Rooftop Systems Inc.

Economizer Catalog
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Version 1.10

PRINCIPLES OF AIR CONDITIONING ECONOMIZER OPERATION

by Rooftop Systems Inc.

Table of Contents 1. 2. 3. 4. 5. Economizer Operation Honeywell Specification Data. Checkout and Troubleshooting Retrofit Jobsite Applications Economizer Savings

BACK GROUND - ECONOMIZER

THE ECONOMIZER EVOLUTION
1950's Early Economizers use increased outdoor air whenever it was below approximately 55 F to help maintain the 55-60 F mixed air temperature to the building. While this produced substantial savings during the cooling season, the summer-winter switch (used to de-activate the option for outdoor air) was often forgotten in the summer position resulting in increased winter heating costs. Such operation is termed wild Economizer by the industry. Example: In Chicago, with a wild Economizer the increase in heating cost was twice the Economizer savings on cooling costs in the summer. Enthalpy-based electronic Economizer systems existed, but costs limited acceptability primarily to larger installations. Early 1970's Changeover controls based upon lowcost electromechanical enthalpy sensors using nylon elements are introduced. While the decision to use outdoor air for free cooling has improved through the use of combined temperature and humidity information, the wild Economizer still predominates, and summer cooling savings are frequently lost during the heating season. Mid 1970's Rising energy costs helped to introduce
the integrated Economizer - one in which outdoor air is used to control mixed air temperature only when cooling is required in the building. Achieved through interconnection of the changeover control with heating-cooling thermostats, control systems were offered by the industry for both single and multizone system. Examples are Honeywell W973 and W936 controllers. Electromechanical temperature and humidity sensors are still most common. Early 1980's Fully integrated thermostat/changeover controls are introduced. Honeywell T7400/W7400 is an example - a multistage, seven-day programmable thermostat with separate set point for Economizer changeover. Mid 1980's Low-cost solid state humidity sensors, combined with thermistor temperature sensors, make low-cost, high-accuracy, high-stability enthalpy sensors a reality for owners of small buildings. In addition to improving the performance of integrated Economizers with changeover control based upon outdoor air enthalpy, the sensor costs permit the use of a second enthalpy sensor to use for the first stage of cooling. Termed differential enthalpy control by the industry, such changeover controls can double the savings vs. single sensor controls.
TYPICAL ECONOMIZER SYSTEMS

ECONOMIZER TYPE

DAMPER POSITION Closed
? (System Shutdown) Out side tem pera ture be low enthalpy setpoint and above M.A. setpoint (System Shutdown) Outside temperature above enthalpy setpoint Out side tem pera ture be low enthalpy setpoint and above M.A. setpoint (System Shutdown) Outside temperature above enthalpy setpoint Out side tem pera ture be low enthalpy setpoint and above M.A. setpoint Out side tem pera ture be low enthalpy set point and below M.A. setpoint

2-Position Economizer

Open Closed

3-Position Economizer

Minimum
Open Closed Minimum Modulating Economizer

Modulating

ECONOMIZER WITH OUTSIDE AMBIENT TEMPERATURE ABOVE ENTHALPY SETPOINT (DAMPER IN MINIMUM POSITION)
DISCHARGE AIR SENSOR OR MIXED AIR SENSOR (56 DEGREES) CONTROL MOTOR DAMPER IN MINIMUM POSITION
ENTHALPY CONTROL COMPRESSOR RUNNING
FRESH AIR INTAKE ROOF SUPPLY

RETURN

RELIEF AIR

CEILING T

THERMOSTAT
SEQUENCE OF OPERATION 1. 2
2405 McIVER LANE CARROLLTON, TEXAS 75006-6510 TELEPHONE: (972) 247-7447 FAX NO. (972) 243-0940
THERMOSTAT CALLS FOR COOLING. ENTHALPY CONTROL SENSES WARM OUTSIDE AIR AND ENERGIZES THE COMPRESSOR. THE ECONOMIZER DAMPER MOVES TO THE MINIMUM POSITION AS REQUIRED BY CODE. DRAW ING #1
ECONOMIZER WITH OUTSIDE AMBIENT TEMPERATURE ABOVE ENTHALPY SETPOINT AND SPACE CO2 SENSOR (DAMPER IN MINIMUM POSITION)
DISCHARGE AIR SENSOR OR MIXED AIR SENSOR (56 DEGREES) CONTROL MOTOR DAMPER IN MINIMUM POSITION MODULATES PER CO2 SENSOR

CEILING

THERMOSTAT CALLS FOR COOLING. ENTHALPY CONTROL SENSES WARM OUTSIDE AIR AND ENERGIZES THE COMPRESSOR. THE ECONOMIZER DAMPER MOVES TO THE MINIMUM POSITION AS REQUIRED BY CODE.
ECONOMIZER WITH OUTSIDE AMBIENT TEMPERATURE BELOW ENTHALPY SETPOINT AND ABOVE MIXED AIR SETPOINT (FRESH AIR DAMPER 100% OPEN)
DISCHARGE AIR SENSOR OR MIXED AIR SENSOR (56 DEGREES) CONTROL MOTOR
ENTHALPY CONTROL COMPRESSOR
FRESH AIR INTAKE ROOF SUPPLY RETURN RELIEF AIR
ECONOMIZER ENERGIZED ON THE FIRST STAGE OF COOLING
CEILING T COMPRESSOR ENERGIZED ON SECOND STAGE COOLING
SEQUENCE OF OPERATION 1. 2 3.
THERMOSTAT CALLS FOR COOLING. ENTHALPY CONTROL SENSES COOL OUTSIDE AIR AND ENERGIZES THE ECONOMIZER. IF THE SECOND STAGE OF COOLING IS REQUIRED. THE COMPRESSOR IS ENERGIZED BY THE THERMOSTAT. DRAW ING #3
ECONOMIZER WITH OUTSIDE AMBIENT TEMPERATURE BELOW ENTHALPY SETPOINT AND BELOW MIXED AIR SETPOINT (DAMPER PARTIALLY OPEN MIXING WITH RETURN AIR TO MAINTAIN 56 DEGREES)

