- Q.What factors must be
considered when deciding whether to use a large hot-air
furnace with two zones or two smaller
furnaces?
A.Jeri Donadee, vice
president of H.B. McClure Co., a heating and
cooling contractor in Harrisburg, Pa.,
responds: A single unit is almost always more
cost effective than multiple smaller units.
Multiple units should be considered only if the
house design will not permit adequate means of
ducting the various zones from a single heating
plant.
With a single unit, the installed cost,
operating costs, and life-cycle maintenance costs
are almost always lower. If the customer wants
options like air conditioning, a humidifier, or an
air cleaner, the installed cost advantage in favor
of a single unit is even greater. Zone system
manufacturers claim that the operating cost of a
single unit can be 30% lower than the cost of two
smaller units.