Baxi Luna 310 Fi User manual

Marathon
International
BAXI LUNA 310 Fi Troubleshooting Guide
Before getting started, remember………..
All BAXI LUNA boilers are tested during manufacture for correct operation and are
shipped to you factory tested for correct operation.
Most of the faults experienced on start up are field issues associated with items
external to the boiler. These are mostly simple problems, such as:
•Venting installed incorrectly
•Air in the system (system must be fully purged)
•Air in the gas line
•Undersized gas line
•System not flushed (cold flush then hot flush)
•Incorrect connection of external equipment
•Leaks in the Heating system and pipe-work
When commissioning the boiler, only a few items need to be checked:
•Inlet gas pressure (static and working inlet pressure of boiler running at
maximum output)
•Maximum and minimum burner pressures
•Power supply for polarity and ground
When troubleshooting BAXI LUNA boilers avoid changing parts prematurely,
assuming that the boiler component is defective. In our experience, items such as the
control PCB are changed incorrectly, when it is another component supplying false
information to it. Likewise, the pump is changed because it has stopped operating.
This is normally due to contamination from a dirty hydronic system. The pump can be
removed and cleaned; after which the heating system must be flushed and cleaned.
Get all the information before going to the job site……………
Get as much information from your customer before you go to the boiler. Model of
boiler, type of venting, type of system and layout connected to the boiler, how long has
the system been installed and is this an isolated breakdown or are they repeatedly
resetting the boiler.
Don’t be afraid to ask the obvious questions! Do they know how to reset the boiler?
Just unplugging the lead and replacing it or turning the boiler off and on again will
not reset the logic board. They have to turn the switch to the “R” to restart the boiler.
Is there any water in the system? Where is the needle on the pressure gauge? This
may save an unnecessary trip to the job site.
April 2004
1815 Sismet Road phone: [phone]
Mississauga, Ontario fax: [phone]
L4W 1P9 CANADA

BAXI LUNA 310 Fi troubleshooting guide
Page 1
Fault Caus
e
Suggested Solution
s
Boiler does not start No power at the ▪Check 120 Vac at power cord outlet.
no LED's lit. boiler ▪Check if main 3.15 amp boiler fuse has blown.
Boiler does not start #14 LED not lit ▪No signal from external control. Remove wires from thermostat connections
but #12 LED is lit. (call for heat) 1&2 at terminal strip and jumper it. If boiler starts replace switching relay.
Boiler does not start #13 LED not lit ▪Open DHW tap fully, has pin moved out from DHW differential assembly to
but #12 LED is lit. (call for DHW) close micro switch (green wires)? No; DHW flow valve diaphragm damaged
replace. If diaphragm OK clean and lubricate DHW valve rod.Yes; check
continuity across DHW micro switch, replace if faulty.
Boiler does not start Low water pressure ▪Re-pressurize heating system till pressure gauge reads between1-2 Bar
but #12 and #13 or on gauge. Check for and repair leaks in heating system.
#14 LED's are lit.
Primary/DHW sensor ▪Check DHW/ Primary temperature sensors for cold resistance of approx
faulty. 11 K Ω(resistance reduces with increase in temp), replace if faulty.
Pump not operating ▪Check for 120 V at pump, if no power and sensors OK, replace main PCB.
▪120 V at pump, but pump not turning. Release jammed pump by removing
vent cap on front of pump and turning shaft counter-clockwise. If pump will not
turn. Drain boiler, remove pump head release and clean pump cartridge.
Air in system ▪If pump is running but the flow switch has not closed, or is "bouncing" up
and down, purge air from the pump and heating system.
Flow switch faulty ▪If pump is running but flow switch has not closed; has pin moved out from
diverter valve to close micro switch?No; flow switch diaphragm damaged,
replace. If diaphragm Ok clean and lubricate flow switch rod.Yes; check
continuity across primary flow micro switch, replace if faulty.
Pump running, flow Air switch not ▪Check air switch has not stuck in the open position. To check, remove room
switch closed fan operating sealed door on boiler and pull suction tube from fan venturi. Gently suck on
not running the end of the sensing tube, you should hear the air switch operating. Re-
connect the sensing tube and retry lighting boiler, (signal from PCB to fan on
start is via the NC terminals on the air switch). If air switch OK replace PCB.

