4. Remove the two screws of the bracket supporting the gas valve on the inlet side (see Figure 72
).
5. Remove the Phillips head screw (see j on Figure 72 ) from the power connector plug, and pull
off the electrical connector from the gas valve.
6. Pull the black tubing (see on Figure 71 ) from the push-to-connect fitting on the gas valve
outlet side.
7. Disconnect the three- (3) wire Molex plug from the gas pressure switches.
8. Unscrew the two (2) bolts of the flange to separate the gas valve inlet from the gas line. Keep
gasket and bolts for re-assembly. (See l on Figure 71 .)
9. Remove the four 5/16" hex head bolts that attach the gas valve assembly to the mixing device.
(See j on Figure 71 .) These bolts should be first loosened slightly in a cross sequence to
prevent deformation of the mating parts.
10. Carefully move aside the gas valve assembly, and retain the O-ring for re-installing.
11. Remove the four (4) ¼" hex bolts that connect the mixing device to the air filter box. The gasket
should remain attached to the air filter box.
12. Remove the four (4) 10mm hex bolts that attach the fan to the heat exchanger lid. An open-
ended wrench or socket is required.
13. With the mixing device still attached, remove the fan by pulling straight up ensuring that no
wires are caught and that the gas line remains in place. Place the removed components in a
clean, dry area
14. Unplug the ignitor from the lid and place in a safe place.
15. Loosen the eight (8) 5mm Allen lid fasteners securing the lid to the heat exchanger. Mark the
orientation of the lid onto the heat exchanger with a marker.
16. Carefully lift up on the lid and remove. Be careful not to damage the refractory insulation. Place
the lid and burner assembly in a clean dry area.
17. Carefully loosen the burner cap screws and remove. Keep the cap screws for re-installation.
18. Separate the burner from lid. Replace the burner gasket upon re-installation.
19.
Re-install the components in reverse order of the steps above.
Warning
After removing a burner, it is imperative that you perform a gap analysis on the
ignitor.
20. Turn on the electric power and gas supply to the boiler.
21. Reset the low pressure switch. For instructions, see Resetting the gas high / low pressure
switches on page 77.
7.3.3 Replacing the burner in the EX 700 and EX 850 models
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