Arkansas HVACR NewsMagazine January 2023

HVACR NewsMagazine January 2023

Tech News

We have a video of an entire class on reading gas pressure, which you can watch HERE, but we'll just cover the basics in this article. You start that by shutting off the gas cock (also known as the shutoff valve). Then, you'll want to remove the inlet and outlet ports of the gas valve (the Gemini valve requires you to loosen the ports instead), where you will replace the ports with your manometer's barbed brass fittings. Attach the manometer's hoses to the barbed fittings. Once the manometer is connected to the gas valve by the fittings and hoses, you have to zero it out to atmospheric pressure; if you're dealing with sealed combustion, zero it out to the combustion chamber's pressure. Open the shutoff valve, run the appliance in heat mode, and measure the pressure on your manometer, ensuring that the inlet pressure stays above the minimum value on the data tag while all the gas appliances are running. Then, make sure the outlet pressure adheres to the value on the data plate.

cap. Remove the cap, insert the screwdriver, and rotate it clockwise to increase the manifold pressure or counterclockwise to decrease the pressure. You will want to adjust the gas to the manufacturer's target pressure to check for proper input. Start by making sure all other gas appliances are off (even fireplace pilots and other seemingly insignificant natural gas appliances). Then, you'll want to make sure the furnace is at high fire or max output. You'll then use a stopwatch to time how long the smallest dial on the gas meter takes to make one full revolution. Then, you do some math to find the hourly BTU output (explained HERE). After you've clocked the meter, you can make additional adjustments to the gas pressure. After adjusting the gas pressure, you can close the shutoff and replace the barbed fittings with the inlet and outlet ports. Make sure that you replace the fittings with the proper ports before you open the gas shutoff valve again. 14. Clock the gas meter.

Begin testing

Once you have a basic idea of how the system operates (and how it should be operating), you can dig into the test procedures.

13. Measure/adjust the gas pressure.

Once you've measured the gas pressure at the inlet and the manifold, you can make any necessary adjustments to match the manufacturer's specs. You would do that by using a flat-blade screwdriver and rotating the brass adjustment screw, which is beneath a