We just purchased a new home in CT. It had the original 1960 Arcoleader oil boiler in it that was eating 35 gallons of oil a month just for domestic hot water. We replaced it with a Buderus G115WS4 linked to a stainless steel crown indirect. Great system by the way, sips oil.
Our installer, who was great and very knowledgeable(licensed Buderus installer), warned us that with a 2 story brick chimney on top of the story of flue in the foundation wall, we would get condensation issues, and probably have to line the chimney with stainless steel, but he said wait and see what happens. Well lo and behold, the boiler finally ran hard all night for the first time this week and we have about a quart or so of water dumping out of the lower flue door every night now from condensation(it's not running back to the boiler, we have a flue access clean-out built into the 10 inch poured concrete foundation).
Our installer is on vacation until December 2nd, so until I can discuss it with him I'm interested in getting as much info as I can.
First of all, our chimney has a combined flue for our living room fireplace and the boiler. If we line it with a reduced size stainless steel flue to reduce condensation and eliminate condensation damage to the mortar, that pretty much means our fire place is DOA correct, or will they be able to set it up so we can still use the fire place? It's just a standard fire place, not a wood burning stove.
Secondly, the installer said that the Buderus' flue exhaust temperature is so low due to it's efficiency, that even with proper sizing and lining, you can't eliminate condensation completely with a 2 story chimney because there is so much cooling off that happens by the time it exits 3 stories above, and it never runs long enough to really heat the chimney up and burn off the condensation. In that case, what do people do to control the moisture? I don't fancy having a water logged towel by our flue every night for the rest of our lives, even if it isn't damaging the chimney anymore. I believe the G115WS4 can be switched to a direct vent set up without a power vent(maybe I'm wrong?), but it would be VERY difficult to meet code with the orientation of our house, and exterior items where the venting would need to be, and costly to modify the chimney this way.
Well, we knew this was probably coming, now it is just a question of making a decision.