Bard MD4000 - Manual (Page 16)

Manual 2100-574
Page 16 of 23
alarm WIrInG
Alarm relays can be wired for NO (close on alarm) or
NC (open on alarm) strategy.
Alarm relays can be used individually if there are
enough available building alarm points, or can be
arranged into smaller groups or even a single group so
that all alarm capabilities can be utilized.
When multiple alarms are grouped together and issued
as a single alarm, there will no off-site indication of
which specific problem may have occurred, only that
one of the alarms in the group has been triggered. The
individual alarm problem will be shown on the LED
display on the face of the controller.
Note: All alarm and output relays are Form C (SPDT)
dry contacts rated 1A @ 24 VAC.
Note: All alarm relay outputs have 10-second delay in
acutally issuing to protect against nuisance alarm signals.
The Power Loss 1, Power Loss 2 and controller alarm
relays are all “reverse actuated”, which means they
are continuously energized (the NO contact is closed)
and switched to NC position upon alarm condition.
Therefore, it is important to closely follow the alarm
board connection diagrams that follow.
Any alarm feature that is not desired can simply be
ignored (not connected).
NOtE: the LED display board can be replaced if
needed independently of the alarm board. Bard
part number is 8612-022.
alarm leD DIsPlaY bOarD
MIS-2042
Note: The LED display board is polarized and will
only fit in one direction as shown. It must be fully
inserted in order for the controller to function properly.

Note: the alarm LeD display board is shipped
uninstalled to protect it from possible damage during
installation of the wiring to main controller board and/
or the alarm board. It is polarity sensitive and is keyed
so it can only be installed in correct position.
ecOnOmIzer FaIlure alarm
Upon failure of either economizer to open on command
or close on command, the Economizer Failure Alarm
will open normally closed contacts to signal the
failure. To utilize this feature, terminals 8 & 9 must be
connected to the shelter alarm panel.
A normally closed economizer fail alarm is available on
terminals 8 & 9 of the Unit 1 & 2 terminal blocks.
DIrtY FIlter alarm
A normally closed dirty filter alarm is available on
terminals 4 & 5 of the Unit 1 & 2 terminal blocks.
2-cOmPressOr run alarm
If both compressors are running at the same time, the
2-Compressor Run Alarm will open indicating this
condition.