Philosophical question

Rob Sisk

I am restoring a 1918 vintage home with a vapor-vacuum two pipe steam heat system. The boiler is enormous as the house has some 1750 sq ft of radiation, though I keep the thermostatic valves on roughly half of the radiators closed in the less-frequented rooms of the house. It takes roughly 20 minutes to generate steam from a cold start. I have installed a programable thermostat. My question is this - Which thermostat philosophy is likely to be more efficient? Set the thermostat to allow the temperature to drop dramatically overnight and during the day when no one is home or maintain temperatures in a tighter band to keep the boiler warm? As a corrollary, should I set the dead band tightly to a degree or two or should I widen it to 4 or 5 degrees?

Fred Harwood

Steam

One old stone house I consult on has over 3,000 sq. ft. of radiation in a 1928, two-pipe vapor-vacuum system. it also takes 20 minutes to heat all mains from a dead cold start. Subsequent heating calls provide almost instanteous heat to the rads. However, I have added a Vaporstat, removed all vacuum vents, and vent at the boiler receivers through two one-inch openings into the boiler room. It has four zones, three of which are motorized, one (baths and dressing rooms) receiving steam with each call for heat. I employ three Honeywell Rounds, which maintain respective zones within one degree of setting, no daily setbacks. Per square foot of living space, the building uses significantly less energy (Western Mass.) than does a 2,000 square foot modern home. Because of the quantity of masonry, inside and out, comfort requires no more than 4 degress of daily setback. Unused zones may be turned off, but must be turned on well in advance of use just to rewarm the masonry. In short, the amount of setback in a "tuned" vapor system matters most to the occupants' comfort needs.