OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M37 Merit® Series 5/2 Day Programmable Thermostat CONTROLS 505,050M 05/05 Supersedes 03/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M37 Merit® Series Thermostat The Lennox Merit® Series 5/2 day programmable electronic thermostat 51M37 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the Home Screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. NOTE − Tables 2 and 3 on page 8 show all system and programming defaults.
HEAT − Using the Heat Mode Heat Mode Disabled ROOM 75 Normal Heat Mode In normal heat mode, both the heat pump and the backup heat source are used to provide heat. If the thermostat detects that the heat pump is not able to provide enough heat (as may be the case in very cold weather), then the backup heat source is activated.
Cooling Demand COOL − Using the Cool Mode Enabling and Disabling Cool Mode Use the COOL button to enable or disable cool mode as desired. If the thermostat is in HEAT or OFF mode, cool mode is enabled when the COOL button is pressed. This is indicated by COOL in the SYSTEM box (see figure 9). Set the thermostat to cool mode to control the cooling equipment.
PROG − Thermostat Programming HOLD − Using Temperature Hold Modes When HOLD is displayed at the HOME screen, the thermostat is in a temperature hold condition. This means that the temperature program data is ignored and the thermostat functions much like a non−programmable thermostat. Adjusting Temperature Setpoint in Hold Mode The temperature setpoint represents the desired temperature of the space around the thermostat. The default temperature setpoint in Hold mode is 70°F.
5. Repeat steps 2 through 4 for periods B, C, and D. 6. Repeat steps 1 through 5 for the 2−day program. NOTE − This thermostat will NOT automatically switch from heating to cooling, or vice versa; operator involvement is required. At the change of seasons, or to accomodate abnormal seasonal temperature swings, you must manually select to the opposite conditioning (Heat or Cool) program. FAN − Controlling the Fan Operation Use the FAN button to select either continuous fan mode or auto fan mode.
Service Indicator Flashing SETTINGS − Balance Point MO TU WE TH FR SA SU I0:i4 79 NOTE − The balance point is only available with the outdoor sensor. If the optional outdoor sensor (X2658) is connected to the thermostat, balance point adjustment is available. The balance point feature allows the measured outdoor temperature to govern operation of the heat pump and backup heat source. Use the SETTINGS button to access the balance point setting.
Default Thermostat Settings CAUTION 24VAC is present on the terminals of the thermostat bracket. If removing the thermostat from the wall, use caution and avoid touching any of the connector terminals on the wall bracket. Default thermostat settings are shown in table 2 and the default program is shown in table 3.
Smart Setback Recovery (via DIP switch #6) Equipment Protection Override Smart Setback Recovery (SSR) affects the way the thermostat responds to program events. If SSR is disabled, the thermostat will react to a program event at the time the event occurs. However, if SSR is enabled, the thermostat will react to a program event before the event occurs such that the desired temperature is reached at the time of the event, not after.
Table 5 THERMOSTAT OUTPUTS Thermostat Output Table Table 5 depicts the 51M37 thermostat output states for various input conditions. The following notes described terms used in the table. S X = output is activated with 24VAC. S BBP: outdoor temperature is below balance point Y1 Y2 G O X X X X X X X X X X Cooling Demands w/Electric Backup (no outdoor sensor) S In all cases, the state of the B terminal is opposite that of the O terminal S Data are tabulated for AUTO fan setting.
OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M35 Merit® Series 5/2 Day Programmable Thermostat CONTROLS 505,049M 05/05 Supersedes 03/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M35 Merit® Series Thermostat The Lennox Merit® Series 5/2 day programmable electronic thermostat 51M35 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the Home Screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. NOTE − Tables 2 and 3 on page 6 show all system and programming defaults.
