Troubleshooting Guide. Honeywell T7300D, Q7300G, T7200E, Q7300D, T7300F

T7200D,E, T7300D,E,F AND Q7300 SERIES 2000 PROGRAMMABLE COMMERCIAL THERMOSTATS AND SUBBASES

Interfacing with

Electromechanical Economizers

(Subbases with Auxiliary Relay)

Mechanical cooling is often used when outside temperatures are in the 50

°

to 60

°

F range and humidity is below 50 percent. In central and northern climates, hundreds of hours fall into this temperature category. By permitting 80 to 100 percent outside air into the system, mechanical cooling may not be needed at all, particularly during Spring and Fall.

An economizer is used to take advantage of the outside air.

The typical economizer consists of an outside air damper, motor, outdoor air changeover control and a minimum position potentiometer. The motor controls the dampers.

Suitability of the outside air for cooling is determined by the outdoor air changeover control. The potentiometer is used for adjusting the minimum position of the economizer dampers, which provide a minimum amount of fresh air for ventilation.

The economizer reduces compressor run time, thereby saving energy and extending the compressor life. The drawback to using the economizer is that during the Unoccupied period, if there is no call for cooling or outdoor air is not suitable for free cooling, the economizer is controlled to minimum position. This position allows some percentage of outdoor air to enter the building, regardless of air suitability. The situation can cause the heating or cooling to run more often than if suitable outdoor air is permitted to enter the building.

The thermostat can take advantage of an economizer by connecting the auxiliary relay contacts (A1 and A2) of the subbase to control the economizer minimum position potentiometer. The contacts close during the Occupied period, allowing the economizer to operate normally. The contacts are open during the Unoccupied period, disabling the minimum position feature of the economizer. The open contacts cause the economizer to drive dampers fully closed instead of staying at minimum open position. This reduces the possibility of unsuitable outdoor air from entering the building, which lowers the internal load on the HVAC system and saves additional energy.

Other Uses for the Auxiliary Relay

Examples of other uses of the auxiliary relay are hot water heaters, lighting or baseboard heat. The additional loads are connected to the auxiliary relay contacts on the subbase. The contacts are rated for 1.6A at 30 Vac, but can be adapted to higher current applications with the use of an external relay and transformer. See Fig. 18.

L1

(HOT)

L2

1

Q7300 SUBBASE

AUXILIARY

RELAY

CONTACTS

A1

A2

A3

2

TROUBLESHOOTING GUIDE

Refer to Table 14 for troubleshooting information.

TO

LOAD

1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

2

RELAY REQUIRED (R8222 OR SIMILAR).

M4944

Fig. 18. Use of external relay and transformer for auxiliary loads greater than 1.6A.

23 63-4355—1

T7200D,E, T7300D,E,F AND Q7300 SERIES 2000 PROGRAMMABLE COMMERCIAL THERMOSTATS AND SUBBASES

Display will not come on.

Symptom

Temperature display is incorrect.

Temperature settings will not change.

(Example: Cannot set heating higher or cooling lower.)

Table 14. Troubleshooting Information.

Possible Cause Action

Thermostat is not being powered.

• Check that X terminal is connected to the system transformer.

• Check for 24 Vac between X and R or RH terminals.

— If missing 24 Vac:

— check if the circuit breaker is tripped—reset the circuit breaker.

— check if the system fuse is blown—replace the fuse.

— check if the power switch on the HVAC equipment is in the Off position—set to the On position.

— check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections.

— If 24 Vac is present, proceed with troubleshooting.

Enter Installer Setup number 37 and reconfigure the display.

Room temperature display has been reconfigured.

Thermostat is configured for

°

F or

°

C display.

Bad thermostat location.

Display shows two dashes and a degree sign.

Upper or lower temperature limits were reached.

The setpoint temperature range stops were configured.

Enter Installer Setup number 14 and reconfigure the display.

Relocate the thermostat.

Installer Setup 22 is set for remote sensing and the sensor is missing or the circuit is open or shorted.

Check the temperature setpoints:

• Heating limits are 40 to 90

°

F (7 to 31

°

C)

• Cooling limits are 45 to 99

°

F (9 to 37

°

C)

Check Installer Setup number 34 and 35 and reconfigure the setpoint stops.

Keypad is locked. When a locked key is pressed, LOC will flash on the LCD.

Installer Setup is locked out

• Reset DIP switch 1 on back of thermostat to enable keypad.

• Enter Installer Setup number 25 or 40 and reconfigure keypad lockout level.

Reset the DIP switch 1 on back of thermostat to enable keypad.

Unable to configure

Installer Setup

Temperature settings change from original setting.

Room temperature is out of control.

Heating will not come on.

Trying to set heating and cooling setpoints too close together. There is a deadband in automatic changeover thermostat models.

Example: cool setpoint=72, deadband=3, heat setpoint=68, changing heat setpoint to 70 will automatically change the cool setpoint to 73.

• Check that the heating setpoint is lower than the cooling setpoint.

• Check Installer Setup number 30 to identify the deadband between heating and cooling setpoints. Reconfigure if desired.

Remote temperature sensing is not working.

Checkout all remote sensors.

No power to the thermostat.

• Check that X terminal is connected to the system transformer.

• Check for 24 Vac between X and R or RH terminals.

— If missing 24 Vac:

— check if the circuit breaker is tripped—reset the circuit breaker.

— check if the system fuse is blown—replace the fuse.

— check if the system switch at the equipment is in the

Off position—set to On position.

— check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections.

— If 24 Vac is present, proceed with troubleshooting.

(Continued)

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