A111_F: One-Hour Lockout: Main Limit/HALC Switch
Status
This is a critical fault. The furnace will not operate in
gas heat modes but all other modes (e.g. cooling) should function.
Description
Alarm "A022_F Main Limit/HALC Switch Open"
and "A111_F One-hour Lockout: Main Limit/HALC Switch" is
logged if the main limit/HALC trips for longer than 150 seconds four times in a
single heat call.
Expected Operation
The limit circuit is monitored during gas heating (including
defrost) and post-purge. If the main limit/HALC trips, control logs "T022_F
Main Limit/HALC Switch Open", shuts off the inducer and gas valves,
and runs the blower at the highest heat speed.
If the limit remains tripped for more than 150 seconds,
alert “T022_F Main Limit/HALC Switch Open” is elevated to an alarm
"A022_F Main Limit/HALC Switch Open". Blower will run at the
highest heat speed. Alarm “A061_F Blower Fault - Motor Cannot Run” is
also logged at this point. Upon reclosing of the limit, the control will clear
alarm "A022_F Main Limit/HALC Switch Open" and transition
to blower off delay without any need for inducer to go through post-purge.
The control then enters a 1-hour soft lockout. Alarms "A111_F One-hour
Lockout: Main Limit/HALC Switch" and "A061_F Blower Fault -
Motor Cannot Run" are declared throughout the duration of the lockout.
After the lockout period expires, both alarms are cleared and normal operation
resumes.
Cause
1. No airflow
2. Insufficient airflow
3. Faulty Limit Control
4. Loose or Faulty Wiring
5. Dead (non-functional) blower
6. Input too high
Solution
1. Check for proper blower operation. Is the blower turning
during heat (or any other) mode? If not, a blower motor fault may also be
present. Check the wiring to the motor then check the motor. It may need
replacing.
2. Check duct work and filters. Determine the static
pressure and make sure it is not above the published values for the furnace.
Check the rate and outlet air temperature for high and low heat using a jumper
wire between R and W/W1 respectively. Compare them to the nameplate maximum
values and adjust if necessary. If a supply air sensor is used cycle power to
the furnace.
3. Replace the faulty limit control.
4. Check wiring and connections. Replace and/or repair as
necessary.
5. Insure properly sized burner orifices are installed.
Check the manifold pressure at high fire and compare to the nameplate values.
Adjust as needed.
6. Input too high, adjust as needed.
