Thanks for the replies tigerdunes. • The insulation is average to good. There is about seven inches of fiberglass batt in the attic and all obvious thermal chimneys have been insulated (i.e.insulation over lighting cans, etc). We have insulation in the walls, but it would be that typical to 1960s and fair at best. We are considering adding another twelve inches of fiberglass batt to the attic but must address certain existing storage complexities. • Of the finished basement, 800sf is below grade and 400sf is at grade (400sf dedicated to a lower level garage is at grade but not included in the figures). • Electric (NStar) is $0.162/KWh unit cost (delivery and generation costs; fixed costs not included). Gas (National Grid) is $1.3463/Therm unit cost (transmission, distribution and supply costs; fixed costs not included). • The current furnace is and new furnace will be located next to the internal chimney in the front-center of the house, primarily because of front-center existing duct work but also for space considerations. • The venting of a high efficiency condensing unit would be somewhat problematic and aesthetically unappealing. If we went with a high efficiency furnace, then we would also like to install a high efficiency gas hot water heater, because it seems counterproductive to install a smaller flue liner for the existing gas fired hot water heater. Due to setback requirements and snow requirements, there may be a very tight area in proximity to the furnace where two exhausts and one intake could be installed; that area is close to the front door and would be unappealing to my wife and would require some additional carpentry work. I don't believe we have a straight shot up the existing flue because of the main floor fireplace, but I have yet to check. • We are unsure whether or not the existing furnace is short-cycling (i.e. shutting itself down for protection reasons). The cycles are certainly short, but I would guess not, only because we do reach thermostat set temperatures, although it wouldn't be a big surprise. • We have not received the Manual J; we have only been told the results from a whole house standpoint. We are requiring the receipt of the load calculations prior to installation but after a vendor has been picked. • The ductwork has been examined by the dealers. We have one large single return for the main level living zone, one large single return for the lower level zone, and a small return in each bedroom in the main level bedrooms zone; the returns are coupled as a common return prior to the furnace. The zoning, ductwork and returns are very good for the 1960s, but uninsulated and based on five inch supplies; so, the system would be undersized for today, I believe. All ducts are internal to the house, although some run through the garage; all ducts are enclosed and finished, other than those in proximity to the furnace. No modifications will be performed to the ductwork, other than any transition needed to the new furnace. • There is seven inches of fiberglass batt between the eight inch ceiling joists (R20). • The zoning control board will control the HVAC system. The new thermostats are dumb, although nicely programable and aesthetic (Aube/Honeywell TH141). In addition to a common (C), the thermostats accept 24V (Rh), heating (W), 24V (Rc), cooling (Y), and fan (G). The new thermostats do not have any second stage inputs or reversing valve input; we have five wires at our existing thermostats; the new thermostats can be battery powered. • The dealers are familiar with zoning, and with either a dumb-simple zoning control board for heating and air conditioning or a smart acculink system; they are less familiar with the combination of smart zoning control board and dumb thermostats or a dumb-sophisticated zoning control board and dumb thermostats. I am personally unimpressed with the smart thermostat systems; to much unnecessary/unused information; to expensive; to large and prominent. What are your thoughts? • The job is simple, although the air conditioning installation would be new but typical. It seems that I should have about $2500-$3000 in air condition installation cost and about $2500 in furnace installation cost and about $1000 in miscellaneous cost (including the $150 zone control board and the media filter), for $1600 in air conditioning equipment cost (2.5 Ton, 15 SEER) and $1800 in furnace cost (80K Btu, 80 AFUE). That would be $6000 to $6500 total cost. What is your experience for pricing of such a system?

I assume you have separate transformers for heating and cooling systems. If that is the case then remove the jumper between the R and Rc terminals. Connect the red wire for heating to R and the red wire for cooling to Rc. I think the rest of the wiring will work as long as you don't mix your similar color wires. You also have to program the thermostat for the correct heating and cooling system.

Trying to install a new Ecobee3 thermostat and have to run a "Common" wire up to the thermostat. Difficult to find any solid information on the Honeywell Aquastat L8048G online (just for the replacement controllers, which are not wired exactly the same as the L8048G). Attached is a diagram of the current (pre-Ecobee3) wiring (boiler, Taco valves, thermostats) - want to make sure it is correct. I have seen some wiring diagrams that show alternate ways to wire the thermostats and Taco valves, so want to make sure my current wiring is actually correct. It always worked before, but want to make sure nothing is installed incorrectly/backwards. The Aquastat has a built-in 24V transformer. How do I know which wire would be used for the COMMON wire? Assume blue wire on "T" would be the "Common"? If not, which wire/terminal would I use? Assume I can pull a common from the Aquastat board/internal transformer, but not sure. If not, should I purchase a stand-alone 24V transformer or the FAST-STAT Common Maker? http://www.fast-stat.net/ If that is the case, how would I wire one into the current system? Please review the diagram and comment/correct as necessary. The boiler has been seemingly fine for 48 years wired as shown, but see various ways to wire thermostats and valves to boiler and want to make sure it is correct. Most important issue is how to add a common wire to this setup most economically. Thank you for any assistance you can provide.

I don't think the CT87N thermostat is going to work with your oil fired boiler. Honeywell makes several variations of the old style round thermostat. The one made for heat only hot water systems is the CT87K thermostat. Page 3 shows a 3-wire installation. I believe your current B wire should be connected to the Y terminal. Both Y and W should be energized when the thermostat calls for heat. If that doesn't work then you can swap Y and W connections. The R terminal is always the 24 V power from the transformer. If you can't return the CT87N then call Honeywell and see if could be used. If you are going to buy another thermostat then consider buying a programmable type so you can program set back settings and save some fuel costs.