Baxi Luna3 Comfort 1.310 Fi High pressure then cuts out ?

Baximan

Hi All, I have a Baxi Luna3 Comfort 1.310 Fi. Connected to Heating only. It was installed in 2010 and the system began to sustain a functional issue around a week ago by way of it only heats for around 30 minutes and then cuts out and will not reheat. The remote controller is calling for heat but nothing. Then after a few hours it throws a resettable error code of 98E. When you press ok to reset, the heater fires up again but only lasts for around 30 minutes and then this whole cycle repeated itself for a few days and now the 98E code does not show any more and after about 6 to 9 hours the heater will decide to fire up and then 30 minutes later cut out. For the last couple of days this cycle has been on repeat. I have observed the water pressure gauge and while all this is happening and have noticed that the heater will fire up when water pressure is around 1bar. Then during the heating cycle it rises up to 4bar and then cuts out. The system seems to fire up hours later when the pressure drops back to 1bar. Any suggestions?

Baximan

Also, during the heating cycle, the built in pressure relief valve leaks water. The leak stops when the heating cycle cuts out.

Jamie Hall

Is there an expansion tank somewhere on the system? It may be waterlogged -- or even somehow valved off.

Baximan

Yes, there is a 10L expansion tank inside the unit

GGross

I would imagine the expansion tank has an issue, over here in the US the relief valve will go off at about 2 bar. 4 bar is way too high pressure

Baximan

Yes, I am beginning to suspect same. However I opened the boiler drain point to reduce the water pressure and brought it back to 1bar. And when I switch it back on, it calls for heat and the pressure immediately rises to 1.5bar and will just sit there for hours with the fan running and no ignition until hours later when it decide to ignite.

Baximan

Wouldn't that indicate a potential problem with the circuit board or igniter probe or even potentially the gas valve - however when it decides to fire up it runs well but for only around 30 minutes?

GGross

Need to follow proper trouble shooting steps, you have a serious safety condition at hand, need to fix the high pressure first before trying to trouble shoot anything else! It is possible you have 2 problems, it is also possible a ton of air enters your system when the relief valve blows off, somewhere in there more water gets added to the system, and with it more air. The air could be stopping your boiler from firing, but it does not matter, your boiler is running at dangerous pressures and blowing off the relief. Your relief needs to be changed, the expansion tank checked, and the fill valve checked, system purged of air, then try running the system. i believe you need to call in a pro

Baximan

I was hoping you were not going to write that last sentence but I ultimately expected it. Sounds like you are a pro. Pity you are not over here in Australia but thank you very much GGross for your advice

GGross

Just don't fire the parts cannon at it until the pressure issue is taken care of! After that make sure the system gets purged of air, if you still have problems at that point then you can look to other potential issues.

we know the relief has been blowing off due to pressure, it is my opinion that when this safety valve has been used under high pressure conditions it should be changed. This is general good practice but not required per se.

The expansion vessel needs to be checked for proper charge, should be near system recommended fill level. this is the most likely culprit, and it possibly needs to be changed

The fill valve for the syste (if there is one) needs to be checked to make sure it is not letting in too much pressure, this is unlikely but you can test by turning off the unit, lower system pressure to the correct level, and see if the unit pressure goes up while the system is off entirely.

Baximan

It does. The pressure was at 1.5 Bar. I switched off the unit at the power socket and then I opened the boiler drain point to reduce the water pressure and brought it back to 0.5 Bar. As soon as I closed the boiler drain point the pressure started to gradually rise. After about 15 minutes, it went back up to 1 Bar.

GGross

The autofill should fill the unit to set pressure, 1 bar is is a pretty standard set pressure, if it does not go above 1 bar while the unit is shut down I would wager the fill valve is functioning correctly. That being said whenever that relief blows off the fresh fill water will introduce oxygen to the system as well

Baximan

Thank you very much GGross. You have been a great help. I will be submitting this discussion string to an expert over here on Australia to assist them in the diagnosis of my Baxi system.

Alan (California Radiant) Forbes