I've just gotten my new Burnham Alpine 150 boiler going in the last few days and I'm trying to get it set up properly. My installer's attitude is pretty much that the standard settings are just fine and I'm happy to experiment with them on my own. I'm in Newton, Mass and my antique house has old-fashioned cast-iron radiators. The outdoor temp since I have installed has been in the 5-20F range.

I have several questions, but let's start with the "smoke" plume, which is more than I expected. It seem to me that if the unit is condensing, there should be little moisture in the exhaust to cause a plume. At the moment I have a setpoint of 139F and return temp maxing out around 130 degrees. Each cycle tends to run about half way indicating "Max efficiency" but seems to drop that indication when the return temp hits about 127. I'm still getting a pretty good plume.

What conditions contribute to the amount of plume?