Electricity is a core part of HVAC work, but the terminology can feel confusing. This guide breaks down the essentials so you can understand the fundamentals without needing an engineering degree.
The Foundation: Ohm’s Law
At its simplest, Ohm’s Law describes the relationship between:
- Voltage (V) — the electrical “force” or pressure
- Current (I) — the flow of electricity
- Resistance (R) — anything that slows or resists that flow
Think of water flowing through a hose:
- Current = water flow
- Voltage = water pressure
- Resistance = a partially closed valve
You don’t need to memorize the math—just understand the relationship.
Voltage, Current, and Safety
Common HVAC voltages include 115V, 208/230V, 460V, and 575V.
- Voltage alone doesn’t cause injury
It’s the combination of voltage + current that becomes dangerous.
- Current is measured in amps, and even small amounts can cause harm when resistance is low (wet skin, metal contact, etc.).
- High voltage can arc
If v