Vaillant 418 problem.

[purpleorange]

After leaving the boiler on full temp setting 75 degrees it decides to just maintain a constant 50 degrees or even 35 degrees. All the air has been removed from the system, and it has been powerflushed. It just does not want to 'ramp' up to full heat, so what things should I be looking for with this fault? The manual does not give a precise answer. I am gsr, but mainly do installs so I'm scratching my head! Thanks in advance.

 

[bennygas]

think my old apprentice had this recently - so long as you're happy it's circulating ok (tried increasing pump speed etc?), and any thermistors are ok, I do have one suggestion. solution he found was to set the output a bit lower. I know it sounds a bit odd, but from what I gather, he aint been back there yet, so it must've worked.

 

[purpleorange]

Thanks benny, I'll look into that.

 

[CES]

Its stuck on low fire. This is due to the difference between flow and return temps being too large. It will initially light on low fire until it gets the correct parameters (I think max differential is 200C ) I've had this before, as benny says you can either increase the pump speed, adjust the auto bypass or decrease the output.

 

[purpleorange]

Its stuck on low fire. This is due to the difference between flow and return temps being too large. It will initially light on low fire until it gets the correct parameters (I think max differential is 200C ) I've had this before, as benny says you can either increase the pump speed, adjust the auto bypass or decrease the output.

Thanks CES, I'll decrease the output, is the procedure for that in the installation manual?

 

[CES]

You need to change the D0 parameter. The value is the output in kW. The procedure for changing it is in the manual. You might also want to change the pump parameter to on d18 to non stop. This is a second level diagnostic, again its in the manual.

 

[purpleorange]

You need to change the D0 parameter. The value is the output in kW. The procedure for changing it is in the manual. You might also want to change the pump parameter to on d18 to non stop. This is a second level diagnostic, again its in the manual.

Thanks CES, so if the pump is changed to 'non stop' does that mean it's going all the time?

 

[CES]

Yes, if its wired into the boiler, it will mean the pump will run all the time the heating/hot water is called for. Sometimes the boiler may think that the heating is satisfied if its on a big circuit and it will go into pump over run and then eventually switch off, potentially levaing distant rads without heat. It really depends on the size of the heating circuit.

 

[thereisawizza]

I've had about 3 400 series that get stuck in S53, similar fault. Called Vaillant out, all they did was slag the system (existing, merely Powerflushed by us) and adjusted the KW....