BAXI DuoTec 40 GA

geofear · March 31

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.

kcopp · March 31

Bummer.

Fuses all good?

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

Duo-Tec-Troubleshooting-guide_061818.pdf

109A_5 · April 1

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.

109A_5 · April 1

So no DHW or Space heat ?

109A_5 · April 1

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.

109A_5 · April 1

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

109A_5 · April 1

All these items seem reasonable ?

hot_rod · April 1

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

geofear · April 1

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 · April 1

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 · April 1

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 · April 1

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.

GGross · April 1

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 · April 1

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

109A_5 · April 1

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.

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.

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 ?

109A_5 · April 1

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.

109A_5 · April 1

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

geofear · April 2

Again, thank you for your thoughts.

There is a thermostat wire (end switch) coming to the Baxi from a Taco controller. I can see the Baxi calling for heat, when the thermostat wire is attached. The circ pump is within the Baxi. There is an Airtrol on the main return line. If there is an airlock in the Baxi, how would it be purged?

Regarding the primary, secondary issue, when the PCB is replaced, I believe it normal for the system to throw the E55 error, requiring automatic calibration. When initiated, nothing happens. Something is stopping the Baxi from firing, and therefore from auto calibrating.

There is a mini-board to the left of the PCB that basically provides low voltage. Blue, red, black . When i check low voltage, I get 24 on blue and red, but when I test blue/black the voltage starts out about 16 volts, and quickly and steadily falls to below 13. ???????

"The procedure is in the Troubleshooting guide posted above, however you probably need a combustion analyzer to complete the procedure once the boiler fires." If only it would fire !

Did you try the new PCB with the old memory stick? I shall, but I have repeatedly verified all the parameters.

Originally I'm thinking this is not being satisfied.

01 I am not sure I am following you on this.

geofear · April 2

I wonder if I can take a new 24 volt transformer and feed the Baxi block….. >???

geofear · April 2

I have tried all Modes. The unit does nothing, regardless. Bottom line, it knows it must be calibrating, and something is preventing it from firing.

109A_5 · April 2

At the point that the startup sequence seems to stop it appears it is looking for data from this sensor to prove water flow.

So since the boiler has not run in a while all the temperature sensors except the outdoor one should read about the same temperature (a sanity check).

Since I believe this sensor is a temperature sensor and not an actual flow sensor, the system must be looking for a temperature change as the circulator starts to move the water. No water flow for what ever reason, no temperature change.

Does this sensor display a reasonable temperature ?

109A_5 · April 3

If this is the board you are referring to, at the Red arrow, it appears it does two things; It makes 24 VAC to possibly power external equipment connected at M2. Also if a 24 VAC thermostat or switch is placed at M2 (the Green arrow) it may control a relay on the board at the Red arrow. The relay contacts may act in parallel to or as a substitute for a 120 VAC thermostat or switch is placed at M1 the Orange arrow.

Your drifting voltage may be normal depending on the points the meter is connected to.

However I am not confident the wiring diagram is showing the whole story.

GGross · April 3

hold on you said you have an airtrol fitting? can you take pics of the install? airtrol is a specific thing that involves a compression style tank, so if you have an airtrol that would tend to mean you have no air vents, which works well for a cast iron system but not when the air gets trapped in the boiler heat exchanger. need pics

geofear · April 3

i03 and i04 reads 254. I have replaced sensors 135 and 528 in the diagram above. Does it make sense that i03 and i04 should read 254 when it is cold? Which sensor produces the i03 and i04 readings?

regarding the comment about items being attached to M2. There are none, except for the end switch thermostat wires from a Taco controller 404 feeding call for heat, connected at the top of M2.

geofear · April 3

At the point that the startup sequence seems to stop it appears it is looking for data from this sensor to prove water flow.

Do you know which sensor that would be?

geofear · April 3

109A_5

"Since I believe this sensor is a temperature sensor and not an actual flow sensor, the system must be looking for a temperature change as the circulator starts to move the water. No water flow for what ever reason, no temperature change.

Does this sensor display a reasonable temperature ?" i03 and i04 read 254. I replaced sensor parts 135 and 6

geofear · April 3

I have since replaced the wet sensor in the lower left (probably what is referred to as the FLOW SENSOR, and now i04 reads a more reasonable 64.4 degrees.

Now I am stuck in the E133 error code, and I can't seem to get out of it.

geofear · April 3

Every so often, I can feel the circ pump come on and run for about 12 seconds and stop. Then nothing else happens. Might the system be airlocked? I drained water out of the system, and added water back to almost 2 bar.

On another note, i07 shows the status of a "thermo fuse" (000/001) . I am showing a reading 001. Where the hell is this fuse?

109A_5 · 12:20AM

If the numbers in the chart below correlate with your display information. I would expect 01, 04, 06 to read basically room temperature since the boiler has not run. 02 should be the outdoor temperature. 12 should be about room temperature however if there is any draft of outdoor air through the air intake / vent system it may be offset a bit by the outdoor temperature.

Any large deviation from expected could be a sensor defect a poor or wrong sensor wiring connection or a compromised (crushed) wire causing issues.

109A_5 · 12:25AM

E133 is an ignition failure. So maybe you have progress (with the flow issue) and maybe moving on to another issue.

109A_5 · 12:26AM

The circulator running, if it is at a regular interval may be an anti freezing strategy.

109A_5 · 1:05AM

I can't find anything I would call a "thermo fuse" the closest thing is item 135, which I believe you changed. I would call it a thermo switch. However it may be a one shot deal. If that thermo switch was defective it may be wired into the system (by design) to disable the Heating flow sensor, hence the crazy temperature reading of 254.

109A_5 · 2:14AM

https://forum.heatinghelp.com/discussion/comment/1893614#Comment_1893614

Does the inducer fan now run with a call for heat ?

pedmec · 2:40AM

Have you done this? there is a symbol that won't copy after press

AUTOMATIC CALIBRATION FUNCTION WARNING

During this function ensure there is maximum heat exchange to the system in the Heating or DHW mode (DHW request)in order to avoid the boiler shutting off due to overheating.Press and together and hold down for at least 6 seconds. When the display indicates "On" press Fip (within 3 seconds after pressing the previous buttons).IMPORTANT INFORMATION If the display indicates "303" the Automatic Calibration function has not been activated. Disconnect the boiler from the mains power supply for a few seconds and repeat the procedure.

BAXI DuoTec 40 GA

Comments

Categories