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.

 

[king of pipes]

This may help you not really familiar with that boiler . Regards kop

 

[geofear]

Thanks, Mate. I have that manual next to my bed. I think I have memorized it by now. ;-)

 

[oz-plumber]

I could almost guarantee its the Transducer.
The part that the rilevator fits onto.

Baxi part no: JJJ000620340.

Patience is required removing the part.
Difficult to get a socket onto. Can't really do it with a spanner.
The faint red light on the rilevator may not sense enough flow for the unit to fire up on DHW demand

 

[geofear]

I could almost guarantee its the Transducer.
The part that the rilevator fits onto.

Baxi part no: JJJ000620340.

Patience is required removing the part.
Difficult to get a socket onto. Can't really do it with a spanner.
The faint red light on the rilevator may not sense enough flow for the unit to fire up on DHW demand

I love the theory, but that part number does not show up on the parts diagram for my particular boiler. Instead it shows B (pic3) "FILTER ASSEMBLY WITH RED.10L-10091" ?

Perhaps your part is just the top piece of that ASSEMBLY ???

In your experience, when DHW demand, does the Rilevator show a constant red light, NOT FLICKERING?

I could almost guarantee its the Transducer.
The part that the rilevator fits onto.

Baxi part no: JJJ000620340.

Patience is required removing the part.
Difficult to get a socket onto. Can't really do it with a spanner.
The faint red light on the rilevator may not sense enough flow for the unit to fire up on DHW demand

 

[ShaunCorbs]

Part no 624

 

[geofear]

Part no 624

Many thanks Shawn, but 624 is the Rilevator itself. I have already replaced it. But if it 'works' with the "transducer", I think we're making progress here. And I see it has a plastic screen at its base.... Perhaps it is just CLOGGED and can be cleaned?

 

[geofear]

I could almost guarantee its the Transducer.
The part that the rilevator fits onto.

Baxi part no: JJJ000620340.

Patience is required removing the part.
Difficult to get a socket onto. Can't really do it with a spanner.
The faint red light on the rilevator may not sense enough flow for the unit to fire up on DHW demand

OZ, are you in Britain?

 

[ShaunCorbs]

Is it making a solid red light when waters flowing ?

Also if you live in a hard water area then yes I would clean the screen

 

[Deleted member 120897]

I think imo it’s flickering?

In your experience, when DHW demand, does the Rilevator show a constant red light, NOT FLICKERING?

Is it making a solid red light when waters flowing ?

Also if you live in a hard water area then yes I would clean the screen

 

[ShaunCorbs]

Yes should be constant sounds like the flow sensor is getting old part no 81

 

[geofear]

Is it making a solid red light when waters flowing ?

Also if you live in a hard water area then yes I would clean the screen

No Shawn, NOT solid at all.... rapid flickers. SHOULD it be solid?

Yes should be constant sounds like the flow sensor is getting old part no 81

Obviously have to turn off the incoming water. But will it back-siphon all the hot water from the lines above this level?

 

[ShaunCorbs]

Easy way to test pop the sensor off keep the wires on / attached and get a magnetic screwdriver and rotate / spin the screwdriver around in the hex bit in a circle motion this will fire the boiler up for hot water so have a tap open after you popped the sensor off

The red light should be constant

 

[geofear]

Easy way to test pop the sensor off keep the wires on / attached and get a magnetic screwdriver and rotate / spin the screwdriver around in the hex bit in a circle motion this will fire the boiler up for hot water so have a tap open after you popped the sensor off

The red light should be constant

To clarify, to test the transducer, rotate a magnetic screwdriver in the rilevator?

 

[ShaunCorbs]

Yes In the part 624 spin a magnetic screwdriver in a circular motion eg move it around in the hex clip

 

[geofear]

Yes In the part 624 spin a magnetic screwdriver in a circular motion eg move it around in the hex clip

Thanks Shaun