We respectfully dedicate this site to four groups:
  • Sussex County, DE Legislators and those with input to their decisions;
    Sussex County, DE Building Code Officials and independent Inspection
    Agencies; Contractors and installers responsible for the work
    documented herein - May this group soon see the error of its ways.
  • The Sussex County, DE homeowners, taxpayers and renters who have
    tolerated untold abuse and incalculable expense for far too long - May
    their lot in life soon improve.
  • The Delaware Board of Plumbing and HVACR Examiners, who are
    actively engaged in correcting the deplorable situation that has existed in
    Sussex County for far too long - God bless you all.
  • The precious few conscientious, knowledgeable contractors and
    installers who couldn't sleep nights if they installed ductwork as
    portrayed here; thanks for your efforts, people - May your tribe increase.


The purpose of this site is to assist homeowners with their heating and air
conditioning questions:
  • Why is my bedroom too cold?
  • What do you think about these proposals?
  • Should I repair or replace?

There are some types of questions we cannot help with:
  • Why is my clothes dryer making a funny noise? (Sorry, we don't do
  • My furnace runs three minutes and cuts off; how do I fix it? (Sorry, this is
    "Service and Repair" - We don't service equipment, we don't repair
    equipment, we can't help).
  • My compressor won't come on, what's wrong? (It's broken, see furnace

Any questions that can be answered within 10 or 15 minutes are done at no
charge. More involved questions (reviewing and commenting on images you
send, commenting on heating-cooling calculations from your contractor,
performing heating-cooling calculations, etc.) are quoted on a case by case
basis and prepaid through PayPal.

Thank you for visiting!

What's New?

We’ve just learned of a third local high SEER job that went terribly wrong. Like
the first two, the AC was so oversized that it could not control humidity running at
low speed. In all three cases, mold growth developed, costing the homeowners
thousands of dollars to remediate. We've updated the
Evaluating Efficiency page
to incorporate things you can check for in your new high efficiency installation.

We all know one reason to buy two stage equipment is to better control humidity,
so how can humidity be substandard with a two stage system? Well people, it’s
back to basics: The compressor must run for extended periods in hot weather to
properly dehumidify the home; so if low speed capacity is greater than the
cooling load, the compressor cycles on low speed, and you’re at risk. The ONLY
way to eliminate the risk of high humidity is to size the AC so that low speed
capacity is less than cooling load: The compressor should run at low speed
continuously, cycling on and off high speed, in very hot weather. That takes a
detailed cooling load calculation.

In the case of replacement equipment, selecting the new unit with low speed
capacity slightly less than original capacity doesn’t guarantee proper humidity
control, as one very reputable local contractor learned to his regret. He replaced
a 3½ ton single stage with a four ton two stage, trusting low stage capacity (67%
of 4 tons, or 2.7 tons) would be OK. Sounds good, right? NOT. Let’s discuss the
existing ductwork: It was so poorly designed and installed that the old air handler
could not deliver rated flow. The contractor didn’t perform the required duct
survey, and didn’t know there were design and installation issues (the excuse
given was “I didn’t want to price myself out of the job”). In fact, we estimated
original flow at about 1,000 CFM, or 2.5 tons; the original job was yet another
case of too much equipment and too little ductwork, probably bandaided by
reducing the refrigerant charge to avoid compressor problems.

Enter the new variable speed air handler. Unlike its predecessor, its motor has
the “muscle” to deliver rated flow through a restricted duct system (search
electronically commutated motor” sometime). Now we’re delivering about 10%
more cooling to the home AT LOW SPEED than we were before, and the new
compressor is cycling more than the old. As we all know, more cycling means
poorer humidity control. All it took to grow mold was a change of occupants: The
old occupant always set the cooling at 72º, and the new occupant preferred 75º.
Add more cycling due to increased delivered capacity to more cycling (and higher
cooling capacity) due to a higher setpoint, and mold develops. Had the
contractor properly sized the unit (3 tons), there never would have been an issue.
As it is, he’s in a bit of a “Sticky Wicket”.

Most contractors prefer to rely on a “Rule of Thumb” - square feet per ton -
instead of spending the time to perform a load calculation. Well, here’s a Rule of
Thumb for residential replacement jobs:


Is it foolproof? Maybe not, but it sure would have saved that homeowner a lot of
Why Employ
Engineering Co.?

We have no axe to
grind: We're not
selling product.

We have real
"Hands On"

We care: It's not
just another job.
Engineering Co.
Residential HVAC Specialists
Fibrous glass
ductwork (AKA
"Duct Board" or just
"Board") runs a
close second, in
terms of abuse.
Substandard board
installations such as
this can literally fall
apart. That doesn't
happen with metal
Flexible ductwork
(AKA "Flex") is the
single most abused
product in the
industry. We'll show
The Good, The
and The Ugly.
We always compare
calculated cooling
requirement with
installed capacity, and
we have never seen a
residential AC
installation that was
too small. Here's our
plan to remove about
25% of capacity from a
large luxury home.

Manufacturers publish ranges of airflows within which their heating and air
conditioning equipment must be operated. The important thing to note is that
operating below the minimum airflow greatly increases the risk of compressor
failure, especially in heat pump systems; there is also an increased risk of heat
exchanger failure in warm air furnaces.

IMPORTANT NOTE: Heat pump compressor failure the first heating season after
installation probably indicates low airflow; multiple failures increase the
probability that low airflow is the cause.