HEAT − Using the Heat Mode COOL − Using the Cool Mode Enabling and Disabling Heat Mode Enabling and Disabling Cool Mode The thermostat must be in the HEAT mode to control the heating equipment. Press the Heat button to enable or disable HEAT mode. If the thermostat is in COOL or OFF mode, pressing the Heat button enables the HEAT mode (indicated by HEAT in the SYSTEM box − see figure 4). Use the COOL button to enable or disable cool mode as desired.
HOLD − Using Temperature Hold Modes PROG − Thermostat Programming When HOLD is displayed at the HOME screen, the thermostat is in a temperature hold condition. This means that the temperature program data is ignored and the thermostat functions much like a non−programmable thermostat. Adjusting Temperature Setpoint in Hold Mode The temperature setpoint represents the desired temperature of the space around the thermostat. The default temperature setpoint in Hold mode is 70°F.
NOTE − This thermostat will NOT automatically switch from heating to cooling, or vice versa; operator involvement is required. At the change of seasons, or to accomodate abnormal seasonal temperature swings, you must manually select to the opposite conditioning (Heat or Cool) program. Reminder Settings Display OFF FAN − Controlling the Fan Operation Use the FAN button to select either continuous fan mode or auto fan mode. To change from continuous to auto fan mode (or vice versa), press the FAN button.
Service Indicator Removing and Installing Thermostat When abnormal equipment operation is detected, the SERVICE indicator will flash on the screen (see figure 17). This indicates that the equipment requires service from a qualified service technician. Service Indicator Flashing MO TU WE TH FR SA SU I0:i4 79 AM PM PROG A B C D ROOM HOLD ° FILTER SERVICE The thermostat hinges on tabs on the top of the subbase; no tool is needed to remove the thermostat from the subbase.
Temperature Setpoint Range Technical Specifications Setting range: 50°F (10°C) to 90°F (32°C) Setting resolution: 1°F (1°C) Thermostat Type Electronic programmable thermostat for 2−Stage (gas or electric) Heat/2-Stage Cool, non−heat pump, non−power robbing applications. Power Supply Range 18VAC − 30VAC (24VAC nominal), 60Hz CAUTION Smart Setback Recovery (via DIP switch #6) Smart Setback Recovery (SSR) affects the way the thermostat responds to program events.
Maintenance Reminder Settings of Off, 6 or 12 (months of chronological time) are available. When programmed time has elapsed, a maintenance indicator MAINT" is displayed. NOTE − The temperature ranges expressed in the following definitions of SMALL/LARGE" demands are for guidance only; actual temperatures may vary.
OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M34 Merit® Series 5/2 Day Programmable Thermostat CONTROLS 505,048M 05/05 Supersedes 03/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M34 Merit® Series Thermostat The Lennox Merit® Series 5/2 day programmable electronic thermostat 51M34 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the Home Screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. Home Screen MO TU WE TH FR SA SU AM PM I2:00 PROG A B C D HOLD ROOM 70 Thermostat Buttons MAINT FILTER SERVICE Prog Day/Time Hold Settings Enter (DOOR OPEN) FAN ON AUTO Figure 3 HEAT Figure 2 At this point, the thermostat will be fully functional; its default temperature setpoint (not shown) is 70°F.
HEAT − Using the Heat Mode COOL − Using the Cool Mode Enabling and Disabling Heat Mode Enabling and Disabling Cool Mode The thermostat must be in the HEAT mode to control the heating equipment. Press the Heat button to enable or disable HEAT mode. If the thermostat is in COOL or OFF mode, pressing the Heat button enables the HEAT mode (indicated by HEAT in the SYSTEM box − see figure 4). Use the COOL button to enable or disable cool mode as desired.
HOLD − Using Temperature Hold Modes PROG − Thermostat Programming When HOLD is displayed at the HOME screen, the thermostat is in a temperature hold condition. This means that the temperature program data is ignored and the thermostat functions much like a non−programmable thermostat. Adjusting Temperature Setpoint in Hold Mode The temperature setpoint represents the desired temperature of the space around the thermostat. The default temperature setpoint in Hold mode is 70°F.
