Baxi Luna no DHW

scott_ro

Baxi Luna HT 1.33 with Modulo Storage Tank



System does not fire up when DHW is requested.

Looking at the Siemens QAA73 control, the DHW actual says that is 205 degrees F, and I see it fluctuating seemingly randomly (when I check it) between 195 F and 230 F.  I have a feeling that the sensor is "not working" properly since the water and pipes are cold. 



Switching to radiator heat seems to fire up fine with no issues.



Similar to others on this board, I am not confident that the original installers knew what they were doing, and the system hasn't been "cleaned" or 'serviced" since 2009.



Anything else I can diagnose on my own?  Any simple things I can clean on my own?

scott_ro

Somewhat Diagnosed... not solved yet

Well..  After focusing mostly on the upper half of the Baxi Luna with Modulo system (thinking that it was mostly just a storage container below), I found that jiggling some wires corrected the measurement of the DHW.  This allowed the system to fire for the DHW.



Yay for hot showers.



Anyway, now my dilemma is trying to narrow down the issue.  Anyone with experience want to provide some tips?



Would the temperature sensor (10k Ohm & 25 C) change that much by jiggling wires, or is it more the wires that are the issue?  I figured if it was the wires, that by moving them into place where they are working, and then taping them there (temporarily) the problem would be solved.  However, even with them taped into place, the sensor shot back up to the 190 F range, even though we set the max to 107 F.

kcopp

prob a bad...

thermister.  There should be a ohms reading  w/ the instructions.

Steve Whitbeck

Bad connection

It could be just a loose connection. Hold the wires firmly with one hand and then wiggle the wires on one side of where you are firmly holding them and see if the temp fluctuates. Then wiggle the other side. If You get a flucuation of the sensor side - hold the wires firmly right at the sensor and wiggle them again. If no change - change the sensor.