RE: High Efficiency HVAC -
the Good, the
Bad, and the Uncomfortable
Dear Website Customer:
Just because they sold you high efficiency
doesnt mean that it really is. Well
before the Department of Energy developed any standards for rating
the output and efficiency of HVAC equipment, consumers asked for
higher efficiency, and manufacturers competed for industry leadership
by racing to be first to the table. Contractors have installed
these products in many cases without any regard for the subtle
requirements of these systems, and subsequently, many of these
systems never obtain the expected efficiency or comfort.
First, lets discuss the key rating
systems in place by the Department of Energy.
AFUE - Annual
Fuel Utilization Efficiency is a measure of the percentage of
heat output to the space versus the amount of fuel that is burned.
(80% is average, 96% is the highest)
Seasonal Energy Efficiency Ratio is a measure of the percentage
of cooling output to the space versus the amount of power that
is consumed. (10 SEER is average, 12 SEER is extremely good,
16 SEER is the highest)
In determining AFUE, SEER, or any one of
the other various efficiency ratings in our industry, each test
in done in strict accordance with extensive published test procedures.
These laboratory conditions are impossible to recreate in your
home or business, but with strict adherence to installation guidelines
we are able to get imperceptibly close. The following is a short
list of the considerations we must examine in order to best provide
the comfortable, high efficiency system you paid for:
- System size - Higher
efficiency equipment is not as tolerant to the old rule of thumb
sizing estimates once used in our industry. It is very
easy to undersize when moving up to higher efficiency, this will
obviously result in poor comfort and longer running hours of
your system. If the system is oversized, many times the space
will feel humid and muggy, and system efficiency may be compromised.
- Ductwork - You
can put the best system in the world on old, leaking, or poorly
designed ductwork and never obtain comfort or efficiency.
Ductwork is always a factor in system replacement or installation.
Dont let your HVAC company overlook it.
- Matched Equipment - Mixing and matching different components on a
system are not by definition a problem. But, it is imperative
to perform the engineering to verify that the sizing of each
component are designed to work with each other for maximum comfort
and efficiency. Although there is no published data on mixing
a Lennox cooling coil with a Carrier condensing unit, many times
we can determine the viability of the match. To be 100% sure,
always use all components of the same manufacturer with certified
Of course this is just a short list of the
major items. We must always pay attention to the special requirements
of each specific product as described in the original installation,
service and operation documentation provided with the equipment.
If you would like data on your specific
HVAC equipment or a reprint from any of the efficiency rating
articles we have in our library please do not hesitate to give
me a call at 214-631-1010. I look forward to hearing from you.
KAHN MECHANICAL CONTRACTORS