Overview
Calculates maximum demand for residential electrical installations per AS/NZS 3000:2018 Appendix C. Supports single dwellings and blocks of living units using Table C1 diversity factors. Two input modes are available: a detailed equipment list with per-group diversity rules, or a simple total-load mode with a user-specified diversity factor. Outputs include maximum demand in VA and amperes, a recommended standard main switch rating, per-phase load balance (for three-phase supplies), and a load breakdown by group.
Input Parameters
Application Configuration
| Parameter | Type | Default | Range | Description |
|---|---|---|---|---|
application_type |
Enum | single_dwelling | — | Type of installation: single_dwelling, blocks_of_units, residential_institutions, commercial_premises (determines Table C1 or C2) |
supply_type |
Enum | single_phase_230v | — | Electrical supply: single_phase_230v or three_phase_400v |
number_of_units |
Integer | 1 | 1 – 100 | Number of dwelling units (for blocks of units) |
Load Input Method
| Parameter | Type | Default | Range | Description |
|---|---|---|---|---|
use_simple_load |
Boolean | false | — | Use simple total-load input instead of detailed equipment list |
equipment_list |
JSON string | (see below) | — | JSON array of equipment items, each with load_group, description, phase, rating_value, rating_unit, quantity, and power_factor |
simple_total_load_w |
Number | 10,000 | 0 – 1,000,000 W | Total connected load in watts (simple mode only) |
simple_diversity_factor |
Number | 0.7 | 0.1 – 1.0 | Overall diversity factor (simple mode only) |
Equipment Item Fields
| Field | Type | Description |
|---|---|---|
load_group |
Enum | Load group key (see Diversity Groups table below) |
description |
String | User description of the equipment |
phase |
Enum: A / B / C | Assigned phase (used for three-phase balance) |
rating_value |
Number | Numerical rating |
rating_unit |
Enum: A / W / kW / points | Rating unit |
quantity |
Integer | Number of identical items |
power_factor |
Number | Power factor (default 1.0) |
Diversity Groups (AS/NZS 3000 Table C1)
| Load Group Key | Code | Name | Diversity Method | Rule |
|---|---|---|---|---|
lighting_general |
ai | Lighting, General | Points | First 20 points: 3A, then 2A per additional 20 points (or part thereof) |
lighting_outdoor |
aii | Lighting, Outdoor >1000W | Percentage | 75% of connected load |
socket_10a_general |
bi | Socket 10A, General Use | Points | Counted together with socket_fixed_10a on the same phase: first 20 points 10A, then 5A per additional 20 points (or part thereof) |
socket_fixed_10a |
bi | Fixed Connection ≤10A | Points | Counted together with socket_10a_general on the same phase (one Table C1 B(i) group) |
socket_15a_general |
bii | Socket 15A, General Use | Fixed | 10A for 1 or more sockets |
socket_20a_general |
biii | Socket 20A, General Use | Fixed | 15A for 1 or more sockets |
cooking_range |
c | Cooking, Range >10A | Percentage | 50% of connected load |
cooking_other |
c | Cooking, Other >10A | Percentage | 50% of connected load |
laundry_appliance |
c | Laundry Appliance >10A | Percentage | 50% of connected load |
air_conditioner |
d | Air Conditioner >10A | Percentage | 75% of connected load |
space_heater |
d | Space Heater >10A | Percentage | 75% of connected load |
sauna_heater |
d | Sauna Heater >10A | Percentage | 75% of connected load |
hw_instantaneous |
e | Hot Water, Instantaneous | Percentage | 33.3% of connected load |
hw_storage |
f | Hot Water, Storage | Percentage | 100% of connected load |
pool_heater |
g | Pool Water Heater | Tiered | Per phase: largest pool 75%, largest spa 75%, remaining 25% |
spa_heater |
g | Spa Water Heater | Tiered | Per phase: largest pool 75%, largest spa 75%, remaining 25% |
ev_charger |
jiv | Electric Vehicle Charger | Percentage | 100% of connected load (Table C1 group (j)(iv), single domestic column) |
motor_lift |
k | Motor, Lift | Tiered | Largest: 125%, next: 75%, remaining: 50% |
motor_general |
l | Motor, General | Tiered | Largest: 100%, remaining: 50% |
other_appliances |
m | Other Appliances >5A | Self-assess | Self-assess maximum demand (100% if uncertain) |
Additional Parameters
| Parameter | Type | Default | Range | Description |
|---|---|---|---|---|
floor_area_m2 |
Number | 150 | 0 – 10,000 m² | Total floor area for lighting calculations |
future_growth_factor |
Number | 1.0 | 1.0 – 2.0 | Multiplier for future load growth |
include_ev_charging |
Boolean | false | — | Account for electric vehicle charging |
Calculation Options
| Parameter | Type | Default | Range | Description |
|---|---|---|---|---|
nominal_voltage_1ph |
Enum: 230 / 240 | 230 | — | Nominal single-phase voltage (V) |
nominal_voltage_3ph |
Enum: 400 / 415 | 400 | — | Nominal three-phase line-to-line voltage (V) |
motor_power_factor |
Number | 0.86 | 0.5 – 1.0 | Power factor used for motor loads |
motor_efficiency |
Number | 0.95 | 0.5 – 1.0 | Efficiency used for motor loads |
Output Results
| Output | Unit | Description |
|---|---|---|
total_connected_va |
VA | Sum of all equipment nameplate ratings |
total_diversified_va |
VA | Total after applying diversity factors and future growth |
overall_diversity_factor |
— | Ratio of diversified load to connected load (before growth) |
max_demand_va |
VA | Final maximum demand (equals total_diversified_va) |
max_demand_a |
A | Maximum demand current |
recommended_main_switch_a |
A | Nearest standard main switch rating ≥ calculated current |
main_switch_utilization_percent |
% | Utilization of recommended main switch |
phase_a_diversified_va |
VA | Diversified load on Phase A (three-phase only) |
phase_b_diversified_va |
VA | Diversified load on Phase B (three-phase only) |
phase_c_diversified_va |
VA | Diversified load on Phase C (three-phase only) |
phase_imbalance_percent |
% | Phase load imbalance percentage (three-phase only) |
load_groups_summary |
— | Breakdown of connected and diversified VA per load group |
compliant |
Boolean | Whether demand is within the maximum standard switch rating (800A) |
Formulas
Rating Conversion to VA
Equipment ratings are converted to VA based on the rating unit:
\[ S = \begin{cases} I \times V & \text{if rated in Amps} \\ P & \text{if rated in Watts} \\ P \times 1000 & \text{if rated in kW} \end{cases} \]Where \(I\) is current, \(V\) is nominal voltage, and \(P\) is power. Items rated in points are handled directly by the points-based diversity rules.
Lighting Diversity (Table C1, Row ai)
General lighting, exhaust fans ≤150W above 2.3 m, and lighting tracks:
\[ I_{\text{lighting}} = 3 + 2 \times \left\lceil \frac{N_{\text{points}} - 20}{20} \right\rceil \quad \text{(A)} \]Where \(N_{\text{points}}\) is the total number of lighting points. For \(N_{\text{points}} \le 20\), the diversified current is 3A.
