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.

 

[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

 

[oz-plumber]

OZ, are you in Britain?

No, I'm not.
I reside in one of the Colony's.

There is a plastic strainer at the bottom of this part and also a wire mesh strainer inside the part.

Just replace the whole part, they do a lot of work and if you get more than 4 years out of them you're doing well.
I always have 2 or 3 of them on hand due to necessity.

 

[geofear]

No, I'm not.
I reside in one of the Colony's.

There is a plastic strainer at the bottom of this part and also a wire mesh strainer inside the part.

Just replace the whole part, they do a lot of work and if you get more than 4 years out of them you're doing well.
I always have 2 or 3 of them on hand due to necessity.

Got one on order. Thanks.

You in the States?