Basic Electric Circuits for HVAC – Electro-Mechanical Controls for HVAC Systems
Basic Electric Circuits for HVAC - If you are new to electricity and want to learn you need to start with the fundamentals of electricity first. Included in the basics of electricity and the primary lesson in electricity is electrical safety. Electricity can be very dangerous and safety needs to be practiced. Electricity is invisible to the eye and can only be felt when touched.

Test the wire or load with a meter. Otherwise, you will never know that the wire you are working with is hot or powered up with electricity. Always ensure using a meter or test load that any circuit you are working on is not powered up. Never touch any electrical wires without first testing. Safety is always first especially when dealing with electricity.

Basic Electric Circuits for HVAC | Circuit in Heating and Cooling Systems

Ensure when adding the wire for a new circuit in an existing circuit that the wire type and size are correct. Furthermore, if you are replacing any wire in any circuit the same rule applies. It must be sized according to the National Electric Code tables for wire sizing.

The wire is sized for the load or amp draw of the load. Additional factors apply including operation temperatures, length of wire, voltage drop, operating conditions, and other possible limitations for the circuit. Most noteworthy, be safe and use the correct wire type and size on any new circuits.

In any basic circuit, you have three elements; A source, a path, and a load. Without any one of the three elements, you will not have a complete circuit.

Basic Electric Circuits for HVAC - Circuit Necessities

  1. The Electrical Source – this is where the power or electricity comes from for the circuit. This can be from your main electrical panel. This is where the electricity comes from the electric power company. Additionally, the electricity can come from a battery in DC circuits. Either way, to have a complete electrical circuit you need a source of electricity to complete the electrical circuit.
  2. The Electrical Path – this is the electrical conductor or electrical wire. The path carries the source electricity to the electrical load. It is very important that this electrical conductor or electrical wire for the path be sized properly. Electrical conductors or electrical wire is sized according to the amount of amperage the load will consume. On average residential wiring circuits for lighting and receptacles #12 AWG (American Wire Gage) wire size is used for the electrical conductor or electrical path from the electrical source to the electrical load. The current minimum wire size used in residential electrical wiring (except for low voltage wiring) is #14 AWG. That is according to the NEC (National Electrical Code).
  3. The Electrical Load – this is a power-consuming device. A load is a light bulb or something you would plug into a receptacle. A load is any electrical power-consuming device. This final element completes the basic electrical circuit.

Electrical Circuit Basics - Source Path and Load - HVAC Systems Controls

Basic Electric Circuits for HVAC - Conclusion

Always remember the three elements of the basic circuit. Additionally, electrical safety is first when dealing with any type of electrical system including HVAC systems. The rules for electrical circuits can be found in the National Electrical Code (NEC). The NEC covers wire sizing tables and many other rules about electrical safety. The NEC includes sections and rules concerning HVAC and electrical wiring. Always follow safety guidelines in the NEC and other electrical safety rules.

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Basic Electric Circuits for HVAC | Heating and Cooling