BAXI Luna 3 - no hot water

[geofear]

I am trying to troubleshoot a Baxi Luna 3 Combi boiler 8 years old, that is not making any hot water. It is in a customers second home, and receives little usage.

Over 2 days, hot water was getting less hot, until now none at all. When I call for heat, and the unit fires fine. There are no error codes.

When there is HW demand, I sometimes hear a click, and the exhaust motor runs for less than 1 second. The gas valve does not open, nor is there any attempt to fire. Something is preventing it.

There are 3 ‘sensors’ in the DHW area; a pressure switch, a NTC sensor, and a ‘Rilevator’. (When calling for hot water, this rilevator flickers a faint red lite, indicating the
flow of water. Both the NTC sensor and the rilevator have been replaced.

I have re programmed the DHW programming.

I have removed the top of the diverter valve motor, and there are no leaks. I can push down the pin inside the valve with my finger. With the diverter motor un-attached, I can get hot water, so the exchanger is not plugged. When calling for heat, the rod at the base of the motor is firm. When calling for DHW, it is loose and easily moves back and forth. It appears to be functioning correctly.

Something is preventing the unit from firing in the DHW mode. Your thoughts on how to troubleshoot, please.

 

[ShaunCorbs]

I believe the uk equivalent is the ga and most often or not it’s the pcb

 

[geofear]

Thank you for your reply. It's about 8-10 years old. I think the GA series is more recent (30, 40, 60). Luna 3 Comfort, 310 Fi is on the plate, but I have seen parts diagrams that is a different unit.

I am not convinced it is not a simple programming issue. Here is a pic of the display.

1) The symbol in the upper left shows it is in DHW mode. Should the 0-24 histogram to the right be blackened, as it is for the CH mode?
2) Is the symbol 1/3 of the way down the right hand side normal? ("Communication with the gas boiler in progress")

I am at a loss....

 

[Deleted member 120897]

Have you tested for correct voltage and polarity?

 

[geofear]

No, I have not. I am open to any suggestions. (But as this system has been installed for 8 years without a problem, the voltages and polarities have not changed.)

 

[king of pipes]

When you run the hot water tap does heat creep down the heating pipework ??

 

[geofear]

no

thank you (but if it did ???)

 

[king of pipes]

A Diverter issue ? it may be as simple as something is stuck especially as you say it's a second home and rarely used ? A Combi has hot water priority so soon as the hot tap is turned on it should operate and produce hot water whatever the timings for heating ? Any fault codes show on this screen ??

 

[geofear]

Thanks for your reply. I do not think it is a diverter issue, since when DMW calls, it does not even try to fire. If a diverter issue, it should fire, but not produce any hot water. ?

 

[geofear]

No faults codes.