What Determines SEER Rating? If you have been in the market
for a new central air conditioning system, you have been researching online or getting quotes
from a few HVAC companies installing new systems. Undoubtedly, you have been hearing terms like SEER
and EER ratings. What is SEER and what influences the actual rating of the system you will buy?
If you go on to AHRIdirectory.org to find out what’s involved in measuring these SEER ratings,
you'll find terms like Wet-Bulb, Dry-Bulb, Static Pressure, Enthalpy, Steady-State Tests, and Cyclic
Tests. But it really comes down to a few things. 1. The outdoor condenser coil.
2. The indoor evaporator coil. 3. The compressor that pumps the refrigerant
4. The blower motor in the furnace pushing the air across the coil.
The condenser coil – Ever wonder why the outdoor air condensers we are installing today are larger
than the ones 20 years ago? Heat transfer and surface area. The outdoor condenser coil can
take the heat absorbed inside and get rid of it easier when the unit's surface area is larger.
The evaporator coil – Jeez! Talk about getting larger.
The evaporators are almost as big as the furnaces we are installing today.
Some of the larger evaporator coils are 30 inches tall or more. Again,
it's all about efficiently absorbing heat and humidity from the house and sending it outside.
The compressor – Today's modern scroll compressors have minimal moving parts. There are single-speed
compressors, two-speed, all the way up to fully modulating. The scroll compressor can move more
refrigerant in a single cycle than previous versions, like the rotary and piston compressors.
The blower motor in the furnace – Motors are more efficient when they run at lower speeds.
A 3-ton air conditioner blower motor will run at one amperage,
while a 5-ton blower motor, with its speed taps adjusted down to a 3-ton capacity, will
run at less amperage than the 3-ton motor. That lowers the amount of energy used by the system,
increasing its SEER rating. Let's look at the SEER ratings
on AHRIdirectory.org for a Trane split system where the AC/condenser is located
on the side of the house, and the furnace is located in the garage, closet, or attic.
In the example, we have the same 4TTL6036A1 condenser. In model number nomenclature,
the first "6" in "6036" means 16 SEER. The "36" stands for 36,000 btu capacity - a 3-ton system.
We can adjust the actual SEER rating of this "16 SEER" condenser by changing the
evaporator coil and furnace matched up with it. See here where we have the same size condenser,
the 4TTL6036 and same furnace with the much larger blower capacity,
but when we use a 005 coil instead of a 007 we get a little lower seer rating.
And on this next screenshot on AHRIdirectory.org we can see we’re using the same outdoor 4TTL6036
condenser, and we use a 003 evaporator coil, and we also step down to a furnace with a
4-ton capacity producing 150 cfm’s less airflow across the coil than the 5-ton air handler.
The outdoor unit determines the “size” of system you are buying. So normally we’d just match you
up with a 3 ton condenser, a 3 ton coil like the 003 above, and a 60,000 btu 3 ton air handler.
And, in this case you still end up getting a 16 SEER system (with only 975 cfm’s of air.)
But our questions was, the outdoor unit says, “Up to 17 SEER. So, am I getting 17 SEER or not?”
It depends on the match-up or model numbers of the units you actually have
installed. This is something you can really pay attention to.
You can ask for the AHRI certicate to see what SEER rating your unit will really be, if you want.
When you use bigger coils and bigger furnaces with your “3-ton system,” you’ll pay more for
them than you would if you just went with the 3 ton evap coil and 3 ton furnace, which in this
case still got you a full-on 16 SEER system. But that’s not always going to be the case.
Let's talk about how much cost savings you can expect when buying a system with, say,
a 16 SEER over a 14 SEER in my next blog. If you really want to nerd out,
we put actual dollar amounts behind the SEER ratings and compare them
with a calculator I made for my website. If this is your first time watching our channel,
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Thanks so much for watching, and we’ll see you on the next video!