2-8
MEGA3 NFPA Medical Gas Notification System
4107 9016 59.03
2.3.8 B50 4-20mA Combination
Board
A Combination alarm can contain a B50
board that contains four 4-20mA inputs that
can be used with a 2 or 3 wire transmitter.
The board also contains seven signal inputs,
which monitor normally closed signal inputs,
and six normally closed dry contact relay out-
puts. Each alarm panel can have a maximum
of one B50 board.
Identify each set of field installed 4-20mA
input signal wires (2 or 3 wires per set) inside
the alarm rough-in box. Route each set of in-
put wires to the appropriate terminals on the
B50 board. Connect each set of signal wires
to the terminal blocks, noting the correct
polarity (Figure 26).
2.3.9 General Fault Relay
The B60 Gas Input board is supplied with an
alarm panel general fault output relay.
This relay has a set of dry contacts that is
wired normally closed.
The relay will activate when ANY alarm on
the ENTIRE alarm panel is activated. Relay
will remain activated as long as alarm condi-
tion is active, even if audible alarm is silenced
by MUTE button.
When alarm condition is corrected, relay will
deactivate. Relay contact ratings are 35A @
30VDC / 3A @ 250VAC. Refer to
NFPA Area
Wiring Diagram (Section 3.2).
2.3.10 Field Wiring Cable Shield
Grounding
All field wiring cable shields must be ground-
ed inside alarm panel rough-in box.
Holes are provided in the top and bottom of
the alarm rough-in box for grounding screws
(Figure 27).
Shields from several cables may be wrapped
together and crimped into one screw (by oth-
ers).
Figure 27: Cable Shield Grounding-Area
Grounding Holes Provided
Figure 26: B50 Board Wire Routing
