MC2: 10/03/12 Page
70
of
90
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
•
Ph: 800-526-0288
GF-115-H
OMM-0083_0B
Modulex MLX Series Gas Fired Boiler System
Operation and Maintenance Manual
Chap 10:
Troubleshooting
FAULT
INDICATION
PROBABLE
CAUSES
CORRECTIVE ACTION
(Continued)
Low temperature
condition may
cause risk of
freezing
2. Defective return
sensor not read-
ing cold temps.
3. Return temp is not
reaching 50°F
(10°C)
4. System has no
external
temperature
sensor switch to
turn on boiler
5. System pipes are
not sufficiently
insulated from cold
6. Water not properly
treated with anti-
freeze.
3. Incorporate a hydronic separator (mixing bottle) to
isolate the boiler from the piping system.
4. Install external temperature sensor to piping system
5. Insulate piping system.
6. Treat water with anti-freeze (install backflow preventer).
E20:
Residual flame
is present after
burner is
switched off
1. Shorted flame rod
2. SSOV not fully closed.
1. Annual Maintenance: Clean the flame rod
2. Check open/close indicator window of Safety
Shut-Off Valve (SSOV) and ensure that the SSOV
is fully closed. If not fully closed, replace the valve
and or actuator. Close gas shut-off valve
downstream of SSOV. Install a manometer or
gauge in a gas test port between the SSOV and
the gas shut off valve. If a gas pressure reading is
observed replace the SSOV valve and or actuator.
E22:
Airflow fault
during ignition
(AFDI)
1.
Inlet filter clogged
2.
Burner clogged
3.
Combustion chamber
clogged
4.
Check valve in gas
manifold not opening
5.
Blower stopped running
due to thermal or
current overload
6.
Blocked Blower inlet or
inlet ductwork
7.
Blocked Blower proof
switch
8.
Blocked blocked-air
inlet switch
9.
Defective Blower proof
1.
Replace filters with new ones
2.
Clean burners (see Sub-section 8.1)
3.
Clear the chamber by brushing and flushing (see
Sub-section 8.1)
4.
Remove check valve from the manifold and
check operation, clean if necessary.
5.
Check combustion blower for signs of excessive
heat or high current drain that may trip thermal or
current overload devices.
6.
Inspect the inlet to the combustion blower
including any ductwork leading up to the
combustion blower for signs of blockage.
7.
Remove the Blower proof switch and inspect for
signs of blockage, clean or replace as necessary.
8.
Remove the blocked-air inlet switch and inspect
for signs of blockage, clean or replace as
necessary.
Table 10-1: Boiler Troubleshooting – PCB Terminal (Continued)
