How to Check a BESS Thermal Management Design: What China's 2023 NEA Requirements Demand (BMS Over-Temperature and Temperature-Difference Protection, H2/CO Detection and One-Air-Change-per-Minute Ventilation in LFP Rooms, Module-Level Fire Tests for New or Expanded Medium and Large Li-ion Stations — for Generation- and Grid-Side Stations), the Standards Stack (GB/T 51048-2025, GB 44240-2024, GB/T 36276-2023) and UL 9540A / NFPA 855 / IEC 62933-5-2

Short answer. None of the Chinese documents retrieved for this guide publishes a cooling-capacity formula; what they define is what the thermal design must achieve and prove. NEA's 25 Key Requirements for Preventing Power Production Accidents (2023), whose storage section addresses generation-side and grid-side electrochemical storage stations, require the BMS to protect against over-temperature and temperature difference (as well as voltage and current faults), to issue graded alarms or trips and to isolate faults locally, and say it should offer cluster-level isolation. For LFP battery rooms they require H2/CO detection that trips room- and cluster-level DC breakers and starts explosion-proof ventilation exchanging at least one room volume per minute, and, in battery rooms of new, rebuilt or expanded medium and large lithium-ion stations, fixed suppression able to extinguish battery fire without re-ignition, verified by module-level real-battery fire tests. The design standard is changing: GB/T 51048-2025 applies from 1 April 2026, replacing GB 51048-2014; the mandatory battery safety standard GB 44240-2024 has applied since 1 August 2025. Outside China, UL 9540A tests thermal-runaway propagation at cell, module, unit and installation level and is the test NFPA 855 cites for large-scale fire testing. A buyer should check the thermal design against these documents clause by clause, not against a vendor's 'liquid-cooled' label.

1. The standards stack and its dates

Only the titles and dates of the Chinese standards are cited here: the GB/T 51048-2025 file published with the announcement is image-only and the other texts were not read. The 2023 NEA requirements refer to GB 51048 for safety distances and room layout and to GB/T 36276 for battery safety performance; since GB/T 51048-2025 replaces GB 51048-2014 from 1 April 2026, a design dated after that should cite GB/T 51048-2025 for the layout references (GB/T 36276 is unaffected by the announcement).

2. What the 2023 NEA requirements say about the thermal chain

Section 2.12 of the 25 Key Requirements (国能发安全〔2023〕22号) is the most specific national text retrieved; it defines the 'storage stations' it covers as generation-side and grid-side electrochemical storage stations, so its requirements are quoted here for that scope.

• Siting and separation. Stations must not adjoin or sit in premises producing, storing or trading flammable or explosive dangerous goods, must not be located in dusty or corrosive-gas locations, and must not be located in protection zones of important overhead power lines; inside power plants or substations, battery rooms keep the GB 51048 safety distances.
• Battery selection. Medium and large stations should use mature, high-safety batteries and be cautious with second-life EV batteries, which need consistency screening and traceability-based safety assessment meeting GB/T 36276, with real-time monitoring of battery parameters in operation.
• Layout and protection. Lithium-ion rooms must not be in crowded places; unit and cluster DC circuits need DC breaking devices and modules structural reverse-connection protection; the BMS must provide over-/under-voltage, voltage-difference and over-current protection and over-temperature and temperature-difference protection, should provide cluster-level isolation, and must issue graded alarms or trips for local isolation.
• Gas detection and ventilation (LFP). Combustible-gas detectors trip room- and cluster-level DC breakers and start emergency ventilation and alarms when H2 or CO exceeds set thresholds; ventilation is explosion-proof, exchanges at least one room volume per minute (net of equipment), places inlets and outlets so that gases of different densities are exhausted, avoids air short-circuits and runs automatically.
• Fire detection and suppression. Automatic fire alarms in electrical rooms; fixed automatic extinguishing in battery rooms of new, rebuilt or expanded medium and large lithium-ion stations, able to extinguish open battery fire without re-ignition, with type, flow, pressure and nozzle layout verified by module-level real-battery fire tests at a qualified body; fire-stopping of penetrations.
• Operations. Before commissioning, an emergency plan for thermal runaway and fire, coordination with local fire services and drills; annual full inspection of fire facilities; fire-trained O&M staff.

