Справочник Пользователя для Honeywell T7984 A

Main output of the thermostat. On the T7984 series that output 

is modulating PI analog (2 to 10 Vdc). That signal uses a 

variable Vdc signal for the control of analog damper actuator 

and analog valve actuator. This type of output on the T7984 

series uses a half wave rectifier bridge. 

There is a status LED mounted internally that indicates the 

action of the output. The green LED intensity is proportional to 

the action of the output. 

Model T7984B has a mode input. This thermostat is designed 

to operate and function in 2 distinct mode of operation 

depending on the application requirements. 

This input is not a changeover input for output 1. 

Installing a jumper on the mode input will reverse modulating 

output 1 to operate as a heating only output & the on/off output 

2 as a cooling only output. (See the control sequence section 

for each thermostat.) 

Models T7984A & C all have the possibility of changeover for 

output 1. Automatic changeover is used on systems were a 

valve or a VAV unit may have cold and hot water or air in the 

same system depending on the season. Basically output 1 is 

primarily cooling (Direct Acting) when the changeover input is 

not activated. Activating the changeover input reverses the 

function of output 1 to heating mode (Reverse Acting) so that 

the thermostat can use the end device as a heating device 

instead of a cooling device. 

A common contact may be used for multiple thermostats. 

For the T7984 series a single, common dry contact or 1 supply 

sensor per thermostat can be used for changeover.  A 

common contact may be used for multiple thermostats. 

If a supply sensor is used, changeover temperature trip point 

from cooling to heating is as follows: 

Output 1 
Heating mode 

Output 1  
Cooling mode  

M24003

(25°C) 

(26°C)

Supply

75°F 

78°F 

Temp 

All thermostats have their internal sensing device (Thermistor) 

mounted internally in the thermostat. On the T7984A, B & C 

models, it is possible to install a remote room or remote duct 

return sensor at a different location than the thermostat. 

See wiring diagram for each model on how to wire the sensor. 

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 the room temperature 

is in the Zero Energy Band. When the room temperature drops 

below the heating setpoint, output 2 output will energize. When 

the room temperature rises above the cooling setpoint, output 

1 will energize. 

Two settings values are available for Zero Energy Band: 

3°F(1.5°C) or 5°F(3°C) , can be adjusted with dip switch (S2). 

Because these thermostats have 2 distinct setpoints; one for 

heating the other for cooling, the thermostat setpoint dial knob 

need to be defined as being either: 

•  The true heating setpoint 

•  The true cooling setpoint 

•  Or centered in the middle of the Zero Energy Band. 

This can be adjusted with dip switch (S3 & S4). (See the 

control curves section for each model.) 

Models with a reheat output have setpoint limitation capability 

compatible with ASHRAE 90.1. Both heating and cooling 

setpoints are internally limited to 75°F (24°C). The cooling 

setpoint cannot go below 75°F while the heating setpoint 

cannot go above 75°F. This setpoint limit can be overridden for 

system checkout by setting the DIP switches S3=1 and S4=1. 

An energy saving mode by which the actual setpoints are 

modified to different value than the ones adjusted on the dial. 

The cooling setpoint will go up and the heating setpoint will go 

down. This mode is energized with a dry contact from a remote 

time clock. 

Two different setup & setback value can be adjusted with a 

DIP switch. 
S5 = 1 

10°F (6°C) heating 

20°F (12°C) cooling setpoint 

setpoint setback 

setup (equivalent to cooling 

shut down) 

S5 = 0 

5°F (3°C) heating 

5°F (3°C) cooling setpoint 

setpoint setback 

setup 

The system LED on the thermostat cover on these models will 

flash to indicate that the thermostat is in night mode. The night 

mode can be overridden for 2.5 hours for each thermostat 

individually by pressing the button switch on the thermostat 

cover. This will bring back the thermostat to the day mode 

setpoints. 

A common NSB timer contact may be used for multiple 

thermostats. 

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