79
110327-07 - 2/23
ALTA
Combi Installation, Operating & Service Instructions
19
Troubleshooting
(continued)
Table 19-5: Active Fault Code and Corrective Actions (continued)
Detailed Fault Code found on "
b
" and "
c
" menus in brackets, e.g. [
1
.
0
].
Code
Name
Possible Cause
Corrective Action
H04
E04
Supply
High Limit
Air in system.
Verify the system is full of water and the air has been
properly purged. Cycle boiler power to initiate pump air
elimination function. Air is removed from boiler loop when
there are no "air noises" in the heat exchanger.
System pump, thermostat, zone
valve or panel problem.
Check pump operation, replace if necessary. Ensure each
zone demand produces expected pump, zone valve, and
boiler response.
Piping problem.
Verify the boiler is piped properly to heating system. See
recommended piping diagram. Repair piping to meet
requirements as required.
Boiler pump problem.
Check boiler differential temperature (supply-return) at
maximum fire. Check piping and boiler pump if differential
temperature is too high. Verify boiler pump is running and
set to speed 3 (Figure 15-2). Check T5.0 A fuse (Figures
20-1 and 20-2), replace if necessary. Replace pump if
necessary.
Is three way valve driven
completely to requested run
mode? (CH or DHW
Valve is unpowered in DHW. Powered in CH. If stuck in
between disassemble valve and clear any debris. Confirm
operator is driving fully to powered position.
Heating load at time of error
below minimum firing rate of
boiler.
Test individual zones and ensure proper zone sizes.
Header sensor not sensing
temperature.
(Boiler is multiple boiler slave
or modulating based on header
sensor)
Check header sensor installation;
• Strap on - use heat conductive grease and insulate.
• Thermowell - ensure inserted fully.
Check header sensor temperature is close to and tracks
with supply sensor. If difference greater than 5ºF (3ºC),
move header sensor to location to better sense boiler
water temperature.
H05
E05
Low
Water
Flow
Air in system.
Verify the system is full of water and the air has been
properly purged.
Cycle boiler power to initiate pump air elimination function.
Air is removed from boiler loop when there are no "air
noises" in the heat exchanger.
Piping problem.
Verify the boiler is piped properly to heating system. See
recommended piping diagram. Repair piping to meet
requirements as required.
Boiler pump problem.
Verify boiler pump is running and set to speed 3 (Figure
15-2). Check T5.0 A fuse (Figures 20-1 and 20-2), replace
if necessary. Replace pump if necessary.
Boiler flow switch defective.
Check boiler flow switch, switch wiring and controller input.
Flow restriction or clogged
strainer.
Verify there are no restrictions and clean strainer if present.
Pump rotor seized (initial start up) Remove silver cap on pump head and spin rotor counter-
clockwise to free pump rotor.
