Honeywell T7984 C, T7984 B, T7984 A User Manual

T7984 A,B,C Electronic Modulating Control

Thermostats

PRODUCT DATA

FEATURES

APPLICATION

These microprocessor-based thermostats provide proportional - integral (PI) individual room temperature control in zoned commercial Heating, Ventilating, and Air Conditioning systems such as hydronic heating and/ or cooling, pressure dependent VAV or by-pass box with or without terminal reheat.

The T7984 family provides modulating analog 2 to 10 Vdc control. Optional features include automatic heat/ cool changeover, reheat control, remote night setback with local timed override, and remote sensor on VAV models.

•PI (proportional and integral) control action provides accurate, stable room temperature control.

•T7984 models are used with Series 70 direct-coupled damper actuators such as ML7161 or ML7984, or with valve actuators such as ML7285, ML7421, VC7930 or M7410.

•All models feature user-friendly set point knob.

•All models feature output status LEDs for installer check-out.

•Locking cover and range stops are standard.

•Night setback models feature selection of two different offset temperatures and use central time switch control.

•Night setback models feature 2 1/2 hour local timed override.

•Heat/cool models feature automatic changeover with 3° or 5°F (1.5°C or 3°C) selectable Zero Energy Band (Z.E.B.) to meet requirements of ASHRAE 90.1

•Heat/cool models have installer-definable setpoint at midpoint of Z.E.B, at heating setpoint, or at cooling setpoint.

•Reheat models feature fast/slow response selection to match heating system dynamics.

•DIP switch selectable 75°F (24°C) high limit heating setpoint and low limit cooling setpoint.

•Horizontal and vertical covers included.

	Contents
Application.........................................................................	1
Features ............................................................................	1
Specifications ....................................................................	2
Ordering Information .........................................................	2
Installation .........................................................................	3
T7984A..............................................................................	4
T7984B..............................................................................	5
T7984C..............................................................................	6
Checkout ...........................................................................	8

95C-10815-2

T7984 A,B,C ELECTRONIC MODULATING CONTROL THERMOSTATS

SPECIFICATIONS

IMPORTANT

The specifications given in this publication do not include normal manufacturing tolerances. Therefore, this unit may not exactly match the listed specifications. Also, this product is tested and calibrated under closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed.

MODELS: T7984A,B,C, 2 to 10 Vdc analog output

Table 1. Model Specifications

			Cool/Heat				Main
			Changeover				Temperature		Mode Selection
	Model	Output 1	For Output 1	Output 2		Night Setback	Sensor *		Input
	T7984A	Modulating 2 to	Dry Contact or	On/off		-	Internal or		-
		10 Vdc	Sensor				remote
	T7984B	Modulating 2 to	-	-		Dry Contact	Internal or		Jumper
		10 Vdc					remote
	T7984C	Modulating 2 to	Dry Contact or	Modulating 2 to		Dry Contact	Internal or		-
		10 Vdc	Sensor	10 Vdc			remote
	* Remote sensor	models are:
	272845 Remote wall mount sensor
	272847 Remote duct mount sensor
	DIMENSIONS				* The maximum heating setpoint and minimum cooling
	See Figure 1.				setpoint is electronically limited to 75°F [24°C].
	MOUNTING: Mounts to single-gang NEMA-standard 2"x 4"				REMOTE SENSOR: 47 kΩ NTC thermistor [part nos. 272845
	electrical box, or directly to wall requires 1 1/8“ [35„mm]
					and 272847].
	access hole for wiring.
					ANALOG OUTPUT: 2 to 10 Vdc, 2 mA max.
	WIRING: Four to eight 1/8“ screw terminals suitable for 2 no.
	18 AWG [1 mm 2] wires each depending on model.				SWITCHED OUTPUT RATING: 0.5A running, 1.1A inrush,
	POWER SUPPLY: 19-30 Vac, 50-60 Hz, 2 VA, Class 2. (Does				24Vac, protected with selfresetting fuse.
	not include actuator or reheat stage power requirements.)				OPERATING PARAMETERS: See Table 2 for installer selections.
	OPERATING AMBIENT:				APPROVALS:
	32-104°F [0-40°C] at 5-95% Relative Humidity (non-				Designed for Class II low voltage installation only.
	condensing).				Case and cover meets UL„94-5V flammability requirements,
	ACCURACY: 1°F (0.6°C) PRECISION: ±1°F (0.5°C) tempera-				and North American codes for line voltage thermostat
					enclosures.
	ture after stabilization.
					Meets requirements of F.C.C. Part 15 Class B, IEC 801-3 for
	PRECISION: ±1°F (0.5°C) temperature after stabilization.				radio frequency interference.
	SETPOINT RANGE: 55-90°F [13-32°C], T7984A.				ACCESSORIES:
	Heating: 55-75°F [13-24°C], T7984B, C*.				272845 - Remote sensor (wall mounted).
					272846 - Adaptor plate for 2-gang NEMA, or British 75 mm
	Cooling: 75-90°F [24-32°C], T7984B, C*.				electrical box.
					272847 - Remote sensor (duct mounted).

