Lennox SLP98UHV Error Code E 110: Low Line Voltage
What Does Code E 110 Mean?
Error code E110 on the Lennox SLP98UHV means the incoming line voltage is lower than the unit's nameplate rating. The SureLight control continuously monitors the 120V supply and flags this error when the voltage drops below its acceptable threshold.
Low line voltage can come from the utility side — a brownout, where the power company delivers reduced voltage during peak demand — or from the home's own wiring: an undersized circuit, a loose connection at the breaker panel, corroded conductors, or too many loads sharing the furnace circuit. E110 belongs to the power-quality family alongside E113 (line voltage too high) and E114 (line frequency not 60 Hz); these three watch the 120V line, while E115 watches the separate 24V transformer secondary.
Running the furnace on low voltage can overheat and damage the variable-speed motors and the control board, and can make the board behave erratically. An electrician should measure the voltage at the furnace disconnect and at the main panel to determine whether the shortfall is on the utility side or inside the home's wiring.
What You'll Notice
- E 110 shown on the furnace control's 7-segment display
- The furnace cuts out, will not start, or restarts on its own during the fault
- Lights flicker or dim elsewhere in the home, suggesting a broader voltage problem
- The code tends to appear during periods of high neighborhood electrical demand or during a brownout
- Other electronics or appliances in the home also act sluggish or reset
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Utility power supply issue or brownout condition | Most common | ✗ Call a pro → |
| Undersized or overloaded electrical circuit | Common | ✗ Call a pro → |
How This Is Diagnosed
Because E110 is a supply-quality fault, a technician or electrician measures the actual voltage rather than replacing furnace parts. Voltage is read at the furnace disconnect while the unit tries to run, then compared to the nameplate rating to confirm it is genuinely low.
The reading is then taken at the main electrical panel. If the panel voltage is also low, the problem is upstream on the utility service and the power company is involved. If the panel is normal but the furnace circuit reads low, the technician looks for an undersized or overloaded circuit, a loose lug, or corroded connections between the panel and the furnace.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace's electrical supply voltage needs to be measured by an electrician
- Lights dim or flicker in the home along with the code
- E110 appears during periods of high neighborhood electrical demand
- The furnace circuit breaker or supply wiring needs professional inspection
Frequently Asked Questions
Is E110 the furnace's fault or the power company's?
E110 only reports that the voltage reaching the furnace is low; it does not say why. Measuring at both the furnace and the main panel is what distinguishes a utility-side brownout from a wiring problem inside the home.
Is it safe to keep running the furnace with E110?
It is not ideal. Sustained low voltage can overheat and shorten the life of the blower motor and control board, so the supply issue should be corrected rather than ignored.
The code cleared by itself — do I still need it looked at?
If it was a passing brownout it may not recur, but repeated low-voltage events point to a wiring or utility problem worth diagnosing before it damages the electronics.
✓ Verified against manufacturer service manual — March 2026