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BAXI Luna 3 - no hot water

View the thread, titled "BAXI Luna 3 - no hot water" which is posted in UK Plumbers Forums on UK Plumbers Forums.

G

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.
 
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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....
 

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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 ??
 
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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
 
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oz-plumber said:
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
Click to expand...
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?
oz-plumber said:
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
Click to expand...

Baxi 2.jpg
Baxi 3.jpg
 
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oz-plumber said:
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
Click to expand...
OZ, are you in Britain?
 
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ShaunCorbs said:
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
Click to expand...
No Shawn, NOT solid at all.... rapid flickers. SHOULD it be solid?
ShaunCorbs said:
Yes should be constant sounds like the flow sensor is getting old part no 81
Click to expand...
Obviously have to turn off the incoming water. But will it back-siphon all the hot water from the lines above this level?
 
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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
 
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ShaunCorbs said:
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
Click to expand...
To clarify, to test the transducer, rotate a magnetic screwdriver in the rilevator?
 
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