Adjust Modulating Gas Valve
How do I adjust the pressure on the modulating stage gas valves?
Adjusting the modulating Stage Gas Valve
Tools needed to adjust a Modulating valve include:
1. A small flat Blade Screwdriver
2. A 3/16” Allen Wrench
3. A 3/16” Barbed fitting
4. A manometer capable of accurately reading Inches of Water Column
5. A length of 1/4” I.D. Hose (Most manometers have ¼” hose connections)
Before adjusting the manifold pressure, first make sure your Gas Inlet Pressure is within the tolerances stated in the Installation Instructions. Static pressure, (Without the furnace running), is not accurate. Inlet pressure should be checked with the furnace operating at 100% firing rate. If there are other gas appliances, (2nd furnace, pool heater, water heater, etc.), it is a good idea to check the inlet pressure while all are burning gas. This will ensure you have enough volume of gas to supply the furnace when all are burning.
The furnace will need to be placed into test mode and forced to stay at 100% firing rate. This can be accomplished via the service menu on the EcoNet T-Stat. If desired, you can remove T-Stat connections, Jumper R to W1, set Dip Switch 10 to OFF, and Dip Switch 11 to ON. Either of these will force the furnace to run at 100% firing rate until you remove the demand.
You will need to turn the incoming gas off and remove the plug for the inlet pressure tap using a 3/16” Allan wrench. Insert a barbed fitting connected to a manometer. Operate the furnace at 100% rate and monitor the inlet pressure. After inlet Pressure is deemed acceptable, turn off the gas, remove the hose, replace the barbed fitting with the plug and tighten.
To read your manifold pressure you will need to remove the plug for the manifold pressure tap using a 3/16” Allan wrench. Insert a barbed fitting connected to a manometer. Operate the furnace, (in test mode), at 100% firing rate and observe the manifold pressure.
Remove the plastic cap so that you can access the plastic manifold screw. Using a small screwdriver, adjust clockwise to increase manifold pressure, or counter clockwise to decrease manifold pressure. When 100% Rate manifold is deemed acceptable, set the furnace to 40% rate and check the manifold pressure there.
Put the furnace into test mode at 40% Rate using the service menu on the EcoNet T-Stat. If desired, you can remove T-Stat connections, Jumper R to W1, set Dip Switch 10 to ON, and Dip Switch 11 to OFF. After manifold pressure is deemed acceptable, turn off the gas, remove the hose, replace the barbed fitting with the plug and tighten. Replace the plastic adjustment screw cap.
Make sure the Manifold pressure is within tolerances.
Natural Gas: 3.5” (±.3) w.c. for 100% Rate, .56” (±.1) w.c. for 40% fire.
L.P.: 10.0” (±.5) w.c. for 100% Rate, 1.6” (±.2) w.c. for 40% Rate.
NOTE: Manifold adjustments should be made no faster than one “click” every 3 seconds. If you go to fast, the valve will stop responding to adjustments. If this happens you may have to cycle power to the furnace.
