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Gas Furnace Systems

  1. DuralokPlusR Primary Heat Exchanger -- The heart of the Dimension furnace operates by burning the fuel inside the heat exchanger that warms the air traveling across the outside of the heat exchanger. Made of high-quality patented ArmorTufT aluminized steel, its patented crimped seam is a Lennox exclusive feature designed to provide longer life and safer operations.
  2. Secondary Heat Exchanger -- Allows the furnace to reach higher efficiency levels by capturing every last bit of available heat and is made of rugged 29-4C stainless steel for corrosion resistance.
  3. In-Shot Burners -- One-piece burner, designed and built by Lennox for quiet and reliable operation.
  4. Insulated Blower Compartment And Cabinet -- Reduces noise for quiet operation.
  5. SureLight Control Board -- Patented adaptive technology adjusts to ever changing conditions for reliable operation.
  6. Two-Stage Control Board -- Control center for two-stage operation.
  7. Two-Stage Gas Valve -- Adjusts amount of gas to accommodate two stages of operation.
  8. Two-Speed Combustion Air Blower -- Adjusts amount of air delivered to accommodate two stages of operation.

Note: Central City Air installs furnaces in the horizontal position whenever possible.

Gas Furnace Operation

Power Supply

Indoor Furnace - Each unit will normally have a disconnect switch mounted on or near it.

The disconnect switch for the equipment may be fused in the disconnect switch box and/or fuses (or circuit breakers) may be located in the main power box of the structure.

Start Up (Make sure to mind gas safety)

Furnaces with Pilot Light

To place furnace in Operation - Lighting the pilot

  1. With the thermostat set below room temperature and power off to furnace, turn the manual knob of the gas valve clockwise to the stop setting. Depress and turn to off position. WAIT 5 MINUTES.
  2. Turn manual knob of the gas valve counterclockwise to on position. Then turn manual knob clockwise to the pilot position.
  3. With the manual knob in the pilot position, press down until it bottoms and hold in place.
  4. Light pilot attached to main burner. (Use a long fireplace match or a regular match taped to a wire. See illustration provided.)
  5. Continue to hold knob down for 60 seconds. Release knob (pilot should stay lit) then turn knob to on position. If the pilot goes out, repeat above instructions.
  6. Turn power on. Set thermostat to desired room temperature.

To shut off furnace:

  1. Set thermostat to lowest setting.
  2. Turn off power supply to the furnace.
  3. Turn manual knob of the gas valve clockwise to the stop. Depress knob and turn to the off position.

Furnaces with Electric Ignition

These units are equipped with an intermittent pilot ignition system. Do not attempt to manually light pilot. Each time the thermostat calls for heat an electric spark ignites the pilot. The pilot does not burn when there is no call for heat.

To place furnace in operation:

  1. *With the thermostat set below room temperature and power to the furnace off, turn the manual knob of the gas valve clockwise to the off position. WAIT 5 MINUTES.
  2. Turn manual knob of the gas valve counterclockwise to on position. Turn power on to the furnace and set thermostat above room temperature.
  3. If furnace does not start, repeat above instructions. Depress reset button on ignition control (Robertshaw only).
  4. Set thermostat to desired room temperature.

To shut off furnace:

  1. Set thermostat to lowest setting.
  2. Turn off power supply to the furnace.
  3. *Turn manual knob of the gas valve clockwise to the on position.

*On some gas valves, the manual knob must be depressed to turn off.

Gas Furnace Maintenance

Your qualified Central City Air technician should perform most maintenance tasks to your furnace; however, there are a few procedures that the equipment owner can perform. Some basic inspection checks follow that you can and should perform at least annually, at the beginning of each heating season.

Caution: Turn off power to unit before performing any maintenance.

A. Flue and Chimney

Check flue pipe and chimney connections occasionally for tightness. Make sure there is no blockage, such as could be caused by bird or insect nests, leaves, etc. Do not operate furnace if any holes or loose connections are found in the flue pipe as combustion products could escape into your home. Your Central City Air technician can best evaluate and repair any suspected flue pipe damage.

B. Combustion Area

The combustion area should be visually inspected before each heating season. Accumulation of dirt and soot can result in loss of efficiency and improper performance. Accumulations on the main burners can cause poor firing and inadequate flame. Your Central City Air serviceman should be consulted if any of these problems occur. Do not operate your furnace until service has been performed.

Before Calling for Service

If your furnace does not appear to be performing properly, or does not operate at all, it may save the cost of an unscheduled service call if you check a few conditions yourself, before calling for service.

A. Insufficient Air Flow

If you sense a change in airflow, a dirty air filter is the most likely cause. Inspect the air filter, following the procedures in the General Maintenance section.

Another cause of insufficient airflow is a blocked return-air or supply-air grille. Be sure that the return air grills are not covered by furniture or other items.

B. Furnace Fails to Operate

If your furnace fails to operate, follow these step-by-step instructions, and proceed only to the next step if the furnace fails to start.

  • Check that your room thermostat temperature selector is set above house temperature, and the SYSTEM switch is in the HEAT position (heating/cooling thermostat).
  • On electric ignition units, turn room thermostat "off", then back "on" to reset the ignition control.
  • Is the unit power supply switch "on"? The power supply switch is often mounted on or near the unit.
  • Check the house fuse box for a blown fuse or tripped circuit breaker.
  • Check the blower access panel. It must be firmly in place for the unit to operate.
  • Check the air filter. An extremely dirty air filter can cause furnace safety controls to shut down the system.
  • Check to be sure that the manual shut-off valve in the gas supply pipe, leading to your furnace is in the open position. The valve is open if the lever points in the same direction the pipe runs, and it is closed if the lever is at a right angle to the pipe. If the valve is closed, (Check and make sure gas is not turned off for safety reasons before proceeding.) open it; then follow the startup procedures.

Note: Before proceeding to the next step, turn OFF the electrical power supply to your furnace, and remove burner access panel.

  • Is the internal manual shutoff valve open? (Electronic ignition units only.)
  • Check the manual knob on the gas valve to be sure that it is in the ON position.
  • If you have a standing pilot furnace, visually check the pilot flame. If the pilot is not lit, follow the startup procedures.

If the furnace still does not operate, please call Central City Air for experienced assistance.


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