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HVACR214 – Electrical for Oil

Lesson 3 – Electrical for Oil

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Circuit

• An electrical circuit is a full path for electricity.

• A circuit must consist of 4 parts– Source– Switch– Path– Load

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Source

• A source for a circuit can be– A battery– A transformer (more on that later)– A wall electrical outlet– A power line– A breaker panel– A power plant

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Path

• A path for an electrical circuit could be– A wire– A circuit board– A piece of grounding strap

• A path must have a very low resistance, this allows electrons to move freely and without heat.

• A path with a high resistance will heat up.

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Switch

• A switch is basically a valve or gate that stops the free flow of electrons.

• It does this by opening the path.• Now we add two more terms:

– Open - A gap (or opening) in the path of a circuit that stops the flow of electrons.

– Closed - A path that is complete that allows the flow of electrons.

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Load

• The portion of an electrical circuit that actually does the work.

• This can be– A light bulb - the work is creating heat and

light– A motor - the work is turning the shaft.– A heat strip - the work is putting off heat.– A coil - the work is creating a magnetic

field.

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Picture of a circuit

•Pictures of circuits are called Schematic Diagrams.•These diagrams are composed of symbols that represent each part of the circuit.•These symbols are called schematic symbols.

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Schematic of a basic circuit

B1

SW1

L1 N

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Schematic of a switch

Single Pole - Single Throw Switch

Single Pole - Double Throw Switch

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Poles and Throw

Single Pole - Double Throw Switch

Pole

Throw

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Source on a schematic

• Can be labeled L1, L2, N, or anything else.• It is usually at one side of the schematic and

everything else works from there.

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Loads on a schematic

• Loads are shown by either an actual schematic symbol for the load or by a circle with a letter and a key.

• Loads are the portion of the circuit that does the work.

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A more complex schematic

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Shop Safety

• Make sure everything you are working with is unplugged and turned off when you are starting your assignment.

• Use black wire for line voltage source• Use white wire for line voltage neutral• Use red wire for control voltage source• Use orange wire for control voltage common

(neutral)

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Shop Safety

• Your instructor must check all circuits before you power it up. That means before you plug it in and turn it on the instructor must check it.

• Make sure the instructor initials your lab sheet.

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First shop project

• You are going to build a basic circuit.• Starting on page 13 of your electrical

handout you will follow the step by step procedures.

• Make sure you ask if you need help or have any questions.

• Everyone in the class is expected to wire and complete this assignment.

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Shop Circuit #1

B1

SW1

120V NSS