NOTE − This thermostat will NOT automatically switch from heating to cooling, or vice versa; operator involvement is required. At the change of seasons, or to accomodate abnormal seasonal temperature swings, you must manually select to the opposite conditioning (Heat or Cool) program. Reminder Settings Display OFF FAN − Controlling the Fan Operation Use the FAN button to select either continuous fan mode or auto fan mode. To change from continuous to auto fan mode (or vice versa), press the FAN button.
Service Indicator Removing/Installing Thermostat When abnormal equipment operation is detected, the SERVICE indicator will flash on the screen (see figure 17). This indicates that the equipment requires service from a qualified service technician. Service Indicator Flashing MO TU WE TH FR SA SU I0:i4 79 AM PM PROG A B C D ROOM HOLD ° FILTER SERVICE The thermostat hinges on tabs on the top of the subbase; no tool is needed to remove the thermostat from the subbase.
Technical Specifications Thermostat Type Electronic programmable thermostat for 1-StageHeat/1-Stage Cool, gas or electric heat, non−heat pump, non−power robbing applications. Power Supply Range Field Offset: via DIP switches to +/−3°F Sampling Method: temperature measurements sampled every 15 seconds. Displayed temperature is the average of the last four measurements.
Maintenance Reminder Thermostat Operating Conditions Settings of Off, 6 or 12 (months of chronological time) are available. When programmed time has elapsed, a maintenance indicator MAINT" is displayed.
OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M39 Merit® Series 7 Day Programmable Thermostat CONTROLS 505,068M 07/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M39 Merit® Series Thermostat The Lennox Merit® Series 7 day programmable electronic thermostat 51M39 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the HOME screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. Thermostat Buttons NOTE − Tables 2 and 3 on page 7 show all system and programming defaults. PROG ABCD HOLD FAN ON AUTO 70 ° Auto Hold (DOOR OPEN) Settings Enter (Outside) COOL OFF AUTO EMG.
HEAT − Using the Heat Mode COOL − Using the Cool Mode Enabling and Disabling Heat Mode Enabling and Disabling Cool Mode The thermostat must be in the heat mode to control the heating equipment. Press the HEAT button to enable or disable HEAT mode. If the thermostat is in cool or off mode, pressing the HEAT button enables the heat mode (indicated by HEAT in the lower right corner − see figure 4). Use the COOL button to enable or disable cool mode as desired.
NOTE − If no buttons are pressed during a demand for cooling, the equipment must operate for at least 4 minutes. After a demand has been satisfied, cooling equipment operation is locked out for 5 minutes. If another cooling demand occurs during this 5−minute interval, COOL" and the snowflakes will flash; however, the cooling equipment will not operate until the 5−minute delay has elapsed.
C Program Example MONDAY PROGRAM: 72° 68° A C Copy a Programmed Day to Another Day D B 64° Repeat steps A and B for as many days as you want the same program. TUESDAY PROGRAM: 72° 68° A D B 64° Copy from MO WEDNESDAY PROGRAM: 72° 68° Heat Cool Prog Auto C A Copy Day/Time C D B 64° Fan Hold (DOOR OPEN) THURSDAY PROGRAM: 72° 68° A C D B 64° Settings Enter FRIDAY PROGRAM: 72° 68° (outside) A C D B 64° Figure 12 SATURDAY PROGRAM: 72° C A 68° B 7.
After either programmed interval has elapsed, the reminder will be displayed as shown in figure 17. Displaying Outside Temperature Pressing the ENTER (Outside) button at the HOME screen displays the outside temperature (see figure 15) for several seconds, then returns to room temperature.
Table 4 Thermostat Outputs Removing and Installing Thermostat Condition The thermostat hinges on tabs on the top of the subbase; no tool is needed to remove the thermostat from the subbase. Pivot the bottom of the thermostat outward (releasing the snaps), then lift up to remove.
