I wasn't able to convince him. He just couldn't get past his habit of oversizing boilers. Old habits are hard to break.
But here's something to consider. Most hot-water-heated homes are over-radiated. You can make this work in your favor. Whenever there's more radiation than the job needs you can take advantage of that by running the boiler at a lower temperature, or better yet, on an outdoor-reset control that will follow the weather and maximize the savings.
Here's an example of what I'm talking about. Let's say you have a room with a heat loss of 5,800 BTUH. If you put in 10 feet of 3/4" baseboard and supplies it with 180-degree water, you’ll match the heat loss on the design day because 3/4" baseboard puts out 580 BTUH when there's 170-degree average water temperature water flowing through it.
But suppose someone before you installed 15 feet of 3/4" baseboard instead of 10 feet? He just ran the stuff from corner to corner. With the same temperature water flowing through it, 15 feet of 3/4" baseboard will put about 8,700 BTUH into the room. That's too much. The burner will cycle too often and the combustion efficiency will suffer.
But since this extra baseboard is already there, you can take advantage of it. Try running 150-degree water through it. At 150-degrees, each foot of 3/4" baseboard will put out 380 BTUH. Since there's 15 linear feet, it will put 5,700 BTUH into the room. That's just about right for the coldest day of the year. It costs less to operate the system at 150 degrees than it does to operate at 180 degrees. To protect the boiler from low-temperature return water, all you’ll need will be an inexpensive Thermic valve, such as ESBE makes:
ESBE Thermic Valve
Combine lower-temperature water with a properly sized boiler and the homeowner wins every time. So does the contractor.
Respectfully,
Dan Holohan
"Plumbers Protect The Health Of The World."