Socket Outlet Diversity (Table C1, Row bi)
General purpose 10A socket outlets and permanently connected equipment ≤10A (one load group):
\[ I_{\text{socket}} = 10 + 5 \times \left\lceil \frac{N_{\text{points}} - 20}{20} \right\rceil \quad \text{(A)} \]Where \(N_{\text{points}}\) is the number of 10A socket points plus fixed ≤10A points on the phase. For \(N_{\text{points}} \le 20\), the diversified current is 10A. Table C1 row B(i) names both kinds of point in one group, so the first 10A block is counted once per phase, not once per kind; the diversified current is shared back to the two load-list groups in proportion to their points.
Fixed Socket Diversity (Table C1, Rows bii/biii)
15A sockets: fixed diversified value of 10A regardless of quantity.
20A sockets: fixed diversified value of 15A regardless of quantity.
\[ I_{\text{15A}} = 10 \text{ A} \qquad I_{\text{20A}} = 15 \text{ A} \]Percentage-Based Diversity
Several load groups use a simple percentage of connected load. The percentage depends on the load type:
\[ S_{\text{diversified}} = S_{\text{connected}} \times \frac{p}{100} \]| Load Group | Percentage \(p\) |
|---|---|
| Cooking (range, other), Laundry >10A | 50% |
| Air Conditioner, Space Heater, Sauna, Outdoor Lighting | 75% |
| Hot Water (instantaneous) | 33.3% |
| Hot Water (storage), EV Charger | 100% |
Motor Tiered Diversity
Lift motors (Table C1, Row k):
\[ S_{\text{motors}} = 1.25 \times S_{\text{largest}} + 0.75 \times S_{\text{next}} + 0.50 \times \sum S_{\text{remaining}} \]General motors (Table C1, Row l):
\[ S_{\text{motors}} = 1.00 \times S_{\text{largest}} + 0.50 \times \sum S_{\text{remaining}} \]Motor ratings in W or kW are converted to VA accounting for power factor and efficiency:
\[ S_{\text{motor}} = \frac{P}{\cos\phi \times \eta} \]Pool and Spa Heater Diversity (Table C1, Row g)
Like every Table C1 single-domestic rule this is applied per phase: the heaters connected to each phase are assessed together and their demand is added to that phase.
Electric Vehicle Charging (Table C1, Row j(iv))
AS/NZS 3000:2018 (Amd 1:2020) Table C1 load group (j)(iv), “charging equipment associated with electric vehicles”, is taken at full connected load for a single domestic installation; the table gives no reduction for managed charging. Where a load-management device limits the charger, enter the charger at the limited current (maximum demand by limitation, Clause 2.2.2).
Overall Diversity Factor
Future Growth
Where \(k_{\text{growth}}\) is the future growth factor (1.0 – 2.0).
Maximum Demand Current
Single-phase (every load is on the one phase, whatever phase it is tagged with):
\[ I_{\text{max}} = \frac{S_{\text{final}}}{V} \]Three-phase (per-phase calculation, then take maximum phase):
\[ I_{\text{phase}} = \frac{S_{\text{phase}}}{V_{\text{ph}}} \qquad I_{\text{max}} = \max(I_A,\; I_B,\; I_C) \]Three-phase, simple mode (assumes balanced):
\[ I_{\text{max}} = \frac{S_{\text{final}}}{\sqrt{3} \times V_{\text{LL}}} \]Main Switch Selection
Select the nearest standard rating \(\ge I_{\text{max}}\):
\[ I_{\text{main}} \in \{25,\; 32,\; 40,\; 50,\; 63,\; 80,\; 100,\; 125,\; 160,\; 200,\; 250,\; 315,\; 400,\; 500,\; 630,\; 800\} \text{ A} \]Duty/Standby Load List (MCP method duty_standby_lf)
The fe_calc_max_demand tool also rolls up a plant load list (no Table C1
diversity). Per load line, with \(n\) duty units of rating \(P_r\) and load factor \(LF\):
Standby units add to installed kW only. Per board, with coincidence (diversity) factor \(k\):
\[ P_{board} = k\,(\textstyle\sum P_{loads} + \sum P_{boards\ fed}) \qquad S = \sqrt{P^2 + Q^2} \qquad I = \frac{S}{\sqrt{3}\,V_{LL}} \text{ (or } S/V \text{ single-phase)} \]Diversity therefore compounds up the hierarchy. Design demand = \(S \times k_{growth} \times k_{spare}\), applied once at each board and never passed upstream.
Worked Examples
The 15 examples below are the validation cases for this calculation. Each one was produced by the calculation engine from the inputs shown, every figure was checked against the independent reference quoted at the end of the example, and the same cases are run against every engine build (see validation scorecard, tool fe_calc_max_demand; worked examples for every calculation).
| # | Case | Method | Demand (kVA) | Current (A) | Main switch / rating (A) | Result |
|---|---|---|---|---|---|---|
| 1 | Single-phase dwelling, 230 V | Table C1 1φ | 16.95 | 73.70 | 80 | PASS |
| 2 | Three-phase dwelling, heaviest phase | Table C1 3φ | 20.99 | 52.17 (C) | 63 | PASS |
| 3 | Small dwelling at the 20-point boundary | Table C1 1φ | 6.79 | 29.52 | 32 | PASS |
| 4 | Dwelling with pump motors and 20 % growth | Table C1 1φ | 15.83 | 68.82 | 80 | PASS |
| 5 | Pool, two spas and a sauna at 240 V | Table C1 1φ | 23.41 | 97.52 | 100 | PASS |
| 6 | Three-phase house over a 32 A supply | Table C1 3φ | 21.73 | 32.48 (B) | 40 | FAIL |
| 7 | All-electric dwelling with an EV charger | Table C1 1φ | 24.83 | 107.96 | 125 | FAIL |
| 8 | Sockets and fixed ≤ 10 A points share one count | Table C1 1φ | 7.74 | 33.65 | 40 | PASS |
| 9 | Pool and spas on different phases | Table C1 3φ | 20.35 | 36.96 (B) | 40 | PASS |
| 10 | EV charger capped by load management | Table C1 1φ | 10.27 | 44.65 | 50 | PASS |
| 11 | One MCC, two duty pumps and a standby | Duty/standby | 148.61 | 206.74 (MCC) | – | |
| 12 | MSB feeding two MCCs with growth and spare | Duty/standby | 313.69 | 436.41 (MSB) | – | |
| 13 | Single-phase lighting and heating board | Duty/standby | 9.33 | 40.55 (DB-L1) | 50 | PASS |
| 14 | Two main boards, one over its rating | Duty/standby | 216.43 | 301.09 (MSB-A) | 400 | FAIL |
| 15 | 11 kV board feeding a 415 V MSB and MCC | Duty/standby | 932.09 | 48.92 (HV-SWBD) | 100 | PASS |
Example 1 — Single-phase dwelling, 230 V
The basic Table C1 build-up: points rules for lighting and sockets, 50 % range, full storage water heater, 75 % air conditioning.
