2.8 Relay circuit wiring
Four relays with Form-C contacts (dry) are provided for controlling door lock mechanisms or alarm signaling.
Each relay has a Common pole (
C
), a Normally Open pole
(NO
) and a Normally Closed pole (
NC
). When
controlling the delivery of power to the door strike, the Normally Open and Common poles are typically used.
When momentarily removing power to unlock the door, as with a mag lock, the Normally Closed and
Common poles are typically used. Check with local building codes for proper egress door installation.
Door lock mechanisms can generate feedback to the relay circuit that can cause damage and premature
failure of the relay, and affect the operation of the LP4502. For this reason, it is recommended that a diode is
used to protect the relay. Wire should be of sufficient gauge to avoid voltage loss.
Diode selection
n
Diode current rating: 1x strike current.
n
Diode breakdown voltage: 4x strike voltage.
n
For 12 V DC or 24 V DC strike, diode 1N4002 (100V/1A) typical.
2.9 Memory and real time clock backup battery
The static RAM and the real time clock are backed up by a lithium battery when input power is removed. This
battery should be replaced annually. If data in the static RAM is determined to be corrupt after power up, all
data, including flash memory, is considered invalid and is erased. All configuration data must be re-
downloaded.
During installation and while the unit is not powered, change the jumper position (J19) from
OFF
to
ON
to
enable the battery backup.
Battery type:
BR2330 or CR2330.
PLT-05246, A.4
16
June 2021
Powering
Trusted Identities
HID Mercury™ LP4502 Controller
Installation and Specifications
