Load List, Electrical Load Schedule.
A load list, or electrical load schedule, is the register of every electrical consumer on a plant or unit: motors, heaters, lighting and small power, UPS loads, and HVAC equipment. Each row carries the load's tag, service, rated power, voltage and phases, duty, and the switchboard or motor control centre it is fed from. It is the document the electrical engineer uses to size supply and distribution equipment.
What Load List, Electrical Load Schedule means.
A plant's electrical design starts from knowing what has to be powered before it can size what powers it. The load list assembles every consumer, from large process motors to lighting and small power circuits, into a single register with the data the electrical design needs: the tag and service description, rated and absorbed power, voltage and number of phases, duty, whether the load runs continuously, intermittently, or only in standby, and the switchboard or motor control centre and feeder it is supplied from. Much of that data does not originate on the load list itself. Tags and duties come from the P&ID equipment list and motor list, rated power comes from the mechanical datasheet, and the feeder assignment comes from the single-line diagram and the motor control centre schedule. The load list is where all of it is brought together so the electrical engineer can sum the connected and operating load, apply diversity, and carry the result into transformer, generator, and switchboard sizing.
What a load list records.
Each row on a load list is one electrical consumer: a motor, a heater, a lighting or small power circuit, a UPS load, or an HVAC unit. Against it, the list carries the tag and service description, the rated power and the absorbed power the load actually draws, voltage and number of phases, the duty classification, continuous, intermittent, or standby, and the starter type where applicable. It also records where the load is supplied from: the switchboard or motor control centre, and the feeder or breaker it is fed through. Together those columns are what the electrical engineer sums and diversifies to size the supply.
Where the data on a load list comes from.
A load list is compiled, not authored from a blank sheet. The equipment list and motor list, both traceable back to the P&IDs, supply the tag, service, and duty for each load. The mechanical datasheet supplies the rated power and any starting characteristics. The single-line diagram and the motor control centre schedule supply the switchboard, feeder, and starter assignment once the electrical design has progressed far enough to make that assignment. Early in a project the load list can carry estimated power figures pending vendor data; it is reconciled against firm datasheet values as procurement closes each package.
Load list versus motor list versus MCC schedule.
A motor list is a subset of the load list, limited to rotating equipment, and is often built first because motors dominate a plant's connected load. The load list adds every other electrical consumer: heaters, lighting, UPS, and HVAC. The motor control centre schedule works the other direction. It starts from the switchboard and lists what each feeder supplies, which is the same information as the load list read from the supply side rather than the load side. On a well-coordinated project the three documents describe the same loads consistently; on a poorly coordinated one they drift and have to be reconciled by hand.
What the load list feeds.
The load list is an input document, not an end product. The electrical engineer uses it to sum connected and operating load, apply diversity, and size the transformer, generator, and main switchboard. It feeds the single-line diagram, the cable schedule for each feeder, and the motor control centre schedule as the design is built out. Motor-driven loads that carry a control signal, a run command, a status contact, also appear on the I/O list, so a motor's row on the load list and its row on the I/O list have to agree on tag and duty or the two documents describe different machines.
Load list columns
The core columns on a load list, and where each value is sourced from.
| Column | Carries | Source |
|---|---|---|
| Tag | The unique identifier for the load | Equipment list, motor list |
| Service | Plain description of what the load does | P&ID, equipment list |
| Rated power | The nameplate power rating | Mechanical datasheet |
| Absorbed power | The power the load actually draws at rated duty | Mechanical datasheet, vendor data |
| Voltage, phases | Supply voltage and number of phases | Electrical design basis, datasheet |
| Duty | Continuous, intermittent, or standby | Process description, equipment list |
| Starter type | Direct-on-line, star-delta, variable frequency drive | Motor list, electrical design |
| Switchboard, MCC | The switchboard or motor control centre supplying the load | Single-line diagram |
| Feeder | The specific feeder or breaker the load is connected to | MCC schedule |
Load list vs motor list vs MCC schedule vs cable schedule
Four documents describing the same electrical loads from different angles.
| Document | Organised by | Shows | Used by |
|---|---|---|---|
| Load list | Load | Every electrical consumer with rating, voltage, and duty | Electrical engineer sizing supply and distribution |
| Motor list | Load, motors only | Rotating equipment with duty and starting data | Electrical and mechanical engineers |
| MCC schedule | Feeder | What each switchboard or MCC feeder supplies | Electrical engineer, panel builder |
| Cable schedule | Cable | The cable, route, and termination for each feeder | Electrical engineer, construction |
Common questions
What is a load list.
What is the difference between a load list and a motor list.
What is the difference between a load list and an MCC schedule.
Where does the rated power on a load list come from.
Does the load list include HVAC and lighting loads.
How does the load list relate to the I/O list.
Who owns the load list on a project.
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