BAXI LUNA 310 Fi troubleshooting guide
Page 2
Fault Cause Suggested Solutions
Fan running, #8 (50°) Air switch not
fault code flashing. operating?
Moisture in air ▪This may be due to excess vent outside of building. Trim vent back to wall.
switch suction tube. Insulate vent in unconditioned spaces.
Dirt in fan venturi. ▪Remove fan transition bend and inspect for debris.
Scale at venturi port ▪Remove fan transition bend and inspect for scale and deposits. Clear venturi
port with #32 index drill. If this does not cure problem replace fan venturi.
Note: scaling is probably due to vent sloping toward the boiler, ensure that
vent is sloping toward the terminal.
Severe local wind ▪Check position of terminal, avoid terminating where other buildings and plantings
conditions. will affect boiler flue operation.
Incorrect vent length ▪Check for incorrect vent installation or excess vent length.
or configuration. ▪If all of the above are OK replace air switch.
Boiler does not light No spark at burner. ▪Check for 120 V at the spark generator. If voltage at spark generator, replace
#6 (30°) fault code spark generator. No voltage at spark generator, replace main PCB.
flashing.
No gas pressure at ▪Check gas supply to boiler, is gas shut off valve open?
gas valve burner test ▪Check gas valve main solenoids with power turned off. Approx175 Ωcold
port. resistance onboth main coils. If low or open, change gas valve.
▪Check inlet screen for blockage on inlet side of the gas valve.
Boiler lights then goes No ground to boiler. ▪Check for good ground at outlet and at boiler.
out, #6 (30°) fault
code flashing. Flame lifting off burner ▪Exhaust venting has come apart, check installation. If long horizontal run of vent
or 'ghosting'. suggest using support spacers, available as an accessory.
▪Exhaust vent does not extend to the end of the terminal, rectify fault.
▪Air supply to boiler insufficient, check for blockage and correct vent installation.
▪Air in gas line.
Week or no signal ▪Check for minimum1 mA flame currant from flame sensing electrode.No; clean
from flame sensor. or replace electrode.Yes; replace main PCB.
Boiler will not Minimum gas pressure ▪Remove black wire from modulating coil while boiler operating, check low fire
modulate. to high. gas setting. Reset if required.
▪Remove modulating pin and inspect. Check that when end is pulled it springs
back into place. If broken replace (this is usually broken when inlet gas pressure
is low, to much adjustment has been made on pin to try to get boiler to high fire).
▪Check voltage across modulating coil when operating, approx10 Vdc high fire
1.5 Vdc low fire.
▪Cold resistance on modulating coil approx40Ω(with power off), if low or open
replace coil.

BAXI LUNA 310 Fi troubleshooting guide
Page 3
Fault Cause Suggested Solutions
Boiler short cycling. Heating output has not ▪Set the "Max R" on the control PCB to match the heating system requirements,
been set. see chart on page 25 in manual for settings.
Short cycling on a ▪In a smaller system make sure theT-Off Jumper on the PCB is set to the left,
short heating circuit. this will give a 3 min. delay when the burner turns off in the heating mode.
▪If zone valves are present in system, the internal bypass is not designed to
handle system flow, it is only used for boiler pump protection. Install a separate
pressure-activated bypass, a buffer tank or a low loss header.
Whistling noise from High fire when using ▪BAXI recommends that only25% inhibited propylene glycolsolutions which are
boiler. Glycol in system. specially formulated for hydronic systems be used in the LUNA boiler. Ethylene
glycol is toxic and can attack gaskets and seals used in hydronic systems.
Check that the glycol ratio is not more than the recommended amount yearly,
a higher ratio can affect the pump performance causing noise at high fire.
Note: Anti-freeze solutions expand more than water. For example a50% by volume
solution expands4.8% in volume for a temperature increase from32°F to 180°F,
while water expands3% with the same temperature rise. Allowances must be
made for this expansion in the system design. A30% mixture of glycol will result
in a BTU output loss of 15% with a 5% increase in head against the boiler pump.
A 50% mixture of glycol will result in a BTU outputloss of 30% with a 50% increase
in head against the boiler pump.
Fluctuating DHW Boiler cycles on and ▪Check that low fire is not set to high. Reset if required.
temperature at tap. off.
Erratic burner ▪Check burner pressure at gas valve test port with manometer while boiler
pressure. operating. If gas pressure fluctuates erratically suspect either primary sensor is
out of calibration or the DHW sensor is dirty. Replace one or both sensors.
Burner pressure ▪Check burner pressure at gas valve test port with manometer while boiler
fluctuates from high operating. If gas pressure fluctuates from high to low then back to high suspect
to low fire. that the DHW plate exchanger is dirty or scaled up. Remove and clean/ de-scale
with suitable cleaner, or replace heat exchanger.
▪If the boiler is being used with a well, make sure that the supply pressure is good.
If the pump setting is set for 40 Psi-on and 60 Psi-off try it at 50 Psi-on and 70 Psi-off.
Fluctuating ▪If previous checks are OK check the temperature of the hot water at a single
temperature at tap (not single lever tap). If the temperature is stable (within 3-5°f) at this tap
shower. suspect that the shower valve cartridge is dirty or faulty, clean or replace cartridge.
Note: taps that have internal plastic parts tend to cause fluctuations in water flow.
Plastic has a faster expansion rate than brass as the water heats it up it tends to
expand and slow the water flow. The tap then needs to be opened further to let the
water flow faster, which in turn increases the water flow through the boiler.
Hot water not hot Incorrect gas ▪Check that the boiler has the correct maximum gas pressure.
enough. pressure.
Faulty/Dirty NTC ▪Check that the DHW sensor is not dirty or scaled up. Check that sensor is not
sensor. out of calibration (10 K Ω@ 25°C). Replace if faulty.
▪If PCB has been changed has the boiler thermostat knob been fitted correctly?

