Setpoints and related data
- Heat limit switch lockout (LimitLO)
- Heat limit 2 switch lockout (Lim2LO)
- Heat limit 3 switch lockout (Lim3LO)
- Reset lockouts (ResetLO)
Inputs
The input for limit is 24VAC monitoring at the limit input on the UCB (Limit, Lim2, Lim3).
Outputs
The output for limit is the output relay for fan and heat stages.
Operation
When the UCB senses 0 VAC at the limit switch input, it energizes the indoor blower relay and it performs the fan delay off when the limit returns to normal and senses 24 VAC.
If the limit trips while in a fan minimum off time, the UCB immediately energizes the indoor blower relay ignoring the fan minimum off time.
The UCB logs the first incident and tracks the runtime. If the limit switch opens three times within one hour of run time, it flags an alarm and lock on the indoor blower relay and disables heating.