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klayland 10-10-2011 11:09 PM

New Thermostat tripping breaker
I just replaced an old Ritetemp 6008 thermostat that wasn't keeping the temperature very constant with a new Honeywell RTH2410 programmable thermostat. Ever since I installed the new thermostat the furnace breaker will trip after the heat has been running for a little while. I can't pinpoint what makes it trip the breaker/ I've seen it cycle on and off without problem but every night I wake up cold and see that the breaker is tripped.

The old rite temp had two incoming wires:
Red Wire - Rh
White Wire - W
And a jumper between the Rh and the Rc. (We don't have a cooling unit, just the furnace).

The new Honeywell didn't have Rh and Rc, just an R terminal so I wired it:
Red Wire - R
White Wire - W/Aux

Any ideas as to what might be causing this to trip? It never happened with the old thermostat so I don't think there is a problem with the wiring at the furnace. Thanks in advance for any suggestions - I've perused the forums before, but this is the first time I've not been able to find an answer from another question so this is my first post.

Houston204 10-10-2011 11:17 PM

Do you have gas or electric heat?

REP 10-11-2011 12:36 AM

Some thoughts,
One is the red and white wires are low voltage and you breaker is line voltage.I would be checking the amp draw on the blower motor or anything else that is line voltage.
Two, red to R and white to W is correct so that is not your problem.
Not likely but check your filter.
If you have a humidifier make sure its not leaking on the line voltage.Or some other leak outside the furnace leaking on anything line voltage.
Lets also check and make sure the breaker isn't weak and needs replacing.

biggles 10-11-2011 10:52 AM

pop the CB panel check the breaker wires going into the furnace power breaker remove the stat from the subbase and jump R to W to get a soild run see if it trips...the motor is the load there maybe short cycling fan with new stat jump will tell if it is if you get a solid no trip run.check the booklet for the new stat see if you have a fan delay or warm up or short cycle whatever there calling it this week...might need an adjustment.when that fan starts it is 10X the rated amps for a milli seconf and the breaker heats up a quick restart will trip it.but as said your stat has nothing voltagewise to do with the power and breaker excet for a fan cycle:wink:

klayland 10-11-2011 03:40 PM

Thanks for the replies.

I've got an electric furnace, no humidifier, and I just changed the filter when we moved in a couple months ago, but I'll double check it. The only special thing the thermostat is supposed to do is start early so that you reach your selected temperature at the time you selected for the program. Other than that, no fan delay or anything fancy.

I'm definitely a beginner when it comes to wiring so it might take me a while to try out all of the suggestions, but I'll let you know if anything seems to work.

biggles 10-11-2011 03:51 PM

so you have resistance heater strips like a giant toaster and that is some load on that breaker forget the motor...might be cycling on a hi limit which again gets back to tht 10X draw on the braeker....check the terminals on the strips for tightness..if i'm right on the electric furnace no gas right:huh:

Master of Cold 10-11-2011 04:23 PM

Make sure the stat is set to electric heat-(stat controls furnace fan).

klayland 10-12-2011 04:19 PM

OK so last night I did a little more tinkering. I checked all the connections on the terminal and they are all secure. I double checked the thermostat and the jumpers are all set for controlling an electric fan (although I don't think this should matter since I didn't hook a wire up to the G terminal for the fan).

There are two breakers for the furnace, and from the wiring diagram it looked like the fan motor and two of the heating elements and their controls are on one breaker and the other two heating elements and their controls are on the other breaker. The breaker that keeps tripping is the one with the motor on it - I'm going to try and run the motor tonight on it's own without switching the heating elements on to see if that trips the breaker too - that would narrow it down to something with the motor, but we'll see what happens.

biggles 10-12-2011 04:32 PM

even better put the motor on the breaker with the heat that isn't tripping....sounds like a weak breaker on the tripping one... lets see:wink:

klayland 10-15-2011 06:30 PM

Just got a multimeter today and it appears that both breakers are fine - so that's not it. Still searching....

Master of Cold 10-15-2011 08:08 PM

Does this meter have an amp clamp?

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