Estimates a facility's diversified maximum demand from a load-category schedule — the design current and switchgear/transformer sizing basis, rather than sizing for the (much higher, unrealistic) sum of every connected load's full nameplate rating simultaneously.
Standards followed
General design practice for load-category demand factors (confirm against your local code or utility rules, e.g. IET On-Site Guide, DEWA/ADDC regulations, NEC Art. 220). Note: the IEC 61439 "rated diversity factor" applies to switchgear assemblies, not to load categories.IEC 60364-7-722 (EV charging diversity requirements)
What it can do
- Per-category connected load and demand factor for 8 common categories (lighting, sockets, HVAC, heating, motors, cooking, EV charging, other).
- Total connected load, diversified maximum demand, effective diversity factor, and design current.
- Recommended main switch/breaker from standard IEC frame sizes.
- Advanced: multi-board site aggregation with a further site-level diversity factor and future growth margin, producing a recommended transformer size.
Example problem
A site has 4 load categories: 100kW lighting at 90% DF, 80kW sockets at 70% DF, 150kW HVAC at 80% DF, and 200kW motors at 75% DF, on a 415V 3-phase supply at 0.9 assumed PF.
- Demand per category = connected load × demand factor: lighting 90kW, sockets 56kW, HVAC 120kW, motors 150kW.
- Total connected load = 100+80+150+200 = 530kW.
- Total diversified maximum demand = 90+56+120+150 = 416kW.
- Effective diversity factor = 416/530 ≈ 78.5%.
- Design current (3-phase) = 416,000 / (√3 × 415 × 0.9) ≈ 643A.
Maximum demand 416kW (78.5% of connected load), design current ≈643A, so an 800A main breaker is the next standard size.
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