74
PHTM II
Installation, Operating & Service Instructions
110331-01 - 5/20
19
Troubleshooting
(continued)
Table 19-5: Active Fault Code and Corrective Actions (continued)
Code
Name
Possible Causes
Corrective Action
H04
E04
Supply
High
Limit
Heating load at time of error
below minimum firing rate of
boiler
Test individual zones and ensure proper zone sizes.
Defective system pump or no flow
in primary loop.
Check pump operation, replace if necessary.
Defective boiler pump and
boiler loop flow is too low or not
consistent.
Check boiler differential temperature (supply-return) at
maximum fire. Check piping or replace pump if differential
temperature is too high. Verify boiler pump is set to speed
3 (Figure 15-2).
Incorrect wiring causing boiler
operation when no zones are
calling.
Check thermostat and zone panel operation to ensure
proper boiler interaction, each zone demand should
produce expected pump and boiler response, repair
wiring or replace panel as necessary.
H05
E05
Low
Water
Flow
Air in system piping.
Verify system is full of water and all air has been properly
purged from system. Cycle power to initiate pump air
elimination sequence.
Blown T5.0A Fuse (supplies
power to pumps).
Check T5.0A Fuse, replace with a 5 Amp, 250V, Slow
Blow, 5x20mm if necessary.
Piping problem.
Verify boiler is piped properly into heating system. Refer to
Figure 10-2.
Pump problem.
Verify boiler pump is running and set to speed 3 (Figure
15-2).
Flow switch defective.
Check boiler flow switch, check switch wiring.
H06
E06
Flue
High
Limit
Heat exchanger dirty.
•
Inspect heat exchanger. Refer to Section 18 Service
and Maintenance for guidance to clean flue side of heat
exchanger.
•
Verify vent/air intake pipes are properly installed and
unobstructed.
Boiler over-fired
Consult manufacturer.
H07
Return
Temp
Higher
Supply
Flow through boiler reversed.
Verify correct piping and pump orientation. Refer to Figure
10-2 in this manual.
Supply or return sensor defective
or not installed properly.
Check supply and return sensors, correct installation or
replace if required.
No boiler water flow.
Verify system is purged of air and that appropriate valves
are open. Also verify pump is running and set to speed 3
(Figure 15-2).
H08
Return
Sensor
Fault
Shorted or miswired return
temperature sensor.
•
Check return sensor wiring, correct wiring if necessary.
•
Check return sensor. Refer to Table 19-7. Replace if
necessary.
