5-5
• Low vacuum pump oil level if equipped with an oil sealed pump.
• Worn internal vacuum pump seals.
• Defective, contaminated, or out of calibration vacuum gage. All of the
information necessary to service this instrument is to be found in the
Granville Phillips Convectron Manual that was shipped with the furnace.
Note: When troubleshooting items that require removal of the main enclosure
please refer to the pictorial drawing “Final Assembly.” Grasp the lid enclosure
firmly on both sides and pull it straight up and away from the lid. Disconnect the
coolant lines and electrical harness from the lid. Locate the #8-32 socket head
set screw that locks the hinge pin to the lid, item 13, and loosen it. Using a pin
punch or similar tool drive the hinge pin, item12, out and remove the lid.
Remove items 5, 9, 10, 11, and remove the hinge half that is attached to the
chamber; finally remove the enclosure, item 4. When installing the hinge pin,
position the milled flat so that when driven to final position the flat and set screw
are aligned.
Excessive Vacuum Pump Smoke or Excessive Oil Consumption
Typical Causes:
• Assuming that the pump smokes with the vacuum valve closed the leak
could be anywhere between the vacuum pump and exhaust valve. Check
the line and the connections between the pump and the furnace.
Referring to the pictorial drawing “Vacuum Circuit,” check each
component and connection between the bulkhead fitting, item 1, and the
exhaust valve, item 6. If the pump smokes only when the vacuum valve
is open check the fittings and the line between the vacuum valve and the
hex manifold located underneath the chamber. If necessary additional
access to the hex manifold can be obtained by laying the furnace over on
the electrical enclosure and removing the access door, item 2, shown on
the Frame Assembly pictorial.
• Process program calls for an excessively long purge, or a programming
error has opened a gas valve and the vacuum valve at the same time.
Water in Vacuum Pump
Typical Cause
• Leaking exhaust heat exchanger. Referring to the pictorial drawing
“Exhaust Circuit,” the heat exchanger is item 16. If this part has failed it
cannot be repaired and must be replaced.
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