Load current (A) Material Ambient (°C) Current-carrying conductors in raceway

Continuous load (3 h or more, size at 125%)

Draft sizing only. Verify conductor size, derating, termination limits, grounding and voltage drop against the current code.

Enter the overall outside diameter of each conductor or cable (from the manufacturer data sheet) and how many.

Diameter 1 (mm)Quantity 1 Diameter 2 (mm)Quantity 2 Diameter 3 (mm)Quantity 3 Diameter 4 (mm)Quantity 4

Conduit type

Estimate only. EMT, bends, mixed insulation and cable fill are not covered. Verify against the current code.

Section 26: receptacles and circuits for a dwelling. Step 1: add each room and its wall lengths. Step 2: fill in the whole-dwelling sections below. Step 3: press Check. Each hint names the Code rule behind the box.

1. The dwelling (26-724)

Change the numbers to match the job. Zero means none.

Dwelling type Perimeter at grade (m)Distance around the building at grade. 20 m or less needs one outdoor receptacle, more needs two (26-724).

2. Rooms and spaces counted (26-654, 26-656, 26-720, 26-724)

Each one below needs a circuit or receptacle of its own. Enter how many there are.

KitchensEach has a refrigerator circuit (26-654 a)). Laundry roomsWith washer spaces, one circuit of their own (26-654 b)). Washer plumbing spaces outside a laundry roomCounted with the laundry rooms (26-654 b)). Utility roomsOne circuit of their own (26-654 c)). Microwave cupboardsEach receptacle in a cupboard for a microwave has its own circuit (26-654 d)). Central vacuum systemsEach system has its own circuit (26-654 e)). EV receptacles requiredOnly where the National Building Code requires one (26-720 n), 26-654 f)). Car spaces (garage / carport)One receptacle for each car space (26-724 3)). Garage door openersOne receptacle within 1 m of each cord-connected opener (26-724 4)).

3. Range, dryer and power supply (26-744)

Tick only what applies.

Provision for a gas range Built-in cooktop or wall oven installed Electric clothes dryer No supply authority power available

Local generation (kW), off-grid onlyOnly for a dwelling with no supply authority power. Under 6 kW changes the range rule (26-744).

Minimums from OESC 2024 Section 26 only. Lighting, bedroom and living room circuit loading and outlets per circuit are in other sections and are not checked here. Verify against the current code.

OESC 2024 Section 64: solar photovoltaic circuits, inverters and interconnection, and energy storage. Fill in what you know; each part is checked only when you give it something to check. Blank answers are shown as questions, never assumed.

Dwelling unit (the 125% interconnection limit and the dwelling-unit rules apply)

1. Solar panels (64-200 to 64-218)

Fill in only what applies to your job. Blank boxes are skipped.

Rated open-circuit voltage, whole source circuit (V)Rated short-circuit current (A)Source circuits in parallelConductor ampacity (A)Source circuit overcurrent device (A)Module nameplate maximum overcurrent protection (A)Voltage drop (% of rated operating voltage)On or in a building?Conductors more than 1 m from the array?

Ground-mounted array whose circuits enter a building used only to house PV equipment

2. Inverter and connection to the panel (64-100, 64-108, 64-112)

Fill in only what applies to your job. Blank boxes are skipped.

Inverter continuous output current (A)or inverter output (kW)AC voltage (V)PhasesInverter overcurrent device marked for continuous operation atBusbar rating (A)Main overcurrent device (A)Inverter overcurrent device (A)Neutral ampacity (A)Maximum load, neutral to one ungrounded conductor (A)

Single conductors (not in a cable) Single-phase, 2-wire inverter output Equipment limits the input and output current of the interconnected systems (64-112 4) g) i)) Equipment combines ac supply circuits only, with one output device and a no-other-loads label (64-112 4) g) ii))

3. Batteries (energy storage) (64-900 to 64-1100)

Skip this part if there are no batteries. Leave a box blank to ask the tool what the Code requires.

Capacity of each system (kWh), separated by commasLocationOccupancyEnergy storage output (kW, for plan review)System voltage (V dc)The battery system's dc voltage from the nameplate.Distance to nearest window or door (m)Measure from the battery to the closest opening.Gap between battery systems (m)Only needed with 2 or more systems. Measure edge to edge. Code minimum is 1 m (64-1100 8).Floor height above grade (m)Ground level is 0. A basement is below grade, so enter a negative number, e.g. -2.5.In a sleeping area or a room opening into one?Manufacturer instructions allow over 50 V dc in a dwelling?Smoke alarm or detector in the room?Fire resistance rating of the room (h)In hours, e.g. 1 for a 1-hour rated room.

Installed below the lowest level of egress In an electrical equipment vault Evaluated to ANSI/CAN/UL 9540A Building has multiple dwelling units

Checks follow OESC 2024 Section 64 and the rules it points to (Rule 8-104, Table 13). Where a rule needs a formula or a judgement the pages do not print, it is flagged for you to confirm with the manufacturer or ESA. Verify against the current code.

Voltage drop from Table D3 of Appendix D (informative) with the limits of Rule 8-102. Choose the circuit, give the load, length and voltage, and either pick a conductor size to get the drop and the longest run, or leave the size out to find the smallest conductor that meets the limit.

Type of circuit (voltage drop factor f)ConductorTable D3 columnConductor sizeLoad current (A)or overcurrent device (A), 80% is usedLength of the circuit conductors (m)Voltage at the source (V)Conductor operating temperatureLimit (%), blank = 3% (Rule 8-102 1) a))Drop in the rest of the circuit (%), for the 5% total

Extra-low-voltage power circuit (Note 4: 0.86 when the load is not more than two-thirds of the copper 60 °C ampacity in Table 2)

K values are Table D3 values (ohms per circuit kilometre), L is the length of the circuit conductors in metres, and f comes from the voltage drop factor table, all as printed in Appendix D, which is informative. Sizes between those printed may be interpolated (Note 5): not done here. Verify against the current code.

Underground raceway ampacities from Tables D11A (copper) and D11B (aluminum) of Appendix D (informative), for insulated conductors or cables rated not more than 5000 V and unshielded, in the configurations of Diagram D11. Pick the number of conductors or cables per phase, then either choose a size to read its ampacity or give the load current to find the smallest listed size.

ConductorConductors or cables per phase (Diagram D11 detail)Conductor sizeLoad current (A)Conductor insulation temperature

Values are the ampacities printed in Tables D11A and D11B, which are informative and apply only to the configurations shown in Diagram D11 and to not more than three current-carrying conductors in each raceway (Note 1). Detail 7 of Diagram D11 is intentionally blank in the Code. Equipment termination temperatures still limit the ampacity: see Rule 4-006. Verify against the current code.

Ontario electrical Code calculators for contractors

Get updates and early access

What each tool does