Electrical Load Schedule & DB Load Calculation (India, IS 732)
Boards, circuits and connected load to maximum demand, phase by phase.
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Project and supply
Design figures
Letterhead for the report
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Distribution boards
A single-phase board sits on one phase of the board above it; a three-phase board spreads its own circuits across R, Y and B. The diversity factor applies to the circuits of that board, and its incoming device is sized on the connected load, because the National Building Code warns that a board must take the whole load connected to it without any diversity.
| Board | Fed from | Phases | On phase | Diversity % | Spare ways | Feeder m | Conductor | Feeder mm² | Remove |
|---|
Leave the feeder size empty and the smallest conductor that keeps the feeder’s drop within the limit is suggested (never below 4 mm²).
Circuits
Points × watts gives the connected load. The device and the cable are sized on that load; the demand factor only reduces what the board and the supply must carry. Leave the device rating or the conductor size empty and the tool suggests one — a run length is needed for the cable. A suggested size is the smallest that keeps the voltage drop within your limit and is never below the minimum size of CPWD’s specification; it is not a current-carrying capacity, so check each cable as installed against its device rating (IS 732 asks for I_B ≤ I_n ≤ I_z).
| Circuit | Load | Points | W each | PF | Phase | Demand % | Run m | Device A | Type | RCD | Cable mm² | Conductor | Remove |
|---|
No circuits on this board yet.
Building summary
Load on each phase
| Phase | Connected (kW) | Demand (kW) | Demand (kVA) | Current (A) |
|---|
Boards
| Board | Phases | Circuits | Connected (kW) | Demand (kW) | Incoming (A) | Feeder |
|---|
Notes
The building summary, the load on each phase and the board totals show here in full once this schedule is unlocked. The pages below are a free preview: the figures the tool worked out are hidden on them, and the Circuits tab shows the first circuits of each board with the rest locked.
Report
Sizing one circuit in detail? The cable size calculator adds the short-circuit check, and the voltage drop calculator works a run out step by step.
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- Based on
- the rules of India, as set out under ‘How each figure is worked out’.
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About the Electrical Load Schedule & DB Load Calculation (India, IS 732)
Build the load schedule of a whole building: the distribution boards, the circuits on each board with their points and watts, and the demand and diversity factors you apply. For every circuit the tool works out the connected load, the design current, a protective device from the preferred ratings of IS/IEC 60898-1, the conductor size that keeps the voltage drop within your limit, and the drop itself; for every board the connected load, the maximum demand, the load on each phase with the imbalance and a better arrangement when one exists, and the incoming device sized on the connected load.
The building summary gives the connected load, the maximum demand in kW and kVA, an allowance for future extension and the transformer or supply rating that covers it from the standard ratings of IS 1180. With a pass, download it as a PDF report with a title block on your letterhead, or as an Excel workbook with live formulas; without one, the free preview shows the report’s pages marked, with the figures the tool worked out hidden. It is an aid to design, not a design: the licensed designer stays responsible for the installation.
How to use it
- On Project, enter the building, the supply voltages (230 V single phase and 415 V three phase in India), the kind of premises, your voltage-drop limits and how much you keep for future extension.
- On Boards, add the distribution boards: which board each one is fed from, one or three phases, the phase a single-phase board sits on, its diversity factor, spare ways and the length of its feeder.
- On Circuits, choose a board and add its circuits — the load, the points, the watts each, the power factor, the phase, the demand factor and the run length. A room template fills several circuits at once; leave the device rating or the conductor size empty and the tool suggests one.
- Read the Schedule: the building summary, the load on each phase, every board with its incoming device and feeder, and the notes the schedule raised (circuit limits, imbalance, drops over the limit).
- Without a pass the schedule stays a free preview: its pages show marked, with the figures hidden. “Ways to unlock” opens the full schedule, the PDF report, the workbook and the summary copy.
