Baxi LUNA 310 Fi Troubleshooting Manual page 4

BAXI LUNA 310 Fi troubleshooting guide
Fault Cause
Boiler short cycling. Heating output has not
been set.
Short cycling on a
short heating circuit.
Whistling noise from High fire when using
boiler. Glycol in system.
Fluctuating DHW Boiler cycles on and
temperature at tap. off.
Erratic burner
pressure.
Burner pressure
fluctuates from high
to low fire.
Fluctuating
temperature at
shower.
Hot water not hot Incorrect gas
enough. pressure.
Faulty/Dirty NTC
sensor.
Suggested Solutions
▪
Set the "Max R" on the control PCB to match the heating system requirements,
see chart on page 25 in manual for settings.
▪
In a smaller system make sure the T-Off Jumper on the PCB is set to the left,
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.
▪
BAXI recommends that only 25% inhibited propylene glycol solutions which are
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 a 50% by volume
solution expands 4.8% in volume for a temperature increase from 32°F to 180°F,
while water expands 3% with the same temperature rise. Allowances must be
made for this expansion in the system design. A 30% 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 output loss of 30% with a 50% increase
in head against the boiler pump.
▪
Check that low fire is not set to high. Reset if required.
▪
Check burner pressure at gas valve test port with manometer while boiler
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.
▪
Check burner pressure at gas valve test port with manometer while boiler
operating. If gas pressure fluctuates from high to low then back to high suspect
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.
▪
If previous checks are OK check the temperature of the hot water at a single
tap (not single lever tap). If the temperature is stable (within 3-5°f) at this tap
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.
▪
Check that the boiler has the correct maximum gas pressure.
▪
Check that the DHW sensor is not dirty or scaled up. Check that sensor is not
out of calibration ( 1 0 K Ω @ 25°C). Replace if faulty.
▪
If PCB has been changed has the boiler thermostat knob been fitted correctly?
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