Lennox SLP98UHV Error Code E 313: Indoor or Outdoor Unit Capacity Mismatch
What Does Code E 313 Mean?
On the SLP98UHV, E 313 is a commissioning-time warning that the capacity code entered for the indoor furnace does not correspond to the capacity code entered for the outdoor unit (the air conditioner or heat pump). It is raised by the SureLight control while a technician is working through Commissioning.
Crucially, this is only a warning — system operation is not impacted at all. The furnace and outdoor unit keep running normally, and the alarm clears automatically the moment Commissioning mode is exited. It exists to prompt the installer to double-check that the entered capacity codes reflect the equipment actually installed.
If the codes are genuinely mismatched — for example, a configuration left over after one unit was replaced — a technician updates the setting to the correct pairing. In many cases the equipment is properly matched and only the entered code needs to be corrected.
What You'll Notice
- The 7-segment display reads E 313 while the technician is in Commissioning mode, flagged as a warning only.
- Heating and cooling continue to operate completely normally despite the code being present.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Indoor and outdoor unit capacity codes don't match in system configuration | Most common | — |
How This Is Diagnosed
A technician confirms this is only a configuration warning by comparing the programmed indoor and outdoor capacity codes against the installation instructions during Commissioning. Because the alarm clears automatically when Commissioning is exited and does not affect operation, the task is to verify the codes match the actual equipment rather than to repair a failure.
- Your indoor or outdoor unit was recently replaced and you want the capacity codes corrected at the next visit
- You are unsure whether the indoor furnace and outdoor unit are properly matched
Frequently Asked Questions
Is E 313 a serious error?
No. On the SLP98UHV it is a commissioning-time configuration warning that the indoor and outdoor capacity codes do not match. It does not affect operation and clears when Commissioning mode is exited.
Will E 313 stop my furnace from working?
No. The system runs normally with this warning present. It is a reminder to verify the capacity codes, not a fault that disables heating or cooling.
How is E 313 fixed?
A technician confirms the correct indoor and outdoor capacity codes against the installation instructions and updates the configuration if needed. Often the equipment is fine and only the entered code needs correcting.
✓ Verified against manufacturer service manual — March 2026