Inspection-lot division rules for installation works: general principle (one design system or equipment group), plan preparation/review procedure, and discipline details for water/sewer, electrical, HVAC, energy saving, industrial, and intelligent buildings

Topic Positioning

Answers "how to divide installation inspection lots": general principles and plan procedures from GB 50300-2013 and GB 55032-2022, plus division details for building water/sewer/heating, electrical, HVAC (incl. energy saving), intelligent buildings, and industrial installation.

Core Conclusions

1. General principles

1. GB 50300-2013, 4.0.5: "Inspection lots may be divided by quantity, floor, section, or expansion joint per construction, quality control, and acceptance needs." Multi/high-rise sub-items may divide by floor or section; single-story by expansion joints; foundation sub-items generally one lot (basement levels may split); roofing by roof level; other divisions by floor; small-quantity sub-items may be one lot. "Installation works generally one lot per design system or equipment group. Outdoor works generally one lot. Aprons, steps, and open drains are included in floor lots." Lot acceptance helps catch defects early.
2. GB 55032-2022, 4.1.1 (full-text mandatory): "Inspection lots shall be divided per construction organization, quality control, and acceptance needs by quantity, floor, and section; sampling shall meet the discipline acceptance standards." Commentary: "installation works divide lots by one design system or equipment group"; foundations and structure by section/floor; single-story by expansion joints; roofing by level; others by floor/position/quantity. Municipal works vary — follow the discipline standards. Sampling: "discipline standards set minimum samples; sampling may increase but never fall below the minimum."

2. Plan preparation and review (procedure)

1. GB 50300-2013, 4.0.7: "Before construction the contractor shall prepare the sub-item and inspection-lot division plan, reviewed by the supervisor. For sub-items and lots not covered by Annex B or the discipline standards, the employer shall organize supervisor and contractor to agree."
2. GB 55032-2022, 4.1.2: "Before construction the contractor shall prepare the division plan for unit/sub-unit/sub-item works and lots, reviewed by the supervisor before implementation. Where site conditions differ from the annexes, divide per actual conditions, jointly determined by employer, supervisor, and contractor." Commentary: the plan is an important basis for organizing acceptance and compiling technical files, closely tied to material re-testing, witness testing, and physical testing — prepared before commencement covering project overview, divisions, and diagrams.

3. Discipline details

1. Building water/sewer/heating (GB 50242-2002, 3.1.5): "Sub-items divide by system, zone, section, or floor. Sub-items divide into lots for acceptance." Examples: a 30-story indoor supply system by 10 or 5 floors per lot; a 5-story drainage system by one lot per unit.
2. Building electrical (GB 50303-2015, 3.4.2) six rules: (1) substations: main substations one lot; several secondary substations not in sub-unit works — one lot each; those within sub-unit works — their sub-items one lot each, records汇总 into division records. (2) supply mains: by supply section and shaft number. (3) power and lighting: boundaries consistent with the civil works (embedded conduits follow civil construction). (4) standby and UPS: one lot each. (5) lightning protection and earthing: artificial and foundation-rebar earthing one lot each, large foundations may split by block; down-conductors one lot for <= 6 stories, high-rises by equipotential-ring interval floors; air terminals one lot per roof; total equipotential bonding one lot, each local bonding one lot, electronic equipment rooms one lot. (6) outdoor electrical: by courtyard size, commissioning sequence, functional zones.
3. HVAC (GB 50243-2016, 3.0.9): sub-items may be accepted once or in parts; lot batches and samples per physical quantity and distribution, covering the whole sub-item; where ducts/pipes of multiple materials/processes are involved, lots preferably split by material. Duct installation sub-items may belong to several sub-divisions (supply, exhaust, AC, smoke control) — check each per the code, no omissions.
4. HVAC energy saving (GB 50411-2019, 10.1.3): division per 3.4.1, or by system/floor as agreed between contractor and supervisor; chilled/hot water acceptance by system zone; air systems by fan/AHU-served systems; large multi-story projects by several floors per lot.
5. Industrial (GB/T 50252-2018): acceptance divides unit/sub-unit/sub-item works; civil, steel, anti-corrosion, insulation, and furnace works may divide lots per their standards (4.1.1); lots may divide by equipment foundation, floor, section, or expansion joint (4.2.1); steel erection by expansion joint/section/rigid unit, multi/high-rise by floor or section; profiled sheet fabrication and erection by expansion joint/floor/section or roof/wall/floor (4.3.1).
6. Intelligent buildings (GB 50339-2013, 3.1.2): sub-divisions and sub-items per Table 3.1.2; by system and class into sub-divisions, then by trade, material, process, equipment into sub-items; hospital intercom, stadium flag systems etc. may be added as sub-divisions.

Applicable Boundaries

• Applies to building installation disciplines and industrial installation; municipal works (roads, bridges, pipes, rail transit, tunnels) vary — follow their discipline standards.
• Sampling per the discipline minimums; may increase, never decrease.
• GB 55032-2022 is a full-text mandatory code — where current standards differ, it governs.
• Division plans before commencement, reviewed by the supervisor; gaps settled by employer-organized agreement.
• This card covers principles, procedures, and details; sampling plans and record requirements per each discipline standard.

Further Reading

• GB 50300-2013, 4.0.5, 4.0.7, Annex B.
• GB 55032-2022, 4.1.1, 4.1.2, Annexes A/B/C.
• GB 50242-2002, 3.1.5; GB 50303-2015, 3.4.2; GB 50243-2016, 3.0.9; GB 50411-2019, 3.4.1, 10.1.3.
• GB/T 50252-2018, 4.1.1, 4.2.1, 4.3.1; GB 50339-2013, 3.1.2 and Table 3.1.2.