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BAXI DuoTec 40 GA

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geofear
geofear Member Posts: 6
in Gas Heating

My Baxi DuoTec stopped working about a week ago. I have had 2 service calls and numerous conversation with Baxi northamerica contractor support. Problem: No heat, no error messages. replaced the PCB and the memory stick. Automatic recalibration goes no where. Circ pump comes on, but no fan or firing. fan tests ok. PLEASE, if you have any thoughts, I would deeply appreciate them.

Comments

  • kcopp
    kcopp Member Posts: 4,680

    Bummer.

    Fuses all good?

    I found this… you prob have it but just in case.

    Duo-Tec-Troubleshooting-guide_061818.pdf

  • 109A_5
    109A_5 Member Posts: 4,015
    edited 2:06AM
    image.png

    With the information you provided and a bit of reading between the lines (Red Arrow). I would suspect the Heating flow sensor (item 11) is not sensing flow (amusing that is actually what it does). Anyway that is where it seems like where the process seems to stop.

    image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015

    So no DHW or Space heat ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015
    edited 2:53AM

    Seems both items 528 may be temperature sensors, the documentation is a bit confusing, apparently different physically and possibly electrically different from the other NTC temp sensors. 624 is a flow sensor but may only be used for DHW use.

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015

    To me this implies there are two FLOW sensors, however I only see one actual flow sensor. Confusing.

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015

    All these items seem reasonable ?

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • hot_rod
    hot_rod Member Posts: 27,466

    what is the pressure at the boiler? It is not uncommon to gave a pressure switch in those boilers, 6-8 psi is common

    The flow switch is typically on the dhw side

    A continuity meter is what you need to check the pressure or flow sensors

    Some trouble shooters would jumper across those switches for a few seconds to confirm their condition

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • geofear
    geofear Member Posts: 6

    thank you, thank you, thank you for all your comments. I have jumped all the sensors to no avail. 2 main fuses are good. Pressure 1.5 bar. Raised until the PRV opened. NADA. All parameters checked after the new board and memory stick installed.

    When auto calibration is started, circ pump comes on, and then nothing. When I reset, it throws a E55, PCB NOT PROGRAMMED. ???????????????????

  • geofear
    geofear Member Posts: 6

    I have read the BAXI "How to reset E55 Fault Code", which is basically a hard reset. nothing.

    Without any error codes, does it make sense to start replacing all the sensors?

  • GGross
    GGross Member Posts: 1,901

    It sounds a lot like when the older viessmann boilers did not make the flow switch. they would not fire or give any error codes, they always said it was a european thing, the flow switch fires the boiler. both companies have a flow dependent boiler, both are european. I would start by purging air personally, and checking the flow switch

    Alan (California Radiant) Forbes
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,723
    edited 2:45PM

    I’ve spent many frustrating hours troubleshooting Baxi boilers. Gave up and started recommending a local Baxi "specialist", but then found out that all he does is quote a new Baxi.

    I'm the kind of guy that doesn't give up easily, but listening to your problem, I'd recommend cutting your losses and replacing the boiler, but not with another Baxi.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    GGross
  • GGross
    GGross Member Posts: 1,901

    install a brand that the local techs know and understand! Baxi doesn't make bad boilers, and if you go to the UK they are a preferred brand, but they are very different than the boilers techs are used to here, and parts are sometimes just not available, they keep exiting and re-entering the US market. I will say the gas adaptive technology is cool, and I think they rebrand their boilers for utica/dunkirk in case you know anyone with experience on those ones.

  • hot_rod
    hot_rod Member Posts: 27,466

    what calls the boiler on for heat?
    It could be as simple as the relay or thermostat is not enabling a heat call

    Is there a TT or CH contact on the terminal strip?

    The wiring schematic is the road map to see where the open circuit is

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • 109A_5
    109A_5 Member Posts: 4,015

    What does it do for DHW mode ?

    Did the symptoms change ???

    You stated there was no codes !

    Now you say there is a code 55. So now you are fighting two issues, the original AND the code 55.

    image.png image.png

    The procedure is in the Troubleshooting guide posted above, however you probably need a combustion analyzer to complete the procedure once the boiler fires.

    Did you try the new PCB with the old memory stick?

    Originally I'm thinking this is not being satisfied.

    image.png

    When the circulator starts the boiler wants to see a temperature change to verify the flow. Presently I would imagine all the sensor temperatures should be close to the same temperature since the boiler has not run in a while (Sanity check).

    If the water can't flow there won't be any temperature change at that sensor. So maybe a bad circulator, the system has too much air in it, or some valve (probably for air purging) is closed blocking the flow.

    Can the original PCB and Memory Key be reinstalled ? I'd try the original Key first (with the New PCB), may get you back to the original issue.

    Was the Manual Control Function tried ?

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015
    https://forum.heatinghelp.com/discussion/comment/1893406#Comment_1893406

    I think the call for heat is valid since the circulator starts, I assume it is the circulator inside the boiler.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 4,015

    Did either service call try to purge the air out of the system ? At least to eliminate that as a possible cause ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System

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