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The single biggest mistake that HVAC salesmen, technicians and
consumers make when it comes to comfort system sales is what I like to call “Appliance Mentality”. Appliance mentality
assumes that if you purchase the greatest and best product you will magically get the best efficiency and performance, just
like buying a refrigerator or a washing machine. The problem is, unlike an appliance, a central comfort system’s reliability,
efficiency and capacity have more to do with planning and installation than it has to do with the actual equipment itself.
This is not to say that the type of equipment is not important, but even the best system will not operate correctly if even
the smallest detail is overlooked. Here are some of the most common portions of a comfort system that receive little, or no
attention during the average sales appointment and system installation.
1. Existing Duct Size – Attaching
a new comfort system to inadequate ducting is the equivalent of buying a new car, then blocking the radiator with cardboard.
Efficiency, reliability and capacity all rely on a properly sized duct system. Two steps should be taken before installing
a new comfort system. First visually inspect the size of the ducts and compare the sizes to ACCA Manual D, the Trane Ductulator
or the duct manufacturers specifications. Secondly, (assuming the existing blower is operational) take an external static
pressure reading on the existing system. If the external static is high on the old system (above 0.4 for a typical residential
unit) then it will certainly be too high when the new equipment is installed.
2. Air
Distribution – One of the most common complaints I hear from consumers who have just purchased new comfort equipment
is that they are still experiencing hot and cold spots in their home or office. The problem lies in the misconception that
new equipment will somehow alleviate air distribution problems. The fact is that the only way to address air distribution
is to face it head on before the new equipment is installed. The customer should be asked if they have hot or cold spots in
their home or office. If there is a problem it should be addressed by improving the duct design, adjusting manual dampers,
installing manual dampers if there are none, or installing an automatic zoning system.
3. Duct Condition –
Air ducts must also be inspected for leakage, insulation breakdown, kinks and proper strapping before new equipment is installed.
This will ensure that the efficiency that the manufacturer lists can actually be achieved.
4. Load Calculation
– There have been many instances in which brand new units must be removed because the same tonnage was installed as the
original without doing a proper load calculation on the space. If the equipment is too small, the space will not cool or heat
to the proper temperature during periods of peak load. If the equipment is too large, it will operate inefficiently and will
not properly deal with the latent (humidity) load. There are several load calculation computer programs that can be used to
easily check the loads against ACCA standards.
5. Copper Lines – I have seen far too many systems attached
to leaking, kinked or improperly insulated copper lines. The problem is that in most cases only a very small portion of the
copper is visible. This is why it is always a good idea to run completely new copper lines. Manufacturers specifications must
be read to ensure that the proper size, trapping and insulation guidelines are met. This is especially a must when it comes
to the installation of R-410a equipment.
6. Evacuation – Even the smallest drop of moisture can wreak havoc
on a comfort system. This is why a vacuum pump and micron gauge must be used to ensure that the proper level of vacuum has
been achieved. This step cannot be skipped or downplayed, if it, is major system problems and possible compressor failure
will ensue.
7. Refrigerant Charging – The problem with refrigerant charging is that every technician and installer
thinks that they have the surefire rule of thumb. I’ve heard everything from “beer can cold suction line” to
“about 200 head” and even, “They come from the factory charged correctly”. The fact is that only the manufacturer
of the equipment knows how their equipment should be charged, so unfortunately the factory literature must be read, and understood.
In general the superheat method is used of fixed metering device systems and subcool method is used on TXV systems. This means
that if superheat and subcool don’t ring a bell then you better hit the books, because the manufacturers specs might
not make sense otherwise.
The point is that even as the HVAC industry is making leaps and bounds forward in the areas
of equipment technology, the average technician and salesman are not capitalizing on these improvements. You will find that
consumers will want to hear what you have to say when you are giving real value by addressing the entire comfort system. You
may sell effectively when you are just “selling an appliance”, but how happy is the consumer when in the end their
refrigerator is working, but their new HVAC system is not?
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