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 25 points; 10 A socket outlets 30 points; ranges 10 kW; storage water heating 3,600 W; air conditioning 5 kW.
| General lighting (A(i)) | 25 points → 3 + 2 × ⌈(25 − 20)/20⌉ = 3 + 2 × 1 = 5 A × 230 V = 1,150 VA |
|---|---|
| 10 A socket outlets (B(i)) | 30 points → 10 + 5 × ⌈(30 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 230 V = 3,450 VA |
| Ranges (C) | 10 kW = 10,000 VA × 50 % = 5,000.0 VA |
| Storage water heating (F) | 3,600 W = 3,600 VA × 100 % = 3,600.0 VA |
| Air conditioning (D) | 5 kW = 5,000 VA × 75 % = 3,750.0 VA |
| Total | S = 1,150.0 + 3,450.0 + 5,000.0 + 3,600.0 + 3,750.0 = 16,950.0 VA; I = 16,950.0 / 230 = 73.70 A |
| Connected load | 90,100 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 16,950.0 / 90,100 = 0.188 |
| Main switch | next standard rating ≥ 73.70 A → 80 A → 73.70 vs limit 80.00 A PASS |
| Result | 1/1 checks pass → PASS; maximum demand 73.70 A → 80 A main switch; governing: main switch |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 single domestic column: lighting 25 points = 3 A + 2 A = 5 A; 10 A sockets 30 points = 10 A + 5 A = 15 A; range 10 kW × 50 % = 21.74 A; storage HW 3.6 kW × 100 % = 15.65 A; air conditioner 5 kW × 75 % = 16.30 A; total 73.70 A at 230 V (16.95 kVA) (validation case c0022-domestic-1ph-230v) |
Example 2 — Three-phase dwelling, heaviest phase
On a three-phase supply each phase is assessed separately and the maximum demand is the most heavily loaded phase.
Given: Three-phase 400/230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 20 points on A; 10 A socket outlets 20 points on A; ranges 12 kW on B; storage water heating 4.8 kW on C; EV charging 7.2 kW on C.
| General lighting (A(i)) – A | 20 points ≤ 20 → 3 A × 230 V = 690 VA |
|---|---|
| 10 A socket outlets (B(i)) – A | 20 points ≤ 20 → 10 A × 230 V = 2,300 VA |
| Ranges (C) – B | 12 kW = 12,000 VA × 50 % = 6,000.0 VA |
| Storage water heating (F) – C | 4.8 kW = 4,800 VA × 100 % = 4,800.0 VA |
| EV charging – C | 7.2 kW = 7,200 VA × 100 % = 7,200.0 VA |
| Per phase | A: 690.0 + 2,300.0 = 2,990.0 VA ÷ 230 V = 13.00 A; B: 6,000.0 VA ÷ 230 V = 26.09 A; C: 4,800.0 + 7,200.0 = 12,000.0 VA ÷ 230 V = 52.17 A → maximum demand = phase C, 52.17 A |
| Total | S = Σ phases = 20,990.0 VA (20.990 kVA) |
| Connected load | 72,000 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 20,990.0 / 72,000 = 0.292 |
| Main switch | next standard rating ≥ 52.17 A → 63 A → 52.17 vs limit 63.00 A PASS |
| Phase imbalance | (Imax − Imin)/Imax = (52.17 − 13.00) / 52.17 × 100 (informative; the component warns above 20 %) → 75.1 vs limit 20.0 % INFO |
| Result | 1/1 checks pass → PASS; maximum demand 52.17 A (C) → 63 A main switch; governing: main switch. Phase imbalance is high (75.1%). Redistribute loads across phases. |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 per phase at 230 V: A = lighting 20 points 3 A + sockets 20 points 10 A = 13 A; B = range 12 kW × 50 % = 26.09 A; C = storage HW 4.8 kW (20.87 A) + EV charger 7.2 kW (31.30 A) at 100 % = 52.17 A; maximum demand = heaviest phase (validation case c0022-domestic-3ph-400v) |
Example 3 — Small dwelling at the 20-point boundary
Exactly 20 lighting and 20 socket points stay in the first block (3 A and 10 A); range at 50 %, air conditioner at 75 %.
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 20 points; 10 A socket outlets 20 points; ranges 4,000 W; air conditioning 2,400 W.
| General lighting (A(i)) | 20 points ≤ 20 → 3 A × 230 V = 690 VA |
|---|---|
| 10 A socket outlets (B(i)) | 20 points ≤ 20 → 10 A × 230 V = 2,300 VA |
| Ranges (C) | 4,000 W = 4,000 VA × 50 % = 2,000.0 VA |
| Air conditioning (D) | 2,400 W = 2,400 VA × 75 % = 1,800.0 VA |
| Total | S = 690.0 + 2,300.0 + 2,000.0 + 1,800.0 = 6,790.0 VA; I = 6,790.0 / 230 = 29.52 A |
| Connected load | 54,400 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 6,790.0 / 54,400 = 0.125 |
| Main switch | next standard rating ≥ 29.52 A → 32 A → 29.52 vs limit 32.00 A PASS |
| Result | 1/1 checks pass → PASS; maximum demand 29.52 A → 32 A main switch; governing: main switch |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 single domestic column: lighting 20 points = 3 A × 230 = 690 VA; 10 A sockets 20 points = 10 A × 230 = 2 300 VA; range 4 000 W × 50 % = 2 000 VA; air conditioner 2 400 W × 75 % = 1 800 VA; total 6 790 VA ÷ 230 V = 29.52 A → 32 A main switch. Connected = 20 × 100 W + 20 × 10 A × 230 V + 4 000 + 2 400 = 54 400 VA. (Former hand-written help-page Example 1.) (validation case c0022-domestic-small-dwelling-20-points) |
Example 4 — Dwelling with pump motors and 20 % growth
Motors rated in watts are converted with pf × η, the largest counts in full and the rest at 50 %; growth multiplies the total.
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 30 points; 10 A socket outlets 40 points; ranges 8,000 W; motors 3,000 W (Pool pump); motors 1,500 W (Bore pump). Growth factor 1.2; motor pf 0.86, η 0.95.
| General lighting (A(i)) | 30 points → 3 + 2 × ⌈(30 − 20)/20⌉ = 3 + 2 × 1 = 5 A × 230 V = 1,150 VA |
|---|---|
| 10 A socket outlets (B(i)) | 40 points → 10 + 5 × ⌈(40 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 230 V = 3,450 VA |
| Ranges (C) | 8,000 W = 8,000 VA × 50 % = 4,000.0 VA |
| Motors | Pool pump 3,000 W; Bore pump 1,500 W; S = P/(cos φ × η) = P/(0.86 × 0.95); 3,672.0 × 1 + 1,836.0 × 0.5 = 4,590.0 VA |
| Total | S = 1,150.0 + 3,450.0 + 4,000.0 + 4,590.0 = 13,190.0 VA × 1.2 growth = 15,828.0 VA; I = 15,828.0 / 230 = 68.82 A |
| Connected load | 108,508 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 13,190.0 / 108,508 = 0.122 |
| Main switch | next standard rating ≥ 68.82 A → 80 A → 68.82 vs limit 80.00 A PASS |
| Result | 1/1 checks pass → PASS; maximum demand 68.82 A → 80 A main switch; governing: main switch |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1: lighting 30 points = 3 + 2 × ⌈10/20⌉ = 5 A (1 150 VA); sockets 40 points = 10 + 5 × ⌈20/20⌉ = 15 A (3 450 VA); range 8 000 × 50 % = 4 000 VA; motors 3 000/(0.86 × 0.95) = 3 671.97 VA at 100 % + 1 500/(0.86 × 0.95) = 1 835.99 VA at 50 % = 4 589.96 VA; sum 13 189.96 VA × 1.2 = 15 827.96 VA ÷ 230 = 68.82 A → 80 A. (Former hand-written help-page Example 2.) (validation case c0022-domestic-motors-growth) |
Example 5 — Pool, two spas and a sauna at 240 V
Pool/spa heaters take 75 % of the largest pool and of the largest spa plus 25 % of the rest; 15 A and 20 A outlets count a fixed 10 A and 15 A.
