Lennox SLP98UHV Error Code E 313: Indoor or Outdoor Unit Capacity Mismatch
What Does Code E 313 Mean?
Error code E313 on the Lennox SLP98UHV is a configuration warning indicating that the capacity codes for the indoor furnace and outdoor unit (air conditioner or heat pump) are mismatched. This code appears during the commissioning process when the system detects the programmed indoor and outdoor unit sizes don't correspond.
Importantly, this is just a warning — system operation is not impacted at all. The furnace and air conditioner will continue to run normally. The alarm clears automatically when the commissioning mode is exited. It serves as a reminder to the installer or technician that the capacity codes should be verified.
If the capacity codes are genuinely mismatched (for example, a 3-ton furnace paired with a 2-ton air conditioner), a technician can update the configuration to reflect the correct pairing. In many cases, the mismatch is simply a configuration entry that was not updated after equipment was installed.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Indoor and outdoor unit capacity codes don't match in system configuration | Most common | — |
- You want the configuration codes corrected during a routine maintenance visit
- Your indoor and outdoor units were recently replaced and the code appeared
- You are unsure whether the indoor and outdoor units are properly matched
✓ Verified against manufacturer service manual — March 2026