Hansen Technologies HSC4H-N10K Specifications, Applications, Service Instructions & Parts page 3

GAS SENSOR LOCATION
Sensors 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
sensing element. Select the unit for harsh environments
where a condensing atmosphere may be present. In
blast freezers, mount the gas sensor below the coil to
avoid high moisture and steam during defrost.
The two generally accepted methods of locating sensors
are "Point" and "Perimeter" detection. "Point" detection
is where sensors are located near the most likely sources
of leakage. "Perimeter" detection is where sensors
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 sensors downstream of
potential leak points.
Any sensor 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 sensor needs to be located higher up.
MOUNTING HEIGHT OF SENSORS
LIGHT GASES (AMMONIA)
LIGHT GASES (AMMONIA)
12" - 24" FROM CEILING
12" - 24" FROM CEILING
FIG. 1
HEAVY GASES (CO2, HALOCARBON)
HEAVY GASES (CO2, HALOCARBON)
MOUNT NEAR GROUND LEVEL
MOUNT NEAR GROUND LEVEL
Typically ammonia sensors are mounted 12˝ – 24˝ (.3 to .5m)
from the ceiling. Sensors 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 sensor.
The number of sensors in each area is a function of local
codes and regulations and the customers' guidelines
for gas detection.
POINT DETECTION
POINT SENSOR
PLACE SENSOR
NEAR OPERATING
EQUIPMENT
PLAN VIEW
PERIMETER DETECTION
PERIMETER SENSOR LOCATION
VENTILATED ROOM
VENTILATED ROOM
3
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
A100g
JULY 2017