Honeywell T8424C Benutzerhandbuch

68-0180-3

12

a

In electric heat models, W and G are energized with calls for heat.

b

W1 and W2 terminals are energized in the T8424C,D models.

The FAN switch settings are On and Auto.

ON:The fan runs continuously.
AUTO:In cooling, the fan starts and stops 

with the cooling equipment. In heating, the 

fan starts a few minutes after the heating 
equipment turns on. When using an 

electric heat thermostat, the fan starts and 

stops with the heating equipment.

With the SYSTEM switch at Heat, the thermostat controls the 

heating system. On a call for heat, the W terminal is energized 

and a flame is shown on the digital display.

With the SYSTEM switch at Cool, the thermostat controls the 

cooling system. On a call for cool, the G and Y terminals are 

energized and a snowflake is shown on the digital display.

A minimum off-timer in the T8400C, T8401C and T8424C,D 

assures that the cooling compressor does not come on again 

for at least five minutes after it turns off. The minimum-off 
timer is triggered when the compressor turns off and when the 

system switch is changed. If the compressor turns off when 

the setpoint is changed, then the minimum-off timer is 
triggered. Power interruption and power restoration also 

trigger the minimum off-timer. The minimum-off timer operates 

only during the cooling cycle on the thermostat. 

1. Slide the system switch to Heat and the fan switch to 

Auto.

2. Press and hold the ▲ key to raise the temperature set-

ting several degrees above the room temperature. After 

approximately ten seconds the W terminal is energized 

and the heating equipment starts.

3. Press the ▼ key to lower the temperature setting below 

the room temperature. Heating equipment should stop.

Do not operate cooling if outdoor temperature is below 

50°F (10°C). Refer to manufacturer recommendations.

To avoid compressor damage, allow the compressor to 

remain off for five minutes before restarting.

1. Slide the system switch to Cool and the fan switch to 

Auto.

2. Press the ▼ key to lower the temperature setting sev-

eral degrees below the room temperature. After approx-

imately five minutes the G and Y terminals are 
energized and the cooling equipment starts.

3. Press the ▲ key to raise the temperature setting above 

the room temperature. Cooling system should shut 
down.

1. Slide the SYSTEM switch to Off and the FAN switch to 

On. The fan should run continuously.

2. Slide the FAN switch to Auto. In heating, the fan is con-

trolled directly by the heating equipment and may start a 

few minutes after the heating equipment turns on (on 
most systems). When using an electric heat thermostat, 

the fan starts and stops with the heating equipment. In 

cooling, the fan starts and stops with the cooling equip-
ment.

Make certain all equipment responds properly to the 
thermostat.

Auto

Off

None

None

None

On

Any

Any

G

None

Auto

Cool

Cooling

G,Y

Auto

Heat

Heating

W

a,b