Lennox International
Lennox is the premium tier of the premium tier. The Lennox SLP98V furnace reaches 98.7% AFUE — the highest efficiency of any residential gas furnace on the US market. The iComfort communicating system is mature and well-integrated. And Lennox has built a strong contractor reputation for build quality and longevity.
The trade-off that every Lennox buyer should understand: Lennox is sold exclusively through its dealer network. Parts aren’t available at general HVAC supply houses — only through Lennox-authorized distributors. This affects how quickly a tech can get your system running again when something breaks.
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What Lennox makes
Lennox’s residential HVAC line runs three tiers:
Dave Lennox Signature Collection (SL/SLXV prefix) — Lennox’s highest tier. Variable-capacity modulating equipment, highest AFUE and SEER2 ratings, iComfort S30 communicating thermostat integration. The SLP98V furnace (98.7% AFUE), SLP98UH (two-stage), and XC21/XC25 ACs are the flagship products.
Elite series (XP/EL/XC prefix) — Lennox’s mid-tier. Two-stage furnaces (SL280V series), two-stage or single-stage cooling. Compatible with standard 24V thermostats. Well-engineered, solid reliability.
Merit series (ML/M prefix) — Lennox’s entry-level. Single-stage, 80% AFUE furnaces and single-stage ACs. This is Lennox’s builder-spec line. Even at entry-level, Lennox components are generally better-built than equivalent Goodman; the installed price reflects that.
Furnaces: SLP98V (98.7% AFUE, variable-capacity), SL280V (80% AFUE, two-stage), ML180 (80% AFUE, single-stage).
Central AC: SL28XCV (variable-capacity), XC21/XC16 (two-stage), ML14XC1 (single-stage, entry).
Heat pumps: XP21 (variable-capacity, cold-climate), XP16 (two-stage), ML14XP1 (single-stage).
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Is Lennox a good brand?
Lennox is the choice when you want the highest efficiency available, the most complete communicating system, and the brand preference of premium-tier HVAC contractors. It has tradeoffs that are worth understanding before you commit.
What buyers typically compare: AFUE (Lennox wins here), SEER2, iComfort integration, brand cache.
What actually differentiates Lennox:
Efficiency leadership. The SLP98V at 98.7% AFUE extracts more heat from the same quantity of gas than any competitor on the market. At current gas prices, the efficiency difference vs. a 96% AFUE competitor is meaningful in heating-heavy climates (the math is roughly 2.7% more gas used over a full heating season). (Verified against Lennox spec sheet and AFUE definition.)
iComfort communicating system maturity. Lennox’s iComfort S30 thermostat and the iComfort system has been in market longer than some competitors’ communicating systems. It provides reliable variable-capacity control, integrated diagnostics visible through the thermostat display, and historically strong software support.
Build quality at the premium tier. Most HVAC contractors who have serviced all major brands put Lennox near or at the top for heat exchanger and cabinet quality in the Signature Collection line. The SL280V and SLP98V have field reputations for longevity that support the brand premium.
The dealer-only trade-off. Lennox parts require ordering through Lennox distributors. In practice, this means:
- A tech without Lennox dealer status may not have your part in their van or at their local supply house
- Parts may require a day or two to arrive from a Lennox distributor vs. off-the-shelf at an open supply house
- Labor rates from Lennox dealers may be higher than non-branded contractors
This matters most for emergency service scenarios (weekend, holiday) and in markets with fewer Lennox dealers. In dense markets, Lennox dealers typically have good parts inventory and can be on-site quickly. In rural areas or markets with few Lennox dealers, this is a genuine limitation.
Merit series trade-off. At the Merit tier, you’re paying a Lennox premium for entry-level equipment. Parts are harder to source than Goodman/Rheem entry-level equivalents. Unless you specifically want to stay in the Lennox dealer ecosystem or the price difference is minimal, the Merit tier is the hardest to justify against competitors.
Bottom line: for the SLP98V or XC21 Signature Collection: Lennox is genuinely the premium choice if your dealer and local market support it. For Merit tier: the parts-availability trade-off is a real drawback. Do your homework on local Lennox dealer density before buying.
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Warranty
Lennox standard warranty with registration (within 60 days of installation):
| Component | Coverage (registered) |
|---|---|
| Heat exchanger | 20-year limited |
| Compressor (AC/heat pump) | 10-year limited |
| Parts | 10-year limited |
Without registration: limited warranty of varying terms — check Lennox terms page for your specific model.
