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Measuring the Manifold Pressure
The manifold pressure must be measured by installing a pressure
gauge (Manometer, Magnehelic Meter, etc.) to the outlet end of
the gas valve as follows:
1. Turn off all electrical power to the appliance.
2. Shut OFF the gas supply at the manual shutoff valve located
outside of the appliance.
3. Using a 3/16" Allen wrench, remove the manifold pressure tap
plug located on the outlet side of the gas valve. See Figure 6
(page 5).
4. Install an 1/8" NPT pipe thread fitting, that is compatible with
a Manometer or similar pressure gauge.
5. Connect the Manometer or pressure gauge to the manifold
pressure tap.
6. Set the room thermostat above room temperature to start the
furnace.
7. Allow the furnace to operate for 3 minutes and then check
the manifold pressure. Compare the measured value with the
value shown in Table 2 (page 3). If the manifold pressure is
not set to the appropriate pressure, then it must be adjusted.
Adjusting the Manifold Pressure
NOTE: Adjustments do not need to be made to LOW fire for
model VR8205Q2381. Refer to Table 2 for manifold pressures.
1. Single stage gas valve: Remove the cap screw from the top of
the gas valve regulator. See Figure 2 (page 4) for VR8205S2890
or VR8215S1289 models.
2-stage gas valve: For VR8205Q2381 models, remove the
plastic cap covering the adjustment screws (Figure 4 page 4).
2. Using a screwdriver or Allen wrench (where appropriate), slowly.
turn the adjustment screw till the appropriate manifold pressure
listed in Table 2 is achieved. See Figure 2 for VR8205S2890
or VR8215S1289 models. See Figure 4 for VR8205Q2381
models or Figure 5 for VR9205Q1127 models.
NOTE: Turning the screw clockwise increases the pressure,
turning the screw counter-clockwise decreases the pressure.
To prevent the screw from backing all the way out from the
valve, turn the screw slowly.
3. Replace and tighten the cap screw or the plastic cap over the
adjustment screw.
SINGLE STAGE VALVES
Inlet
Pressure
Tap
ON/OFF
Switch
Model VR8215S1289
2-STAGE VALVE
ON/OFF
Knob
Inlet
Pressure
Tap
Model VR8205Q2381
Figure 5. Inlet & Manifold Pressure Tap Locations
ON/OFF
Inlet
Switch
Pressure
Tap
Manifold
Manifold
pressure
pressure
Tap
Model VR8205S2890
Manifold
pressure
Tap
ON
OFF
Removing the Manometer/Pressure Gauge
After the manifold pressure is properly adjusted, the Manometer
or pressure gauge must be removed from the gas valve.
1. Turn the thermostat to its lowest setting.
2. Turn OFF the main gas supply to the unit at the manual shut-
off valve, which is located outside of the unit.
3. Turn OFF all of the electrical power supplies to the unit.
4. Remove the pressure gauge adapter from the gas valve and
replace it with the 1/8" NPT manifold pressure plug that had
been removed earlier. NOTE: Make sure the plug is tight and
not cross-threaded.
5. Turn ON the electrical power to the unit.
6. Turn ON the main gas supply to the unit at the manual shut-off
valve.
COMPLETING THE CONVERSION
Do not alter or remove the original rating plate from
the furnace.
1. Attach the following labels:
• The conversion warning label should be affixed to the outside
of the unit door.
• The conversion information label should be affixed near the
rating plate on the inside of the control area.
• The gas valve conversion label should be affixed on the gas
valve.
NOTE: Each label should be prominently visible after installation.
2. Reinstall the appliance door.
3. Run the appliance through 3 complete cycles to assure proper
operation.
REPLACING THE PRESSURE SWITCH(ES)
1. Turn off all electrical power to the appliance.
2. Remove the door from the burner compartment.
3. Label and remove the wires from the terminals of the pressure
switch(es).
4. Label and remove tubing from pressure switch(es)
5. Remove the tubing from the pressure switch(es).
6. Remove the screws mounting the pressure switch(es).
7. Install the appropriate pressure switch in the same location
using the supplied screws.
8. Reconnect the tubing to the proper pressure switch(es).
9. Reconnect the wires to the proper pressure switch terminals.
Tap
WARNING:
5
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