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Smoke detector locations, Fig. 58 -- controller assembly – Carrier 50HCQA User Manual

Page 34

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34

Duct smoke sensor

controller

Fastener

(2X)

Controller cover

Conduit nuts

(supplied by installer)

Conduit support plate

Cover gasket

(ordering option)

Conduit couplings

(supplied by installer)

Terminal block cover

Controller housing

and electronics

Alarm

Power

Test/reset
switch

Trouble

C08208

Fig. 58 -- Controller Assembly

Duct smoke sensor

See

Detail A

Exhaust tube

Plug

Sampling tube

(ordered separately)

Intake

gasket

Cover gasket

(ordering option)

TSD-CO2

(ordering option)

Sensor housing
and electronics

Exhaust gasket

Coupling

Sensor cover

Detail A

Magnetic
test/reset

switch

Alarm

Trouble

Power
Dirty

C08209

Fig. 59 -- Smoke Detector Sensor

Air is introduced to the duct smoke detector sensor’s

sensing chamber through a sampling tube that extends into

the HVAC duct and is directed back into the ventilation

system through a (shorter) exhaust tube. The difference in

air pressure between the two tubes pulls the sampled air

through the sensing chamber. When a sufficient amount of

smoke is detected in the sensing chamber, the sensor

signals an alarm state and the controller automatically

takes the appropriate action to shut down fans and

blowers, change over air handling systems, notify the fire

alarm control panel, etc.

The sensor uses a process called differential sensing to

prevent gradual environmental changes from triggering false

alarms. A rapid change in environmental conditions, such as

smoke from a fire, causes the sensor to signal an alarm state

but dust and debris accumulated over time does not.

For installations using two sensors, the duct smoke

detector does not differentiate which sensor signals an

alarm or trouble condition.

Smoke Detector Locations

Supply Air —

The Supply Air smoke detector sensor is located to the left

of the unit’s indoor (supply) fan. See Fig. 60. Access is

through the fan access panel. There is no sampling tube used

at this location. The sampling tube inlet extends through the

side plate of the fan housing (into a high pressure area). The

controller is located on a bracket to the right of the return

filter, accessed through the lift--off filter panel.

Smoke Detector Sensor

C08245

Fig. 60 -- Typical Supply Air Smoke Detector Sensor

Location

Return Air without Economizer —

The sampling tube is located across the return air opening

on the unit basepan. See Fig. 61. The holes in the

sampling tube face downward, into the return air stream.

The sampling tube is connected via tubing to the return air

sensor that is mounted on a bracket high on the partition

between return filter and controller location. (This sensor

is shipped in a flat--mounting location. Installation

requires that this sensor be relocated to its operating

50H

C

Q

A