We recently moved and I'm trying to understand the furnace and hot water setup. It would appear that the previous owner put a great deal of thought and planning into home heating, so I'd really like to understand what I'm looking at in order to take advantage of it. The house has 2 boilers, a weil mclain series 3 oil boiler and a Tarm 404 wood/coal boiler. Initially, my purpose for investigating was that I felt that the oil furnace was running far too frequently. While the house is large, I believe our heat usage is below average. The house has 3 zones, of which zone 1 (upstairs) is turned off completely, zone 2 (half of 1st floor) is kept at 65, leaving zone 3 the primary zone. Despite using zone 3 most frequently, the thermostat is pre-programmed and the average temperature is 68. Plus, the room we use most frequently is an add-on sunroom with electric baseboards, opening to the kitchen (zone 3). There is no wall between the sunroom and the kitchen and the thermostat for zone 3 just inside the kitchen, often resulting in the kitchen and sunroom being much warmer b\c of the sunroom baseboards, but the other parts of zone 3 being a little colder. The other day I was in the furnace room playing with the Tarm boiler, trying to get a wood fire started. I noticed that the oil furnace would fire up about ever 3-5 minutes and run anywhere from 2-5 minutes before shutting off again. I've also noticed in the middle of the night if I get up to use the bathroom, more times than not I can hear the furnace running. So the other day I go down in an effort to understand the setup. The one interesting thing I noticed was that the oil furnace has what appears to be a tankless water heater. I recognized it because our previous house had a tankless hot water system running off the oil furnace. The reason I thought this was odd is because right next to the furnace we have a large electric hot water heater. I don't know if the electric hot water heater was an after thought, but why would I need to sources of hot water? I would think that this might explain why the oil furnace runs so frequently, being that it needs to maintain water temp for hot water. The previous owner (not the orig owner, that was 2 owners ago) told me that he turns off the oil furnace in the summer b\c if not, it would run frequently and kill him on oil. I don't need to mention that they still had hot water in the summer time with the furnace being turned off, proving that the electric hot water heater is providing hot water service to the house. I've posted a couple pics of the furnace, including one in which a copper pipe running from the top of the furnace runs up to a tank mounted in the ceiling. Hopefully the web of pipes might make a bit more sense to some of you than they do to me. What I'd really like to know is if it would be ok (and how) to disable the tankless hot water so that the furnace only runs for heat. I'd like to think that would dramatically cut down on my oil usage. Thanks for the help.