FRESH AIR INTAKE ROOF

SUPPLY

CEILING T THERMOSTAT

SEQUENCE OF OPERATION 1. THERMOSTAT CALLS FOR COOLING. 2 ENTHALPY CONTROL SENSES COOL OUTSIDE AIR AND STARTS TO OPEN THE OUTSIDE AIR DAMPER. 3. AS THE OUTSIDE AIR (O.A.) ENTERS THE ECONOMIZER. THE MIXED AIR SENSOR (M.A.S.) SENSES THAT IT IS BELOW THE SETPOINT OF 56o. 4. THE ECONOMIZER DAMPERS MODULATE (MOVE) TO A POSITION THAT MIXES O.A. WITH RETURN o AIR TO MAINTAIN 56 M.A. TEMPERATURE. DRAW ING #2
ECONOMIZER WITH THE RETURN AIR ENTHALPY HIGHER THAN THE FRESH AIR ENTHALPY (DIFFERENTIAL CONTROLS)

ENTHALPY CONTROL

COMPRESSOR ENERGIZED ON SECOND STAGE COOLING
SEQUENCE OF OPERATION 1. 2 THERMOSTAT CALLS FOR COOLING. ENTHALPY CONTROL IN THE OUTSIDE AIR AND THE ENTHALPY CONTROL IN THE RETURN AIR DETERMINE THAT THE OUTSIDE AIR IS THE COOLEST. THE ECONOMIZER DAMPER OPENS 100%. IF THE SECOND STAGE OF COOLING IS REQUIRED. THE COMPRESSOR IS ENERGIZED BY THE THERMOSTAT. DRAW ING #4

OPERATING FLOW CHART FOR AN ECONOMIZER WITH A SINGLE ENTHALPY CONTROL

STAGES OF COOLING

OUTSIDE TEMP. IS BELOW THE ENTHALPY RANGE
OUTSIDE TEMP. IS ABOVE THE ENTHALPY RANGE
4 OUTSIDE TEMP. ABOVE M.A.S. o SETPOINT (56 ) (6) OUTSIDE TEMP. BELOW M.A.S. o SETPOINT (56 ) (6)

SEE DRAWING #1 & #4

COMPRESSOR
COMPRESSOR OPERATES WITH THE DAMPER IN MINIMUM POSITION
DAMPER 100% OPEN DAMPER MODULATING MIXED AIR MINIMUM DAMPER POSITION

SEE DRAWINGS #3 & #4

SEE DRAWING #2

SEE DRAWING #1

NOTES 1. 2. 3. 4. Y1 = FIRST STAGE OF COOLING. Y2 = SECOND STAGE OF COOLING. ASSUMES RETURN AIR IS WARMIER THAN OUTSIDE AIR. NORMALLY CLOSED CONTACTS (OPTIONAL) THAT ARE OPENDED BY WINTER MORNING WARMUP, NIGHT SHUTDOWN, FIRESTATS, ETC. 5. NORMALLY CLOSED CONTACTS (OPTIONAL) THAT ARE OPENED BY FIRESTATS, ETC. 6. M.A.S. = MIXED AIR SENSOR. ECONOPSE
OPERATING FLOW CHART FOR AN ECONOMIZER WITH DIFFERENTIAL ENTHALPY
OUTSIDE AIR ENTHALPY CONTROL
RETURN AIR ENTHALPY CONTROL
OUTSIDE TEMP. IS BELOW THE RETURN AIR TEMP.
OUTSIDE TEMP. IS ABOVE THE RETURN AIR TEMP.
4 OUTSIDE TEMP. ABOVE M.A.S. o SETPOINT (56 ) (7) OUTSIDE TEMP. BELOW M.A.S. o SETPOINT (56 ) (7)
NOTES 1. 2. 3. 4. Y1 = FIRST STAGE OF COOLING. Y2 = SECOND STAGE OF COOLING. ASSUMES RETURN AIR IS WARMER THAN OUTSIDE AIR. NORMALLY CLOSED CONTACTS (OPTIONAL) THAT ARE OPENED BY WINTER MORNING WARMUP, NIGHT SHUTDOWN, FIRESTATS, ETC. NORMALLY CLOSED CONTACTS (OPTIONAL) THAT ARE OPENED BY FIRESTATS, ETC. DIFFERENTIAL ENTHALPY COMPARES THE RETURN AIR TO THE OUTSIDE AIR AND USES THE COOLEST OF THE TWO. M.A.S. = MIXED AIR SENSOR. ECONOPDE
FRESH AIR DAMPER POSITION CHART
Standard Economizer Damper Position Modu-Trol Multi-Trol (2) (2) Closed Closed & Down 1. 2. 3. Closed Open Open Open Open Modulating Closed 80 Open 75 Open Open Open Opening/ Closing 75 Open Open Modulating Open Open Opening/ Closing Open Open Open Open Open Closed Open Closed Differential Enthalpy Damper Position Return Modu-Trol Multi-Trol Temp. (2) (3) (2) (3) Closed Closed

Outside Temp. (1)

Stan dard econo mizer po si tion based on en thalpy con trol set on the A setting and 50% relative humidity. Closed po si tion is ei ther the mini mum po si tion or fully closed de pend ing on job setting. Open ing/Clos ing is de pend ent upon the mixed air tem pera ture.