Given: Single-phase 240 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 45 points; outdoor lighting 1,500 W; 10 A socket outlets 25 points; 15 A socket outlets 15 A × 240 V (Workshop 15 A outlet); 20 A socket outlets 20 A × 240 V (Garage 20 A outlet); pool heating 5 kW; spa heating 3 kW (Spa 1); spa heating 2 kW (Spa 2); sauna 6 kW. Supply rating 100 A.
| General lighting (A(i)) | 45 points → 3 + 2 × ⌈(45 − 20)/20⌉ = 3 + 2 × 2 = 7 A × 240 V = 1,680 VA |
|---|---|
| Outdoor lighting (A(ii)) | 1,500 W = 1,500 VA × 75 % = 1,125.0 VA |
| 10 A socket outlets (B(i)) | 25 points → 10 + 5 × ⌈(25 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 240 V = 3,600 VA |
| 15 A socket outlets (B(ii)) | 15 A × 240 V → fixed 10 A × 240 V = 2,400 VA |
| 20 A socket outlets (B(iii)) | 20 A × 240 V → fixed 15 A × 240 V = 3,600 VA |
| Pool/spa (G) | 0.75 × 5,000 (largest pool) + 0.75 × 3,000 (largest spa) + 0.25 × 2,000 = 6,500.0 VA |
| Sauna (D) | 6 kW = 6,000 VA × 75 % = 4,500.0 VA |
| Total | S = 1,680.0 + 1,125.0 + 3,600.0 + 2,400.0 + 3,600.0 + 6,500.0 + 4,500.0 = 23,405.0 VA; I = 23,405.0 / 240 = 97.52 A |
| Connected load | 90,400 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 23,405.0 / 90,400 = 0.259 |
| Main switch | next standard rating ≥ 97.52 A → 100 A → 97.52 vs limit 100.00 A PASS |
| Supply rating | I = 97.52 A against the given supply rating → 97.52 vs limit 100.00 A PASS |
| Result | 2/2 checks pass → PASS; maximum demand 97.52 A → 100 A main switch; governing: supply rating |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 at 240 V: lighting 45 points = 3 + 2 × ⌈25/20⌉ = 7 A (1 680 VA); outdoor lighting 1 500 W × 75 % = 1 125 VA; sockets 25 points = 15 A (3 600 VA); 15 A outlet → 10 A (2 400 VA); 20 A outlet → 15 A (3 600 VA); pool/spa 0.75 × 5 000 + 0.75 × 3 000 + 0.25 × 2 000 = 6 500 VA; sauna 6 000 × 75 % = 4 500 VA; total 23 405 VA ÷ 240 = 97.52 A → 100 A main switch; 100 A supply passes at 97.52 %. (validation case c0022-domestic-pool-spa-240v) |
Example 6 — Three-phase house over a 32 A supply
Each phase is assessed on its own (points, 33.3 % instantaneous water heating, 125 % lift motor); growth 1.15 pushes the heaviest phase past a 32 A supply.
Given: Three-phase 400/230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 25 points on A; 10 A socket outlets 35 points on A; other cooking 3 kW (Cooktop) on A; instantaneous water heating 9 kW on B; laundry 2.4 kW (Dryer) on B; fixed ≤ 10 A connections 10 points on B; space heating 4 kW on C; lift motors 1.5 kW (Home lift) on C; other appliances 1,000 W (Rack) on C. Growth factor 1.15; motor pf 0.86, η 0.95; supply rating 32 A.
| General lighting (A(i)) – A | 25 points → 3 + 2 × ⌈(25 − 20)/20⌉ = 3 + 2 × 1 = 5 A × 230 V = 1,150 VA |
|---|---|
| 10 A socket outlets (B(i)) – A | 35 points → 10 + 5 × ⌈(35 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 230 V = 3,450 VA |
| Fixed ≤ 10 A connections (B(i)) – B | 10 points ≤ 20 → 10 A × 230 V = 2,300 VA |
| Other cooking (C) – A | 3 kW = 3,000 VA × 50 % = 1,500.0 VA |
| Instantaneous water heating (E) – B | 9 kW = 9,000 VA × 33.3 % = 2,997.0 VA |
| Laundry (C) – B | 2.4 kW = 2,400 VA × 50 % = 1,200.0 VA |
| Space heating (D) – C | 4 kW = 4,000 VA × 75 % = 3,000.0 VA |
| Lift motors – C | Home lift 1.5 kW; S = P/(cos φ × η) = P/(0.86 × 0.95); 1,836.0 × 1.25 = 2,295.0 VA |
| Other appliances – C | 1,000 W = 1,000 VA × 100 % = 1,000.0 VA |
| Per phase | A: 1,150.0 + 3,450.0 + 1,500.0 = 6,100.0 VA × 1.15 = 7,015.0 VA ÷ 230 V = 30.50 A; B: 2,300.0 + 2,997.0 + 1,200.0 = 6,497.0 VA × 1.15 = 7,471.5 VA ÷ 230 V = 32.48 A; C: 3,000.0 + 2,295.0 + 1,000.0 = 6,295.0 VA × 1.15 = 7,239.2 VA ÷ 230 V = 31.47 A → maximum demand = phase B, 32.48 A |
| Total | S = Σ phases = 21,725.8 VA (21.726 kVA) |
| Connected load | 127,236 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 18,892.0 / 127,236 = 0.148 |
| Main switch | next standard rating ≥ 32.48 A → 40 A → 32.48 vs limit 40.00 A PASS |
| Supply rating | I = 32.48 A against the given supply rating → 32.48 vs limit 32.00 A FAIL |
| Phase imbalance | (Imax − Imin)/Imax = (32.48 − 30.50) / 32.48 × 100 (informative; the component warns above 20 %) → 6.1 vs limit 20.0 % INFO |
| Result | 1/2 checks pass → FAIL; maximum demand 32.48 A (B) → 40 A main switch; governing: supply rating |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 per phase at 230 V: A = lighting 25 points 5 A (1 150 VA) + sockets 35 points 15 A (3 450 VA) + cooktop 3 000 × 50 % = 6 100 VA; B = instantaneous HW 9 000 × 33.3 % = 2 997 VA + dryer 2 400 × 50 % = 1 200 VA + fixed ≤10 A 10 points 10 A (2 300 VA) = 6 497 VA; C = space heater 4 000 × 75 % = 3 000 VA + lift 1 500/(0.86 × 0.95) = 1 835.99 VA × 125 % = 2 294.98 VA + other 1 000 VA = 6 294.98 VA; × 1.15 ÷ 230: A 30.50 A, B 32.48 A, C 31.47 A → maximum phase B 32.48 A > 32 A supply (FAIL); main switch 40 A; imbalance (32.48 − 30.50)/32.48 = 6.1 %. (validation case c0022-domestic-3ph-growth-supply-fail) |
Example 7 — All-electric dwelling with an EV charger
Current-rated loads convert at the phase voltage and multiply by quantity; the EV charger counts in full and the total passes 100 A, failing an 80 A supply.
