Main Breaker

Related terms

• Main Shutoff Valve

  The valve stopping all water to the house. Every homeowner should know its location; remodels often add accessible zone shutoffs.

• Load Calculation Oversizing

  Installing equipment larger than the calculated load — a frequent mistake that causes short cycling, poor dehumidification, and higher cost.

• Make-Up Air

  Replacement outdoor air supplied when powerful exhaust (large range hoods, whole-house fans) depressurizes a house. Code-required above s…

• Load Calculation (Electrical)

  An NEC calculation of total demand to verify the service/panel can carry added loads. The basis for whether a service upgrade is required.

• Manifold / Home-Run

  A PEX distribution method with individual lines from a central manifold to each fixture, improving pressure balance and isolation.

• Line Set

  The insulated copper tubing connecting the outdoor condenser to the indoor coil. Replaced or flushed when changing refrigerant type.

• Manual J Load Calculation

  The industry-standard room-by-room heating/cooling load calculation that correctly sizes equipment. The right basis for any system replac…

• Knob-and-Tube Wiring

  Obsolete early-1900s wiring with no ground. Often must be replaced during remodels and can affect insurance and insulation.