ECONOMIZER MINIMUM POSITION ADJUSTMENT PROCEDURE
A. To adjust the amount of minimum Outside Air (O.A.) required on an economizer the following items must be determined. 1. 2. 3. B. The amount of O.A. required as a percentage of total unit CFM. (Example: 200 CFM outside air for 2000 CFM unit = 10% O.A.) The return air temperature. The outside air temperature.
After the above criteria has been determined follow the directions below to set the economizer. 1. Adjust the minimum potentiometer for the following formula: DT = (OAP x OAT) + (RAP x RAT) Where DT = Discharge Temperature (supply) with Fan Only OAP = Percentage of O.A. required OAT = Outside Air Temperature RAP = Percentage of Return Air RAT = Return Air Temperature

Example:

Unit requires 10% fresh air. The return air is 80 degrees and the outside air is 40 degrees.
DT = (10% x 40 Degrees) + (90% x 80 Degrees) DT = 4 + 72 DT = 76 Degrees (Fan Only in operation)
2405 McIver Lane, Car roll ton, Texas 75006- 6510 Phone (972) 247- 7447 Fax (972) 243- 0940
STEP BY STEP MODULATING ECONOMIZER CHECKOUT & TROUBLE SHOOTING
OUTSIDE ENTHALPY ABOVE SET POINT Condition on Logic Module Should Be 1. Red LED Not Illuminated Conditions Not Met 1. If the LED glows the Module thinks it is in the Economizer mode. Verify the conditions are above the enthalpy set point. Check note 2. Check wiring to Enthalpy Control for a short from {S0} and {+}. 2. Check the wiring from [G] and [C] on the unit low voltage terminal strip. {TR} and {TR1} power the Motor. 3. Verify there is a call for cooling from the thermostat. Without a call for cooling the compressor will not be in the normal A/C mode. 4. If there is not 24 VAC on {2} and {TR1} then the internal switch 1S is not set correctly. Remove the {So} wire from the module. If there is 24 volts to {2} and {TR1} then the enthalpy control is bad or the {So} and {+} wiring is shorted together. If no voltage to {2} and {TR1} then the module is bad.
24 Vac to Terminals: {TR} and {TR1} 24 Vac to Terminals: {1} and {TR1} 24 Vac to Terminals: {2} and {TR1}
Continuity on Terminals: {1} and {2} {3} and {4}
5. If there is not a continuity for {1} to {2} then the internal switch 1S is not in the correct position, and either the module or the enthalpy control is defective. If there is continuity from terminals {1} and {2} then the red LED should not be illuminated. If there is continuity and the LED does glow, then the module is defective. If there is continuity on terminals {3} and {5} then the internal switch 1S is correctly energized. Damper motor should be in a modulating mode. 6. Check the wiring from {2} to Y1" on the unit low voltage control board. Verify that there is not 24 VAC to Y1" and C on the unit.
6. Compressor does not operate with all above conditions correct. Second Stage 7. 24 Vac to Terminals: {3} and {TR1}

Verify that you have a 2-Stage thermostat. Check for a call for a second stage cooling. If there is not 24 VAC on {3} and {TR1} check wiring from Y2" on the thermostat to module.
24 Vac to Terminals: {4} and {TR1}
8. If {4} and {TR1} does not have 24 VAC then the internal switch 1S is not in the correct position if {3} and {TR1} has 24 VAC. The Module is defective. 9. If all other functions are correct, check the wiring from {4} to Y2" on the unit low voltage terminal board.
9. Compressor does not operate with Second Stage conditions met.
{ } Terminals on the Logic Module. [ ] Low Voltage input from unit or thermostat
OUTSIDE ENTHALPY BELOW SET POINT Condition on Logic Module Should Be 1. Red LED Illuminated 1. Conditions Not Met Jumper terminals {So} and {+}. If the LED glows the Module is okay. Check note 2. Check wiring to Enthalpy Control.
24 Vac to Terminals: {TR} and {TR1} 24 Vac to Terminals: {1} and {TR1} No Continuity on Terminals: {1} and {2}
2. Check the wiring from [G] and [C] on the unit low voltage terminal strip. {TR} and {TR1} power the Motor. 3. Verify there is a call for cooling from the thermostat. Without a call for cooling the motor will not be in the Economizer mode. 4. If there is continuity from terminals {1} and {2} then the red LED should not be illuminated. If there is continuity and the LED does glow, then the module is defective. 5. If there is continuity on terminals {3} and {5} then the internal switch 1S is correctly energized. Damper motor should be in a modulating mode. 6. Jumper the Mixed Air Sensor, {T} and {T1}. If the Motor begins to operate, then check the wiring to the Sensor. If it is correct, then the temperature is below the sensor set point, or it is defective. If the Motor does not operate, and the wiring is correct, and the temperature is above the sensor set point, then the motor is bad.
Continuity on Terminals: {3} and {5}
6. Motor does not operate with all above conditions correct.
Second Stage 7. 24 Vac to Terminals: {3} and {TR1} 7. Verify that you have a 2-Stage thermostat. Check for a call for a second stage cooling. If there is not 24 VAC on {3} and {TR1} check wiring from Y2" on the thermostat to module.
24 Vac to Terminals: {5} and {TR1}
8. If {5} and {TR1} does not have 24 VAC then the internal switch 1S is not in the correct position assuming {3} and {TR1} has 24 VAC. The Module is defective. 9. If all other functions are correct, check the wiring from {5} to Y2" on the unit low voltage terminal board.
STEP BY STEP 3-POSITION ECONOMIZER CHECKOUT & TROUBLE SHOOTING
OUTSIDE ENTHALPY ABOVE SET POINT Condition on Logic Module Should Be 1. Red LED Not Illuminated Conditions Not Met 1. If the LED glows the Module thinks it is in the Economizer mode. Verify the conditions are above the enthalpy set point. Check note 2. Check wiring to Enthalpy Control for a short from {S0} and {+}. 2. Check the wiring from [G] and [C] on the unit low voltage terminal strip. {TR} and {TR1} power the Motor. {X} and {TR} provide power for minimum position. 3. Verify there is a call for cooling from the thermostat. Without a call for cooling the compressor will not be in the normal A/C mode. 4. If there is not 24 VAC on {2} and {TR} then the internal contacts are not set correctly. Remove the {So} wire from the module. If there is 24 volts to {2} and {TR} then the enthalpy control is bad or the {So} and {+} wiring is shorted together. If no voltage to {2} and {TR} then the module is bad. If there is not a continuity for {1} to {2} then the internal contacts are not in the correct position, and either the module or the enthalpy control is defective. If there is continuity from terminals {1} and {2} then the red LED should not be illuminated. If there is continuity and the LED does glow, then the module is defective. If there is continuity on terminals {3} and {5} then the internal contacts are correctly energized. Damper motor should be in the Economizer mode.

