Motors in single-line diagram of a typical building electrical distribution system
I am confused by the use of Motors in this diagram, what are Motor Starter vs Large Motors and small motors and controls? Can someone provide specific examples of them?
Thank you!
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Since the motors are at the end of the diagram(similar to the lights and receptacles) I would say it shows that they are what are "pulling" the power, or what is using the electricity. They account for the electrical load. Some of which have controls included. In the text it refers to them as utilization items.
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I love this kind of material because they're really intuitive once you understand what's going on, they're simple enough and really quick to answer correctly (usually), but if you're looking at the diagram never having seen one before, it's completely obfuscated.
This is an electrical single line diagram/block diagram. Think of it like a flowchart for the power coming in and being used in the building. It's the absolute simplest way you can show electrical circuitry - lots of details are omitted (each line in the diagram is actually at least 3 wires in the building, and may be as many as 5 wires for 3-phase 208V power. Room-size equipment (like the transformer and sometimes like the large motor) and the ceiling light in your kitchen are both reduced to simple graphics. The diagram shows the flow and control of power from the utility to all of the loads in the building.
At the scale of a house, an electric dryer and an electric oven and the central HVAC unit all have dedicated circuits as shown here by the large motor because they use so much electricity - there's a breaker in your breaker box for the dryer, that is connected to a set of wires that runs to a single outlet that the dryer is connected to, and nothing else. This particular diagram shows something more at the scale of a factory or large apartment complex, though - the large motor is likely hard-wired and represents something like an industrial chiller, or a big piece of machinery or equipment - something the scale of a person or larger. Electric motors are a load, and their starting capacitor and associated circuits pull even more power than the motor itself while the motor is starting up.
The lighting and appliance panels are subpanels that break out the circuits from the distribution panel into even smaller circuits - this is uncommon in a house, but frequently done in a larger facility to limit the number of wires running all the way across the building unneccesarily - more wiring is more labor to install and more material cost too! The small motors + controls would be something like a ceiling fan at the scale of a house, or smaller machinery at the scale of a factory - standalone appliances and equipment that are large enough to be hardwired but small enough to not require their own power supply directly from the main panel.
Below is a lightly-annotated copy of that drawing with a little information that is key - know that you won't be asked anything on the ARE that is too in-depth about a diagram like this, the exam is concerned with your general ability to recognize the diagram and understand the basic information being conveyed.
Best,
Ralph, the Amber Book Team
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