Stack limit
1. Dirty heat exchanger
2. Incorrect “Stack limit setpoint”
1. Inspect and if required clean the combustion chamber and/or heat exchanger.
2. Unless installed in Canada with PVC exhaust venting, set “Stack limit setpoint” to maximum setting of 220ºF (104ºC). In Canada PVC exhaust venting is limited to 149ºF (65ºC).