24 Vac to Terminals: {TR} and {TR1} {X} AND {TR} 24 Vac to Terminals: {1} and {TR} 24 Vac to Terminals: {2} and {TR}
6. Compressor does not operate with all above conditions correct. Second Stage 7. 24 Vac to Terminals: {3} and {TR}
6. Check the wiring from {2} to Y1" on the unit low voltage control board. Verify that there is not 24 VAC to Y1" and C on the unit.
Verify that you have a 2-Stage thermostat. Check for a call for a second stage cooling. If there is not 24 VAC on {3} and {TR} check wiring from Y2" on the thermostat to module.
24 Vac to Terminals: {5} and {TR}
8. If {4} and {TR} does not have 24 VAC then the internal switch 1S is not in the correct position if {3} and {TR} has 24 VAC. The Module is defective. 9. If all other functions are correct, check the wiring from {4} to Y2" on the unit low voltage terminal board.
OUTSIDE ENTHALPY BELOW SET POINT Condition on Logic Module Should Be 1. Red LED Illuminated 1. Conditions Not Met Jumper terminals {So} and {+}. If the LED glows the Module is okay.Check note 2. Check wiring to Enthalpy Control.
24 Vac to Terminals: {TR} and {TR1} 24 Vac to Terminals: {1} and {TR} No Continuity on Terminals: {1} and {2}
2. Check the wiring from [G] and [C] on the unit low voltage terminal strip. {TR} and {TR1} power the Motor. 3. Verify there is a call for cooling from the thermostat. Without a call for cooling the motor will not be in the Economizer mode. 4. If there is continuity from terminals {1} and {2} then the red LED should not be illuminated. If there is continuity and the LED does glow, then the module is defective. 5. If there is continuity on terminals {3} and {5} then the internal contacts are correctly energized. Damper motor should be in a modulating mode.
Jumper the Mixed Air Sensor, {6} and {D}. If the Motor begins to operate, then check the wiring to the Sensor. If it is correct, then the temperature is below the sensor set point, or it is defective. If the Motor does not operate, and the wiring is correct, and the temperature is above the sensor set point, then the motor is bad.
Second Stage 7. 24 Vac to Terminals: {3} and {TR} 7. Verify that you have a 2-Stage thermostat. Check for a call for a second stage cooling. If there is not 24 VAC on {3} and {TR} check wiring from Y2" on the thermostat to module.
8. If {5} and {TR} does not have 24 VAC then the internal switch 1S is not in the correct position assuming {3} and {TR} has 24 VAC. The Module is defective. 9. If all other functions are correct, check the wiring from {5} to Y2" on the unit low voltage terminal board.

HONEYWELL ECONOMIZER ELECTRICAL FLOW
with the First Stage of Cooling and Outdoor Enthalpy Above Desired Cooling Setpoint

ELECTRICAL CURRENT FLOW

ELECTRONIC SWITCH THAT CLOSES ON LOW ENTHALPY

A/C UNIT

with the First Stage of Cooling and Outdoor Enthalpy Below Desired Cooling Setpoint
with the Two Stages of Cooling and Outdoor Enthalpy Below Desired Cooling Setpoint

Con~raiulations! You are the owner of on&of the finest thermostats t?w produced by Honeywell. The unique features of the T7400 Programmable Commercial Thermostat,satisfy the special requirements of commercial single zone aif conditioning systems, and provide convenience and temperature control accuracy that is un~oralleled in the industrv n7is thermostat also includes enerav saving feaiures which allow it to minimize the &rgy

needed outdoor

to maintain air for We

comfort cooling

conditions whenever

by using possible.

A thorough review of this Owners Guide will help you identify those features which will maximize comfoit, convenience and savings in your application. Terms and words that may not be familiar to you are explained in the glossary at the end of this guide.