BAXI LUNA 310 Fi troubleshooting guide
Page 4
Fault Cause Suggested Solutions
Cold water mixing ▪Check that the flow from the hot tap is not more than 3.3 GPM (18 seconds
with hot to taps. to fill a 1 gallon bucket). If bucket fills faster the tap is mixing with cold water.
Water temperature ▪During the winter months the cold water temperature entering the boiler can be
in the winter. 10°f lower than in the summer, this will reduce the hot water by 10°f at full flow.
No water pressure Flow restrictor in ▪There is not a problem with the hot water pressure . It is essential to
at bath tap. boiler. educate the user how the boiler uses the flow regulator to get the correct temperature
rise at full flow. Bath taps are normally 3/4" and in some cases with a 3/4" supply
pipe. With a restrictor fitted to the boiler it may appear as if there is a problem with
the flow rate.
Little or no hot water Hot and cold pipes ▪Suspect the installer has connected the hot outlet pipe to the inlet valve. To check
at tap. crossed at boiler. operate the heating in order to warm up the domestic hot water heat exchanger.
Open hot tap; if incorrectly installed, the right hand 1/2" pipe, which should remain co
will become warm.
Dirt in the 3 port ▪Diverter valve does not fully closein the DHW mode. To check, with heating
diverter valve. cold or cool, run the hot water and feel the heating supply pipe approx 2-3 feet
from the boiler. If the pipe gets hot this indicates that the 3 port valve is not closing
fully. Strip diverter valve, clean and lubricate, or replace.
Boiler slow to start Dirt in DHW venturi. ▪If the hot tap needs to be fully opened before the boiler fires, there is dirt in the
in DHW mode. venturi. Strip down and clean the water pressure sensor (venturi).
Boiler has been Dirty DHW heat ▪This can be especially true when the boiler has been installed on an existing
operating for some exchanger. system. Suspect contamination from older parts of system. Surfaces of DHW heat
time with no problems exchanger has been coated, not allowing heat transfer to take place from the primary
until hot/cold problem water, with the result that the boiler shuts down on its safety thermostat.
ie: with shower ▪If in a hard water area, suspect the potable side of the heat exchanger is scaled up
becomes apparent. causing the same problem. De-scale or replace DHW heat exchanger.
#6 (30°f) fault code. Flame failure. ▪Check gas supply, flame signal or ground to boiler.
#7 (40°f) fault code. Safety thermostat ▪Check continuity across thermostat terminals, when cool more than1Ωresistance.
activated. ▪Check for scaling or contamination in primary heat exchanger.
#8 (50°f) fault code. Fault on fan or flue. ▪Check venting, fan venturi, air switch sensing tubes and air switch.
#9 (60°f) fault code. Fault on pump or low ▪Check low system pressure, air in system, jammed or faulty pump.
system pressure.
#10 (70°f) fault code. Fault on DHW sensor. ▪Check DHW sensor for correct resistance reading or is open circuit.
#11 (80°f) fault code. Fault on primary ▪Check primary sensor for correct resistance reading or is open circuit.
sensor.
Note: in some instances the #6 (30°f) fault will flash as well as another fault code
light. This is because the boiler will show this fault code if the boiler has not detected
a flame after 10 seconds on start up.