Hansen Technologies HGD-EC-NH3-100 Specifications, Applications, Service Instructions & Parts page 3

GAS DETECTOR LOCATION
Detectors should be located in an accessible area
for maintenance and testing, but away from moving
equipment that could accidentally come in contact with
the sensor. Avoid thermal extremes (close to heaters)
and do not place unprotected in direct, strong drafts/
airflows, near exit doors, or areas where falling water
or condensing moisture are present. If high humidity is
always present, power up the unit as soon as possible,
as long term exposure can shorten the life of the gas
sensor element. In blast freezers, mount the gas detector
below the coil to avoid high moisture and steam during
defrost.
The two generally accepted methods of locating
detectors are "Point" and "Perimeter" detection. "Point"
detection is where detectors are located near the most
likely sources of leakage. "Perimeter" detection is where
detectors completely surround the area in question.
The size and nature of the area will help to decide
which method is the most appropriate. Air flow should
be considered in a ventilated room. Place detectors
downstream of potential leak points.
Any detector which is to be used for detecting a gas
with a vapor density greater than one (i.e. heavier than
air) should generally be located nearer ground level.
Conversely, for any lighter than air gases such as
ammonia, the detector needs to be located higher up.
Typically ammonia detectors are mounted 12˝ – 24˝ (.3 to
.5m) from the ceiling. Detectors should not be located
too close to the ceiling as hot air trapped under the
ceiling may act to buffer the target gases from reaching
the detector.
The number of detectors in each area is a function of local
codes and regulations and the customers' guidelines
for gas detection.
MOUNTING HEIGHT OF DETECTORS
LIGHT GASES (AMMONIA)
LIGHT GASES (AMMONIA)
12" - 24" FROM CEILING
12" - 24" FROM CEILING
POINT DETECTION
POINT SENSOR
PLACE SENSOR
NEAR OPERATING
EQUIPMENT
PLAN VIEW
PERIMETER DETECTION
PERIMETER SENSOR LOCATION
VENTILATED ROOM
VENTILATED ROOM
3
FIG. 1
HEAVY GASES (CO2, HALOCARBON)
HEAVY GASES (CO2, HALOCARBON)
MOUNT NEAR GROUND LEVEL
MOUNT NEAR GROUND LEVEL
FIG. 2
OPERATING
EQUIPMENT
FIG. 3
PLACE SENSORS
AROUND PERIMETER
OF LARGE ROOM
FIG. 4
AIR FLOW
PLACE SENSOR(S)
BETWEEN EQUIPMENT
AND EXHAUST FAN
JANUARY 2020
A100h