- Manual J A/C sizing
Another unique service we
provide to builders and homeowners is Manual J A/C Sizing.
Sizing
Heating and Cooling Systems
Older space conditioning systems (more than 10 years old)
are often unreliable and much less efficient than a modern
system. When it's time for a new replacement, choosing one
of the correct size (heating and/or cooling output) is
critical to getting the best efficiency, comfort, and lowest
maintenance and operating costs over the life of the new
system. Some national surveys have determined that well over
half of all HVAC contractors do not size heating and cooling
systems correctly.
The most common sizing mistake
in new home construction is over sizing. This not only makes
the system more expensive to install, but also forces it to
operate inefficiently, break down more often, and cost more
to operate. Oversized heating equipment also often creates
uncomfortable and large temperature swings in the house.
Oversized air conditioners (and heat pumps) do not run long
enough to dehumidify the air, which results in the "clammy"
feeling and unhealthy mold growth in many air-conditioned
houses.
Manual J: The
Correct Way to Size a System
Correct system sizing requires considering many factors
other than simply reading the nameplate of the existing
unit. Key factors for correctly sizing a heating and cooling
system include the following:
- The local climate
- Size, shape, and
orientation of the house
- Insulation levels
- Window area, location,
and type
- Air infiltration rates
- The number of
occupants
- Occupant comfort
preferences
- The types and
efficiencies of lights and major home appliances (which
give off heat).
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