Quantity-calculation rules and itemizing method for busways (low-voltage enclosed plug-in busway / common-enclosure busway): by centre-line length, supports included, accessories listed separately by count - distinct from strip busbars

Topic Positioning

Quantity-calculation rules and BOQ/quota itemizing method for busway (low-voltage enclosed plug-in busway, common-enclosure busway) installation, covering the distinction from strip-busbar calculation rules, the separate itemizing of accessories, and quota sub-item application essentials.

Core Conclusions

1. Busway body: calculated by the centre-line length of the design dimensions (unit m)

DB11/T 2382-2024 "Construction Consumption Standard", Clause 6.4.22, original text: "The construction consumptions of common-enclosure busway and low-voltage enclosed plug-in busway installation shall include the work content of support installation. Quantities shall be calculated by the centre-line length of the dimensions shown on the design."

• The busway is a three-phase integral finished product, measured by centre-line length (m), not per-phase length x 3;
• Support installation is included in the installation consumptions and not listed separately (unlike cable trays, whose support fabrication must be listed separately in kg).

Clause 6.4.21, original text: "Bus installation shall set corresponding items by bus type, model and installation position; the construction consumptions of strip steel-busbar installation shall be executed under the copper-busbar installation items."

2. Accessories itemized separately, calculated by count

Clause 6.4.24, original text: "Quantities of copper-busbar expansion joints, penetration boards, wall bushings, supporting insulators, tap-off (plug-in) boxes and end (staring) boxes shall be calculated by the numbers shown on the design. Quantities of flexible copper connections shall be calculated per 'phase/unit'." That is, tap-off boxes, end boxes etc. are listed separately by design count (unit/each); flexible copper connections are per "phase/unit".

3. Strip busbars follow different rules (do not mix)

Clause 6.4.23, original text: "Strip-busbar installation quantities shall be calculated by the per-phase length of the design dimensions (including reservation lengths); where the design and the codes are silent, the added quantities from strip-busbar installation reservations may follow Table 6.4.23." Table 6.4.23 strip-busbar installation reservations: strip-busbar termination 0.30 m/length (from the last support point); termination to branch line 0.50 m/length (branch reservation); termination to equipment 0.50 m/length (from the equipment terminal interface).

4. Quota sub-item application tips

The "low-voltage enclosed plug-in busway" sub-items of DB11/T 2382-2024 Appendix C, Table C.4.14 (e.g. C4-3-30 "horizontal (up to A) 1000") are measured in m, banded by installation position and current rating; the work content already includes "support/hanger installation, busway installation, accessory connection, positioning, fixing, end-cover installation, expansion units, vibration-isolation springs, insulation testing, joint cleaning and treatment, touch-up painting, earthing etc." - no duplicate itemizing. Recommended itemizing: busway body per m under the plug-in busway sub-items (by position and current band); tap-off and end boxes per unit under their sub-items; expansion joints and flexible connections per unit (phase); supports not re-applied (included).

5. National BOQ and corroborating bases

• GB/T 50856-2024 "Standard for Calculation of Quantities of General Installation Works": the item setting, feature-description content, measurement units and calculation rules of bus installation follow Table D.3.1 (code 030403); Appendix D note D.17.6: enclosed busbars mean phase-isolated enclosed busbars and common-enclosure busways; flexible-busbar installation reservations per Table D.17.3-1, rigid-busbar installation reservations per Table D.17.3-2.
• SJG 111.3-2022 "Consumption Standard for Urban Utility Tunnel Works (Volume 3: Ancillary Facility Installation Works)": "Low-voltage (voltage class <= 380 V) enclosed plug-in busway installation is measured in metres by the installation axis length shown on the design, per rated current per phase. Tap-off boxes and end (staring) boxes are installed per current capacity and counted in units per the design quantities." Consistent with the centre-line-length basis - corroborating evidence.

Applicable Boundaries

• The busway calculation rules rest directly on Clauses 6.4.22-6.4.24 of DB11/T 2382-2024 (a Beijing local standard, for Beijing-area consumption pricing); other regions follow their local bases - which agree with SJG 111.3-2022 and GB/T 50856-2024 and may be referenced.
• Busways (common-enclosure busway, low-voltage enclosed plug-in busway) and strip busbars must not be interchanged: the former by centre-line length (m), the latter by per-phase length (including reservations).
• "Support installation included" expressly applies to the common-enclosure and low-voltage enclosed plug-in busway installation items; the supporting insulators and penetration boards of strip busbars are counted separately by design quantities.
• Dual track of BOQ and quota quantities: compile the BOQ per GB/T 50856-2024 Table D.3.1, apply consumptions per the applicable consumption standard.

Further Reading

• DB11/T 2382-2024 "Construction Consumption Standard", Section 6.4 electrical equipment installation works: Clauses 6.4.21-6.4.24, Table 6.4.23; Appendix C, Table C.4.14 low-voltage enclosed plug-in busway sub-items (e.g. C4-3-30, banded by installation position and current rating).
• GB/T 50856-2024 "Standard for Calculation of Quantities of General Installation Works", Appendix D electrical equipment installation works: Table D.3.1 bus installation (code 030403), notes D.17.6, Table D.17.3-1 (flexible-busbar reservations), Table D.17.3-2 (rigid-busbar reservations).
• SJG 111.3-2022 "Consumption Standard for Urban Utility Tunnel Works (Volume 3: Ancillary Facility Installation Works)", electrical equipment installation works, Sections 2.2.3 and Chapter 15 sub-items.