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ICP · Furnace troubleshooting

Check inlet gas pressure

What is going on

Low inlet gas pressure prevents setting the right input and causes ignition/pressure switch faults.

Check in this order

  1. Warning: Never purge gas into the combustion chamber; leak test with soap solution only.
  2. Gas off; remove 1/8 in. NPT plug at the gas valve inlet tap and connect a manometer.
  3. Power on, gas on, jumper R to W/W1 and W2 for maximum heat.
  4. With burners lit, inlet pressure must be between 4.5 and 13.6 in. w.c. (natural gas).
  5. Remove jumper, gas off, remove manometer, refit plug with a little pipe dope and leak test.
  6. Do not set maximum heat manifold pressure below 3.2 in. w.c. on natural gas - change orifices instead.

Applies to: ICP F9MAE / G9MAE modulating variable-speed condensing gas furnaces (060, 080, 100, 120 kBtu/h)

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Source: ICP (F/G)9MAE Service and Technical Support Manual 440 04 4700 00, Check Inlet Gas Pressure / Adjust Manifold Pressure. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.