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

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)

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

75°F OVERRIDE

1 1

HEATING DIAL 0

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

10°F (5°C)

20°F (10°C)

5°F (3°C)

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.

Do not use remote sensor in supply or discharge air

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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