Dedication
We respectfully dedicate this site to four groups:
Purpose
The purpose of this site is to assist homeowners with their heating and air
conditioning questions:
There are some types of questions we cannot help with:
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:
NEVER INSTALL A BIGGER UNIT THAN WHAT’S THERE NOW.
Is it foolproof? Maybe not, but it sure would have saved that homeowner a lot of
grief.
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.
Purpose
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
appliances). - 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
above).
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:
NEVER INSTALL A BIGGER UNIT THAN WHAT’S THERE NOW.
Is it foolproof? Maybe not, but it sure would have saved that homeowner a lot of
grief.
| Why Employ Weldin Engineering Co.? We have no axe to grind: We're not selling product. We have real "Hands On" experience. We care: It's not just another job. |
| Weldin Engineering Co. Residential HVAC Specialists |
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| 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 ductwork. |
| Flexible ductwork (AKA "Flex") is the single most abused product in the industry. We'll show you The Good, The Bad 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. |
BEWARE OF LOW AIRFLOW
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.
The 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
29º.
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 here.
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
difference.
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.
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.
The 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
29º.
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 here.
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
difference.
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). |
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| The "Dirty Little Secret" 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 inefficiently forever: What started as a 13 SEER is now 10 or 11; and there's a corresponding reduction in cooling capacity (Your four ton system may then be delivering three tons). It happens all the time. 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 profits. |
| Interested in the Weldin family? Click here. |
| Did You Know? "Manual J" is a book published be "ACCA" (Air Conditioning Contractors of America) that describes how to calculate heating and cooling requirements. Several companies have developed software to automate the manual process spelled out in the book. Again, Manual J is a book; anyone using the software must first understand the book to produce accurate load estimates. |
| 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 BTU/Hour (AKA "BTUH"). |
| Fred's duct repairs saved him nearly 15%. Here is the documentation. Fred's new 14.5 SEER reduced household energy usage 16% beyond the duct repair savings. Here is that documentation. |
| Check Out Our Recently-Posted New Home Special |