Bryant 581J Smoke Detectors, Outside and Return Air Enthalpy Sensor, Wiring, System

581J

Return Air Enthalpy Sensor —

Mount the return-air enthalpy sensor (33CSENTSEN) in the return-air section of the economizer. The return air sensor is wired to the enthalpy controller (33CSENTHSW). See Fig. 54.

		– 4-20	24V		RED		PL6-1 (24-V)
		Main	GND		BLK		PL6-4 (COM)
		+ VDC
							CTB ECON
		Out	LOW		GRA	7
							(RTU Open: to J2-6)
		Outside Air
		Enthalpy Switch
	+ 24-36				Return Air
		VDC In			Enthalpy
		– 4-20 Main			Sensor
		Out
							C11170
Fig. 54 - Outside and Return Air Enthalpy Sensor
				Wiring

To wire the return air enthalpy sensor, perform the following:

1.Use a 2-conductor, 18 or 20 AWG, twisted pair cable to connect the return air enthalpy sensor to the enthal- py controller.

2.Connect the field-supplied RED wire to (+) spade connector on the return air enthalpy sensor and the

(+)terminal on the enthalpy controller. Connect the BLK wire to (-) spade connector on the return air en- thalpy sensor and the (-) terminal on the enthalpy controller.

Smoke Detectors

Smoke detectors are available as factory-installed options on 581J models. Smoke detectors may be specified for Supply Air only or for Return Air without or with economizer or in combination of Supply Air and Return Air. Return Air smoke detectors are arranged for vertical return configurations only. All components necessary for operation are factory-provided and mounted. The unit is factory-configured for immediate smoke detector shutdown operation; additional wiring or modifications to unit terminal board may be necessary to complete the unit and smoke detector configuration to meet project requirements.

Units equipped with factory-optional Return Air smoke detectors require a relocation of the sensor module at unit installation. See “Completing Installation of Return Air Smoke Sensor:” on page 36 for details.

System —

The smoke detector system consists of a four-wire controller and one or two sensors. Its primary function is to shut down the rooftop unit in order to prevent smoke from circulating throughout the building. It is not to be used as a life saving device.

Controller —

The controller (see Fig. 55) includes a controller housing, a printed circuit board, and a clear plastic cover. The controller can be connected to one or two compatible duct smoke sensors. The clear plastic cover is secured to the housing with a single captive screw for easy access to the wiring terminals. The controller has three LEDs (for Power, Trouble and Alarm) and a manual test/reset button (on the cover face).

Duct smoke sensor

	controller
	Conduit nuts
	(supplied by installer)
	Conduit support plate
	Terminal block cover
Controller housing	Cover gasket
and electronics	(ordering option)
Conduit couplings	Controller cover
(supplied by installer)
	Fastener
	(2X)

	Trouble
Alarm	Power
	Test/reset
	switch

C08208

Fig. 55 - Controller Assembly

Sensor Module —

The sensor module (see Fig. 56) includes a plastic housing, a printed circuit board, a clear plastic cover, a sampling tube inlet and an exhaust tube. The sampling tube (when used) and exhaust tube are attached during installation. The sampling tube varies in length depending on the size of the rooftop unit. The clear plastic cover permits visual inspections without having to disassemble the sensor. The cover attaches to the sensor housing using four captive screws and forms an airtight chamber around the sensing electronics. Each sensor includes a harness with an RJ45 terminal for connecting to the controller. Each sensor has four LEDs (for Power, Trouble, Alarm and Dirty) and a manual test/reset button (on the left-side of the housing).

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

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