FieldBench
Lennox codes

Lennox

Excess OA

Protect

Excess outdoor air

Damper open past the commanded minimum with no economizer or DCV request.

Walk Excess OA in Diagnose

2 plates — walk the one on the cabinet

First check

1 Damper position vs command

On Lennox LGH look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Commanded position vs blade. Feedback saying 80% when the board asked 15% is actuator/linkage.

Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.

The rest of the walkthrough is Diagnose.

On the plates

  • Commanded position vs blade. Feedback saying 80% when the board asked 15% is actuator/linkage.
  • Barometric relief / power exhaust stuck open looks like excess OA at the space.
  • Unoccupied damper should go to the unoccupied minimum, often 0. A 24 V occupancy point stuck high holds min all night.

Plates that use Excess OA

Same number, other makers

Excess OA on Lennox is not the same code on these plates.