M Definitions

Definition Categories

Maximum water level

The maximum water level is the highest level the water can reach before it spills out over the edge.

Mechanical draft appliance

A mechanical draft appliance creates positive pressure in the vent system that forces combustion gasses through the vent system.  Contrast with natural draft appliances that rely on the negative pressure caused by the natural tendency of hot gas to rise. Category I fan-assisted appliances, including most medium efficiency furnaces, are not mechanical draft appliances. They are natural draft appliances.

Monolithic (slab)

A monolithic slab is a type of residential foundation in which the footing and the foundation slab are poured in one continuous process.

Multiwire branch circuit

A multiwire branch circuit is a three wire branch circuit with two hot (ungrounded) wires and one neutral (grounded) wire. In residential electrical systems, the voltage between the two hot (ungrounded) wires is 240 volts and the voltage between the hot (ungrounded) wires and the neutral (grounded) wire is 120 volts. When a multiwire branch circuit is operating as intended, the voltage on the shared neutral (grounded) wire is zero. Split-wired receptacles that provide the required two 20 amp kitchen countertop receptacle circuits are one example of a multiwire branch circuit. Clothes dryer and range circuits are another example. Water heater and air conditioning condenser circuits are usually not multiwire branch circuits because there is no neutral (ungrounded) wire in the circuit.