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 15 points; 10 A socket outlets 18 points; air conditioning 2 × 12 A × 230 V (Split system); storage water heating 4.8 kW; ranges 11 kW; EV charging 7.4 kW. Supply rating 80 A.
| General lighting (A(i)) | 15 points ≤ 20 → 3 A × 230 V = 690 VA |
|---|---|
| 10 A socket outlets (B(i)) | 18 points ≤ 20 → 10 A × 230 V = 2,300 VA |
| Air conditioning (D) | 2 × 12 A × 230 V = 5,520 VA × 75 % = 4,140.0 VA |
| Storage water heating (F) | 4.8 kW = 4,800 VA × 100 % = 4,800.0 VA |
| Ranges (C) | 11 kW = 11,000 VA × 50 % = 5,500.0 VA |
| EV charging | 7.4 kW = 7,400 VA × 100 % = 7,400.0 VA |
| Total | S = 690.0 + 2,300.0 + 4,140.0 + 4,800.0 + 5,500.0 + 7,400.0 = 24,830.0 VA; I = 24,830.0 / 230 = 107.96 A |
| Connected load | 71,620 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 24,830.0 / 71,620 = 0.347 |
| Main switch | next standard rating ≥ 107.96 A → 125 A → 107.96 vs limit 125.00 A PASS |
| Supply rating | I = 107.96 A against the given supply rating → 107.96 vs limit 80.00 A FAIL |
| Result | 1/2 checks pass → FAIL; maximum demand 107.96 A → 125 A main switch; governing: supply rating. Maximum demand (108.0A) exceeds 100A. Coordinate with DNSP for supply upgrade. |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 at 230 V: lighting 15 points 3 A (690 VA); sockets 18 points 10 A (2 300 VA); air conditioners 2 × 12 A × 230 = 5 520 VA × 75 % = 4 140 VA; storage HW 4 800 VA (100 %); range 11 000 × 50 % = 5 500 VA; EV charger 7 400 VA (100 %); total 24 830 VA ÷ 230 = 107.96 A → 125 A main switch; exceeds an 80 A supply (FAIL). (validation case c0022-domestic-ev-over-100a) |
Example 8 — Sockets and fixed ≤ 10 A points share one count
Table C1 row B(i) puts 10 A socket-outlets and permanently connected equipment ≤ 10 A in one group: 18 + 7 = 25 points earn one 10 A block plus one 5 A step, not two 10 A blocks.
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 18 points; 10 A socket outlets 18 points; fixed ≤ 10 A connections 7 points (Dishwasher, rangehood, fans); storage water heating 3.6 kW. Supply rating 35 A.
| General lighting (A(i)) | 18 points ≤ 20 → 3 A × 230 V = 690 VA |
|---|---|
| 10 A sockets + fixed ≤ 10 A (B(i)) | 18 socket + 7 fixed = 25 points → 10 + 5 × ⌈(25 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 230 V = 3,450 VA |
| Storage water heating (F) | 3.6 kW = 3,600 VA × 100 % = 3,600.0 VA |
| Total | S = 690.0 + 3,450.0 + 3,600.0 = 7,740.0 VA; I = 7,740.0 / 230 = 33.65 A |
| Connected load | 62,900 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 7,740.0 / 62,900 = 0.123 |
| Main switch | next standard rating ≥ 33.65 A → 40 A → 33.65 vs limit 40.00 A PASS |
| Supply rating | I = 33.65 A against the given supply rating → 33.65 vs limit 35.00 A PASS |
| Result | 2/2 checks pass → PASS; maximum demand 33.65 A → 40 A main switch; governing: supply rating |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 at 230 V: lighting 18 points → 3 A (690 VA); B(i) 18 socket + 7 fixed = 25 points → 10 + 5 × ⌈5/20⌉ = 15 A (3 450 VA); storage HW 3 600 VA at 100 %; total 7 740 VA ÷ 230 = 33.65 A → 40 A main switch; 35 A supply passes. Counting the two kinds separately (10 A + 10 A) would give 8 890 VA = 38.65 A and fail the 35 A supply. (validation case c0022-domestic-sockets-fixed-b1-combined) |
Example 9 — Pool and spas on different phases
Table C1 is applied per phase, so the pool heater's demand stays on phase B and the two spas' on phase C.
Given: Three-phase 400/230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 30 points on A; 10 A socket outlets 30 points on A; pool heating 6 kW on B; ranges 8 kW on B; spa heating 3 kW (Spa 1) on C; spa heating 2 kW (Spa 2) on C; air conditioning 6 kW on C.
| General lighting (A(i)) – A | 30 points → 3 + 2 × ⌈(30 − 20)/20⌉ = 3 + 2 × 1 = 5 A × 230 V = 1,150 VA |
|---|---|
| 10 A socket outlets (B(i)) – A | 30 points → 10 + 5 × ⌈(30 − 20)/20⌉ = 10 + 5 × 1 = 15 A × 230 V = 3,450 VA |
| Pool/spa (G) – B | 0.75 × 6,000 (largest pool) = 4,500.0 VA |
| Pool/spa (G) – C | 0.75 × 3,000 (largest spa) + 0.25 × 2,000 = 2,750.0 VA |
| Ranges (C) – B | 8 kW = 8,000 VA × 50 % = 4,000.0 VA |
| Air conditioning (D) – C | 6 kW = 6,000 VA × 75 % = 4,500.0 VA |
| Per phase | A: 1,150.0 + 3,450.0 = 4,600.0 VA ÷ 230 V = 20.00 A; B: 4,500.0 + 4,000.0 = 8,500.0 VA ÷ 230 V = 36.96 A; C: 2,750.0 + 4,500.0 = 7,250.0 VA ÷ 230 V = 31.52 A → maximum demand = phase B, 36.96 A |
| Total | S = Σ phases = 20,350.0 VA (20.350 kVA) |
| Connected load | 97,000 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 20,350.0 / 97,000 = 0.210 |
| Main switch | next standard rating ≥ 36.96 A → 40 A → 36.96 vs limit 40.00 A PASS |
| Phase imbalance | (Imax − Imin)/Imax = (36.96 − 20.00) / 36.96 × 100 (informative; the component warns above 20 %) → 45.9 vs limit 20.0 % INFO |
| Result | 1/1 checks pass → PASS; maximum demand 36.96 A (B) → 40 A main switch; governing: main switch. Phase imbalance is high (45.9%). Redistribute loads across phases. |
| Reference | Hand calculation, AS/NZS 3000:2018 Table C1 per phase at 230 V: A = lighting 30 points 5 A (1 150 VA) + sockets 30 points 15 A (3 450 VA) = 4 600 VA; B = pool 0.75 × 6 000 = 4 500 VA (group G) + range 8 000 × 50 % = 4 000 VA = 8 500 VA; C = spas 0.75 × 3 000 + 0.25 × 2 000 = 2 750 VA (group G) + air conditioner 6 000 × 75 % = 4 500 VA = 7 250 VA. Currents A 20.00 A, B 36.96 A, C 31.52 A → maximum phase B 36.96 A → 40 A main switch; total 20 350 VA. (validation case c0022-domestic-3ph-pool-spa-per-phase) |
Example 10 — EV charger capped by load management
Table C1 group (j)(iv) counts EV charging at full connected load with no managed-charging discount; a charger held to 16 A by a load-management device is entered at 16 A (maximum demand by limitation).