STARTUP

When power is first applied, an internal startup prcgrom begins. This reauires 1 minute to complete. and takes place after any total loss of power (supply voltage and backup battery). During this titie, default temperature set point values exe used for temperature control. These CIIC: heating 68 F (20 C]. economizer 72 F (22 C), and cooling 78 F (26 C]. Following the statiup period. you can enter new set points which will @e ,used in place of these default values. Should a power failure occur after your time and temperature schedule entries are made, the backup battery will maintain your schedule. As long as either system or battery backup power is present, your program is available and will be used for temperature control.

OPERATION

IMPORTANT: Note that the T7400 svstem will not read instonton~usly to s&t point changes. Except os mentioned below, the minimum stage on- and otftimes will oIwoys be followed. Although the temperature control monitoring occurs constantly, the temperature display updates approximately every 2 minutes unless the ROOM TEMPERATURE key is depressed. The temperature control program takes effect after the startup period. If space temperature is far below set point, CI stage of heat could turn on within 1 minute of startup. This is the only exception to the heating minimum off-time of 2 minutes. If mechanical cooling is called for. the minimum time of 4 minutes will elapse after the 1 minute startup period (5 minutes total). off-
cycle timing illustrations
Fig. 1 -Thermostat MINUTES 1COOLING 1 HEATING 1 OPERATIONAL
POWER-UP MINUTES I I I 0. Power on (1 st applied or after ioss of supply voltage and backup battery.

xe temizerature

= 70 F; heat

PROGRAM

SCHEdJCE
Intelligent Recovery, based on CI set point ramping feature, is used when switching from Unoccupied operation to Occupied operation. This selves energy by varying switchover time depending on prevailing weather conditions. The time used to achieve the occupied set point is the shortest possible time that will still ensure comfort conditions are reached by the occupied stat time.
Each day of the week ccl be individually programmed with an Occupied and an Unoccupied period to make maximum use of schedule variations. In addition to the Occupied and Unoccupied mode of thermostat operation. there is CI third mode called Intelligent Recovery. Occupied operation is based on 3 set points: heat. economizer. and cool. Unoccupied operation is based on 2 set points: heating and cooling. l%he economizer is operational during the Unoccupied period, but at a s&point fixed at 3 F (2 C) helow the Unoccupied cool set point.

Fig. 2-17400

program

schedule

and temperature

control.

Convenient keyboard layout provides effortless program entry.youi avenue to maximum energy and cost savings. The following pages provide function-by-function instructions to progrcrr the T7400 Programmable Commercial Thermostat.
The following general steps are required to enter your weekly time and temperature schedule into the T7400. See the pages indicated for detailed programming instructions.
Enter the correct time and day. (3ee pages 14 through 17.) Enter the temperature set points you want for heating. economizer, and cooling system operation. (See pages 18 through 27.) For each day of the week. enter starting time for the periods when your building will be occupied and unoccupied. (See pages 28 through 31.)
To review program entries. simply press the same function keys used to begin each programming step. ~For example. to review the ECONOMIZER temperature set point, press the ECONOMIZER key. For sample schedules and their programs. see pages 32 through 37.
SELECTING~HE DESIRED OPERATING DISPLAY (Optional)
. PRESENT TIME and ROQM TEMPERATURE keys allow you to select c@tinuous display of time or temperature. respectively. ~ If neither key is pressed, T7400 will automatically revert to a display of,,present time within 2 minutes of the last keypress.

T7400 will default to Occupied mode and control to respective Heat, Economizer. and Cool set points of 68 F. 72 F, and 78 F until thermostat is reprogrammed.
LOSS Of External Power l Blinking display of time or temperature indicates loss of external power. The backup botteiy maintains your time and temperature schedule during the power loss. l Keyboard and red indicator lights exe inoperative while the 77400 is on batteN power Failure of Temperature Sensor. While in the ROOM TEMP display display of () indicates failure the temperature sensor. System will safely deenergize all cooling stages if cI sensor failure

PROBLEM INDICATORS

Loss of Stored Program l Blinking display of 3 dashes (- -) indicates 10% of stored program. (Three steady dashes represent an occupied or unoccupied time slot that is not programmed.)
mode. 0 of wiring or heating occurs. and
TEMPORARILY OVERRIDING THE 17400s PROGRAM (optional)
3 HOUR OCCUPIED key allows you to <activate the temperature set points programmed for your buildings occupied period for 3 hours. Once pressed. the 3 HOUR OCCUPIED key can be pressed again to cancel this command, and return the T7400 to program control. CONTINUOUS UNOCCUPIED key allows you to activate the temperature set points programmed for your buildings unoccupied period for an indefinite time.
Once pressed. the CONTINUOUS UNOCCUPIED key must be pressed again to cancel this command, and return the 17400 to piogiam control. The 3.HOUROCCUPIED and CONTINUOUS UNOCCUPIED keys cannot be used at the same tir&The last key pressed will be in control. Red indicators near the display window show when 3 HOUR OCCUPIED and CONTINUOUS UNOCCUPIED ovenide functions are activated.

SET CLOCK KEYS

TO SET CLOCK
1. Press CLOCK 2. Press + or - until display shows correct time.
The + and keys adjust and back.respectively. theclock ahead As you approach the correct time, repeatedly tap the + or - key to adjust minutes one at a time.