CNWattHub reading: the thermal-management system (air or liquid cooling, heaters, dehumidification) is not named in section 2.12. What is named is the chain that must work when it fails — temperature and temperature-difference protection in the BMS, gas detection, ventilation, suppression and the plan. A thermal design review should therefore ask how the cooling system keeps cells inside the limits the BMS enforces, and what happens at each alarm grade.

3. The NEA safety notices around the design

• 2022 (国能综通安全〔2022〕37号). Incoming inspection of batteries and BMS by qualified storage testing bodies; fire-protection acceptance before commissioning; regular health assessment of the battery system; reporting of battery safety performance to the monitoring platform; staff trained to know thermal-runaway and fire characteristics.
• 2023 (国能综通安全〔2023〕131号, generation-side and grid-side stations). Power companies monitor the operating safety state of battery packs, BMS, EMS, PCS, fire systems, cyber-security and the operating environment; monitoring capability by 31 December 2024; all new and existing such stations in scope from 2025.
• 2025 (国能综通安全〔2025〕65号, five departments). A written safety-conditions-and-facilities analysis at feasibility stage, a safety-facility check after completion or trial run and a post-evaluation after a period of operation; faster standards on design, construction, acceptance, connection and operation linked to the mandatory battery standard; safety facilities designed, built and commissioned with the main works.

CNWattHub reading: the 2023 monitoring notice means the cell-temperature and environment data a thermal design produces are not only for the BMS; they feed a company-level monitoring platform, so the data model and sensor coverage should be specified.

4. How UL 9540A, NFPA 855 and IEC 62933-5-2 frame it

UL Solutions describes UL 9540A as the US and Canadian national test method for thermal-runaway fire propagation in battery ESS, the only consensus standard explicitly cited in NFPA 855 for large-scale fire testing, and the method used when design or installation conditions exceed the limits of NFPA 855, NFPA 1, the IFC or the IRC. Its cell test characterises thermal runaway and gas composition and flammability; the module test, propagation tendency, heat and gas release and ignition or deflagration danger; the unit test, fire spread between modules and re-ignition; the installation test mainly the fire-protection system. The 2026 edition of NFPA 855 adds Annex G.11 on large-scale fire testing (fire spreading between BESS units, separation distances, active protection), and UL 9540A edition 6 updates the installation-level test with a challenging post-deflagration scenario, while unit-level tests remain required for residential BESS and for non-residential BESS with an active thermal-runaway propagation prevention system.

IEC 62933-5-2:2025 (edition 2.0, published 9 December 2025) covers safety for people and surroundings of grid-connected storage with an electrochemical subsystem across the whole BESS life cycle, adds provisions beyond IEC 62933-5-1 and treats the storage system as a system; the 2020 first edition shows a withdrawal date of 9 December 2025.

CNWattHub reading: China's module-level real-fire verification of suppression systems and UL 9540A's module- and unit-level propagation tests ask related questions; a vendor's UL 9540A report is useful evidence in China, but it does not replace the Chinese module-level test of the suppression system or the GB/T 51048-2025 layout rules.

Reading table

Checklist

CNWattHub editorial method, not a sourced rule:

1. Ask which design standard the layout follows (GB 51048-2014 or GB/T 51048-2025) and for the safety-distance and room-layout calculation.
2. Ask for the BMS protection table: over-temperature and temperature-difference thresholds, alarm grades, trip actions and whether cluster-level isolation is implemented.
3. Ask how the cooling system keeps cells within those thresholds across the site's ambient range, and what the BMS does when cooling fails.
4. Check gas detection (H2/CO), the trip logic to DC breakers and the ventilation rate, explosion-proof rating and inlet/outlet placement.
5. Ask for the module-level real-fire test report of the suppression system, the GB/T 36276 battery test report and the GB 44240 conformity evidence.
6. Request the thermal-runaway emergency plan, the fire-service coordination record and the monitoring-platform data list.
7. For export or international financing, map the evidence to UL 9540A levels, NFPA 855 (2026) and IEC 62933-5-2:2025.

Scope limits

One MOHURD announcement, five standard information pages, one NEA requirements document, three NEA notices, one UL Solutions page and two IEC pages only. No clause of any Chinese standard is quoted, no temperature window, temperature-difference limit or cooling-sizing rule is quoted, and UL 9540A and NFPA 855 are described only as UL Solutions describes them. Not engineering or procurement advice.