Examples
Eight 6 A socket outlets at 100 W each, power factor 1, 230 V, run 22 m, copper, 3% drop limit
Connected 800 W → 3.48 A → 6 A type B device, 1.5 mm² copper, drop 2.30 V = 1.00%; the same conductor is good for 66 m
The 100 W per 6 A outlet is the design figure of CPWD’s specification; the drop follows IEC 60364-5-52 Annex G.
One 16 A socket outlet at 1,000 W, 230 V, run 14 m
4.35 A → a 16 A device (the outlet can draw its rated current) and 4 mm² copper, the minimum CPWD’s specification sets for power wiring
Three 2 kW water heaters, all put on phase R
Phases differ by 300% of the average; moving two of them to Y and B brings it to 0%
Three floor boards of 10.65 kW each at 70% diversity, plus a lift, a pump and staircase lights · 20% kept for extension
Connected 37.82 kW · maximum demand 27.30 kW (29.30 kVA at power factor 0.93) · with the allowance 35.16 kVA → a 40 kVA transformer rating
Common uses
- Electrical contractors applying for a sanctioned load and sizing the service.
- Consultants issuing a DB schedule and a load calculation with the drawings.
- Site engineers checking a panel schedule against the wiring actually installed.
- Builders working out the transformer or DG size a building needs.
How each figure is worked out
- Connected load = points × watts per point. Demand = connected load × the circuit’s demand factor; a board then applies its diversity factor to the demand of its own circuits.
- Current: apparent power ÷ the line-to-neutral voltage for a single-phase circuit, ÷ (√3 × the line-to-line voltage) for a three-phase one. A final circuit’s device and cable are sized on its connected load — the demand and diversity factors only reduce what the board, the feeder and the supply must carry.
- Protective device: the smallest preferred rated current of IS/IEC 60898-1 (6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100 and 125 A) that is at least the design current, and at least the rating of a socket outlet on the circuit. Type B, C and D are that standard’s instantaneous tripping ranges: 3–5, 5–10 and 10–20 times the rated current.
- Conductor: the smallest IEC 60228 size whose voltage drop over the run stays within your limit, never below the minimum CPWD’s specification sets (1.5 mm² for light wiring, 4 mm² for power wiring). The drop uses IEC 60364-5-52 Annex G with its own values for resistivity in service and reactance.
- Incoming device of a board: sized on the connected load, because the National Building Code warns that a distribution board must be of sufficient rating to take the total load connected to it without the application of any diversity.
- Transformer or supply: the smallest standard rating of IS 1180 (Part 1) that covers the maximum demand with your allowance for extension.
What the tool checks for you
- A lighting circuit of more than 800 W or more than ten points — CPWD’s specification keeps a lighting circuit to 800 W or ten points, whichever is less, with more points allowed only where the load per point is small (LED or CFL points).
- More than one point above 1 kW on one circuit, which that specification controls by its own suitably rated device.
- A socket outlet behind a residual-current device of more than 30 mA.
- A device rating below the design current, which IS 732 cl. 5.3.3.2 does not allow (I_B ≤ I_n ≤ I_z).
- A voltage drop over your limit, and the longest run that would stay within it.
- A three-phase board whose phases differ by more than 15 %, with the better arrangement when one exists, and a three-phase circuit left on a single-phase board.
- A power factor below 0.85, the lower limit supply conditions usually set.
What this tool does not do
It does not supply current-carrying capacities. The capacity of a cable depends on how it is installed — in conduit, on a tray, buried, bunched with others, in an ambient temperature, under thermal insulation — so the I_z of your cable as installed must come from the cable maker’s table or the code’s own tables with their derating factors, and then be checked against the device rating. The same goes for the earth-fault loop impedance, the short-circuit withstand of the cable (the cable size calculator has the adiabatic check) and the discrimination between devices.