SET DAY KEYS

TO SET DAY
1. Press DAY key. 2. Press + or - until pointer on the display identifies the correct day of the week.
Su=Sundoy: Mo=Monday; Tu=Tuesday; We=Wednesday; Th=Thursday: Fr=Friday; Sa=Saturdav.
L UNOCCUPIED HEAT SETKEYS
TO SET UNOCCUPIED TEMPERATURE
UNOCCUPIED HEAT temperature is the heating system set point for the period when your building will be unoccupied. Maximum sewing cannot exceed the OCCUPIED HEAT set point (red OCCUPIED indicator comes on while + key is depressed to show when you have reached the upper adjustment limit). __ Lower limit of the UNOCCUPIED 32 F (4 C]. HEAT setting is
1. Press UNOCCUPIED HEAT. Red UNOCCUPIED and HEAT indicators show that you have selected the WOCCUPIED HEATset point for programming. The display will show either the default or last entered unoccupied heat set point. 2. Press + 01 - until display shows the heating temperature you want to maintain during the unoccupied period.
Upper limit of UNOCCUPIED HEAT setting can be changed by adjusting the OCCUPIED HEAT set point. (See example in Fig. 3, page 37.)

[~~~Jl

~~~-;;-J~,

OCCUPIED TO SETOCCUPIED

HEAT TEMPERATURE SET KEYS
Minimum OCCUPIED HEAT setting cannot be lower than the UNOCCUPIED HEAT set point (red UNOCCUPIED indicator comes on while the key is depressed to show when you hove reached the lower adjustment limit). Maximum OCCUPIED HEAT setting is 2 F (1 C] lower than the economizer set point (red ECONOMIZER indicator comes on while the + key is depressed to show when you have reached the upper adjustment limit). Limits of OCCUPIED HEAT setting can be changed by adjusting the UNOCCUPIED HW 1 and ECONOMIZER set points. (See example in ?,~^ ^-~ FIQ. J, PClQe d,.)

HEAT TEMPEL!ATURE

1. Press OCCUPIED HEAT. Red OCCUPIED and HEAT indicators show that you have selected tlx OCCUPIED HEATset point for programming. The display will show either the default or last entered occupied heat set point. 2. Press + or until display shows the heating temberature you want to maintain during the occupied period.
OCCUPIED HEAT temperature is the hentinn system set point for the period whei n vow buildina will be occupied.
ECONOMIZER TO SETECONOMIZER TEMPERATlJRE

TEMPERATURE SET KEYS

Minimum ECONOMIZER setting is 2 F (1 C) higher than the OCCUPIED HEAT set point (red HEAT indicator comes on while the - key is depressed to show when you have reached the lower adjustment limit). Maximum ECONOMIZER sewing is 3 F [2 C) lower than the OCCUPIED COOL set point (red COOL indicator comes on while the + key is depressed to show when you have reached the uppF!adjustment limit). Limits of ECONOMIZER setting can be changed by adjusting the OCCUPIED HEAT and OCCUPIED COOL set points. (See example in Fig. 3. page 37.)

1. Press ECONOMIZER. Red OCCUPIED and ECONOMIZER indicators show that you have selected the ECONOMIZER set point for programming. The display will show either the default or last entered economizer set point. 2. Press\+ or - until display shows the temperature you would like to maintain with economizer operation during OCCUPIED period.
ECONOMIZER set point is the temperature at which the economizer (free outdoor air cooling) is allowed to function if conditions allow. The programmed ECONOMIZER set point is active only during your buildings OCCUPIED period. During the unoccupied period, the economizer is controlled at 3 F [2 C) below the programmed UNOCClJPlED COOL set point.
OCCUPIED TO SET OCCUPIED TEMPERATURE COOL
COOL TEMPERATURE SET KEYS
Minimum OCCUPIED COOL setting is 3 F (2 C) higher than the ECONOMIZER set point (red ECONO indicator comes 0 while the - key is depressed to showwhe you-have reached the lower adjustment limit). Maximum OCCUPIED COOL sewing cannot exceed the UNOCCUPIED COOL set point (red UNOCCUPIED indicator comes on while the + key is depressed to show when you have reached the upper adjustment limit). Limits of OCCUPIED COOL setiing can be changed by adjusting the ECONOMIZER and UNOCCUPIED COOLset points. (See example in Fig. 3, page 37.)
I. Press OCCUPIED COOL. Red OCCUPIED and COOL indicators show that you have selected the OCCUPIED COOL set point for programming. The display will show either the default or last entered occupied cool set point. 2. Press + or - until display shows the mechanical cooling temperature you want to maintain for the occupied period.
OCCUPIED COOL temperature is the mechanical cooling system set point for the period when your building will Se occupied.

UNOCCUPIED

COOI _ TEMPERATURE SET KEYS
UNOCCUPIED COOL temperature is the mechanical cooling system set point for the period when ycxr building will be unoccupied. Minimum lower than OCCUPIED depressed adjustment UNOCCUPIED COOL setting cannot be the OCCUPIED COOL set point (red indicator comes on while the - key is to show when you have reached the lower limit).
1. Press UNOCCUPIED COOL. Red UNOCCUPIED and COOL indicators show that you have selected the UNOCCUPIED COOLset point for programming. The display will show either the default a last entered unoccupied cooling set point. 2. Press + or until display shows the mechanical cooling temperature you want to maintclin for the unoccupied period.
Lower limit of UNOCCUPIED COOL setting can be changed by adjusting the OCCUPIED COOL set point. (See example in Fig. 3. page 37.) Upper

(40 C).

limit of the UNOCCUPIED

COOL sewing

is 99 F
SET START TIME KEYS TO SE3 START TIMES

