Lennox International Inc 51M37 51M42 Terminal Designations, Equipment Protection Timers

Table 5

51M42 Terminal Designations

Term. Description

BReversing valve, heat active

O Reversing valve, cool active

R24VAC

Y1	First-stage cooling/heating, compressor
	energized
W1*	Auxiliary heating, furnace energized
Y2	Second-stage cooling/heating, compressor
	energized
E*	Emergency heat

GFan control

LService 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. If sep- arate wires are not provided for both E and W1, jumper the E terminal to the W1 terminal on the thermostat sub- base. For applications involving the use of a balance point (whereby the outdoor temperature is to be used to restrict either heat pump operation or backup heat source operation), the outdoor sensor (part number X2658) MUST be installed.

Equipment Protection Timers

Minimum Compressor OFF time: 5 minutes

Minimum Compressor ON time: 4 minutes

Minimum Furnace ON time: 3 minutes

Minimum furnace cycle time (elapsed time between any furnace activation and the next furnace activation): 6 min- utes.

Minimum elapsed time between any compressor activa- tion and the next compressor activation: 6 minutes.

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.

Equipment Protection Override

Both the minimum compressor OFF timer and the mini- mum equipment cycle timer can be over−ridden by press- ing and holding either the HEAT or COOL button down for 4 seconds.

Over−Temperature Protection

Thermal-mechanical switch opens W1, Y1, Y2, and E at 93°F+/−6°F.

Filter Reminder

Settings of Off, 1, 3, 6 or 12 (months of fan run time) are available. When programmed time has elapsed, a FILTER indicator is displayed.

Maintenance Reminder

Settings of Off, 6 or 12 (months of chronological time) are available. When programmed time has elapsed, a mainte- nance indicator

Service Reminder

The SERVICE indicator is displayed only under the follow- ing conditions:

Sif the thermostat Y1 terminal has been activated with 24VAC for at least 5 minutes, AND the L terminal is shorted to the R terminal;

OR

Sif the thermostat Y1 terminal has been activated with 24VAC for at least 5 minutes, AND the L terminal is shorted to the C terminal.

Power Loss/Recovery

Thermostat memory is retained for a minimum of 24 hours during a power loss (includes retention of clock setting, program information, HOLD status, programmed temper- ature setpoint, heat/cool and fan mode settings, filter re- minder status, maintenance reminder status, and equip- ment protection timers). After 24 hours of power loss, programmed settings will be lost and replaced with default settings.

IMPORTANT

Power must be applied for at least six consecutive hours prior to a power loss in order for memory to be retained for the specified time.

LCD Backlight

Activated for 30 seconds when any button is pressed.

NOTE − During an electrical storm or similar disturbance, the backlight may activate for a few seconds. This is nor- mal and will no longer occur after the electrical disturbance has passed.

Thermostat Operating Conditions

35°F to 105°F, 5% to 90% RH

Thermostat Storage Conditions

−40°F to 185°F, 5% to 95% RH

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