HVACopediaRheem · Furnace troubleshooting
Checking furnace input rate
What is going on
Clocking the gas meter to confirm the Rheem 96V/96MDV isn't over-fired. Input must never go above the rating plate.
Likely causes
- Manifold pressure set too high
- Oversized orifices installed
- Unadjusted for altitude or a different heating value than expected
Check in this order
- Make sure all other gas appliances are off, except pilot burners, so the meter reads only the furnace.
- Start the furnace and time the meter for one cubic foot of gas.
- Compare the calculated input with the rating plate and the input rate table, because the numbers should agree.
- If input is high, adjust manifold pressure or orifice size.
- Never set input above the rating plate.
- This is gas work for a licensed technician. Recheck input after any adjustment.
Applies to: 96V and 96MDV gas furnaces
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Source: 96V installation instructions, p. 103. 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.