: 1. Press SELECT DAY. Display shows CI day-of-week indicator. 2. Press + or - until indicator identifies the dnv of week you want to program (Sunday. for &ample). 3. Press OCCUPIED START TIME. Red OCCUPIED indicator shows that VW have selected the OCCUPIED period forprogromming. Display shows the start time currently programmed for the OCCUPIED period. If no start time has been programm&d. 3 dashes (- -) will be displayed. 4. Press + or - until the start time you want for a OCCUPIED period appears on the display. If you do not want a OCCUPIED period to start on the selected day, press CLEAR START TIME. 5. Press UNOCCUPIED STARTTIME. Red UNOCCUPIED indicator shows that you have selected tl?e UNOCCUPIED period for programming. Display shows the start time currently programmed for the UNOCCUPIED period. If no start time has been programmed. 3 dashes (- -) will be displayed.
6. Press + and -until the start time you want for UNOCCUPIED period appears on the display. If you do not want an UNOCCUPIED period to start on the selected day, press CLEAR STARTTIME. 7. Repeat steps 1 through 6 for each remaining day of the week, or refer to following steps on Copy Day.

Program

times are entered

in IO-minute

increments.
Each day of week has one OCCUPIED START TIME and one UNOCCUPIED START TIME slot available for programming. Each day is the 24.hour period a.m. (midnight to midnight). If you want the more days. you DAY feature to entry See next from 12 am. to 12
same schedule of start times on 2 or have the option of using the COPY avoid repeating the daily schedule 2 pages for COPY DAY instructions.

COPY DAY KEYS

;:TO COPY DAY
; 1. Press SELECT DAY 1 2. Press + or - until display indicator identifies the day with OCCUPIED START TIME and UNOCCUPIED START TIME YOU want to CODY to another dov. I 3. Press COPj DAY to begin <he copy. 4. Press + or until CI seconddisplay indicator identifies the day to which you want to copy the first davs schedule. 5. Press 6OPY DAY to complete the copy. 6. If you want to copy the same schedule to additional days. repeat steps 4 and 5 for each additional day.
The COPY DAY procedure is optional. Start times for each day of the week con be programmed as described in the preceding instructions, TO SF3 START TIMES. If you use the COPY DAY feature. review all start time schedules to verify that copying was completed without error.

SAMPLE SCHEDULE 1

In this sample schedule, the owner wants the buildings temperature to be at the OCCUPIED HEAT/COOL set point beginning at 7:00 a.m. on Monday~through Saturday! The buildings UNOCCUPIED times vary On Monday, Tuesday, Thursday, and Friday. the building is UNOCCUPIED beginning at 500 p.n?. The UNOCCUPIED period starts later on Wednesday (9~00 p.m.). and earlier on Sotway (II:00 a.m.). On Sunday, the building is unoccupied all day. Neither an OCCUPIED period nor an UNOCCUPIED period starts on Sunday. The building is UNOCCUPIED starting at II:00 am, on Saturday. and remains UNOCCUPIED until Monday morning at 7:OO am In programming Sundays schedule, the CLEAR START TIME key would be used to clear OCCUPIED START and UNOCCUPIED START times for Sunday. Note that start times for Tuesday. Thursday. and Friday are identical to those for Monday. Each day can be programmed separately. Optionally. Mondays start times can be entered, then the Monday schedule copied into each of the other 3 days with the aid of the COPY DAY key.

Sunday Monday Tuesday Wednesday Thursday Friday Saturdav
OCCUPIED Stari times (CLEAR) 7:oo a.m. 700 a.m. 700 a.m. 7:oo a.m. 7:oo a.m. 700 a.m.
UNOCCUPIED Start times (CLEAR) 500 p.m. 5:oo p.m. 9:oo p.m. 500 p.m. 5:oo p.m. 1 I:00 a.m.

SAMPLE SCHEDULE 2

In this sample schedule, the owner wants the buildings temperature to be at the OCCUPIED HEAT/COOL set point storticg at 1 I:00 a.m. Monday through~saturday. The Ocoupied period will end at I:00 a.m. on the following weekday mornings. and at midnight on Saturday. On Sunday, the building will be unoccupied all day, so the CLEAR STARTTIME key would be used to clear Sunda\is OCCUPIED START time. The UNOCCUPIED START times vary. The bu/lding is occupied on Saturday from 1 I:00 a.m. until midnight. Since Saturday ends ond Sunday begins exactly at midnight (17~00 am.). an UNOCCUPIED period should start at 1200 o.m on Sunday. This gives the desired result of on UNOCCUPIED set mint ail day Sunday when Sundays OCCUPIED START time has been cleared. The building will remain unoccupied until Monday at 1 I:00 am. No UNOCCUPIED START time is needed on Monday because the UNOCCUPIED period would have aireody been established on Sunday. in programming Monda\/s schedule, the CLEAR STARTTIME key would be used to clear the UNOCCUPIED START time for Monday. On Tuesday through Saturday, the building is unoccupied starting at I:00 a.m. Unlike Sample Schedule 1, the UNOCCUPIED periods on these days start before the OCCUPIED periods. Remember, o 24. hour day begins at 1200 am. Each day3 set point schedule should be planned by reference to this time. Doily schedules of start times ore identical for Tuesday through Saturday. Each day co be programmed separately. Optionally, Tuesdays start times con be entered, then the Tuesday schedule copied into each of the other 4 days with the aid of the COW DAY key.
Sunday Monday Tuesday Wednesday Thursday Friday Saturday oTime at which the OCCUPIED point. hime at which control at the temperature
OCCUPIED Start timesa CLEAR 11:oo a.m. ll:oo a.m. 1 I:00 a.m. II:00 a.m. II:00 a.m. II:00 a.m. you want your building HEAT/COOL temperatUre

UNOCCUPIED stars fimesb 1200 a.m. CLEAR I:00 a.m. I:00 0.m. I:00 a.m. I:00 a.m. I:00 a.m. to reach
you want your building to UNOCCUPIED HEATiCaL set point.
FORM TO ENTER YQUR SCHEDULE OF OCCUPIED AND UNOCCUPIED START TIMES
OCCUPIED Start timesa Sunday Monday Tuesday Wednesday Thursday Friday Saturday UNQCCUPIED

start time&

