Allied Furnace: Measuring manifold gas pressure
Measuring manifold gas pressure on a Allied furnace: Manifold pressure is measured at the gas valve outlet with a manometer after the furnace reaches steady state. It tells you whether the valve is delivering the right pressure to the burners. Compare it with the Supply Line and Manifold Pressure table.
Applies to: All sizes
Common causes of measuring manifold gas pressure
- Manifold pressure out of range, causing yellow, lifting or unstable flame
- Wrong orifices for the fuel
- Gas valve regulator needing adjustment or replacement
- Bad supply pressure upstream
How to fix measuring manifold gas pressure: step by step
- Remove the threaded plug from the outlet side of the gas valve and install a field-provided barbed fitting, with the gas off.
- Connect a manometer to the barbed fitting.
- Start the unit and let it run 5 minutes to reach steady state, because pressure shifts as the valve warms up.
- Check that the flame is stable, does not lift from the burner, and burns blue for natural gas.
- After 5 minutes, record the manifold pressure and compare it with the Supply Line and Manifold Pressure table.
- Shut off the unit, remove the manometer and barbed fitting, and replace the threaded plug.
- Leak-check the plug with bubble solution. This is gas work, so use a licensed technician.
If the unit shows an error code, look it up: Allied Furnace codes
Source: Allied 92G1UH installation manual, p. 47. 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.