Forced Air Furnace not reaching thermostat setting

[shep999]

My Amama 115,000 btu forced air system (1987) with White-Rodgers controller is not reaching its thermostat setting. My thermostat is a Honeywell set-back model. The furnace has a particular problem in the morning to raise the temperature from the low temperature that is used at night.

1. Thermostat calls for heat.
2. Induced Draft motor starts
3. Furnace makes a clicking noise and ignitor turns on
4. Blower turns on.
5. High temperature limit turns off burners (after 4 minutes)
6. Ignitor turns on
7. Gas lights and stays on for about (4 minutes)
8. Furnace turns off without reaching thermostat setting

I can shut the power off to reset the furnace and it will light off again for about 15 minutes again. I have changed the Flame senor to be sure that it is not causing the problem.

Is there anything anyone has to offer on what might be tripping the furnace?

[shep999]

My Amana 115,000 btu forced air system (1987) with White-Rodgers controller is not reaching its thermostat setting. My thermostat is a Honeywell set-back model. The furnace has a particular problem in the morning to raise the temperature from the low temperature that is used at night.

1. Thermostat calls for heat.
2. Induced Draft motor starts
3. Furnace makes a clicking noise and ignitor turns on
4. Blower turns on.
5. High temperature limit turns off burners (after 4 minutes)
6. Ignitor turns on
7. Gas lights and stays on for about (4 minutes)
8. Furnace turns off without reaching thermostat setting

I can shut the power off to reset the furnace and it will light off again for about 15 minutes again. I have changed the Flame senor to be sure that it is not causing the problem.

Is there anything anyone has to offer on what might be tripping the furnace?

[Joseph Meehan]

Get the instructions for the thermostat out and take a look for anything a bout an anticipator. It may not be set properly for your furnace.

The other idea that comes to mind is that a high heat sensor on the furnace is kicking in for some reason.

[shep999]

Joe, Two excellent suggestions. The thermostat is an older model that has "adaptive setting" that is disengaged. Do you know where the high heat sensor might be located? Is it part of the temperature fan controller?

Thanks,

[trader4]

How do you know it's the high limit that's turning off the furnace? If it is, then that would indicate either there isn't sufficient air flow, or the high limit switch is cutting off the furnace at a normal operating temp.

It's also easy to rule out if this has anything to do with the thermostat. Set the thermostat way higher than room temp and if the furnace still cuts off the same way instead of running, it;s not the thermostat.

[shep999]

.

[58plumbers]

The limiters might be shutting it down due to decreased air flow either in the combustion air flow or the blower air flow. Often there is gunk in the combustion motor housing which you can clean with a pipe cleaner. Or harder to fix is gunk in the heater core itself which requires a professional take down.

[Zyp]

Shep;

Sounds like a dirty air filter or the cooling coil is blocked from a build up of material [dirt.] A high limit control trip is a clear sign that there's an airflow problem. Make sure the filter is clean, all the supply registers are open and you can "feel" air flow when the unit runs the fan. If not, look at the duct or the evaporator coil for a blockage.

[Joseph Meehan]

Sorry if this is a duplicate. Please let me know if it is, it appears it did not make it the first time.