Thema "Re: Vitodens 050 W A9 error" in Gas

Vitodens 050 W A9 error

Nicolas_ — Tue, 25 Oct 2022 20:25:44 GMT

Hi,
I have a Vitodens 050 W (24kW) used in an apartment floor heating system. Lately I keep getting the A9 error. I've reset the boiler and I've changed the batteries in the wired wall thermostat (Honeywell CM707) but the error randomly appear.

There is also a mechanical thermostat mounted on the floor distribution heating system, wired connected in boiler.

The system settings are as follows: 45*C set on primary heating circuit in boiler control panel, 24*C set on the wall wired thermostat, 40*C set on mechanical thermostat mounted on the floor distribution heating system.

As far as I've read, A9 error in Vitodens 050 W could be related to the thermostat connections but the wires are fine, no changes on this side.

Would you please advise, is there anything else that I can check or change?

Also, the optimal functional regime will be using the higher temperature setpoint set on the boiler primary heating circuit or on the mechanical thermostat mounted on the floor heating distribution system?

Thank you,

Betreff: Vitodens 050 W A9 error

Fiedel — Wed, 26 Oct 2022 04:36:57 GMT

Hi Nicolas,

please send us the serial number of your Vitodens.

With best regards

Fiedel

Re: Vitodens 050 W A9 error

Nicolas_ — Wed, 26 Oct 2022 17:15:38 GMT

Hello,

Sure, attached. Thank you,

Re: Vitodens 050 W A9 error

Fiedel — Thu, 27 Oct 2022 04:52:20 GMT

Unfortunately the Viessmann database does´nt know this number.

But if we talk about this heater, A9 says:

A9 Control mode without OpenTherm influence
Communication error, OpenTherm device Check connections and lead; replace OpenTherm if required

Serv.Man.

I would think you should doublecheck the connections of the Honeywell or replace the device.

May be the relay in it is worn.

Re: Vitodens 050 W A9 error

Nicolas_ — Thu, 27 Oct 2022 16:29:01 GMT

Great! Good to know, thanks.

Re: Vitodens 050 W A9 error

Nicolas_ — Thu, 27 Oct 2022 22:01:24 GMT

I have a question on this subject.

The mechanical thermostat mounted on the floor distribution heating system (not the wall ambient thermostat) should be set at a value higher than the value set in the Vitodens primary heating circuit or lower?

e.g. Vitodens heating set to 45*C, mechanical thermostat mounted on the floor distribution heating system 40*C OR Vitodens heating set to 40*C, mechanical thermostat mounted on the floor distribution heating system 45*C ? Thanks,

Re: Vitodens 050 W A9 error

Fiedel — Fri, 28 Oct 2022 04:19:58 GMT

Vitodens heating set to 40*C, mechanical thermostat mounted on the floor distribution heating system 45*C

This is correct: This mechanical thermostat ist a safety- thermostat, that protects your floor heating system

from higher temp´s, that might damage it. If too high temp´s go into the floor, this thermostat opens its

switch, and stops the floor heating pump.