Weil McLain A 41 code

Ericjeeper1965

Wmb80/120/155 boiler keeps throwing an A41 code. I have cleaned the mounting surfaces, replaced both sensors. Still getting the error after it sits for an extended period of hours.  Unit is 3 years old,worked fine until this season. I did change out the near boiler piping to 1" as it was originally plumbed 3/4". I also added an 80 gallon water tank as storage.the storage tank is on the return side.
  This unit is a closed system that heats a flat plate heat exchanger. The piping and tank are all that I have changed.So not sure if it is related or not. Thanks in advance.

109A_5

Hello @Ericjeeper1965,

I would re-seat the sensor connectors at the controller board. I would verify the sensor resistance all the way back to the controller board. Sensor resistance at a given temperature is in the manual. Also the proper position of the sensors in the boiler.

With the additional load of the 80 Gallon tank a performance curve may have to be changed or relearned.

It seems odd to me the error pops up when the unit is idle for a while. Maybe the lower in-cabinet temperature is influencing a connection somewhere.

Ericjeeper1965

Thanks,I crimped the connections down a bit. We will see if that changes anything.