Replacing a Lennox Rooftop Unit: Curb Compatibility Guide

By Taylor Metals — SMARTCurb Engineering  ·  Updated August 24, 2026  ·  4 min read

75 verified Lennox RTU curb footprints, five current product lines, and the much larger legacy CHA/GCS reality most contractors actually run into on an older roof.

What SMARTCurb has on file for Lennox

SMARTCurb has verified curb geometry for 75 Lennox rooftop-unit models, spanning small packaged units up through large commercial platforms. Every one has a page with its overall curb footprint and a fabrication-ready adapter path — browse the full list on the Lennox hub.

Lennox's current lines, at a glance

Five current product lines cover most of what Lennox sells new today. L Series (LC/LCA/LCC-prefixed models) is the long-running packaged line, still sold alongside its own legacy variants at 3–25 ton. Raider covers packaged heat pumps, including the ZHB-prefixed models. Strategos (SCC-prefixed) covers 3–24 ton packaged units, including a 20–24 ton tier on file at 115.125″ × 86.125″.

Enlight and Xion both use the same A/B/C cabinet-box sizing convention, which is worth understanding once rather than per-model: an A-box covers roughly 3–6 ton on a curb around 79.75″ × 41.5″, a B-box steps up to roughly 7.5–12.5 ton at about 95.375″ × 54.25″, and a C-box covers 13–25 ton at around 102″ × 86.125″. Enlight uses LGT for the A/B boxes and LCT for the C-box; Xion uses the LGX prefix across all three. A real Xion A-box example sits on the Lennox LGX024S5xx1Y page, and a Raider example is on the Lennox ZHB036S4B page. Knowing the cabinet-box convention means a size jump between two models in the same line is rarely a surprise — it almost always tracks the A/B/C boundary.

What Xion replaced

Xion is worth knowing by name specifically because of what it superseded: SMARTCurb's source documentation notes that Xion supersedes the older Landmark and Energence naming, both of which have since dropped off Lennox's current product pages entirely. If you're standing in front of a rooftop unit badged Landmark or Energence, it predates Xion — SMARTCurb still has curb geometry on file for the legacy version, and Xion is exactly what you'd cross-shop for a modern equivalent on the same footprint family.

The legacy CHA/GCS reality

Here's the part that matters more than the current lineup for most replacement jobs: a large share of the Lennox units actually still in service on Vancouver-area roofs aren't from any of the five lines above at all. They're older commercial packaged units carrying CHA, CHP, or GCS model prefixes — dozens of distinct curb footprints in SMARTCurb's atlas, most sourced as secondary documentation rather than current manufacturer literature, which is exactly what you'd expect from equipment old enough that Lennox no longer markets it under a named line. A real example sits on the Lennox CHA16120/150 page — its source documentation specifically notes this curb interface is shared across three brand badges: Allied Air, Comfort Aire, and Lennox. That's not unusual for this era of equipment; badge-sharing across affiliated brands was common practice, and it means a CHA-prefixed Lennox unit and an Allied Air or Comfort Aire unit of the matching size can share the same physical curb.

Practically, this means the honest first move on an older Lennox rooftop unit is to read the nameplate carefully rather than assume it's one of the five current lines. A CHA/CHP/GCS prefix means older commercial equipment, still fully covered in SMARTCurb's atlas, just not part of the current catalog Lennox itself would point you to.

Every Lennox page carries its original pattern drawing

All 75 Lennox model pages include the original curb pattern drawing alongside the verified footprint, viewable directly on the page. For the CHA/GCS legacy units especially — where documentation quality varies more than it does for the current lines — that drawing is a useful second source to check against what you measure on the roof before ordering.

Reading a Lennox model number in the field

For the current lines, the letters at the front of the model number tell you the line and cabinet almost immediately — LGX for Xion, LGT/LCT for Enlight, SCC for Strategos, ZHB for Raider, LC/LCA/LCC for L Series — and the digits that follow step up with tonnage inside that family, the same pattern as the cabinet-box sizing above. For the legacy CHA/GCS units, the convention is looser: a CHA or GCS prefix followed by a numeric code that doesn't map to a clean tonnage rule the way the current lines do, which is exactly why pulling the specific model page and comparing the pattern drawing matters more for this older equipment than for anything Lennox currently markets.

Before you order

Whether it's a current-line unit or a decades-old CHA/GCS packaged unit, the sequence is the same: confirm the exact model designation on the nameplate, pull the real curb dimensions using the outside-corner datum convention, then cross-check both against the matching model page's footprint and pattern drawing. Older equipment especially tends to have been modified, resized, or re-flashed at some point in its service life in ways a model number alone won't reveal.

When the replacement isn't Lennox-to-Lennox

Most RTU replacements aren't same-manufacturer swaps, and SMARTCurb doesn't require one. Each model page also lists nearest-footprint compatible pairings across manufacturers as a starting point. Open the SMARTCurb workspace, pick your existing Lennox unit and whatever you're replacing it with, and the adapter compiles live from the real geometry on both sides.