Extended labor warranty is available through Lennox dealer networks in some markets.
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What a Lennox system costs (installed)
Data note: Cost ranges sourced from BidSmart regional bid data and US industry surveys. Lennox commands the highest installed prices among Tier-1 brands, particularly at the Signature Collection tier. Installed cost varies by region, equipment tier, and labor market — get 2–3 local quotes before budgeting.
| System type | Merit (entry) | Elite (mid) | Signature Collection |
|---|---|---|---|
| Gas furnace (replacement) | $3,500–5,000 | $5,500–8,000 | $8,000–12,000 |
| Central AC (replacement) | $4,500–6,500 | $6,500–9,500 | $9,500–15,000 |
| Heat pump (replacement) | $5,500–7,500 | $7,500–11,000 | $11,000–18,000 |
| Full HVAC (furnace + AC) | $8,500–12,500 | $13,000–19,000 | $19,000–28,000+ |
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How to find your Lennox’s age
Lennox serial numbers on most post-2001 units encode the manufacture date in the first 4 digits:
Format: YYWWXXXXXX (first 2 = year, next 2 = week)
- Example:
2142XXXXXX= year 2021, week 42 (October 2021)
Some older Lennox units and units manufactured at specific facilities use different encoding. If this doesn’t match your serial format, call Lennox at 1-800-953-6669 with the full serial and model number.
Record the decoded date — along with the model number, warranty, and service history — in HomeDoc. It keeps everything in one place when you need a service quote or are deciding whether to repair or replace.
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Lennox furnace fault codes
Lennox fault codes depend on the system type:
Standard (non-iComfort) furnaces: single LED flash code on the control board. The door label is the T0 source for your specific board. Some older Lennox furnaces have limit switches that do not automatically reset — if the limit trips, the furnace locks out and requires manual reset (typically a power cycle or a reset button on the switch itself).
iComfort-enabled Lennox furnaces: fault history visible through the iComfort thermostat — Menu → Settings → System Diagnostics. The thermostat logs recent fault events with codes.
→ See Lennox Furnace Fault Codes for the complete guide.
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Common Lennox system problems
- Furnace trips high-limit or short cycles: filter first — Furnace Blowing Cold Air; HVAC Short Cycling
- Limit switch won’t auto-reset (older Lennox): manual reset required after addressing airflow — Lennox Fault Codes
- AC not cooling: AC Not Cooling
- iComfort thermostat showing fault: → Lennox Fault Codes
- Outdoor fan won’t start: capacitor — Capacitor Guide
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Thermostat compatibility
Lennox Merit and Elite series furnaces and ACs use standard 24V wiring. Compatible with any thermostat (ecobee, Nest, Honeywell, Sensi, etc.).
Lennox Signature Collection (iComfort-enabled): the SLP98V and XC21/XP21 are iComfort-communicating. For full variable-capacity modulation, pair with:
- Lennox iComfort S30 (native communicating thermostat)
- Lennox iComfort E30 (mid-tier communicating thermostat)
Standard 24V thermostats work but force two-stage operation — you lose variable-capacity modulation. For an iComfort-enabled system, use an iComfort thermostat to get what you paid for.
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Lennox vs. other brands
Lennox vs. Carrier: Lennox leads on AFUE (SLP98V 98.7% vs. Carrier’s top at ~98%); Carrier’s INFINITY has broader distribution and parts availability. For most markets, the choice comes down to dealer preference and specific quote.
Lennox vs. Trane: both are mature premium products. Lennox’s efficiency edge at the Signature Collection tier; Trane’s comfort if parts availability is a concern. Trane XR/XB are more contractor-accessible.
Lennox vs. Goodman/Rheem: fundamentally different market tiers. The Merit-tier Lennox vs. Prestige Rheem comparison is where Lennox’s dealer-only limitation is most costly — the premium doesn’t pay off as clearly at the entry tier.
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Buying guides and cost
- How Much Does a New Furnace Cost? — installed cost ranges for Lennox models by tier, including the dealer-channel markup typical of Lennox installs
- Best Furnace Brands — where Lennox ranks against Carrier, Trane, Goodman, and Rheem across price tiers
- Furnace Repair vs. Replace — if your Lennox furnace needs a major repair, how to decide whether it’s worth fixing (Lennox’s dealer-only parts network affects the repair calculus)
- IRA Tax Credits for HVAC Equipment — if you’re replacing with a qualifying heat pump or high-efficiency furnace, federal credits of up to $2,000 may apply
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