Trane
Limit
ProtectOpen limit
Overtemp / airflow. 80% coils still dirty.
Walk Limit in Diagnose
9 plates — walk the one on the cabinet
First check
1 Airflow before you touch the limit
On Trane S8B1 a limit is airflow or overfire until proven otherwise. Do not replace the limit first. Filter, blower wheel, A-coil, and the heat-speed setting for THIS motor (tap, model plug, or communicating CFM — not a sister SKU chart). Filter, A-coil on top, blower tap/speed.
Expect: Rise in the rating-plate window. Static vs this cabinet’s blower chart.
The rest of the walkthrough is Diagnose.
On the plates
- Heat tap vs rise range on the S9X2 chart — not the S9V2 menu.
- Filter, coil, return, wheel.
- Rollout is a different switch — inspect exchanger before you reset.
- Heat tap / PSC speed vs rise. Filter, coil, return.
- There is no ‘high-fire rise’ — it is one fire rate.
- Filter, A-coil on top, blower tap/speed.
- Closed supply or a winter-sealed return. Rise vs plate.
- Rollout: exchanger / burners / flue. Manual reset.
Plates that use Limit
Same number, other makers
Limit on Trane is not the same code on these plates.