Honeywell T7984 C, T7984 B, T7984 A User Manual
T7984 A,B,C Electronic Modulating Control
Thermostats
PRODUCT DATA
FEATURES
• 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.
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.
• 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
Changeover
Model Output 1
T7984A Modulating 2 to
10 Vdc
T7984B Modulating 2 to
10 Vdc
T7984C Modulating 2 to
10 Vdc
* Remote sensor models are:
272845 Remote wall mount sensor
272847 Remote duct mount sensor
DIMENSIONS
See Figure 1.
MOUNTING: Mounts to single-gang NEMA-standard 2"x 4"
electrical box, or directly to wall requires 1 1/8“ [35„mm]
access hole for wiring.
WIRING: Four to eight 1/8“ screw terminals suitable for 2 no.
18 AWG [1 mm 2] wires each depending on model.
POWER SUPPLY: 19-30 Vac, 50-60 Hz, 2 VA, Class 2. (Does
not include actuator or reheat stage power requirements.)
OPERATING AMBIENT:
32-104°F [0-40°C] at 5-95% Relative Humidity (non-
condensing).
ACCURACY: 1°F (0.6°C) PRECISION: ±1°F (0.5°C) tempera-
ture after stabilization.
PRECISION: ±1°F (0.5°C) temperature after stabilization.
SETPOINT RANGE: 55-90°F [13-32°C], T7984A.
Heating: 55-75°F [13-24°C], T7984B, C*.
Cooling: 75-90°F [24-32°C], T7984B, C*.
For Output 1 Output 2 Night Setback
Dry Contact or
Sensor
- - Dry Contact Internal or
Dry Contact or
Sensor
On/off - Internal or
Modulating 2 to
10 Vdc
Main
Temperature
Sensor *
remote
remote
Dry Contact Internal or
remote
* The maximum heating setpoint and minimum cooling
setpoint is electronically limited to 75°F [24°C].
REMOTE SENSOR: 47 kΩ NTC thermistor [part nos. 272845
and 272847].
ANALOG OUTPUT: 2 to 10 Vdc, 2 mA max.
SWITCHED OUTPUT RATING: 0.5A running, 1.1A inrush,
24Vac, protected with selfresetting fuse.
OPERATING PARAMETERS:
APPROVALS:
Designed for Class II low voltage installation only.
Case and cover meets UL„94-5V flammability requirements,
and North American codes for line voltage thermostat
enclosures.
Meets requirements of F.C.C. Part 15 Class B, IEC 801-3 for
radio frequency interference.
ACCESSORIES:
272845 - Remote sensor (wall mounted).
272846 - Adaptor plate for 2-gang NEMA, or British 75 mm
electrical box.
272847 - Remote sensor (duct mounted).
See Table 2 for installer selections.
Mode Selection
Input
-
Jumper
-
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
OUTPUT 2 ON/OFF CPH
T7984B only
For more information, see on/off output cycle per hour application note.
CYCLES/HOUR S1
FAST 8 CPH 1
SLOW 4 CPH 0
It is possible to fix the number of times per hour the on/off
output will be energized.
ZERO ENERGY BAND T7984B & C only
ZEB S2
5°F (3°C) 1
3°F (1.5°C)
0
On models which have 2 outputs, 1 for cooling and 1 for
heating, it is possible to adjust the zero energy band value
(dead band between heating and cooling endpoints).
SETPOINT DIAL DEFINITION
T7984B & C only
For more information, see setpoint dial definition & setpoint limitation application note.
Models with cooling and heating outputs
» Setpoint dial centered, 75˚F limitation not active.
» Setpoint dial defined as heating, 75˚F limitation active.
DEFINITION S3
S4
75°F OVERRIDE
1 1
HEATING DIAL 0
1
COOLING DIAL
1 0
CENTERED HC
0 0
» Setpoint dial defined as cooling, 75˚F limitation active.
» Setpoint dial centered, 75˚F limitation active.
DAY/NIGHT SETBACK
T7984B & C only
HEAT SETBACK COOL SETUP
S5
10°F (5°C)
20°F (10°C)
1
5°F (3°C)
5°F (3°C)
0
Night mode setpoints can be adjusted
to different values depending on the
application.
REMOTE SENSOR T7984A, B & C
On model T7984A, switch S7 & S8 are not used.
MAIN SENSOR
LOCAL INTERNAL
REMOTE SENSOR
For duct return air or remote room sensor control only.
1
S6
Do not use remote sensor in supply or discharge air
0
control applications.
ON = 1
OFF = 0 1 2 3 4 5 6
Table 2. Option Settings
T7984 Model
Parameter Selection
Reheat Time
Constant
Zero Energy
Fast (7.5 min.); or Normal
(15 min.)
3°F (1.5°C); or 5°F (3°C) • •
A B C
•
Band
Setpoint
Definition
Night
Setback
Heating; Cooling or H/C
midpoint
5°F (3°C) heat/cool offset, or
10°F (5°C) setback / cooling
• •
• •
shutdown
Main Sensor Remote or internal • • •
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 218AWG 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.
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
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).
thermostat.
T7984A,B,C
Main sensor, internal or remote.
Table 3. T7984 DIP Switch Definition
3 95C-10815–2
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