Baxi Luna 310fi

Chippy

I posted this on a previous thread from 2019 so maybe nobody will see it. I have a problem with the system losing pressure and not lighting up. The pressure relief valve discharges water (into a plastic container under the discharge pipe) so there is no pressure in the system and it fails to light up. I have replaced the PRV twice over the years but I am beginning to suspect the expansion tank however the instruction manual says it is pre-charged and I cannot find a a air valve to test/recharge it. It is also at the back of the boiler behind everything and would mean dismantling the whole unit. I was wondering if fitting and external expansion vessel is the answer and if so what size would you recommend.

Tom_133

Yes, an external would be helpful. It will at the least help the dripping PRV, but when you are making hot water the 3 way valve closes the heating side, so the external may only help during heating. The production of hot water, may make it drip, typically not. Put the expansion on the return side if you are not piped primary secondary.

EBEBRATT-Ed

and the expansion tank probably has little to do with the boiler not starting

Chippy

It seems to happen much more often in the heating mode and presumably the boiler has a lockout if there is no water pressure in the system.

I will probably just have to live with topping it up every couple of days as I don’t want the heating off at -26C!!!

Tom_133

To add an expansion tank would take less than an hour. Its better to just add the tank and move on. Its not great to add that much fresh water to your system

Alan (California Radiant) Forbes

You might get some input from Baxi technical support at (844) 422-9462

Chippy

Thanks for all your help I will try calling Baxi Tech Support to see if it is possible to check the expansion tank pressure without dismantling the boiler.

Derheatmeister

Did you clean the Ignition and Flame sensing rods ?
Condensate trap should also be cleaned at least once a year..