Troubleshooting: Heating Sequence of Operation

NO

HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE

 

 

ABNORMAL HEATING MODE

 

 

 

 

 

 

 

 

 

 

 

 

POWER ON

 

 

 

 

 

 

 

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INDOOR BLOWER DELAY OFF.

CONTROL SELF−CHECK OKAY?

 

 

LED SLOW FLASH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(RESET CONTROL BY TURNING MAIN POWER OFF.)

 

 

YES

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IS POLARITY CORRECT?

 

 

LED FLASHES CODE 1 − POLARITY REVERSED.

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

IS THERE A PROPER GROUND?

 

 

LED FLASHES CODE 2 − IMPROPER GROUND.

 

 

YES

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LED FLASHES CODE 13 − LOW LINE VOLTAGE.

 

 

IS VOLTAGE

 

 

 

 

 

CONTROL WILL NOT RESPOND TO A CALL FOR

 

 

ABOVE 70 VOLTS?

 

 

 

 

HEATING UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

NO

LED FLASHES CODE 8 − ROLLOUT SWITCH OPEN.

 

 

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

ROLLOUT SWITCH CLOSED?

 

 

INDOOR BLOWER ON.

 

 

 

 

 

 

 

 

 

 

 

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

 

 

YES

 

 

 

 

 

 

AND POWER IS RESET OR T’STAT IS INTERRUPTED

 

 

 

 

 

 

 

FOR MINIMUM OF 1 SECOND.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

LED FLASHES CODE 12 − FLAME SENSED

 

 

BURNER OFF?

 

WITHOUT GAS VALVE ENERGIZED.

 

 

 

 

(Flame sensed without gas valve energized)

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

 

YES

 

 

 

 

 

 

INDOOR BLOWER ON HEATING SPEED.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NORMAL OPERATION:

 

 

 

 

 

LED SLOW FLASH

 

 

 

YES

 

THERMOSTAT CALLS FOR HEAT:

LED FLASHES CODE 7 − PRIMARY LMIT

OPEN. COMBUSTION AIR INDUCER

LED SLOW FLASH

OFF.INDOOR BLOWER ON

 

YES

NO

 

PRIMARY LIMIT SWITCH. CLOSED?

 

 

 

 

 

 

 

 

LED FLASHES CODE 11 − PRESSURE

 

 

 

YES

 

 

 

 

 

 

SWITCH CLOSED.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GAS VALVE OFF COMBUSTION AIR

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IS COMBUSTION AIR

 

 

 

INDUCER OFF. INDOOR BLOWER

 

 

 

 

 

 

 

 

 

 

PRESSURE SWITCH OPEN?

 

 

 

 

OFF WITH DELAY.

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

(Sequence holds until pressure switch

 

 

 

 

 

 

 

 

opens or thermostat resets control.)

 

 

 

 

 

 

 

 

 

 

 

 

 

IS COMBUSTION AIR INDUCER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ENERGIZED?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

NO

LED FLASHES CODE 9 − PRESSURE SWITCH FAILED

 

 

YES

 

 

 

 

 

HAS COMBUSTION AIR PRESSURE

TO CLOSE OR OPENED DURING HEAT DEMAND.

 

 

 

SWITCH CLOSED IN 2.5 MINUTES?

 

PRESSURE SWITCH IS IN WATCHGUARD MODE. GAS

 

 

 

 

 

 

 

YES

 

 

 

VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

 

 

 

 

 

INDOOR BLOWER OFF WITH DELAY. IS 5-MINUTE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET PERIOD COMPLETE?

 

 

 

CONTINUED NEXT PAGE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page 39

Page 39
Image 39
Lenox Lennox Merit Series Gas Furnace Upflow/Horizontal air discharge, ML180UHE Heating Sequence of Operation

Lennox Merit Series Gas Furnace Upflow/Horizontal air discharge, ML180UHE specifications

The Lenox ML180UHE is a reliable and efficient gas furnace that falls within the Lennox Merit Series. This model is designed for upflow or horizontal air discharge, making it versatile for various installation requirements. With its robust construction and advanced technology, the ML180UHE is ideal for homeowners seeking a dependable heating solution that combines comfort and efficiency.

One of the main features of the ML180UHE is its impressive 80% Annual Fuel Utilization Efficiency (AFUE) rating. This efficiency means that 80 cents of every dollar spent on fuel is used to heat your home while minimizing waste. This furnace is equipped with a multi-speed blower motor that enhances the overall air circulation in your home, providing consistent temperatures and improved comfort.

The ML180UHE features a durable heat exchanger made of high-quality materials, which ensures longevity and reliable performance. The design of the heat exchanger maximizes heat transfer efficiency, allowing the furnace to quickly warm your home while also maintaining optimal efficiency levels throughout its lifespan.

Lennox has integrated advanced technologies into the ML180UHE to enhance its operation and user experience. The unit is compatible with a variety of thermostats, including Lennox's innovative iComfort S30 Smart Thermostat, allowing for easy temperature control and programming capabilities. This smart technology can learn your preferences, optimize energy usage, and enable remote access through a smartphone app.

In addition to its energy efficiency, the ML180UHE offers quiet operation, making it an excellent choice for residential environments. The well-insulated cabinet helps to reduce noise levels, providing a peaceful indoor atmosphere.

Installation and maintenance are simplified with the ML180UHE due to its compact design and accessible components. The furnace is designed to fit into tight spaces, allowing for flexible installation options. Regular maintenance is uncomplicated, ensuring that homeowners can keep the unit running at peak performance with minimal effort.

Overall, the Lennox ML180UHE gas furnace provides users with a reliable, efficient, and quiet heating solution. With its combination of advanced technology, durable design, and ease of use, it is an excellent choice for anyone looking to enhance the comfort of their home while optimizing energy consumption.