We first heard of small, highly efficient, condensing boilers from Melissa when she did our Energy Audit. After some research, I found many recommendations for the Triangle Tube boilers. They have stainless steel heat exchangers, and copper piping. They are among the most efficient boilers on the market today, although a flyer came with the boiler that placed it at 90% efficient, vs. the 93.5 or 95% efficiency that is advertised for this system.
In a condensing boiler the water returning to the boiler may be quite cool, unlike a non-condensing boiler that must have warm water entering the system. Energy is actually derived from cooler return water making the boiler even more efficient. The flue extracts heat from the waste gasses by condensing them into liquid. There is a condensate drain to channel away the slightly acidic waste from this process. A fan is used in the boiler to exhaust the remaining gasses from the system and an outside fresh air intake is employed. It is possible to use a concentric vent (two vents in one) so that both fresh air and exhaust are in one pipe. Using this special vent pipe will allow the use of the existing flue from the old boiler system.
The boiler saves a lot of room in the utility area, it hangs on the wall and is only 9 1/2 inches deep, 17 3/4 inches wide and the C105 version is 25 1/2 inches tall. Two three inch pipes above the boiler will be connected to the concentric flue where the existing flue exits through the roof.
Domestic hot water, heat, gas and electrical connections are on the bottom of the boiler. Internal flue pipe (black) is on the left, fan on the right. There is a 2 gallon tank behind the fan that is used in the domestic hot water function. UPDATE: There is no tank in the Challenger–the specs I was using were from another line of Triangle Tube boilers. The heat exchanger in the Challenger is aluminum not stainless steel.
The boiler is capable of delivering 2.5 gallons of hot water per minute. With low water spigots and shower heads that should be plenty without a separate storage tank, although the system is also able to incorporate an extra storage tank to hold a reservoir of hot water for peak use times. Hot water circulation is also possible as long as there is an aquastat control in the circulation pipe to prevent constant flow.