T
HERMO
90 / 90 S
5TROUBLESHOOTING
5-5
5.5.2 Rear Wall with Metal Evaporator
• The pilot flame exit bore (Fig. 5-4) must not be
clogged, otherwise there will be no start.
Remedy
Replace burner assembly
• Cracks, delaminations, as well as black or other
discolorations of the evaporator do not cause a
burner failure and are meaningless.
• Coke deposits on the evaporator surface (except for
the pilot flame exit bore) are normal and must not be
removed. When the load changes from full load to
part load and vice versa the burner normally is
self-cleaning.
5.5.3 Combustion Chamber
• The combustion chamber (Fig. 5-5) should not be
damaged (e.g. dented).
A combustion chamber with dents may cause
insufficient combustion or coking of the heater.
Remedy
Replace burner assembly
• The air bores (Fig. 5-5) in the combustion chamber
must not be coked. Coked air bores may cause a
no-start or insufficient combustion.
Remedy
Removal of coke deposits by careful scraping.
5.5.4 Burner Assembly
• The cables of the glow pin and flame sensor must be
routed as shown in Fig. 5-3.
• The screwed connection of the housing and
combustion chamber must be secure (Fig 5-5).
• Housing and combustion chamber (Fig. 5-5) must be
connected securely without any play (check by slight
movement of fuel pipe).
• The O-ring must have a tight fit around the fuel
chamber upper edge (Fig. 5-3) and must seal
completely.
• The gap between housing edge and combustion
chamber upper edge (Fig. 5-5) must be equal
around the entire circumference.
• The insulation (4, Fig. 5-3) must be present.
Fig. 5-4 Visual Inspection, Pilot Flame Exit Bore Fig. 5-5 Visual Inspection, Burner Assembly
