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Low Water Reset - Utica Boiler
You were right (also spoke with Utica - they were great as well). What appears to have happened is that the roofers wrapped the base of the chimney with a tarp as a precaution against rain damage. They likely rested the tarp or somehow momentarily blocked the flue - creating the back pressure in the flue.
The Utica Boiler has two resets - one for the flue. One press of the reset and the boiler fired on a call for heat. The draft in the chimney is strong. With the knowledge that the wrapping happened exactly when the boiler when down I feel fairly confident that nothing was dropped down the chimney.
Sorry to confused the issue with the Low Water condition.
Thank you all for the help. It's nice to be warm again!