Goodman Furnace: Clocking a gas meter
Clocking a gas meter on a Goodman furnace: Clocking the meter tells you how much gas the furnace really burns, which feeds the BTU input calculation in the heating performance test. Run the furnace at 100% firing rate until it reaches steady state, usually about 15 minutes, then time one revolution of the test dial. Meters that are shared with other appliances give junk numbers, so isolate the furnace first.
Applies to: All 34.5in chassis gas furnaces
Common causes of clocking a gas meter
- Heating performance test needs an actual input figure
- Suspected over-fire or under-fire after a gas conversion or altitude change
- Complaints of weak heat or flame problems where manifold pressure alone is not conclusive
How to fix clocking a gas meter: step by step
- Turn off all other gas appliances in the home, including water heater pilots that may cycle on, and check the meter dial is not moving
- Turn on the furnace and confirm it runs at 100% firing rate, not low stage
- Wait about 15 minutes of steady operation so the burners and heat exchanger settle
- Time one full revolution of the smallest dial with a stopwatch. The one cubic foot dial is used in the example
- Find the seconds for one revolution in the gas rate table and read CFH from the matching dial column
- Example: 40 seconds on the 1 cu ft dial gives 90 CFH
- Multiply CFH by the gas heating value to get BTU/h and compare with the rating plate
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 service and troubleshooting manual, p. 40. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.