Baxi 130HE anticycle CH problem (only works after DHW run)

[Nostromo]

Have problem with Baxi 130HE. DHW works fine, but when timer calls for CH it goes into anticycle (start is code 21, takes few seconds for diverter to move, then 26 displayed). The strange thing is if the DHW is running and the timer is calling for CH, then when the DHW stops the CH kicks in normally (after the normal CH shutoff it displays code 26 for a while - assume this is normal?)

Originally thought it may have been diverter valve , but changed to no effect, Has anyone seen this - Im going to put multimeter on flow switch (in case it is somehow sticking). The boiler had been drained and not in use for 6 months so took pump out to clean and inspect (bit of deposit, but looked not too bad)

Any ideas??
Cheers

 

[Nostromo]

Put meter on primary flow sensor and seems to be working ok. Starting to worry it might be the control board. Any idea of ways to isolate without starting to swap parts??

 

[Nostromo]

Have found that when the CH is starting from the system being cold it works first time. After that it goes back to giving the 26 anticycle on startup (even after waiting for 1hour between tests).

Does anyone know what triggers the Anticycle on startup - the Baxi manual says if CH flow is restricted it can give this error, but would this be a result of the primary flow sensor (as I have check that this seems to be working fine). is there any sensor feedback on pump to indicate restricted flow? Assume it would not be faulty thermister, but will check those next

 

[Nostromo]

Checked flow & return thermostats and seem fine. Also performed more short CH test runs from a cold start. Switch on and off for short period while bringing up CH temp (1min type runs) - everything working fine.
After running for longer period (approx 3 mins with CH temp rising to 65 - 70 deg) it will not start up again. This is after waiting for 3 mins to complete normal anticycle lockout - then restart - initialising diverter etc (code21) -then goes into the anticycle 26. (further attempt to start result in same symptom)
Again, in this anticycle lockout state, the CH can be kicked in normally by running DHW (CH kicks in after DHW demand stopped).

Will put more flushing agent in system in case HE is blocked up (is aluminium so bit worried its clogged and restricting flow). Also thinking of fitting second pump to assist with flow.

 

[Agile]

Do you know that if yours is the last posting that you can add or edit that if you have something further to say?

 

[Agile]

Its probably the PCB.

However, a common cause of that senario on other models is the primary flow switch failing to make on CH. But when its been operated on DHW and CH is immediately selected then the switch stays made.

Probably unlikely in your case as it would most likely give a unique fault code. But its easy to check by measuring the voltage across it which will fall to zero when its activated.

Few people seem to use that method of testing although it shows not only that a switch has been made but also that its contacts have a low resistance.

Tony Glazier

 

[Nostromo]

Thanks Tony, Sorry didnt realise I should have been editing the original post. Yes I checked flow switch with meter and it is being engaged during CH initialisation (but will check again) . I had suspected control board, but the fact that CH runs fine at lower temp made me wonder.

 

[Agile]

I know that you had checked it before.

However, when investigating more obscure faults its often necessary to continually monitor an operational parameter during boiler operation in order to diagnose the problem.

In an ideal boiler world you would have a "scope" type display showing the state of all the variable aspects of a boiler's operation. Thats not difficult to achieve now that everything can be done in software. After all they manage that in planes for the FDR and the Airbus and some Boeings even transmits a data set with its ACARS system.

Tony

 

[rogbrimb]

Hi Nostromo, did you get to the bottom of the problem of the baxi sticking on 26? I have one exactly the same, a colleague advised to check the return filter but it was clear. I also saw an error Ld at one point (but only once) which would be a flow temp lockout.

Thanks,