E4.2 Flame rollout switch open

What the control is telling you

A rollout switch on the burner box tripped, meaning flame escaped the heat exchanger inlet. Treat as a combustion/venting safety issue.

Applies to: Trane S8V2 only

Likely causes

• Wrong orifices (natural gas drill 45; LP drill 56 or per guide)
• Vent undersized, poorly pitched or blocked
• Burners dirty or misaligned
• Blocked or sooted heat exchanger
• Cracked heat exchanger

Test and repair steps

1. Warning: Do not reset rollout switches repeatedly without finding the cause - possible CO hazard.
2. Power off; check orifice size is correct for the fuel.
3. Check the flue is sized right and horizontal runs slope at least 1/4 in. per foot.
4. Remove, clean and refit the burners, then press the red reset on both rollout switches.
5. Run heat all burners should light within 5 seconds with tight flames into the heat exchanger.
6. If flames change when the blower starts or roll back, inspect the inducer, vent and heat exchanger for blockage; replace the heat exchanger if damaged.
7. Replace the rollout switch only if everything else is correct.

Settings for these units

Clearance to combustibles · Trane S8V2

24 in. front service access.

3 in. in front of the combustion air openings.

Return filter size by cabinet width · Trane S8V2

Filters are field supplied and mounted outside the cabinet.

Over 1600 CFM upflow: return on both sides, one side plus bottom, or bottom only.

Models that show this code

12 models in Trane S8V2

Other codes on the same units

• E3.3 2nd stage pressure switch (PS2) closed when it should be open
• E3.4 2nd stage pressure switch (PS2) open when it should be closed
• E4.0 Main high limit open
• E4.1 Reverse airflow limit open
• E05 Flame sensed when no flame should be present
• E6.1 120 V polarity reversed
• E6.2 Ground not detected
• E6.3 Igniter open or igniter relay fault