Product Data

ManualsBrandsPeco Controls ManualsHeating SuppliesHeating and Cooling Thermostat w/ auto changeover

Terminal Description

CHECKOUT

1. Verify the system voltage.

2. Make sure the fan switch and the system switch voltages are the same.

3. If a transformer is being used make sure it is large enough to support the current

demands of all controls wired to the transformer.

4. Make sure devices being controlled do not exceed the power handling ability of the

T155. Refer to Table-1 for current handling specifications.

5. If a remote sensor (thermistor) is in use, make sure pin pair jumper cap, JP1, has been

removed.

6. When verifying system operation connect a voltmeter in parallel across the heat output

terminal, TB3-1, and common terminal, TB1-4. Read the meter to verify whether the

output is powered when it should be. In cooling mode check for voltage across cooling

terminal, TB3-2 and common terminal, TB1-4.

THEORY OF OPERATION

All T155 models are electronic thermostats. A variable resistance device called a thermistor

senses the room temperature and sends a resistance value to the T155. For example: in

heat mode, the T155 measures the temperature represented by the resistance value of the

onboard thermistor (or remote thermistor if used). If the sensed temperature value drops 1F

(0.6C) or more degrees below the set point the heating output will be powered. A valve or

damper opens to heat the space. When the temperature reaches the set point the heating

output will be turned off, closing the valve or damper. The 155 series thermostats maintain

temperatures with a 1F (0.6C) degree differential in both heating and cooling.

MAINTENANCE

The T155 series requires no maintenance. Replace defective units.

Regular maintenance of the total system is recommended to assure sustained, optimum

performance.

FIELD REPAIR

None. Replace any damaged or failed units with functional replacements.

JP1

Terminal Block 3

1 Heat

2 Cool

3 Sw'd power

Terminal Block 2

1 L1

2 High

3 Med

4 Low

5 Fan hot

Terminal Block 1

4 L2 or neutral

3 No connection

2 Remote sensor

1 Remote sensor

CONNECTIONS

TB1

TB2

TB3

Figure-9 Terminal Definitions.