Navien NCB300-28K Service Manual page 99

Checking all Piping for Leaks
Eliminate all system or boiler leaks. Continual fresh makeup
water will reduce boiler life. Minerals can build up in sections,
reducing heat transfer, overheating heat exchanger, and causing
heat exchanger failure. Leaking water may also cause severe
property damage.
1. Inspect all water and gas piping and verify to be leak free.
2. Look for signs of leaking lines and correct any problems
found.
Checking the Flue System and Air Piping
1. Visually inspect the entire gas flue system for blockage,
deterioration or leakage. Repair any joints that show signs of
leakage. Verify that air inlet pipe is connected and properly
sealed (if installed).
2. Verify that boiler flue discharge and air intake are clean and
free of obstructions.
WARNING
Failure to inspect for the above conditions and have them
repaired can result in severe personal injury.
Checking the Water System
1. Verify all system components are correctly installed and
operational.
2. Check the cold fill pressure for the system. Verify it is correct
(must be a minimum of 0.8 bar).
3. Watch the system pressure as the boiler heats up (during
testing) to ensure pressure does not rise too high.
If the system contains glycol, test for proper
Note
●
concentration as recommended by manufacturer.
Excessive pressure rise indicates expansion tank
●
sizing or performance problem.
4. Inspect automatic air vents and air separators. Remove air
vent caps and briefly press push valve to flush flue.
5. Replace caps. Make sure flues do not leak. Replace any
leaking flues.
98 Inspection and Maintenance Schedule
Inspecting the Ignition and Flame Detector Electrodes
1. Remove the ignition and flame detector electrodes from the
boiler heat exchanger.
2. Remove any deposits accumulated on the ignition/flame
detector electrode. If the electrodes cannot be cleaned
satisfactorily, replace with new ones.
3. Replace ignition/flame detector electrode, making sure
gasket is in good condition and correctly positioned.
Checking the Ignition Ground Wiring
1. Check that the ground wire is in good condition and
securely attached to the boiler casing.
2. Check ground continuity of wiring using continuity meter.
3. Replace ground wires if ground continuity is not satisfactory.
Checking all Boiler Wiring
Inspect all boiler wiring, making sure wires are in good condition
and securely attached.
Checking the Control Settings
Check settings of external limit controls (if any) and adjust if
necessary.
Performing Start-up and Checks
1. Start boiler and make sure that the boiler is operating
properly.
2. Verify cold fill pressure is correct and that operating pressure
does not go too high.
Check the Burner Flame
1. Inspect flame through observation window.
2. If the flame is unsatisfactory at either high fire or low fire,
check for obstructions in the flue.