ORDERING INFORMATION

When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number.

If you have additional questions, need further information, or would like to comment on our products or services, please write or phone:

1.Your local Honeywell Automation and Control Products Sales Office (check white pages of your phone directory).

2.Honeywell Customer Care 1885 Douglas Drive North

Minneapolis, Minnesota 55422-4386

In Canada–Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9.

International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.

95C-10815–2

2

T7984 A,B,C ELECTRONIC MODULATING CONTROL THERMOSTATS

Table 2. Option Settings

		T7984 Model
Parameter	Selection	A	B	C
Reheat Time	Fast (7.5 min.); or Normal		•
Constant	(15 min.)
Zero Energy	3°F (1.5°C); or 5°F (3°C)		•	•
Band
Setpoint	Heating; Cooling or H/C		•	•
Definition	midpoint
Night	5°F (3°C) heat/cool offset, or		•	•
Setback	10°F (5°C) setback / cooling
	shutdown
Main Sensor	Remote or internal	•	•	•

Fig. 1. Dimensions in inches (mm)

INSTALLATION

Location

Install the thermostat about 5 ft. (1.5 m) above the floor in an area with good air circulation at average temperature conditions.

Do not install thermostat where it may be affected by:

•drafts, or dead air spots behind doors and in corners.

•hot or cold air from ducts.

•radiant heat from sun or appliances.

•concealed pipes and chimneys.

•unheated (cooled) areas such as an outside wall behind the thermostat.

Mounting

The thermostat can be mounted directly on the wall with or without a wallplate or a standard single gang electrical box, or double gang with adaptor plate (accessory part 272846).

CAUTION

Disconnect power supply to prevent electrical shock or equipment damage.

Wiring

Typical wiring connections are shown in Fig.2 to Fig.7. Wiring connections may be made to the screw terminal block with 2- 18AWG or 1-14AWG, solid or stranded copper wires. Connect the system wires to the thermostat terminals. Push excess wire back into hole. Plug hole to prevent drafts.

Auxiliary screw terminal strip may be used in a junction box when the application requires multiple wires to be brought down at the thermostat. This can make troubleshooting, startup and servicing easier.

DIP Switch Settings

T7984 thermostats must be configured for proper operation by setting DIP switches.

T7984B

Reheat output control action: 7.5 or 15 minutes.

T7984B,C

Zero energy band (ZEB): 3°F (2°C) or 5°F (3°C)

Setpoint adjustment: cooling,centred, heating centred with limit override for commissioning.

Night setback amount: see Table 2 for complete listing of option settings.

T7984A,B,C

Main sensor, internal or remote.

Table 3. T7984 DIP Switch Definition

	OUTPUT 2 ON/OFF CPH				T7984B only
	For more information, see on/off output cycle per hour application note.
	CYCLES/HOUR			S1	It is possible to fix the number of times per hour the on/off
	FAST	8 CPH		1	output will be energized.
	SLOW 4 CPH			0
					T7984B & C only
	ZERO ENERGY BAND
					On models which have 2 outputs, 1 for cooling and 1 for
		ZEB		S2
	5°F (3°C)			1	heating, it is possible to adjust the zero energy band value
	3°F	(1.5°C)		0	(dead band between heating and cooling endpoints).
							T7984B & C only
	SETPOINT DIAL DEFINITION
	For more information, see setpoint dial definition & setpoint limitation application note.
	DEFINITION			S3	S4			Models with cooling and heating outputs
	75°F OVERRIDE			1	1		» Setpoint dial centered, 75˚F limitation not active.
	HEATING DIAL			0	1		» Setpoint dial defined as heating, 75˚F limitation active.
	COOLING DIAL			1	0		» Setpoint dial defined as cooling, 75˚F limitation active.
	CENTERED HC			0	0		» Setpoint dial centered, 75˚F limitation active.
	DAY/NIGHT SETBACK								T7984B & C only
	HEAT SETBACK			COOL SETUP				S5	Night mode setpoints can be adjusted
									to different values depending on the
	10°F (5°C)			20°F (10°C)				1
									application.
	5°F (3°C)			5°F (3°C)				0
	REMOTE SENSOR				T7984A, B & C
	On model T7984A, switch S7 & S8 are not used.
	MAIN SENSOR			S6				For duct return air or remote room sensor control only.
	LOCAL INTERNAL			1				Do not use remote sensor in supply or discharge air
	REMOTE SENSOR			0				control applications.

ON = 1

OFF = 0 1 2 3 4 5 6

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