aTime at which you want your building to reach the OCCUPIED HEAT/COOL temperature set point. ~__ % ~me at which you want your building to control at the UNOCCUPIED HEAT/COOL temperature set point,
-Fig. J-Example of temperature
set points and resulting adjustment ranges.
Review and write down the program contained in the.thermostat. Use th#? form on the preViOUS page. information. The battery results in the loss of the
It is not necessary to disconnect power supply to the system during battery replacement. This would cause backup battery operation and battery drain until the system is powered up. Reattach T7400 to wallplate. and secure by tightening both Allen screws along bottom of thermostat. Do not overtighten. Reprogram the 77400 thermostat using the program written down earlier.
NOTE: Save the program replacement procedure thermostat program.
Loosen Allen screw at each corner alo; the bottom of thermostat. Remove thermostat by winging bottom away and upward from wallplate or subbase (see Fig. 4). If bottew replacement is required, replace only with o f&hMailo~ MNlM)4or equiv&nt C?-v61t alkaline battery. Place battery in the clip on the wallplate or subbase. Fold the battery wire!; against the wallplate (subbase).

Fig. 4-Install

backup

battery

L3ackupBattery-A bat& located in the 17400 thermostat that provides electricity to maintain your time and temperature schedule during power loss. If the battery is dead or runs down during o power failure, the time and temperature schedule will be lost. However. the thermostat will control to 11 standard Set of default set points when bower is restored Default Set Points-Temperature sewings of 458 F for heating, 72 F for economizer. and 78 F for ccooling that ore built into the T7400. These assure that the system will remain operational even if the thermostat is not programmed or the time and temperature schedules are lost due to battery failure.
Economizer-An auxiliary control system which allows use of COOI outdwr air for ke Caling. in place of eiectrical air conditioning equipment. The T7400 has 2 cooling set points. economizer and mechanical cooling. Based on the availability of outdoor air for free cooling, the 77400 will control at the lower economizer set point providing increased comfort without the extra expense of running mechanical cooling. Only if outdoor air cannot or does not sufficiently cool the space will mechanical cooling be allowed to run. and then only at the higher mechanical cooling set point. Free Cooling-See Economizer.

intelligent Recovery-A control method which ,i adjuGs the heating warmup and cooling pulldown time periods based on outside weather conditions. Commonly refered to OS optimized start. Mechanical Cooling-Cooling running compressors to extract conditioned space. that is provided heat from the by
Occupied Ti?mperoture Set Point-The heating, economizer. and cooling temperature settings used when the room or building is scheduled to be occupied. -_ Occupied Start Time-The selected time at which the air conditioned space is to reach the comfort temperature for people occupying the room. Set Point-The selected temperature at which the heating/cooling system is to maintain the conditioned space. There ore separate set points for heating. economizer. and cooling in the OCCUPIED and UNOCCUPIED time pefiods.
Minimum ON/Oft Times-Fixed minimum on/off equipment run times used to prevent harmful short cycling (turning on and off too often) which con significantly reduce equipment life or cause permanent damage.
Single Zone Air Conditioning System-A packaged system that includes heating, cooling, and air distribution equipment. It might also include an economizer (see Economizer). These systems are selfcontained. often roof mounted. and condition the air in q specific local area v&h its own thermostat. Larger buildings may have 2 or more areas or zones, each with its own air conditioning system and thermostat. Thermostat Cycle-The time necessary for the heating or cooling equipment to come on, operate. and turn and remain off until the next tir& it is needed. Cycle time is controlled by thethermostat. For example. mechanical cooling equipment might turn on and then go off 4 times in an hour.
Unoccupied Temperature Set Point-The heating and cooling temperature settings used when the room or building is scheduled to be unoccupied. Unoccupied Start Time-The selected time at which the air conditioned space is allowed to become cooler/warmer to save energy. NOTE: can be temporarily overridden by using the 3-Hour Override key. 7-Day Program-Each day of the week (7 days) be individually scheduled for occupied or unoccupied start times. This allows maximum flexibility for building scheduling. may

IF. Heating Cooling

will not come on. or will not come on. with blinking display of time or
No heating/cooling temperature. Too wcxm (cooling), Too cool (heating). Blinking display

of 3 dashes

Steady display gramming.

-) during

Then. Wait for the minimum off-time delay of 2 to 4 minutes. Recall temperature set points to verify correct settings. There will be no heating/cooling as the heating/ cooling system power is off. The backup battery is maintaining the program schedule. Recall the Occupied Start schedule to check for the desired time. Also check the temperature set points to verify correct settings. Indicates loss of stored time and temperature schedule. Check/replace the backup battery and reenter time and temperature schedule. Indicates an Occupied or Unoccupied time that is not programmed.
maintenance supervisor or service technicjon.
or. If these steps do not solve your problem,

call your building