Thermostat Type Display range: 35°F (2°C) to 99°F (37°C) Display resolution: 1°F (1°C) Display Accuracy: +/−1°F Electronic programmable thermostat for 2−Stage (gas or electric) Heat/2-Stage Cool, non−heat pump, non−power robbing applications. If the Fahrenheit/Celsius display must be changed, use a plastic, non−conductive tool to push the dip switch to the right position (see figure 18).
NOTE − All protection timers (except the compressor OFF timer) can be over−ridden if a heating or cooling demand is initiated or terminated using the UP, DOWN, HEAT, or COOL buttons.
OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M42 Merit® Series 7−Day Programmable Thermostat CONTROLS 505,069M 07/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M42 Merit® Series Thermostat The Lennox Merit® Series 7−day programmable electronic thermostat 51M42 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the HOME screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. NOTE − Tables 2 and 3 on page 8 show all system and programming defaults. Thermostat Buttons Heat Cool Prog Auto Copy Day/Time HOME Screen PROG ABCD HOLD MO AM PM FAN ON AUTO I0:26 ROOM 70 Fan ° Hold (DOOR OPEN) Settings Enter (Outside) COOL OFF AUTO EMG.
HEAT − Using the Heat Mode Heat Mode Disabled 75 ROOM Normal Heat Mode In normal heat mode, both the heat pump and the backup heat source are used to provide heat. If the thermostat detects that the heat pump is not able to provide enough heat (as may be the case in very cold weather), then the backup heat source is activated. Emergency Heat Mode In emergency heat mode, only the backup heat source provides heat the heat pump is disabled.
COOL − Using the Cool Mode Enabling and Disabling Cool Mode Use the COOL button to enable or disable cool mode as desired. If the thermostat is in heat or off mode, cool mode is enabled when the COOL button is pressed. This is indicated by COOL on the right side of the display (see figure 9). i0:30 75 70 Cool Prog Auto Copy Day/Time 66 Fan Hold AUTO − Using the Autochangeover Mode When in either heat mode or cool mode, autochangeover can be enabled or disabled by pressing the AUTO button.
Temporary (2-Hour) Hold Program Example At any time the program is running, from the HOME screen, set a temporary 2-hour hold by pressing the Up/ Down arrow buttons until the desired setpoint is displayed; HOLD" flashes (see figure 12). This overrides the program for 2 hours from the last button press, then returns to the program.
FAN − Controlling the Fan Operation SETTINGS − Filter/Maintenance Reminders Use the FAN button to select either continuous fan mode or auto fan mode. To change from continuous to auto fan mode (or vice versa), press the FAN button. Note whether a fan icon in the FAN box is present (indicating that the fan is running) or not (fan not running).
To adjust the balance point up or down, press the Up/Down arrow buttons to the right of the display screen. The balance point setting increases by 1°F each time the Up button is pressed and decreases by 1°F each time the Down button is pressed. After the desired balance point setting is reached, the HOME screen will reappear after about 15 seconds. NOTE − The balance point feature allows the outdoor temperature to rise or fall 3°F above or below the balance point.
Default Thermostat Settings Default thermostat settings are shown in table 2 and the default program is shown in table 3. Table 2 Default Thermostat Settings Mode Heat Setpoint (Perm Hold) Cool Setpoint (Perm Hold) Fan Filter Reminder Maintenance Reminder Equipment Protection Timers Heat (Perm. Hold) 70°F (or 21°C) 78°F (or 26°C) Auto OFF OFF Reset Back to Zero Autochangeover OFF With a LARGE cool demand, temperature is: above setpoint +1.5F OR 30-minute upstage timer HAS expired.
Indoor Temperature Measurement Range Technical Specifications Thermostat Type Electronic programmable thermostat for heat pump, 3-stage heat/2-stage cool. NOTE − 2 stages of heat pump heat and one stage of auxiliary (gas or electric) backup heat are supported. Power Supply Range 18VAC − 30VAC (24VAC nominal), 60Hz CAUTION Measurement Scale: Fahrenheit Measurement Range: 35°F to 99°F Measurement Resolution: 0.
