A2L machinery rooms: which Table 1102.3 column trips which detector

Here's the thing: in a commercial refrigeration machinery room, the numbers in Table 1102.3 don't just describe a refrigerant — they set the trip points on the detectors that protect the room. California's January 2026 CMC errata corrected those numbers for the Safety Group A2L blends, and if you design supermarket racks or cold-storage plants, one corrected value can move a setpoint on every detector tied to it.

The short version, if you didn't catch it on the residential side: the errata revised the RCL and LFL values for eleven A2L blends — R-444A, R-445A, R-446A, R-447A/B, R-451A/B, R-454A/B/C, and R-455A — to fix errors carried in from the 2019 edition of ASHRAE Standard 34 and its addenda. This post is the machinery-room half: which column feeds which requirement, and why the lowest value in the room wins.

Four columns, four jobs

Open Table 1102.3 to an A2L row and you'll see four columns the code actually reaches into: Safety Group, OEL (ppm), RCL (lb/Mcf), and LFL (lb/Mcf). Each drives a different requirement.

Safety Group decides your electrical-classification path. Per §1106.11.6, when the only flammable refrigerants are A2L or B2L, you can run the room on mechanical ventilation plus refrigerant detection — or designate it Class I, Division 2 per NFPA 70. Add any A2, A3, B2, or B3 refrigerant and Class I, Division 2 becomes mandatory (§1107.1.8). The whole "skip the hazardous-location wiring" option turns on that group letter.

OEL sets the alarm-and-ventilation setpoint. §1106.2.5 requires detectors that alarm and start ventilation at a setpoint not more than the OEL in Table 1102.3, and §1106.11.9(3) makes the governing value the lowest OEL of any refrigerant designation in the room.

Verified against the live CMC Chapter 11 text: §1106.2.5 ties its detector setpoint to "the corresponding Occupational Exposure Limit, OEL" — not the RCL. The RCL ceiling is a separate requirement, in §1106.11.9(4).

RCL sets the emergency setpoint. §1106.11.9(4) holds the detector setpoint not more than the RCL, again the lowest RCL of any refrigerant designation in the room. Per Table 1106.11.10.2, the RCL setpoint drives the emergency alarm and Level 2 ventilation with a ≤15-second response — versus the OEL setpoint's trouble alarm, Level 1 ventilation, and ≤300-second response.

LFL sets the de-energize trip. §1106.11.6.2 says detection above 25 percent of the LFL (or the detector's upper limit, whichever is lower) must automatically de-energize refrigerant compressors, refrigerant pumps, normally closed automatic refrigerant valves, and other unclassified ignition sources rated over 1 kVA. For an A2L/B2L room taking the electrical relief, §1107.1.7.2 carries the same 25%-of-LFL de-energize trip for compressors, pumps, and normally closed automatic valves.

Why the lowest value governs

This is the part that bites in a real room. A supermarket rack house or cold-storage plant rarely runs a single refrigerant. For OEL and RCL, the code is explicit: the governing setpoint is the lowest value among all refrigerant designations present (§1106.11.9(3) and (4)). So if the errata moved the RCL on a blend that happens to be the lowest in your room, the emergency setpoint for the whole room moves with it.

Here's a concrete one. In the corrected table, R-454A's LFL was revised from 18.3 down to 17.5 lb/Mcf (its RCL went the other way, from 3.2 up to 4.4). A lower LFL means the 25%-of-LFL de-energize trip sits lower — the detector has to cut power to compressors and pumps at a smaller leak than the first printing implied.

Verified against the corrected Table 1102.3 in the 2025 CMC errata packet (p. 252) and the BSC Information Bulletin 26-01 redline (p. 6): R-454A RCL 3.2 → 4.4 lb/Mcf, LFL 18.3 → 17.5 lb/Mcf.

One precision note: that explicit "lowest value governs" language is attached to OEL and RCL. The 25%-of-LFL trip in §1106.11.6.2 is written against "the LFL," and §1106.11.9(1) requires the detector to be capable of detecting each refrigerant designation in the room — so verify the LFL basis for every refrigerant present rather than trusting one blend to cover the rest.

What to check on the next refrigeration submittal

Pull the corrected Table 1102.3 — it's reprinted on the buff replacement pages of the 2025 CMC errata packet (pages 251–252). Then, for the machinery room you're reviewing:

• List every refrigerant designation in the room and find the lowest OEL and lowest RCL among them. Those govern the detector setpoints under §1106.2.5 and §1106.11.9.
• Confirm the 25%-of-LFL de-energize trip is set against the corrected LFL for the refrigerant(s) present (§1106.11.6.2, §1107.1.7.2).
• If the design skips Class I, Division 2 wiring, confirm it qualifies for the A2L/B2L path in §1106.11.6 / §1107.1.7 — and that the ventilation and detection it depends on are actually shown.

If a submittal cites an RCL or LFL that doesn't match the corrected table, that's your correction. As always, confirm the governing values with your local authority having jurisdiction — this is a plan-check pointer, not legal advice.

What CrossBeam does with it

CrossBeam checks refrigerant and machinery-room submittals against the current Mechanical Code — Table 1102.3 as corrected by the January 2026 errata, with the lowest-value-governs rule applied across every refrigerant in the room. So a detector setpoint or a de-energize trip is measured against the numbers that are actually enforceable today.