Modine Manufacturing 6-558.6 - Manual (Page 26)

26
TROUBLESHOOTING GUIDE
2. Yellow Tipping. Yellow tipping of a normally blue flame is
caused by insufficient primary air, and indicates incomplete
combustion producing carbon monoxide ethylene, aldehyde,
and fee carbon (soot). A dirty orifice or one that is out of
line, can also reduce primary air and cause yellow tipping.
Check main burner orifices, clean, realign, or replace if
necessary. With propane gas, some yellow tipping is always
present, but is not objectionable.
3. Flashback. Flashback occurs when air-gas mixture ignites
inside the mixer tube to burn near the orifice. Flashback on
ignition or during burner operation usually can be eliminated
by reducing primary air. The burner may also be operating
below its rated capacity. Check input rate and adjust to
correct value by increasing orifice size or manifold gas
pressure.
Figure 17
Wavering Flame or Misalignment
4. Wavering Flames. Drafts across burners may cause flames
to appear unstable. Wavering flames can lead to incomplete
combustion if flames impinge on cool surfaces. Wavering
can be caused by air drafts into the burner compartment or
by misalignment of the burner. Draft-blown flames may
indicate a cracked heat exchanger.
Figure 18
Floating Flame Condition
5. Floating Flames. Floating flames are long — do not have
well-defined cones, roll around in the combustion chamber,
sometimes completely off the main burner ports. Usually an
aldehyde odor is present to indicate incomplete combustion.
If combustion air supply is reduced too far, burner flames
will float. Often the pilot flame goes out. Lack of combustion
air causes burner flames to float. The unit may be overfired
so its flue outlet area may be too small for the increased
firing rate. Check input rate and reduce if necessary. Soot or
dust may be blocking the heat exchanger. Check and clear
any blockage. Adjust primary air to get rid of yellow tipping
that may produce soot to block heat exchanger. Make sure
combustion air piping is not blocked.
Intermittent Pilot Ignition Systems
1. Pilot will not light or stay lit.
GOOD BAD
Possible Cause Possible Remedy
1a. No spark at ignitor. 1a. Check connections. Check for proper
spark gap, cracked or broken
electrode ceramic, blown controller
fuse or brittle, cracked or loose high
tension cable. Check power
exhauster pressure switch. Replace if
defective.
1b. Defective flame 1b. Check mili-amps of sensor. Tighten
sensor or loose loose connections. Replace flame
connections to sensor if necessary.
flame sensor.
1c. Pilot valve electrical 1c. Tighten connections.
connections loose.
1d. Defective pilot valve. 1d. Replace.
1e. Poor ground 1e. Check grounding means.
connections.
1f. No power from 1f. Check transformer voltage on
control transformer. secondary side for 25v.
1g. Spark not located in 1g. Correct or replace pilot.
pilot gas stream.
1h. Dirty or plugged 1h. Clean or replace.
pilot orifice.
1i. Pilot line kinked 1i. Correct or replace pilot line.
or obstructed.
1j. Pilot flame too low. 1j. Check pilot flame and adjust per
manufacturer’s recommendations.
1k. Flame sensor out 1k. Reposition.
of position.
1l. Defective ignition 1l. Replace.
controller.
CAUTION
Do not attempt to reuse an ignition control which has been
Replace defective control.
Heater Parts from ACF Greenhouses