Table 5 51M42 Terminal Designations Over−Temperature Protection Term. B O R Y1 Description Reversing valve, heat active Reversing valve, cool active 24VAC First-stage cooling/heating, compressor energized W1* Auxiliary heating, furnace energized Y2 Second-stage cooling/heating, compressor energized E* Emergency heat G Fan control L Service Indicator C 24VAC common T Outdoor temperature sensor connection 1 T Outdoor temperature sensor connection 2 * For most applications, E will be jumpered to W1.
OPERATION MANUAL E2005 Lennox Industries Inc. Dallas, Texas, USA 51M38 Merit® Series 7 Day Programmable Thermostat CONTROLS 505,067M 07/05 Litho U.S.A. Table of Contents RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE 51M38 Merit® Series Thermostat The Lennox Merit® Series 7 day programmable electronic thermostat 51M38 provides excellent temperature control and a large, easy-to-read display.
Within a few seconds, the HOME screen appears (see figure 2) with default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed. Thermostat Buttons HOME Screen PROG ABCD HOLD MO AM PM FAN ON AUTO 70 ° Prog Auto Fan Hold (DOOR OPEN) Settings Enter COOL OFF AUTO EMG. HEAT (Outside) Figure 3 Figure 2 At this point, the thermostat will be fully functional; its default temperature setpoint (not shown) is 70°F.
HEAT − Using the Heat Mode COOL − Using the Cool Mode Enabling and Disabling Cool Mode Enabling and Disabling Heat Mode The thermostat must be in the heat mode to control the heating equipment. Press the HEAT button to enable or disable heat mode. If the thermostat is in cool or off mode, pressing the HEAT button enables the heat mode (indicated by HEAT in the lower right corner − see figure 4). Use the COOL button to enable or disable cool mode as desired.
Temporary Hold Temperature Mode HOLD − Using Temperature Hold Modes When HOLD is displayed at the HOME screen, the thermostat is in a temperature hold condition. This means that the temperature program data is ignored and the thermostat functions much like a non−programmable thermostat. i0:30 72 Adjusting Temperature Setpoint in Hold Mode The temperature setpoint represents the desired temperature of the space around the thermostat.
1. Press and release the PROG button. "MO" (Monday), "AM 6:00", period "A", "COOL SETPOINT 78", and "HEAT SETPOINT 70" are displayed. "AM 6" flashes. 2. Use the Up/Down arrow buttons to select the desired hour; press the PROG button when the desired hour is reached; use the Up/Down arrow buttons again to select desired minute. The selected hour/minute is when the program will start. Press the PROG button. 3. Use the Up/Down arrow buttons to select the desired heat setpoint; press the PROG button. 4.
The default setting for the reminders is OFF (disabled). Press Up/Down arrow buttons to select the desired reminder intervals. Table 1 Filter and Maintenance Reminders Buttons to Use SETTINGS (1st press) then Arrows to scroll selections SETTINGS (2nd press) then Arrows to scroll selections Available Settings and Reminder How to Use FILTER Total fan run time expressed in Enter Under some abnormal conditions, it may be necessary to reset" the thermostat to its default condition.
Table 3 CAUTION Default Program Settings (Time & Temp.) Programs All days − A All days − B All days − C All days − D Time 6:00am 8:00am 6:00pm 10:00pm Temp. − Heat 70_F / 21°C 62_F / 17°C 70_F / 21°C 62_F / 17°C 24VAC is present on the terminals of the thermostat bracket. If removing the thermostat from the wall, use caution and avoid touching any of the connector terminals on the wall bracket. Temp.
Smart Setback Recovery (via DIP switch #6) Equipment Protection Override Smart Setback Recovery (SSR) affects the way the thermostat responds to program events. If SSR is disabled, the thermostat will react to a program event at the time the event occurs. However, if SSR is enabled, the thermostat will react to a program event before the event occurs such that the desired temperature is reached at the time of the event, not after.
