North American Differential Pressure Air/Gas Ratio Regulator
Instructions & Parts List 7288-1
Ref: Instructions 7218-2, Bulletin 7288
INSTALLATION 1. Install 7288 Regulator horizontally with diaphragm case below gas line. 2. Install regulator in clean pipe, free from scale, dirt, or chips. Use unions or flanges to permit removal for servicing. 3. Protect from excessive heat. Ambient temperature should not exceed 180°F. Provide shields or cooling air if necessary.
3. Slowly open main air valve until high fire is achieved. It maybe necessary, during this transition, to readjust limiting orifice gas valve to maintain a stable flame. 4. Adjust limiting orifice gas valve for required high fire air/gas ratio. 5. Slowly close the main air valve to low fire. Remove spring adjusting cover from 7288 Regulator. Turn spring adjusting plug (clockwise for more gas, counterclockwise for less gas) for required low fire air/ gas ratio.
4. Regulator must supply only those burners supplied by the corresponding air valve.
6. Repeat steps 3 to 5. Readjust if necessary.
5. Impulse lines must be adequate size. Use 3⁄8 " tubing for lengths up to 10', ½ " tubing for longer runs. Locate the air and gas impulse taps on the top or sides of the piping, but not on the bottom.
Note that the pressure drops across the air metering orifice and the 1807 Valve will be proportional, but not necessarily equal.
7. Replace adjusting screw covers on limiting orifice valve and regulator.
6. To minimize effects of turbulence, all air and gas pressure connections must be located as illustrated.
TROUBLE-SHOOTING
5D 3D
5D
If the regulator action is slow or there is no response, some or all of the following action should be taken:
GAS
1807
1. Manually shut off gas supply.
3 psi max. inlet
2. Disconnect all piping and tubing. Check to make sure that all thread protection plugs have been removed: These are a common problem. 3. Check for undersized or plugged impulse lines. Replace or clean as is necessary. 4. Check regulator valve seat and disc for foreign matter: To do this, remove body plug and all (4) impulse lines; then connect a 16 osi (approx.) air supply to upstream air port. Wipe seat and disc surfaces with a clean cloth. Replace body plug and impulse lines. 5. Check regulator diaphragms by disconnecting all (4) impulse lines and following this procedure:
max. P pressure drop 20"wc
AIR
Air Control Valve
10D
per orifice mfgr's specs.
Connect a rubber tube to the impulse connections, one at a time.
Piping for 7288 Regulator. Number of pipe diameters shown are recommended minimum distances for connection tap locations upstream and downstream of orifice plate, regulator, and valves.
Blow into tube. That section of case should pressurize.
ADJUSTMENT
If pressure does not build up, a diaphragm is ruptured and must be replaced.*
1. Open 1807 Limiting Orifice Valve (6) turns from full closed position.
* Field repairs are not recommended. Return the unit to North American for replacement.
2. Start burner(s) at minimum firing rate.
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