Macurco GD-2A Operating Instructions
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MACURCO GAS DETECTORS
GD-2A
INSTALLATION & OPERATING INSTRUCTIONS
GENERAL INFORMATION
The GD-2A is a low voltage (12-24 VAC or VDC) all electronic detector of combustible gases, that has
been evaluated by UL for methane (natural) and propane (LP) gas. The GD-2A is designed for connection to UL
Listed alarm control panels (Fire or Fire/Burglar type or Critical Process Management Equipment), although it
may be used alone, with UL Listed Class 2 limited energy power supplies. The GD-2A has a SPDT Alarm relay,
for connection to control panels or other devices. See the GD-2A data sheet for more technical information.
LOCATION
If the gas used is natural (methane) mount the GD-2A on a wall about one foot down from the ceiling. If
the gas used is propane (LP), mount the GD-2A on a wall or column one foot above the floor. Do NOT mount the
GD-2A in a corner.
INSTALLATION
The detector can mount on either a 4 X 4 or two gang electrical box. The GD-2A front cover will need to
be removed before mounting. This is done by firmly grasping and slightly squeezing the sides of the front cover,
while pulling it away from the rear part. The cover will snap off exposing the electronics and mounting plate. Use
the appropriate hole pattern for mounting. The four holes toward the center of the mounting plate match the hole
pattern of a two gang box. The four holes near the corners match the pattern of a four inch square box. Mount the
GD-2A so the “TOP” marked side of the mounting plate is at the highest side.
Snap the front cover back on when finished, making sure that the lights line up with the access holes.
An optional back cover is available for the GD-2A to allow mounting directly over a single gang electrical
box. This device, Macurco # 40120, is of matching white plastic and provides an attractive enclosure to cover the
electronic components.
See the back of the GD-2A data sheet for more information on Installation.
OPERATION
When power is first applied to the detector, it will go through a warm-up period of one and one half to two
minutes, during which alarms are inhibited. The green light will turn on and off during the delay period. The
green light will turn on continuously (ARMED) afterwards to indicate the unit is in normal operation.
Once the GD-2A is operational (the green light on continuously), if gas is detected the red light (ALARM)
will illuminate at the same time the alarm relay switches. Any devices connect to the relay should be activated.
The unit, in its normal configuration as shipped from the factory, will automatically reset itself, by
shutting off the red light and returning the relay to the standby condition, once the air clears. The GD-2A can be
modified, either before or after installation, to have a latching output. Pull off the cover and locate the jumper wire
labeled “CLIP FOR LATCH IN” on the printed circuit board in the upper right hand side. Clip or cut this jumper
wire. Now the unit will stay in alarm (once gas has exceeded the pre-set threshold) until the power is interrupted.
When replacing the cover, make sure the lights line up with their access holes.
TROUBLE SIGNALS
The trouble signal is determined mostly by the configuration of the alarm panel, with the GD-2A trouble
relay only providing an open circuit for actuation. A failure of the gas-sensing element will result in both lights
turning on and off and the trouble relay opening. Failure of power supplies in the GD-2A or a lack of power to the
detector will result in the trouble relay opening.
The most common expected trouble would be a break in the wiring between the panel and the GD-2A.
TESTING
Once the unit is fully operational (the green light is on steady), test the unit by directing gas from an
unlighted butane cigarette lighter into the detector near the left hand side through one of the vent holes. It will be