Harman PB105 shut off issue

[smwilliamson]

Need help here. First off, it throws no error codes, ever. It always starts. Low temp set for 140 high temp set for 180. Dip switches all off except #2 on. Black esp. Have outside air temp hooked up. The water temp will be 140 but the unit is off. We start it up with a call for heat...it will start then slowly extinguish itself like the demand is met but it is not. Haven't been out there yet but am going on Thursday. Could his be something like the sun warming the air temp sensor? Aqua stat seems to be working as there is no 7 blink issue.

 

[mepellet]

Hi Scott,

Not sure how the controls work on the PB105 but I do know that outdoor temp sensors are typically located on the north side of the building to prevent false readings.

Is the 140-180 based on a certain outdoor air temp and below and then the water temps slowly decrease when the outdoor temp is higher?

 

[wil lanfear]

Page number 26 explains how the outdoor temp sensor functions. This sensor is a PIA in the spring and fall, the reason I do not use it.

http://hearthnhome.com/downloads/installManuals/PB105.pdf

 

[katman]

could be the sensor for the on-board aquastat. If it is off at 140 (low set point) it may think it is idling at upper limit. Fires with call for heat but then shuts down because it thinks it is at upper limit. I'd take it out of the well and ice it to see if the boiler kicks on. Also, try disconnecting the outside sensor.

 

[ScotL]

I would suspect the aquastat too. Mine was never right from the beginning and I had to pull it off the bottom of the well a little for it to work right.
You could test it by pulling it out of the well completely and see if it still shuts itself down. Just can't leave it unattended while it's out.

 

[Delta-T]

never trust the temp guage on the top of the machine...notorious liars! If you have DDM you can see what the auquastat and the outside air sensor are reading.