Furnace or Tstat?

[~Shado~]

Hey all,
Have an issue and at a loss how to solve.This is in my home and not in my area of expertice. Mod's, please move if in wrong area, not sure where to post this.

I have a Carrier furnace and TStat. For the last year it has worked fine except with the oddity of the TStat screen going blank when it is heating the home.

Since Thursday, it started allowing a 4-6 degree drop in temp before kicking on, then it wont heat above 69 degrees (normal temp set for 72) unless I turn off/on the toggle disco at furnace, then heat runs cycle. I pulled stat cable and checked continuity...good, then reconnected and bypassed tstat....furnace comes on, same with fan (no AC in home). So, I figured the stat was bad and bought new one.

Problem is old stat had terminal for common wire, but new one doesn't(Honeywell, can't find a Carrier one locally as of yet). Called Honeywell and they said isn't required. Yet it wont function the furnace (big help). Returned and got different one, same issue.

I reinstalled old stat and am having to do the ol disco trick to keep heat in home (daughter is worried about her pet Beta fish).

I haven't worked in months and living on savings, so can't call HVAC tech out to fix. Is this something specific with Carrier brand? Not accepting other brand TStats? Am I missing something or overlooked?

Thanks....

 

[DaveTap]

Hey all,
Problem is old stat had terminal for common wire, but new one doesn't(Honeywell, can't find a Carrier one locally as of yet).

Called Honeywell and they said isn't required. Yet it wont function the furnace (big help). Returned and got different one, same issue.

Honeywell is correct there isn't a need for a common wire in a t-stat (unless its an older one that required it for charging a battery or display).

Think of T-stat as a switch (or group of switches)
Red is power from transformer (hot)
White turns on heat relay and/or gas valve of furnace,
Green turns on fan relay
Yellow turns on air conditioner contactor (outside)

If there is a common its usually a blue wire (just because its the only color left in 5-wire t-stat cable) going back to the other side of the transformer. But is not needed in most thermostats.

Normally the only exterior connection to "common" is the return from the air conditioning relay outside.

 

[aline]

Try cleaning or replacing the flame detector. It's called a "Flame Proving Electrode (FSE)" on my furnace schematic.
If the furnace quits detecting the presence of the flame I think it shuts down and goes into a fault condition. Toggling the power off and back on resets the fault.

The furnace may also have some led lights on it to indicate what the fault is.

It sounds like something is causing it to go into fault mode and that is why you have to toggle the power to get it to reset.

 

[~Shado~]

O....Thanks wise ones...:smile:

I replaced the tstat and vaccumed out the furnace. Turned on and ...thought I was saved.

After it ran, I now see a code 13....Limit Circuit Lockout....
Is this something I can fix or am I going to have to bust into the bills budget and bring someone out? This is so disappointing.......

Thanks again....

edit...Carrier furnace - 58STA110
Carrier TStat (old one) - CCBAC01-B
Honeywell Tstat (new one) - RTH110B

 

[alfiesauce]

Seems like that code 13 is telling you that the furnace believes that the air exchanger is getting to hot which would usually be caused by a lack of air flow across the exchanger when it's up to temp.

Does your t-stat have a fan- on/auto switch? If so switch it to on and make sure your fan is running.

The common point on a tstat should only be needed to allow you to run the thermostat without the need of batteries.
Have you tried running the unit with just the R and W connected? Those two wires are the only two you need for heating to function properly.
G = Manual fan
Y = Cooling
C = 24V between R and C (the points that will give you the no need for a battery in your thermostat ability)

 

[alfiesauce]

make sure the fan that is running is the main air handling fan and not just the fan that pushes the exhaust up the chiminey.

 

[~Shado~]

WOO HOO!!!!

I have heat!!!

I went back in and recleaned everything with a lil paint brush, and cranked her on.

Yep alfiesauce I think that might have been one of the probs....when I turn her back on, the blower started up 1st and ran for about a minute or so, then clicked off. About 10 min later all started up as supposed to...and no LED saying its unhappy!!

Thats what kept me going nuts...I knew a stat is just a switch, but couldn't get my head around no return on the common....
Control stuff....mad headache....I dont even like messing with electrical on my vehicles.

I should take some classes on this and get knowledgable so I don't get so panicked and upset when I run across these things........

Thanks again oh wise ones...I humbly bow before you...

 

[LarryFine]

I should take some classes on this and get knowledgable ........

You just did. :smile: