Measuring & Adjusting Furnace Gas Pressure X2

Matt Milton’s tools include two Testo Smart Probes, tubing, two hose adapters (which come in a few different sizes), a service wrench, and an Allen wrench (3/16″). He begins his process by shutting off the gas line, making sure the valve is perpendicular to the pipe. While the gas is off, he removes his supply and manifold plugs, eventually replacing them with the hose adapters connected to the tubing and Smart Probes. He opens the gas valve and views his readings in the measureQuick app, which he compares to the values on the data plate. Matt needs to adjust his gas pressure with a screwdriver, and he turns the screw counter-clockwise to get the desired pressure.

With the gas pressure adjusted, Matt waits for the furnace to shut down and cool naturally. Once that’s finished, he removes his testing materials and replaces the plugs.

Robert Severson measures gas pressure on a Carrier package unit. He starts off by checking the data plate and noting the rated gas pressure. He follows a similar process to Matt’s where he shuts off the gas, locates the supply and manifold plugs on the gas valve, removes them, and replaces them with his testing materials. He prefers using a ratcheting service wrench over an Allen wrench, but both work fine for removing the plugs. Robert also uses a Fieldpiece manometer instead of Testo Smart Probes, which also works well and can test pressure switches.

Robert turns on his manometer, zeroes it out, and reads the gas pressure with the gas back on. He measures the gas pressure when the furnace is in low fire, and the gas pressure is slightly elevated. Slightly higher pressure is usually okay as long as it isn’t more than 5% above the rated gas pressure. In high fire, however, the furnace kicks up significantly and needs its gas pressure adjusted.