CHECKOUT:

1. Check Basic Operation

• Start the furnace with a call for heat from the thermostat.
• Ensure that the inducer motor starts and runs properly.
• Ensure that ignition takes place properly.
• Observe furnace operation for at least 5 minutes.
  • Monitor 24VAC between "W" and "C" on the LTB.
  • Make sure burners do not cycle off during the heat cycle.
    • "W" drops-out when burners cycle-off = Thermostat Cycling
    • 24VAC present on "W" when burners cycle-off = Safety Trip --> Check control board diagnostics

2. Check Temperature Rise

• Check the return air temperature entering the furnace.
  • Unusually low return air temperature = Cold Air Infiltration --> Check Ductwork
• Check the supply air temperature near the furnace.
• Compare the actual temperature rise to the furnace rated temperature rise.
  • Actual Temp Rise > Rated --> Step 3. Check Air Filter
  • Actual Temp Rise < Rate --> Step 4. Check Gas Pressure
  • Actual Temp Rise = Normal --> Step 5. Check Indoor Airflow

3. Check Air Filter & Coil

• Remove the air filter and recheck temperature rise.
  • Temperature rise drops into rated range = Clogged Air Filter
  • Temperature rise still high --> Step 4. Check Gas Pressure

4. Check Gas Pressure

• De-energize the call for heat and allow the furnace to cool.
• Turn off power to the furnace and close the gas safety shut-off.
• Hook-up a gas pressure gauge to the manifold (leaving) test port on the gas valve.
• Open the gas safety shut-off valve and re-apply furnace power.
• Activate a call for heat and monitor the manifold gas pressure when the gas valve opens.
  • Natural Gas = 2.5" w.c. minimum to 3.5" w.c. maximum
  • LP Gas = 9" w.c. minimum to 11" w.c. maximum
    • Gas Pressure Low --> Adjust as necessary
      • Gas pressure won't come-up --> Check inlet gas pressure

5. Check Indoor Airflow

• Check airflow at the supply registers in the space.
  • Unusually low airflow = Ductwork problems

6. Check Space Sq. Ft.

• Calculate the approximate square footage of the space being conditioned by the unit.
  • Sq. Ft. = Length X Depth
    • For example: A single story home that is approximately 50' long and 25' deep.
      • Length (50) X Depth (25) = 1250 sq. ft.
• Use the following table to determine if the equipment is properly sized.

• * Worst Case = Very Loose Construction with Little to No Insulation
• ** Best Case = Very Tight Construction, Heavily Insulated or Foamed