Given: Single-phase 230 V supply, single domestic installation (AS/NZS 3000 Table C1). Loads: general lighting 20 points; 10 A socket outlets 20 points; storage water heating 3.6 kW; EV charging 16 A × 230 V (32 A charger capped at 16 A by load management). Supply rating 63 A.
| General lighting (A(i)) | 20 points ≤ 20 → 3 A × 230 V = 690 VA |
|---|---|
| 10 A socket outlets (B(i)) | 20 points ≤ 20 → 10 A × 230 V = 2,300 VA |
| Storage water heating (F) | 3.6 kW = 3,600 VA × 100 % = 3,600.0 VA |
| EV charging | 16 A × 230 V = 3,680 VA × 100 % = 3,680.0 VA |
| Total | S = 690.0 + 2,300.0 + 3,600.0 + 3,680.0 = 10,270.0 VA; I = 10,270.0 / 230 = 44.65 A |
| Connected load | 55,280 VA (lighting 100 W per point, sockets 10 A per point); overall diversity = 10,270.0 / 55,280 = 0.186 |
| Main switch | next standard rating ≥ 44.65 A → 50 A → 44.65 vs limit 50.00 A PASS |
| Supply rating | I = 44.65 A against the given supply rating → 44.65 vs limit 63.00 A PASS |
| Result | 2/2 checks pass → PASS; maximum demand 44.65 A → 50 A main switch; governing: supply rating |
| Reference | Hand calculation, AS/NZS 3000:2018 (Amd 1:2020) Table C1 at 230 V: lighting 20 points 3 A (690 VA); sockets 20 points 10 A (2 300 VA); storage HW 3 600 VA; EV charging (j)(iv) at full connected load 16 A × 230 = 3 680 VA; total 10 270 VA ÷ 230 = 44.65 A → 50 A main switch; 63 A supply passes. (validation case c0022-domestic-ev-load-limited) |
Example 11 — One MCC, two duty pumps and a standby
The duty/standby method on a single board: standby units count to installed kW only; running kW = n × P × LF / η.
Given: Load list by duty/standby and load factor (method duty_standby_lf). Boards: MCC 415 V 3φ (top level). Loads: M-01 on MCC: 2 duty + 1 standby × 75 kW output, LF 0.8, η 0.95, pf 0.85. Growth 1, spare capacity 1.
| M-01 | P = 2 × 75 (shaft kW) × 0.8 / 0.95 = 126.316 kW; Q = P × tan(acos 0.85) = 78.283 kVAr; + 1 standby (installed only) |
|---|---|
| MCC | P = 126.316 kW; Q = 78.283 kVAr; S = √(P² + Q²) = 148.607 kVA, pf 0.850; I = 148,607 / (√3 × 415) = 206.74 A; installed 225.0 kW |
| Result | MCC design 148.6 kVA = 206.74 A |
| Reference | Hand calculation: P = 2 duty × 75 kW × 0.8 / 0.95 = 126.316 kW; Q = P × tan(arccos 0.85) = 78.283 kVAr; S = P / 0.85 = 148.607 kVA; I = 148 607 / (√3 × 415) = 206.74 A; standby unit excluded from demand, included in installed 3 × 75 kW (validation case demand-duty-standby-single-board) |
Example 12 — MSB feeding two MCCs with growth and spare
Diversity compounds up the hierarchy (0.9 at MCC-1, 0.95 at the MSB) while growth and spare apply once to each board's own demand.
Given: Load list by duty/standby and load factor (method duty_standby_lf). Boards: MSB 415 V 3φ (top level), diversity 0.95; MCC-1 415 V 3φ fed from MSB, diversity 0.9; MCC-2 415 V 3φ fed from MSB. Loads: P-101 on MCC-1: 2 duty + 1 standby × 55 kW output, LF 0.85, η 0.94, pf 0.86; H-101 on MCC-1: 1 duty × 30 kW input, LF 1, pf 1; CV-201 on MCC-2: 1 duty × 132 kW output, LF 0.75, η 0.95, pf 0.85. Growth 1.1, spare capacity 1.2.
| P-101 | P = 2 × 55 (shaft kW) × 0.85 / 0.94 = 99.468 kW; Q = P × tan(acos 0.86) = 59.021 kVAr; + 1 standby (installed only) |
|---|---|
| H-101 | P = 1 × 30 (electrical kW) × 1 = 30.000 kW; Q = P × tan(acos 1) = 0.000 kVAr |
| CV-201 | P = 1 × 132 (shaft kW) × 0.75 / 0.95 = 104.211 kW; Q = P × tan(acos 0.85) = 64.584 kVAr |
| MCC-2 | P = 104.211 kW; Q = 64.584 kVAr; S = √(P² + Q²) = 122.601 kVA, pf 0.850; I = 122,601 / (√3 × 415) = 170.56 A; design S × 1.1 × 1.2 = 161.833 kVA = 225.14 A; installed 132.0 kW |
| MCC-1 | P = 0.9 × (99.468 + 30.000) = 116.521 kW; Q = 0.9 × (59.021 + 0.000) = 53.119 kVAr; S = √(P² + Q²) = 128.058 kVA, pf 0.910; I = 128,058 / (√3 × 415) = 178.15 A; design S × 1.1 × 1.2 = 169.036 kVA = 235.16 A; installed 195.0 kW |
| MSB | P = 0.95 × (116.521 + 104.211) = 209.695 kW; Q = 0.95 × (53.119 + 64.584) = 111.818 kVAr; S = √(P² + Q²) = 237.645 kVA, pf 0.882; I = 237,645 / (√3 × 415) = 330.61 A; design S × 1.1 × 1.2 = 313.692 kVA = 436.41 A; installed 327.0 kW (feeds MCC-1, MCC-2) |
| Result | MSB design 313.7 kVA = 436.41 A |
| Reference | Hand calculation: MCC-1 = 0.9 × (2 × 55 × 0.85/0.94 + 30) = 116.521 kW, 0.9 × 59.021 = 53.119 kVAr; MCC-2 = 132 × 0.75/0.95 = 104.211 kW, 64.584 kVAr; MSB = 0.95 × (220.732 kW, 117.703 kVAr) = 209.695 kW, 111.818 kVAr → 237.645 kVA; design 237.645 × 1.1 × 1.2 = 313.692 kVA = 436.41 A at 415 V (validation case demand-duty-standby-hierarchy) |
Example 13 — Single-phase lighting and heating board
Electrical-input ratings skip the efficiency; a single-phase board's current is S/V; growth 1.1 lifts the design current, checked against a 50 A board rating.
