25
Servicing should only be performed by a Quali
fi
ed Service Technician
Check
fl
ame signal
1. At high
fi
re the
fl
ame signal shown on the display should be at least 10 microamps.
2. A
lower
fl
ame signal may indicate a fouled or damaged
fl
ame sense electrode. If cleaning the
fl
ame sense
electrode does not improve, ground wiring is in good condition, and ground continuity is satisfactory,
replace the
fl
ame sense electrode.
3. See Troubleshooting section in this Service Handbook for other procedures to deal with low
fl
ame signal.
Cleaning heat exchanger
For recommended materials; including brush, appropriate extension(s), refractory cover, and detailed
instructions, refer to Table 6 - Heat Exchanger Cleaning Kits.
1. Shut down water heater:
• Follow the “To Turn Off Gas to Appliance” instructions for the water heater in Start-up section of the
XP Water Heater Instruction Manual.
• Do not drain the water heater unless it will be exposed to freezing temperatures. If using freeze
prevention
fl
uid in system, do not drain.
2. Allow time for the water heater to cool to room temperature if it has been
fi
ring.
3. Remove the nuts securing the heat exchanger access cover to the heat exchanger and set aside.
4. Remove the heat exchanger access cover, burner, and gas/air arm assembly.
The water heater contains ceramic
fi
ber materials. Use care when handling these materials per the instructions
on Page 3 of this Service Handbook. Failure to comply could result in severe personal injury.
5. Remove the condensate hose from the heat exchanger end. Connect a
fi
eld supplied 3/4" diameter hose
to a drain pan. Using
fi
eld supplied means, cover the refractory in the back of the combustion chamber
of the heat exchanger.
6. Use a vacuum cleaner to remove any accumulation on the water heater heating surfaces. Do not use
any solvent.
7. Brush the heat exchanger while dry using a nylon bristle brush. Caution: DO NOT use a metal brush. Re-
vacuum the heat exchanger after cleaning.
8. Finish cleaning using a clean cloth dampened with warm water. Rinse out debris with a low pressure
water supply.
9. Allow the heat exchanger to thoroughly dry.
10. Remove the
fi
eld supplied rear refractory cover from the back of the combustion chamber of the heat
exchanger and reassemble.
11. Close isolation valves on piping to isolate water heater from system. Attach a hose to the water heater
drain and
fl
ush water heater thoroughly with clean water by using purging valves to allow water to
fl
ow
through the water make-up line to the water heater.
12. Perform start-up and check-out procedures in the Check Flame and Combustion of Start-up section in the
XP Water Heater Instruction Manual.
13. Replace the access cover and restore water heater to operation
