Relay & Contactor Module

A contactor is chosen for the load it switches, and the current on the nameplate is rarely that load. A motor draws several times its rated current at start, so the utilisation category matters more than the headline rating: the same device that carries a resistive heater comfortably may be marginal on a pump. Coil voltage has to match what the panel actually supplies, AC or DC, and the auxiliary contacts decide what the control circuit can report back. DIN rail mounting and a socket keep replacement a one-minute job.

How it is specified

• Pole count and contact arrangement: normally open, normally closed, or changeover
• Coil voltage, AC or DC, and the consumption of the coil
• Rated current, and the utilisation category the rating applies to
• Auxiliary contacts, and whether they are needed for status or interlocking
• Mounting: DIN rail with socket, or direct panel fixing
• Mechanical and electrical life, at the switching frequency expected
• Indication and manual override, and coil suppression for DC coils
• Whether a thermal overload relay is fitted alongside for motor duty

Where it is used

• Control cabinets and automation panels
• Motor starters and pump or fan switching
• Building plant and HVAC control
• Interlocking and safety circuits