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OPERATION
®
MANUAL
2003 Lennox Industries Inc.
Dallas, Texas, USA
®
Merit Series Thermostat
CONTROLS (51M32)
504,865M
09/04
Litho U.S.A.
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
Table of Contents
®
Merit Series Thermostat . . . . . . . . . . . . . . . . . . . . . . 1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Initial Thermostat Power-up . . . . . . . . . . .
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Display − Home Screen Heat Mode Enabled ROOM ROOM 70 69 FAN FAN AUTO AUTO SYSTEM SYSTEM 64 SETPOINT HEAT HEAT Figure 2 Figure 4 Figure 2 illustrates the HOME screen. Note that an indoor room temperature of 70°F is initially displayed. After about 1 minute of warm−up time, the actual room temperature will If the thermostat is in heat mode, heat mode is disabled be displayed. HEAT mode is the system default (as indi- when the HEAT button is pressed. This is indicated by OFF cated in the SYSTEM box
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Heating Demand Cooling Demand ROOM ROOM 72 79 FAN FAN AUTO AUTO SYSTEM SYSTEM 88 COOL HEAT Figure 6 Figure 7 NOTE − The cooling equipment is activated for at least 4 minutes if no buttons are pressed during the demand inter- When the actual temperature rises above the temperature val. Cooling equipment operation is locked out for 5 min- setpoint, the flame icon will disappear. This indicates that utes after a demand has been satisfied. If another cooling the heating demand has been satisfied and
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Fan Control Filter Reminder The 51M32 thermostat includes a filter reminder feature. The FAN button is located behind the small door on the The filter reminder can be set for 1, 3, 6, or 12−month inter- right-hand side of the thermostat. See figure 3. The FAN vals. The SETTINGS button, located behind the door on button can be used to select either continuous fan mode or the right−hand side of the thermostat is used to set the filter auto fan mode. reminder interval. See figure 3. Press the SETTI
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Service Indicator Technical Specifications Thermostat Type When abnormal equipment operation is detected, the Electronic nonprogrammable thermostat for 1H/1C, gas or SERVICE indicator will flash on the upper-right corner of the screen. This indicates that the equipment requires ser- electric heat, non−heat pump, non−power robbing applica- vice from a qualified service technician. The SERVICE indi- tions. cator is shown in figure 13. Power Supply Range 18VAC − 30VAC (24VAC nominal), 60Hz Service
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Equipment Protection Override Power Loss/Recovery Thermostat memory is retained for a minimum of 24 hours Both the minimum compressor OFF timer and the mini- during a power loss (includes retention of programmed mum equipment cycle timer can be over−ridden by press- temperature setpoint, heat/cool and fan mode settings, fil- ing and holding either the HEAT or COOL button down for 4 ter reminder status, and equipment protection timers). Af- seconds. ter 24 hours of power loss, programmed settings
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OPERATION ® MANUAL 2003 Lennox Industries Inc. Dallas, Texas, USA ® Merit Series Thermostat CONTROLS (51M33) 504,931M 09/04 Litho U.S.A. RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE Table of Contents ® Merit Series Thermostat . . . . . . . . . . . . . . . . . . . . . . 1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Initial Thermostat Power-up . . . . . . . . . . .
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Enabling and Disabling Heat Mode Display − Home Screen Use the HEAT button to select normal heat mode, emer- gency heat mode, or to disable heat modes as desired. If ROOM the thermostat is in off mode, normal heat mode is enabled 70 when the HEAT button is pressed. This is indicated by FAN HEAT in the SYSTEM box as shown in figure 4. AUTO SYSTEM Normal Heat Mode Enabled ROOM HEAT 69 FAN Figure 2 Figure 2 illustrates the HOME screen. Note that an indoor AUTO room temperature of 70°F is initially
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Enabling and Disabling Cool Mode Heat Mode Disabled Use the COOL button to enable or disable cool mode as necessary. If the thermostat is in off mode, cool mode is en- ROOM abled when the COOL button is pressed. This is indicated 69 by COOL in the SYSTEM box. FAN If the thermostat is in cool mode, cool mode is disabled when the COOL button is pressed. This is indicated by OFF AUTO in the SYSTEM box. SYSTEM 64 Cooling Demand SETPOINT The thermostat must be in cool mode in order to properly OFF co
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Fan AUTO with Icon Setpoint Display and Adjustment ROOM ROOM 73 69 FAN FAN AUTO AUTO SYSTEM SYSTEM 64 SETPOINT HEAT HEAT Figure 11 Figure 9 To change from continuous to auto fan mode and vice versa, press the FAN button. Also note the presence of a fan icon in the FAN box. This icon indicates that the fan is running. After the desired setpoint is reached, the HOME screen will Filter Reminder reappear after about 8 seconds. The 51M33 thermostat includes a filter reminder feature. The filter remin
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DOWN arrow keys to the right of the display screen. The Display of Filter Reminder balance point setting will increase by 1°F each time the UP key is pressed. The balance point setting will decrease by FILTER ROOM 1°F each time the DOWN key is pressed. 72 After the desired balance point is reached, the HOME FAN screen will reappear after about eight seconds. AUTO NOTE − The balance point feature allows the temperature to rise or fall 3°F above or below the setpoint. This prevents SYSTEM excessiv
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Table 2 Default Thermostat Settings 51M33 Terminal Designations Default Thermostat settings are in table 1. Connections Description Table 1 O Reversing valve, cool active Default Thermostat Settings B Reversing valve, heat active Mode Heat R 24VAC Setpoint 70°F (or 21°C) G Fan control Fan Auto Y1 First stage cooling/heating, compres- Filter Reminder OFF (reminder setting = 0) sor generated Equipment Protection reset back to zero W1 Auxiliary heating, furnace generated Timers L Service Indicator
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Service Reminder IMPORTANT The SERVICE indicator is displayed only under the follow- Power must be applied for at least six consecutive ing conditions: hours prior to a power loss in order for memory to be if the thermostat Y1 terminal has been activated retained for the specified time. with 24VAC for at least 5 minutes, AND the L LCD Backlight terminal is shorted to the R terminal; Activated for 8 seconds when any key is pressed. OR NOTE − During an electrical storm or similar disturbance,
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Table 3 Thermostat Output States Condition W1 Y1 G O E Electric Heat Backup − No Outdoor Sensor small heat demand X X large heat demand X X X emergency heat demand X X cool demand X X X no demand dc Gas Heat Backup (Dual Fuel) − No Outdoor Sensor small heat demand X X large heat demand X emergency heat demand X cool demand X X X no demand dc Electric Heat Backup − Outdoor Sensor Attached small heat demand (BBP) X X large heat demand (BBP) X X X small heat demand (ABP) X X large heat demand (ABP)
