HVAC / runnable MCP tool
Run the A2L Refrigerant Charge Limit Calculator in your AI assistant
Through the free Intry MCP server, Claude, ChatGPT, or Cursor runs this exact calculator and hands back a verdict and the cited source, not a guess. Tool name: a2l_charge_limit.
What you get back: the limit, the governing term, the m1/m2 thresholds, and the release height used.
How it computes the answer
Computed from the UL 60335-2-40 Annex GG maximum-charge formula (the smaller of the gravity term, the ANSI/ASHRAE 15.2-2024 concentration cap, and the 52 x LFL ceiling), with the m1 exemption of 15.2-2024 Figure 9-1 applied first, and the IEC ed 6 gravity-only value as a cross-check.
What it cites
Your assistant calls the same engine the interactive calculator calls, with the inputs listed under Inputs. These are the sources that engine reads.
- UL 60335-2-40 (4th ed) Annex GG
- The primary maximum-charge formula: m_max is the smaller of a gravity dispersal term (2.5 x LFL^1.25 x h x sqrt(area)), a concentration cap, and a 52 x LFL ceiling (Annex GG.9.1DV.2, Eqs GG.15DV / GG.17DV). The airflow factor doubles the gravity term when continuous or refrigerant-detection-initiated circulation is present.
- ANSI/ASHRAE 15.2-2024
- The residential charge-limit standard this tool follows, and the copy we hold and have read: the compliance path of Figure 9-1, the m1 and m2 charge levels of Table 9-1 (Section 9.3), the LFL conversion factors of Table 9-2, the room-area charge table of Table 9-3 and the ventilation adder of Table 9-4, all checked cell by cell against the purchased base text. It supplies the concentration-cap term, 0.5 x LFL x h x area (M = LFL x h x Area / SF with the with-circulation safety factor SF = 2), and the release-height clamp (not less than 0.6 m / 2.0 ft, not more than 2.7432 m / 9.0 ft, Table 9-3 footnote a). Corroborated by the JCI/York R-454B whitepaper (p.8, CF = 0.5). The engine applies the SF = 2 cap in every case as a conservative floor.
- ASHRAE 34-2019 Addendum f (LFL values)
- The lower flammability limit for each A2L blend (Tables 4-1/4-2). For R-454B the engine uses the UL Table BB.1DV worst-case value (0.296 kg/m3), which reproduces the JCI/Trane R-454B installation tables and is the more conservative choice (a smaller LFL yields a smaller allowed charge). Daikin is NOT named here: Daikin, Goodman and Amana chose R-32, so their tables are the R-32 check, not the R-454B one.
- IEC 60335-2-40 ed 6 / EN 378 (gravity-only)
- The secondary result shown alongside: the older gravity-only limit (2.5 x LFL^1.25 x h0 x sqrt(A), capped at 26 x LFL) that current EU installation manuals still follow, so the two regimes can be compared directly.
These are A2L room-charge safety-standard limits, computed by the engine from the release height, room area, and refrigerant LFL you enter, not a field measurement. The equipment listing and the manufacturer's installation manual for your exact unit, plus your AHJ, have final say; the tool holds the SF = 2 concentration cap on in every case as a conservative floor.
The full receipt, with every source and how each is cross-checked, is on the interactive A2L Refrigerant Charge Limit Calculator.
Ask your assistant
The one rule that makes it reliable: name Intry in your question. That is what tells Claude to run the a2l_charge_limit tool and answer with the real number, the verdict, and the citation. Leave Intry out and Claude may just guess from memory, which is exactly what you are trying to avoid. Type something like:
Inputs
| Field | Required | Accepts | What it is |
|---|---|---|---|
| refrigerant | yes | r-454b, r-32, r-452b, r-454a, r-454c, r-455a, r-1234yf, r-1234ze, r-290 | Refrigerant id, e.g. 'r-454b' or 'r-32'. |
| direction | optional | max-charge, min-area | 'max-charge' = biggest charge for a room (give areaFt2); 'min-area' = smallest room for a charge (give chargeLb). Default max-charge. |
| mounting | optional | floor, window, wall, ceiling, custom | Indoor-unit release-height class: floor (0.6 m), window (1.0 m), wall (1.8 m), ceiling/cassette/supply register (2.2 m), or custom (with heightFt). Default wall (the more conservative common height). |
| areaFt2 | optional | number | Floor area in ft2 of the ONE space this call sizes (max-charge direction). This tool answers for a single space and takes no list of spaces. On a system with more than one indoor unit, ANSI/ASHRAE 15.2-2024 section 9.4.1 makes the governing space the one with the smallest dispersal VOLUME, which section 9.4 defines as floor area multiplied by dispersal height, so the smallest room by AREA is not always the one that governs: a larger room with a lower indoor unit can be the binding one. Where the units sit at different heights, call this tool once per space and take the smallest result, or use the web calculator, which takes the whole system. Default 150. |
| chargeLb | optional | number | System refrigerant charge in lb, nameplate plus field-added for line-set length (min-area direction). Default 6. |
| heightFt | optional | number | Release height in ft when mounting = 'custom' (clamped to 2.0 to 9.0 ft per ANSI/ASHRAE 15.2-2024 Table 9-3 footnote a). Default 7.2. |
| circulation | optional | boolean | Continuous or RDS-initiated air circulation (AF = 2, doubles only the gravity term). Default false. |
Add Intry to Claude
One paste and Claude can run this tool and every other Intry calculator, right from your phone.
- Claude opens with the Intry connector already filled in. Review it and click Add.
- (If a field is blank, paste the link below into the URL field.)
- In any chat, tap + then Connectors and switch Intry on. Then name Intry in your question (“use Intry to…”) so Claude runs the tool instead of guessing.
https://www.intrysys.com/api/mcpNo login, no API key, and it works on every Claude plan, right from your phone.
Using ChatGPT, Cursor, or a dev tool? See the developer setup on the main page. The endpoint is https://www.intrysys.com/api/mcp.
Every answer comes with the UL 60335-2-40 and ANSI/ASHRAE 15.2-2024 standards it came from, so you can check it or show an inspector. The numbers come from the same calculator we run on intrysys.com, and we re-check every one automatically before anything goes live, so the number Claude hands you matches the code.