Given: Load list by duty/standby and load factor (method duty_standby_lf). Boards: DB-L1 230 V 1φ (top level), diversity 0.9, rated 50 A. Loads: LTG-01 on DB-L1: 1 duty × 3.6 kW input, LF 1, pf 0.95 (LED lighting); HTR-01 on DB-L1: 2 duty × 2.4 kW input, LF 1, pf 1 (Panel heaters); EF-01 on DB-L1: 1 duty × 0.75 kW output, LF 0.9, η 0.8, pf 0.8 (Exhaust fan). Growth 1.1, spare capacity 1.
| LTG-01 | P = 1 × 3.6 (electrical kW) × 1 = 3.600 kW; Q = P × tan(acos 0.95) = 1.183 kVAr |
|---|---|
| HTR-01 | P = 2 × 2.4 (electrical kW) × 1 = 4.800 kW; Q = P × tan(acos 1) = 0.000 kVAr |
| EF-01 | P = 1 × 0.75 (shaft kW) × 0.9 / 0.8 = 0.844 kW; Q = P × tan(acos 0.8) = 0.633 kVAr |
| DB-L1 | P = 0.9 × (3.600 + 4.800 + 0.844) = 8.319 kW; Q = 0.9 × (1.183 + 0.000 + 0.633) = 1.634 kVAr; S = √(P² + Q²) = 8.478 kVA, pf 0.981; I = 8,478 / 230 = 36.86 A; design S × 1.1 = 9.326 kVA = 40.55 A; installed 9.2 kW; design current against its 50 A rating → 40.55 vs limit 50.00 A PASS |
| Result | 1/1 checks pass → PASS; DB-L1 design 9.3 kVA = 40.55 A; governing: board rating:DB-L1 |
| Reference | Hand calculation: LTG-01 3.6 kW (input) → Q = 3.6 × tan(acos 0.95) = 1.183 kVAr; HTR-01 2 × 2.4 = 4.8 kW, Q = 0; EF-01 0.75 × 0.9 / 0.8 = 0.8438 kW, Q = 0.6328 kVAr; Σ = 9.2438 kW, 1.8161 kVAr × 0.9 = 8.319 kW, 1.634 kVAr → S = 8.478 kVA, I = 8478.4 / 230 = 36.86 A; design × 1.1 = 9.326 kVA = 40.55 A ≤ 50 A (81.1 %). (validation case demand-duty-standby-single-phase-db) |
Example 14 — Two main boards, one over its rating
Each top-level board is assessed independently; a load factor above 1 (service-factor running) pushes MSB-B past its 250 A rating.
Given: Load list by duty/standby and load factor (method duty_standby_lf). Boards: MSB-A 415 V 3φ (top level), diversity 0.9, rated 400 A; MSB-B 415 V 3φ (top level), rated 250 A. Loads: CH-01 on MSB-A: 2 duty + 1 standby × 90 kW output, LF 0.8, η 0.95, pf 0.88 (Chillers); AHU-01 on MSB-A: 2 duty × 30 kW output, LF 0.9, η 0.93, pf 0.85; CMP-01 on MSB-B: 1 duty × 110 kW output, LF 1.1, η 0.95, pf 0.87 (Compressor, service factor); OVN-01 on MSB-B: 1 duty × 60 kW input, LF 1, pf 1 (Curing oven). Growth 1, spare capacity 1.
| CH-01 | P = 2 × 90 (shaft kW) × 0.8 / 0.95 = 151.579 kW; Q = P × tan(acos 0.88) = 81.814 kVAr; + 1 standby (installed only) |
|---|---|
| AHU-01 | P = 2 × 30 (shaft kW) × 0.9 / 0.93 = 58.065 kW; Q = P × tan(acos 0.85) = 35.985 kVAr |
| CMP-01 | P = 1 × 110 (shaft kW) × 1.1 / 0.95 = 127.368 kW; Q = P × tan(acos 0.87) = 72.183 kVAr |
| OVN-01 | P = 1 × 60 (electrical kW) × 1 = 60.000 kW; Q = P × tan(acos 1) = 0.000 kVAr |
| MSB-B | P = 127.368 + 60.000 = 187.368 kW; Q = 72.183 + 0.000 = 72.183 kVAr; S = √(P² + Q²) = 200.792 kVA, pf 0.933; I = 200,792 / (√3 × 415) = 279.34 A; installed 170.0 kW; design current against its 250 A rating → 279.34 vs limit 250.00 A FAIL |
| MSB-A | P = 0.9 × (151.579 + 58.065) = 188.679 kW; Q = 0.9 × (81.814 + 35.985) = 106.019 kVAr; S = √(P² + Q²) = 216.425 kVA, pf 0.872; I = 216,425 / (√3 × 415) = 301.09 A; installed 330.0 kW; design current against its 400 A rating → 301.09 vs limit 400.00 A PASS |
| Result | 1/2 checks pass → FAIL; MSB-A design 216.4 kVA = 301.09 A; governing: board rating:MSB-B |
| Reference | Hand calculation: MSB-A: chillers 2 × 90 × 0.8 / 0.95 = 151.579 kW, Q = P × tan(acos 0.88) = 81.814 kVAr; AHUs 2 × 30 × 0.9 / 0.93 = 58.065 kW, 35.985 kVAr; × 0.9 → 188.679 kW, 106.019 kVAr, S = 216.425 kVA = 301.09 A ≤ 400 A; installed (2 + 1) × 90 + 2 × 30 = 330 kW. MSB-B: compressor 110 × 1.1 / 0.95 = 127.368 kW, 72.183 kVAr + oven 60 kW → S = 200.792 kVA, I = 200792 / (√3 × 415) = 279.34 A > 250 A (FAIL). Headline = larger top board = MSB-A. (validation case demand-duty-standby-two-boards-overload) |
Example 15 — 11 kV board feeding a 415 V MSB and MCC
Three levels at two voltages: diversity compounds (0.9 then 0.95 then 1.0), a standby-only line adds installed kW but no demand, and 25 % spare is applied to each board once.
Given: Load list by duty/standby and load factor (method duty_standby_lf). Boards: HV-SWBD 11,000 V 3φ (top level), rated 100 A; MSB 415 V 3φ fed from HV-SWBD, diversity 0.95, rated 1,600 A; MCC-1 415 V 3φ fed from MSB, diversity 0.9. Loads: P-001 on HV-SWBD: 1 duty × 500 kW output, LF 0.85, η 0.96, pf 0.88 (HV slurry pump); CV-01 on MCC-1: 1 duty × 160 kW output, LF 0.75, η 0.95, pf 0.86; P-101 on MCC-1: 2 duty + 2 standby × 45 kW output, LF 0.8, η 0.93, pf 0.85; P-102 on MCC-1: 0 duty + 1 standby × 37 kW output, LF 1, η 0.93, pf 0.85 (Spare-only pump); LTG-MSB on MSB: 1 duty × 40 kW input, LF 1, pf 0.95. Growth 1, spare capacity 1.25.
