Evaluating Efficiency
How Do I Determine Which Efficiency Option Is Best for Me?

First, we've updated this page to include problems we've encountered, and listing
some things too look for in your new variable speed, two stage system. Scroll
down.

We get a lot of questions about efficiency, and we were faced with the situation
ourselves
in 2009. Here's how to go about it.

AHRI (Air-Conditioning, Heating and Refrigeration Institute) operates a website
documenting approved combinations of heating and cooling equipment.

Input
www.ahrinet.org.

At the upper right corner of the home page click the blue button "Search the AHRI
Certification Directory". That'll take you to the Directory.

Click on "Air Conditioners and Air Conditioner Coils" or "Heat Pumps and Heat
Pump Coils" (You'll have to scroll down for that) under "Residential".

That'll take you to what looks like a pretty complicated Search page. Not to worry,
it's not all that bad: Click "Active" under "Model Status" (Upper right); Input your
outdoor and indoor unit model numbers below that; then select the outdoor unit
manufacturer in the third line down at the center. Click "NO" at the bottom
("Exclusively for Canada or Export"). Click "Search".

That brings you to your system ratings; operating costs are at the far right.

Clicking "Modify" at the upper left will enable to start your next search; repeat the
procedure until you've evaluated all your options.

Our options are listed below.

Weldin Residence Heat Pump (Bryant)

Option        Fan Coil           Heat Pump        SEER        Cost        Difference
01          FY4ANF024        213ANA024      13.00          N/A              N/A
02          FX4CNF030       213ANA024       14.50         $335           -$35
03          FV4BNF003       265ANA024       16.00       $1,099         +$99

Notes:
1.   “Cost” is the increment, with the 13’s ($1,717) as the basis; these numbers
are alleged to be “Contractor Cost” for the equipment, and do not include
contractor markup or installation.
2.   “Difference” is the increment in the ARI costs to operate, with the 13’s annual
operating cost ($568) as the basis; note that ARI believes the 16 will cost $99
more to operate.

Comments:
1.   Option #02 includes a fan coil unit (AKA "air handler") with a more efficient
blower motor; we chose it despite the long payback (9.6 years).
2.   Option #03 includes variable speed blower; it is truly a non-event in terms of
payback (Spending $1,099 adds $99 per year to energy costs).
3.   This replaces an oversized, improperly manufactured 2-1/2 ton 10 SEER
International Comfort Products system (See left).
4.   We’ll track savings.

Bryant offers an online Savings Calculator for dealers. We had a friend access
that to see what Bryant thinks the savings would be:
Option #02 - $42.00/year for an 8.0 year payback.
Option #03 - $54.00/year for a 20.4 year payback

Again we see the high tech combination makes absolutely no sense: Payback
exceeds service life; and then there's the high probability of having to buy a $1,000
replacement blower motor at least once during those 20+ years.

A Follow Up To Fred's Downsize

Fred returns from golf on Sunday April 26 and indexes the new system to "COOL"
for the first time; it's 91 degrees outside (that's one degree higher than the local
ASHRAE 1% value of 90 degrees) and 79 degrees inside. It drops the indoor
temperature 3 degrees in a little over two hours, by which time the outdoor
temperature has risen a degree. The GOOD NEWS is the system performs
flawlessly: There's air circulation and moisture removal, and it's comfortable. The
BAD NEWS is that Fred might have been able to downsize further: Lowering the
temperature three degrees in two hours in very hot weather indicates there's still
some oversizing.

Marketing High SEER – One Contractor’s Approach

We were recently contacted by a couple who were building a home; they’d been
presented proposals from a contractor for 16 SEER and 13 SEER, and wanted
advice (the price difference wasn’t much, you see). The cooling load was 3-1/2
tons, but because that line of 16 SEER units didn’t come in half ton sizes (don’t
know of any that do), 4 tons of equipment and ductwork was proposed; we
reviewed the proposal and asked why the contractor bid the 13 SEER at 4 tons,
instead of the 3-1/2 he’d calculated was necessary (13 is available in half sizes).
Needless to say, the price difference increased significantly and the couple made
what we felt was the right decision.

VERY IMPORTANT NOTE: 16+ SEER isn't available in half ton sizes; by going to
16+, you may be buying more capacity than you'll ever need.
Here's how to tell
whether spending
a lot of money on
"Bell$ and
Whistle$" is really
worth it.
As you'll see, Fred
went to 14.5, but it
was a stretch;
the additional
increment of cost  
to go to 16 wasn't
worth it.

