Honeywell T8141A Manual Download Page 7

T8141A ELECTRONIC HEAT PUMP THERMOSTATS

68-0169—1

7

LED Indicators

The light-emitting diodes (LED) indicators will light under the
following conditions:

AUX. HEAT: Lights when the AUX. HEAT Relay is on.
EM. HEAT: Lights when the system switch is set for EM.

HEAT. Also lights when the heat pump shuts down and
needs maintenance.

GEO LOCK (on systems with GEO LOCK):  Lights when

the heat pump shuts down and needs maintenance.

OPERATION

The thermostat controls heat pump operation and fan
operation. The setting range is 45

°

F to 90

°

F (7

°

C to 32

°

C) for

heating and 60

°

F to 95

°

F (16

°

C to 35

°

C) for cooling.  The

system retains the setpoint during a power outage. In first
stage operation, for both heating and cooling, a minimum off-
timer delays the compressor from starting and stopping the
heat pump for at least five minutes.

CHECKOUT

When installation is complete, turn on power supply and
check thermostat operation as follows.

CAUTION

Do 

not operate the cooling system when the outside

temperature is below 50

°

F (10

°

C). See compressor

manufacturer instructions for further information.

Heating

NOTE:

When the heating setting is changed, a minimum off-
timer delays the compressor from starting or
stopping the heat pump for at least five minutes.

A

Set the thermostat system switch to HEAT or GEO
HEAT and the fan switch to AUTO.

B

Set the temperature to about 10

°

F (6

°

C) above the

room temperature.

C

Heating and fan should start after a delay. The AUX.
HEAT LED should light.

D

Change the temperature setting to about 10

°

F (6

°

C)

below the room temperature.

E

Heating equipment, fan and LED should shut off after a
delay.

F

To return to normal operation, set the thermostat
system switch to HEAT or GEO HEAT; set the fan
switch to AUTO. Change the temperature setting to
desired room temperature.

Cooling

NOTE:

When the cooling setting is changed, a minimum off-
timer delays the compressor from starting or
stopping the heat pump for at least five minutes.

A

Set the thermostat system switch to COOL or GEO
COOL and the fan switch to AUTO.

B

Set the temperature to about 10

°

F (6

°

C) below the

room temperature.

C

Cooling and fan should start after a delay.

D

Change the temperature setting to about 10

°

F (6

°

C)

above the room temperature.

E

Cooling equipment and fan should shut off after a delay.

F

To return to normal operation, set the thermostat
system switch to COOL or GEO COOL; set the fan
switch to AUTO. Change the temperature setting to
desired room temperature.

Fan

Move the thermostat system switch to OFF and the fan switch
to ON. The fan should run continuously. With the system
switch still in the OFF position, move the fan switch to AUTO;
the fan should stop.

CALIBRATION

Thermometer

The thermometer in your thermostat was accurately
calibrated at the factory. Adjustment should be needed only if
the thermometer was dropped or jarred. If the setpoint knob
and the thermometer reading do not agree:

A

Remove the left side of the thermostat cover.

B

Set the thermostat cover on a table near an accurate
thermometer.

C

Allow five minutes for the cover thermometer to sense
the area temperature; then compare the readings. Be
careful not to touch the thermometer or breathe on it.

D

If the readings are the same, replace the cover and put
the system into operation.

E

If the readings are different, use a hex wrench to adjust
the thermostat thermometer to the other thermometer.
See Fig. 8.

Fig. 8. Thermometer calibration.

F

Replace the thermostat cover and put the system into
operation.

NOTE:

Radiant heat from your hands will offset the
thermometer reading. After making each
adjustment, wait five or ten minutes for the
thermometer to stabilize before comparing.

If problem persists, check that the hole in the wall behind the
thermostat is sealed.

M8386

INCREASE 

Summary of Contents for T8141A

Page 1: ...32 C for heating and 60 F to 95 F 16 C to 35 C for cooling Retains setpoint temperature during power outage Cover thermometer Fan mode selection of AUTO ON System mode selections of EM HEAT HEAT OFF COOL some models have EM HEAT GEO HEAT OFF GEO COOL LED display for second stage AUX HEAT operation LED display for EM HEAT selection and external fault indication some models have GEO LOCK EM HEAT LED...

Page 2: ...oducts from your contractor distributor or Honeywell sales representative please specify 1 Model number 2 Color choice for Heat or Cool changeover thermostat Cool Only changeover thermostat is only available in taupe 3 Thermostat changeover desired 4 System switches desired If you have additional questions need further information or would like to comment on our products or services please write o...

Page 3: ...behind the thermostat If Replacing an Existing Thermostat A Turn off the thermostat power at the heat pump In two transformer systems with two switches or disconnects turn off power to both B Remove any existing wallplate or subbase from the wall C To avoid miswiring later as the wire is removed label or write down each wire color with the letter or number on the wiring terminal If New Installatio...

Page 4: ...thermostat UP WALL MOUNTING SCREW M5948B TERMINAL STRIP TERMINAL WIRES FAN SWITCH SYSTEM SWITCH TEMPERATURE SETPOINT TEMPERATURE CONTROL DIAL 1 1 2 SNAP THE THERMOSTAT INTO THE TOP HINGES ON THE MOUNTING PLATE M8552 TERMINAL STRIP TERMINAL WIRES THERMOSTAT CABLE OPENINGS FOR STRAIGHT INSERTION STRIP 5 16 IN 8 MM FOR WRAPAROUND STRIP 7 16 IN 11 MM RESTRICT WIRING TO THIS AREA FRONT VIEW OF TERMINAL...

Page 5: ...RELAY AUX HEAT RELAY COOL CHANGEOVER VALVE B HEAT CHANGEOVER VALVE L SYSTEM MONITOR M7777A E H O O C E H O C E H O C E H O C A EM HEAT HEAT OFF COOL SYSTEM SWITCH FAN SWITCH ON AUTO EM HEAT RED AUX HEAT GREEN FAN COMPRESSOR HEAT RELAY AUX HEAT RELAY THERMOSTAT LOGIC POWER SUPPLY TEMPERATURE SENSOR INTERNAL SYSTEM SWITCHES DESIGNATED AS E EM HEAT H HEAT O OFF C COOL INTERNAL FAN SWITCHES DESIGNATED...

Page 6: ...nt during a power outage Temperature Setting Move the temperature control dial to the desired temperatures for heating and for cooling See Fig 7 System and Fan Switching System switch positions control thermostat operation as follows OFF Heating and cooling are off If the fan switch is in the AUTO position the cooling fan is also off HEAT or GEO HEAT Heating system is controlled by the thermostat ...

Page 7: ...ature Cooling NOTE When the cooling setting is changed a minimum off timer delays the compressor from starting or stopping the heat pump for at least five minutes A Set the thermostat system switch to COOL or GEO COOL and the fan switch to AUTO B Set the temperature to about 10 F 6 C below the room temperature C Cooling and fan should start after a delay D Change the temperature setting to about 1...

Page 8: ... the COOL position If the air conditioner comes on compressor could have reached its high limit temperature protection and shut down If cooling still does not start and the fault indicator is connected to terminal L and the EM HEAT indicator is on contact the Original Equipment Manufacturer or your HVAC dealer If the EM HEAT indicator is off contact Honeywell Customer Assistance at 1 800 468 1502 ...

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