User manual HONEYWELL T7400

`. , 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 Owner's 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- > i , cycle timing illustrations Fig. 1 -Thermostat MINUTES 1COOLING 1 HEATING 1 OPERATIONAL POWER-UP MINUTES II I 0 . Power on (1 st applied or after ioss of supply voltage and backup battery. /I/ xe temizerature = 70 F; heat 1 7 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. I 10 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. l l l 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.) l l 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. 11 I 12 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. l 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 17400's PROGRAM (optional) l l l 3 HOUR OCCUPIED key allows you to