Nest thermostat problem with ATAG CV

[FamilieGraham]

We have a ATAG E244EC ketel in combinatie met mijn Nest Thermostat V2.

Mijn Atag Ketel gaat continu in storing (C151) en dit direct bij het opstarten van de Ketel, resetten of een hard reset door de stroomvoorziening los te koppelen hebben soms geen effect.

Na de reset doet de ketel het opeens weer, maar na gebruik van warm water slaat de ketel weer in de C151 storing.

We worden er moedeloos van. 

Heeft ruim 5 jaar zonder problemen gewerkt en van de een op de andere dag constant C151 storing tweemaal zelfs de ventilator vervangen.

De Nest thermostaat vervangen door de oude en nu ruim 5 maanden werkt de ketel weer zonder problemen.

Wie weet voor deze probleem de oplossing.

Alles is aangesloten zoals bij de Opentherm aansluitschema hoort te zijn.

[luciaaa · Accepted solution]

Hi, @FamilieGraham!

I appreciate you reaching out to the community. It's understandable you're discouraged by the intermittent C151 error on your ATAG E244EC, particularly after investing time in fan and thermostat replacements. Help’s here!

Because error code C151, directly from your system, points to a boiler problem and the system's inconsistent performance (working after restarts but failing with hot water) and appears to function with your previous thermostat, I recommend contacting a qualified technician to pinpoint whether the Nest Thermostat or a general system fault is responsible.

Don’t hesitate to reply if you have any questions.

Best regards, 

Ana

[FamilieGraham]

Hello Ana,

a qualified technician has found this problem.

He had read online of this problem with an ATAG CV boiler and the Nest thermostate.

He has disconnected the Nest and replaced it with a simpel thermostate and it is now working for several weeks.

Before the qualified technician pinpointed the problem to the boiler, but after the third change of the ventilator the problem was back.

Then he found on internet that is was probably the heatsink from the Nest.

Is there a way to check this?

Every time we change the ventilator it cost us  600 euro's.

We have always used the Nest thermostate and were very glad with it. 

We would like to use the Nest again.

With kind regards,

William Graham

[luciaaa]

Hi, @FamilieGraham!

Thank you for your prompt response. I truly appreciate the detailed information and for letting me know you've already hired a qualified technician to inspect the system. Based on the information provided, it seems the technician has identified the Nest thermostat as the source of the inconvenience. You've inquired whether this issue is related to the Nest thermostat's heatsink and expressed a desire to reuse the device. I recommend contacting a Nest Pro technician for a precise diagnosis of the Nest thermostat.

Please keep me updated.

Best regards,

Ana