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T7984 A,B,C Electronic Modulating Control

Thermostats 

PRODUCT DATA 

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. 

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. 

  

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 

Summary of Contents for T7984 A

Page 1: ...lve 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 featu...

Page 2: ...lization 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 ORDERING INFORMATION 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 sel...

Page 3: ...hermostats 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...

Page 4: ...act or the changeover sensor across Fig 2 T7984A Wiring Input 2 10 Vdc 24 Vac Common 2 10 Vdc valve or VAV analog actuator Duct or Room Not used Remote sensor input 0 Vac Output 1 2 10 Vdc Changeover input for Out 1 Changeover contact OR Changeover sensor 24 Vac Power supply 0 Vac 24 Vac Transformer SEQUENCE SETPOINT DIAL CENTERED End Heating mode End Opened Cooling mode Device Device changeover 1...

Page 5: ... Device closed off 2 Vdc 0 OUTPUT 2 ON OFF OUTPUT 1 ANALOG ZERO ENERGY BAND Temperature increase Fig 6 T7984B Sequence Mode A DIP SWITCH SETTINGS DEFINITION S3 S4 75 F OVERRIDE 1 1 HEATING DIAL 0 1 COOLING DIAL 1 0 CENTERED HC 0 0 SETPOINT DIAL DEFINITION ZEB S2 5 F 3 C 3 F 1 5 C 1 0 ZERO ENERGY BAND CYCLES HOUR S1 FAST 8 CPH 1 SLOW 4 CPH 0 OUTPUT 2 ON OFF CPH ON 1 1 2 3 4 5 6 OFF 0 COOLING SETPOI...

Page 6: ... valve or VAV analog actuator 24 Vac Transformer Fig 9 T7984C Wiring SEQUENCE SETPOINT DIAL DEFINITION SETPOINT DIAL DEFINITION SETPOINT SETPOINT HEATING COOLING HEATING COOLING SETPOINT CENTERED SETPOINT SETPOINT CENTERED End End Device closed 2 Vdc IN ZERO ENERGY BAND OUTPUT 2 ANALOG OUTPUT 1 ANALOG SETPOINT End IN ZERO End End Device Device 100 ENERGY BAND 100 Device Device opened 10 Vdc 50 End...

Page 7: ...model on how to wire the sensor The remote sensor are not to be used for supply control applications Zero Energy Band T7984B C Thermostats which have cooling and heating outputs T7984B C have 2 distinct setpoints one for heating the other for cooling see the control curves section for each model When the room temperature is between these to setpoints both heating and cooling outputs are off and th...

Page 8: ...ctuator or SCR power controller which is normally used to control terminal reheat in a zone system This type of output on the T7984C uses a half wave rectifier bridge If the same transformer is to be used for the thermostat and the end device be sure to select end devices which also use a half wave rectifier bridge There is a status LED mounted internally that indicates the action of the output Th...

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