References: IS 732 (code of practice for electrical wiring installations), the National Building Code of India Part 8 Section 2 (electrical and allied installations), CPWD’s General Specifications for Electrical Works Part 1: Internal, IS/IEC 60898-1 (circuit-breakers for household and similar installations), IEC 60364-5-52 Annex G (voltage drop) and IS 1180 (Part 1) (distribution transformers). The published documents of the first three are available from BIS and CPWD.
The Excel workbook
The workbook has the design figures as entries, every circuit with its connected load, demand, apparent power and current as formulas, every board added up from the circuits sheet with SUMIF, and a summary with the building totals, the load on each phase and the transformer rating. Yellow cells are entries: change a wattage, a demand factor or a diversity factor and the schedule recalculates in Excel, LibreOffice or Google Sheets. The devices, conductor sizes and drops are the figures this tool worked out and stay values.
Limitations
- An aid to design, not a design: the licensed designer is responsible for the installation and for compliance with IS 732, the National Building Code and the supply authority’s conditions.
- No current-carrying capacities or derating factors: the I_z of the cable as installed must come from your own table and be checked against the device rating.
- No earth-fault loop impedance, no short-circuit withstand check and no discrimination study.
- Diversity is applied per circuit and per board; the table of typical allowances in the National Building Code also has rules per kind of load that you apply yourself through those factors.
- Motor starting currents, harmonics and neutral loading of discharge lighting are not worked out.
- Projects are kept in this browser on this device: download a backup to move them or keep them safe.
Privacy
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Frequently asked questions
What do I get without a pass?
Without a pass, Electrical Load Schedule & DB Load Calculation (India, IS 732) shows the report as page images marked “MySmartCoPilot preview · not for use”, with every load, current, device and cable the tool worked out drawn as a bar. Until you unlock it, the result can’t be downloaded or copied. A Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
What is the difference between connected load and maximum demand?
The connected load is everything wired up, added together. The maximum demand is what the installation is expected to draw at once: the connected load reduced by the demand factor of each circuit and the diversity factor of each board. The supply and the feeders are sized on the demand; a distribution board is sized on the connected load.
Which demand and diversity factors should I use?
Your own, from experience — which is what the National Building Code says. Its table of typical allowances for diversity gives, for lighting, 66 % of the total demand in an individual household installation, 90 % in small shops, stores, offices and business premises and 75 % in small hotels and boarding houses; choosing the kind of premises starts new lighting, fan and socket circuits at that figure, and every circuit and board keeps its own factor that you can change.
How is the MCB rating chosen?
The smallest preferred rated current of IS/IEC 60898-1 that is at least the circuit’s design current, and at least the rating of a socket outlet on it. The standard’s preferred values are 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100 and 125 A; above that range a moulded-case circuit-breaker is needed. You can type your own rating instead, and the tool says if it is below the design current.
Does the cable size include the current-carrying capacity?
No. The size suggested is the smallest that keeps the voltage drop within your limit and is not below the minimum size for that kind of circuit. The current-carrying capacity of the cable as installed, with its derating for grouping, ambient temperature and installation method, must come from your own table and be checked against the device rating (IS 732 asks for I_B ≤ I_n ≤ I_z).
How does the phase balance work?
A single-phase board puts its whole load on the phase it is fed from; a three-phase board spreads its own circuits by the phase each one is on, and a three-phase circuit counts a third on each phase. The schedule shows the load on R, Y and B, how far they differ from the average, and — where a better arrangement exists — which circuits or boards to move to which phase.
Where does the transformer rating come from?
The standard ratings of IS 1180 (Part 1) for outdoor oil-immersed distribution transformers: 16, 25, 63, 100, 160 and 200 kVA up to 11 kV, then 250 to 2,500 kVA, with 6.3, 10, 20 and 40 kVA marked non-preferred in that standard. The tool takes the smallest rating that covers your demand plus the allowance for extension and says when a rating is a non-preferred one.
Where is my data kept?
In this browser on your device. You don’t need an account; download a backup from the Project tab to keep your projects safe or open them on another device.