HERE are Fred's
savings.

His total household
energy use
was reduced
more than 16% in
the first year.

That's about what
you might expect to
save when going
from a 10 SEER
(Fred's ICP was
less) to a 14.5.
The International
Comfort Products
Story

The builder bought
junk.
Note how the coil is
assembled: The
aluminum fins
protect the bottom
tube (at right)
against "rubthrough"
leaks. The damage
depicted in the
image sent to ICP
had to occur
BEFORE the coil
was assembled; that
is clearly an unusual
manufacturing
defect. That they
elected to "HIDE"
behind their
warranty speaks
volumes about this
manufacturer, and
viewers would be
well advised to
avoid their
products, given the
chance to do so
More of What Contractors Won't Tell You About Variable Speed

We've already mentioned the $1,000 blower motor you might have to pay for
some day (That's just for the part, remember); now let's discuss an airflow design
flaw introduced by variable speed.

Floor diffusers must be selected to project (The technical term is "Throw") air to
head height to properly cool a room. That's fine with constant volume systems,
but when you have a variable speed blower the throws will be less at "Low Cool":
A six foot throw at "High Cool" will become four feet or less at "Low Cool"; when
you consider that most systems are oversized, you realize that a variable speed
will rarely run at "High Cool". That means the throws will be less than four feet
most of the time.
Have you ever experienced the sensation wherein your
head's hot but the rest of you is comfortable?

Similarly, ceiling registers must be selected to throw the air to the floor to properly
heat a room.
Think about cold feet and ankles in the winter.

There are parts of the country that have very dry climates ("Negative grains of
moisture" is the technical term); the correct design approach in a dry climate is to
deliver a high rate of airflow per ton of capacity to minimize the dehumidification
capability of the air conditioner (450 CFM/Ton is used). Well folks, there are
contractors out there selling variable speed in dry climates as we speak, and
touting its ability to control humidity as they do so. Let's think about that:
If there's
no humidity to control, should I buy variable speed to control humidity....
YOU KNOW, THERE MUST BE A FEW EXTRA SIGNS AROUND HERE
SOMEWHERE. STEP RIGHT UP!
Yet more of What Contractors Won't Tell You: Variable Speed
and Poor Ductwork

Here are air delivery specs from a three ton 16 SEER air handler:
0.50" SP 266W
1.00" SP 425W
That's saying the blower will consume 159 watts more power at 1.00" static
pressure (typically met or exceeded with poor ductwork) than it will at 0.50" static
pressure (the most you'd find with proper duct design).

Doing a little math, we see the 159 watts will reduce the SEER to about 14.9; in
other words, the bad ductwork causes the system to use about 7% more
energy.


This is called "Bait and Switch": You bought 16, the contractor provided 14.9.
WHAT DO I NEED TO WATCH OUT FOR?

So you've opted for "Bells and Whistles", and bought into high SEER. Here are a
few things to keep in mind.


Make sure your ductwork meets today's standards - If you don't, you're just
wasting your time and money. For a fact, it's possible to save more on duct
repairs than improved equipment efficiency. For a fact, that hard to cool
room/floor is more likely caused by a duct problem than insufficient capacity.


Make sure it's the right size - It should run all day long at low speed in very hot
weather, periodically cycling up to high and back. If it doesn't get to high, it's too
big. If it cycles on low only, it's
REALLY too big. The correct fix for this condition is
to replace the outdoor unit (and possibly the indoor unit too - you must end up
with an AHRI approved combination). Don't accept a "band-aid" (lowering the
delivery from 400 CFM/Ton to 350 CFM/Ton) - You want a smaller system!


Make sure it works - Have the installer demonstrate to your satisfaction that the
blower operates at both low speed and high speed, and that the compressor
does the same. If you have doubts about the staging, ask him to point out the
wiring connections in the thermostat, at the indoor unit and at the outdoor unit, so
you can verify the "1" and "2" wires are all connected.

Make sure the blower is set for the correct airflow and tonnage. Typically, 400
CFM/Ton is used, but you'll need 450 in a dry climate or 350 in a moist climate.

Well, my installer's a reputable guy, why should I go to all that trouble? Because
we've documented three instances (so far) of too much capacity (cycling on low
speed only during hot weather, and there was mold growing)
, and installers who
didn't wire the second stage and/or set the airflow too high (no dehumidification
taking place, and mold was growing).