the connections, then start checking the furnace.
In any case, ditch the mercury t-stat (recycle it properly) and get a new programmable one if at all posible. It will pay for itself many times over by turning your heat down in the middle of the night and back up by morning.

SOURCE: honeywell rth230b won't shut off heat

Sounds like a relay sticking. Possibly in the thermostat or possibly the furnace relay at the furnace. The next time it happens, unplug the thermostat from the wall. If the furnace still runs then it's the furnace relay.

Hope that helps...

Geno

SOURCE: heat pump auxiliary heat does not turn on

Turn up your outside thermostat in the outside unit.
You should have about 3 degrees difference in one stage to the next. So I would change the thermosat with one that has three stages of heat.

SOURCE: my honeywell central heating system turns off on

Hi, Just to let you know I have repaired central Heat & Air systems for 33 years and Have seen this problem on many occasions. Lets see if I can save you so many trips.It says you have a programmable stat? On this stat and on a mechanical stat, they have what is called a heat anticipator that controls how many and how often your thermostat turns you're unit off and on and how long it cycles after the stat is satisfied. If you have ever seen under the cover of a mechanical stat, ( mercury switch type) you will see a dial with an arrow with numbers as .1, .3, .4 1.0, or .15 to 1.0 amps.Some are fixed and some are adjustable. On a digital stat, you will have to get into the program and see what the heat anticipator is set on. They come from the factory at .4, but to really find out what you'res should be it takes an amprobe to do this. The setting you need is what you're gas valve requires.I am sure I have lost you, but I am just giving you a little food for thought. If you can get into you're program and set this to .4, great. If the problem continues, your anticipator on this stat is more than likely, shorted, which would require you to buy a new stat.With a shorted anticipator, it will seem to be working like you say, but when satisfied, the temp.keeps falling until you reset power, then it fires and repeats this. Change the stat. If this is central heat and air, just follow red-rc which will have a red jumper to rh for heat, white to w, green to g=fan, and yellow or blue to y = cooling. If you have central heat only, you will find 2 wires red and white.Red to rh with jumper still installed to rc and then white to w.This is quite a long explanation, but I wanted you to know a little more then the next guy about your stat. Please let me know.
Sincerely,
Shastalaker7

SOURCE: Furnace cuts off before reaching set temp.

You can make sure it is not the thermostat by crossing or jumping the R and W terminals (or associated wires) together. This will keep the furnace calling for heat. As it is approaching set temperature, get in front of the furnace and inspect the air filter to make sure it is clean, watch the control module for any error codes that may be turning off the system prematurely.

On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the igniter does not energize (bad control, bad igniter), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not light (dirty pilot), the burner does not light (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).