| P-001 | P = 1 × 500 (shaft kW) × 0.85 / 0.96 = 442.708 kW; Q = P × tan(acos 0.88) = 238.949 kVAr |
|---|---|
| CV-01 | P = 1 × 160 (shaft kW) × 0.75 / 0.95 = 126.316 kW; Q = P × tan(acos 0.86) = 74.951 kVAr |
| P-101 | P = 2 × 45 (shaft kW) × 0.8 / 0.93 = 77.419 kW; Q = P × tan(acos 0.85) = 47.980 kVAr; + 2 standby (installed only) |
| P-102 | 0 duty units (standby only) → 0 kW; installed 1 × 37 = 37.0 kW |
| LTG-MSB | P = 1 × 40 (electrical kW) × 1 = 40.000 kW; Q = P × tan(acos 0.95) = 13.147 kVAr |
| MCC-1 | P = 0.9 × (126.316 + 77.419 + 0.000) = 183.362 kW; Q = 0.9 × (74.951 + 47.980 + 0.000) = 110.638 kVAr; S = √(P² + Q²) = 214.155 kVA, pf 0.856; I = 214,155 / (√3 × 415) = 297.93 A; design S × 1.25 = 267.694 kVA = 372.42 A; installed 377.0 kW |
| MSB | P = 0.95 × (40.000 + 183.362) = 212.194 kW; Q = 0.95 × (13.147 + 110.638) = 117.597 kVAr; S = √(P² + Q²) = 242.601 kVA, pf 0.875; I = 242,601 / (√3 × 415) = 337.51 A; design S × 1.25 = 303.251 kVA = 421.88 A; installed 417.0 kW (feeds MCC-1); design current against its 1,600 A rating → 421.88 vs limit 1,600.00 A PASS |
| HV-SWBD | P = 442.708 + 212.194 = 654.902 kW; Q = 238.949 + 117.597 = 356.545 kVAr; S = √(P² + Q²) = 745.668 kVA, pf 0.878; I = 745,668 / (√3 × 11,000) = 39.14 A; design S × 1.25 = 932.085 kVA = 48.92 A; installed 917.0 kW (feeds MSB); design current against its 100 A rating → 48.92 vs limit 100.00 A PASS |
| Result | 2/2 checks pass → PASS; HV-SWBD design 932.1 kVA = 48.92 A; governing: board rating:HV-SWBD |
| Reference | Hand calculation: MCC-1: CV-01 160 × 0.75 / 0.95 = 126.316 kW (74.951 kVAr); P-101 2 × 45 × 0.8 / 0.93 = 77.419 kW (47.980 kVAr); P-102 0 duty → 0; × 0.9 = 183.362 kW, 110.638 kVAr; installed 160 + 4 × 45 + 37 = 377 kW. MSB: (MCC-1 + lighting 40 kW, 13.147 kVAr) × 0.95 = 212.194 kW, 117.597 kVAr → 242.601 kVA = 337.5 A at 415 V (design × 1.25 = 421.9 A ≤ 1 600 A). HV-SWBD: P-001 500 × 0.85 / 0.96 = 442.708 kW, 238.949 kVAr + MSB → 654.902 kW, 745.668 kVA; design × 1.25 = 932.085 kVA = 48.92 A at 11 kV ≤ 100 A; transformer losses not added. (validation case demand-duty-standby-hv-three-level) |
Standards & References
- AS/NZS 3000:2018 — Electrical installations (known as the Australian/New Zealand Wiring Rules)
- Appendix C — Maximum demand assessment for electrical installations
- Table C1 — Domestic installations (single dwelling and blocks of living units) — diversity factors by load group
- Table C2 — Non-domestic installations — diversity factors for commercial and industrial premises
- AS/NZS 3008.1.1:2017 — Cable selection (used downstream when sizing the main cable based on maximum demand current)
Tips & Limitations
Tips
- Use the detailed equipment list mode for accurate results. The simple mode is useful for quick estimates only.
- For three-phase installations, distribute loads across all three phases to minimise imbalance. The calculator warns if imbalance exceeds 10%.
- Apply a future growth factor of 1.1–1.2 to allow spare capacity for additional loads.
- EV chargers count at full rating. A load-management device that caps the charger lowers the demand only through its limit setting: enter the charger at that limited current.
- The diversity factors in Table C1 are informative (not normative). Final design should be verified with the local DNSP requirements.
- Points-based groups (lighting, 10A sockets) use a step function — each additional block of 20 points adds a fixed current increment, making the diversity benefit stronger for larger installations.
- Motor loads rated in W or kW are automatically converted to VA using the configured motor power factor and efficiency.
Limitations
- Residential focus — currently implements Table C1 diversity rules only (single dwellings and blocks of units). Table C2 (non-domestic) is not yet fully implemented.
- No inter-unit diversity — for blocks of units, Table C2 inter-dwelling diversity factors are not applied. The calculator treats each dwelling independently.
- Single voltage per phase — assumes a uniform phase voltage across all load groups.
- No automatic phase balancing — users must manually assign loads to phases A, B, and C. The calculator reports imbalance but does not redistribute loads.
- Connected load estimate for lighting — lighting connected load is estimated at 100W per point; actual connected load may differ.
Developer Guide
Architecture
File layout:
components/c0022_max_demand/component.py— Component registration, PARAMETER_SCHEMA, LOAD_GROUPS dict, MaximumDemandCalculator class, SVG generators, summary card buildercomponents/c0022_max_demand/calculations.py— Pure calculation functions and DIVERSITY_RULES_C1 lookup table (no Django dependencies)components/c0022_max_demand/equations.py— Equation builder generating HTML with LaTeX for calculation stepscomponents/c0022_max_demand/excel_generator.py— Excel export generation
The calculator class is MaximumDemandCalculator, which
extends ElectricalCalculator. It delegates to
calculate_maximum_demand() in calculations.py.
Key data structures:
LOAD_GROUPS— dict mapping load group keys to metadata (code, name, description, table, applies_to)DIVERSITY_RULES_C1— dict mapping load group keys to diversity method and rule text- Equipment list items are JSON objects with fields: load_group, description, phase, rating_value, rating_unit, quantity, power_factor
SVG generators:
generate_load_breakdown_svg()— pie chart of diversified VA by load groupgenerate_phase_balance_svg()— bar chart of per-phase load balance (three-phase only)
Code Paths
Key functions in calculations.py:
| Function | Purpose |
|---|---|
calculate_maximum_demand(data) |
Main entry point; orchestrates grouping, diversity, and current calculation |
convert_rating_to_va(rating_value, rating_unit, voltage, pf, eff) |
Convert equipment rating (A, W, kW, points) to VA |
apply_diversity_lighting_general(loads, voltage) |
Points-based diversity for general lighting (row ai) |
apply_diversity_socket_10a(loads, voltage) |
Points-based diversity for row bi (10A sockets + fixed ≤10A); _b1_share() counts
both sub-groups together on a phase and shares the result back by points |
apply_diversity_percentage(loads, voltage, percentage, pf, eff) |
Generic percentage-based diversity (rows c, d, e, f, etc.) |
apply_diversity_tiered_motors(loads, voltage, load_group, pf, eff) |
Tiered diversity for lift and general motors (rows k, l) |
apply_diversity_pool_spa_heaters(pool_loads, spa_loads, voltage) |
Pool/spa heater diversity (row g) for the heaters on one phase |
calculate_diversity_for_load_group(load_group, loads, voltage, pf, eff) |
Dispatcher: routes each load group to its diversity function |
select_standard_main_switch_rating(current_a) |
Select nearest standard main switch rating ≥ current |
Testing
Running tests:
pytest calcs/test_c0022_max_demand.py -vWorked examples: the examples above are generated from the validation corpus
(mcp_public/validation/cases/fe_calc_max_demand/) (including the duty/standby load-list examples, which have no calcs component and publish here) by
python manage.py generate_help_examples --tool fe_calc_max_demand, which writes
_max_demand_examples.html. Add or change a case there, then regenerate; the
fragment is never edited by hand.
How to extend:
- Add new load groups by extending
LOAD_GROUPSincomponent.pyand adding a corresponding entry inDIVERSITY_RULES_C1incalculations.py. - Implement Table C2 diversity rules by creating a
DIVERSITY_RULES_C2dict and routing based onapplication_typeincalculate_diversity_for_load_group(). - For inter-dwelling diversity (blocks of units), add a post-
processing step in
calculate_maximum_demand()that applies Table C2 inter-unit factors based onnumber_of_units. - Write tests covering each new diversity rule with boundary conditions (e.g., exactly 20 points, 21 points, zero loads).