Choose a contact configuration based on the switching function: DPDT contacts support two circuits with normally open and normally closed paths, while form C outputs suit changeover applications such as fail-safe or fail-secure access control. Select a load rating that meets or exceeds the connected device’s voltage and current, accounting for whether the load is AC or DC and any startup or inrush current, with relay options in this assortment ranging from lower-current control loads to contacts rated up to 5A at 220VAC or 28VDC.

Dry contact relay modules require low-voltage DC operating power, such as 6, 12, or 24 VDC, depending on the relay, while the dry contacts switch a separate circuit. Access power controllers typically accept a 12- to 24-volt AC or DC input and control relay outputs through an open-collector sink or normally open dry trigger.

Dry contact relays provide electrically isolated switch contacts that let access control, security, and building automation equipment trigger or monitor devices such as locks, door holders, alarms, readers, sensors, and auxiliary controls. Depending on the relay and application, installers can use normally open or normally closed contacts for functions such as fail-safe or fail-secure control, alarm signaling, fire alarm release, line seizure, and polarity reversal.

When installing dry contact relays, match the relay’s control voltage, contact configuration, and contact ratings to the connected equipment, and confirm that the relay supports the required switching application and continuous-duty operation. For new or expanding access control systems, also consider the number of independently controlled outputs, fuse or PTC protection, fail-safe or fail-secure operation, trigger method, and fire alarm disconnect requirements.