Nobody wants to fund a major, unexpected repair. Here’s a tip to identify airflow
problems, and to troubleshoot future problems: Buy a pocket thermometer with a
range that goes to at least 150° F (for furnaces - 120° F is fine for heat pumps);
digital types respond faster than dial types. Drill small holes in the supply and
return ducts at your unit (Caution: Don’t drill into the cooling coil whatever you
do!), and record temperatures in and out.

temperature difference (“TD”) between in and out is an important number.
In cooling, you should find 15º to 20º; if it’s significantly higher than that, you
probably have low airflow. If you have a gas or oil furnace, the nameplate will
specify acceptable “temperature rise” (30-60, 45-75, etc.); if your temperature rise
is higher than the specified range, you have a real problem with low airflow. If you
have a heat pump your TD in heating at 47º outdoor temperature should be 25º to

IMPORTANT NOTE: Call a professional if your TD’s are substandard; do not
change a thing until the issue is resolved.

IMPORTANT NOTE: Record your heating and cooling TD’s so you have
benchmarks for comparison after any changes, or if problems arise (
this is
especially important if you’re attempting air balancing

Troubleshooting Duct Problems with Your Thermometer

Supply Side: Measure temperature at unit outlet and compare with temperatures
at registers and diffusers; a difference of more than a degree or two could
indicate substandard duct insulation.

Return Side: Measure temperature at unit inlet and compare with temperatures
at return grilles; a difference of more than a degree or two could indicate
substandard duct insulation, or inleakage to the return duct (from unconditioned
spaces surrounding the ducts).

"Wasting Energy Efficiently"

The most basic things you need are an airtight, well insulated duct system and a
tight, well insulated home with good windows. When these basics are not
provided and high efficiency equipment (90+% furnaces, high SEER heat pumps
or air conditioners) is used, we say the home is
“wasting energy efficiently”.

The Economic$ of Contracting

The ideal job for a heating & air conditioning contractor is to pick up a window AC
at the supply house and deliver it to you for DIY installation: There’s no field labor
and no risk; assuming the guy’s not brain dead, he’s guaranteed to make a profit.

Taking this a step further, another type of ideal job is one with “high dollar”
equipment; thus the rise of variable speed, two stage, two speed, etc. This
increases the material to labor ratio, reducing the installation labor risk and
increasing profits; these types of units will also generate more expensive service
and repair business, a very attractive business proposition for those contractors
who are in it for the long run.

FACTS: Incremental savings from “bells and whistles” do not pay back quickly, if
ever; increased repair risk is huge. Learn how to evaluate efficiency options

FACT: Replacing a variable speed blower motor will cost around $1,000 for the
part at 2008 rates; installation labor and incidental materials are extra.

RATIONALIZATION: “But variable speed improves humidity control”.

FACT: So does properly sizing the AC.

FACT: Certain contractors have another motive for selling variable speed; now
they think they can safely increase sales by deliberately oversizing systems,
without the risk of uncontrolled humidity. Some of those contractors are well-
intentioned people, others are downright unscrupulous; it's hard to tell the

RATIONALIZATION: “But it cuts down on air noise”.

FACT: So does properly designing and installing the duct system; in fact, air
noise is one of the more important duct design criteria.

The absolute worst type of job is installing ductwork: Materials cost is low and
field labor
required to do the job right (do note the emphasis) is quite high; the
process is “labor intensive”. This presents the contractor a dilemma: He must
spend more of his money (
here’s an important concept - it is his once you sign
a contract, you know
) to do the job right; unscrupulous contractors profit by
spending too little time and delivering substandard duct systems (this is most
prevalent in large “cookie cutter” housing developments, where saving $50 or
$100 per house can put thousands of dollars in the contractor’s pocket). The end
result often costs too much to operate, provides substandard comfort levels and
generates high repair costs; in extreme cases, mold growth develops and
occupants can suffer various adverse health effects.
From top: Drilling a
3/16" hole where it
won't hurt anything;
supply temperature;
return temperature.
The difference,
about 16° F, was
within the
"acceptable range"
of 15° F to 20° F
(the heat pump
system was running
in the cooling mode
at the time).
The "Dirty Little

Now we get to the
"Nitty Gritty": If the
installer finds his
new system is low
on airflow (most
are), he'll simply
adjust the
refrigerant charge
to compensate.

It'll operate
forever: What
started as a 13
SEER is now
10 or 11; and
there's a
reduction in cooling
capacity (Your four
ton system may
then be delivering
three tons).

It happens all the

That's one reason
they sell you more
than you need:
It provides a
"Safety Net" for a
bad duct system.

Another reason is,
of course,
increased sales and
Interested in the
Weldin family?

Click here.
Did You Know?

"Manual J" is a
published be
"ACCA" (Air
Contractors of
America) that
describes how to
calculate heating
and cooling

Several companies
have developed
software to
automate the
manual process
spelled out in the

Again, Manual J is a
book; anyone using
the software must
first understand the
book to produce
accurate load
Did You Know?

A "Ton" is that
amount of heat
required to melt a ton
of ice at 32 degrees
Fahrenheit: 12,000
"British Thermal Units"
(AKA "BTU's").

A ton of cooling is that
hourly rate of heat
removal, 12,000
Fred's duct repairs
saved him nearly

Here is the

Fred's new 14.5
SEER reduced
household energy
usage 16% beyond
the duct repair

Here is that
Check Out Our

New Home Special
Here's a nice
article by Proctor
Group on the