HVAC PRODUCTS/DESIGN MISCUES
Over the years, many promising inventions (and “improvements”)
have adorned HVAC equipment. Not all of
them proved to be of great value. Some
even turned out to be problematic, and remain in place on systems we encounter. The same applies to a few furnace and A/C
unit designs too. Trial and error is a
basic part of the design process.
That’s how “better mousetraps” come about. In any large industry, people all have different likes and
dislikes. Mine are quite similar to
those of most of my experienced colleagues.
We’ve all been fooled by smoke and mirrors marketing at least once or
learned over time that certain designs just didn’t work as well as expected or
created undesired side effects.
Olden day devices
white plastic box a local electric company installed on (or near) your
outside A/C unit with the homeowner’s consent many years ago, in order to
“reduce their peak demand”. In
return for allowing this to be installed on their systems, the homeowner
received a $10 a month discount for 3 months during the A/C season. The box contained a thermostat and a
timer mechanism, and it would cycle the outside system off for 5 minutes
every half hour after the outdoor temperature reached a certain number of
degrees. This would cause many
systems not to be able to keep up on warmer days. It also caused them to use more
electricity, because it didn’t cycle off the indoor blower system during
the off cycle. The program was
discontinued several years ago, but many of the boxes are still
installed. The electric company
doesn’t want the boxes back. And
they need to be disconnected if they are still there. The electric company will not send
people out to remove them. (The
electric companies are now using a different strategy to control, i.e.
minimize peak demand by installing radio controlled thermostats in
customer’s homes. This method
gives them more control over the peak demand than the old plastic box
“energy saving” boxes installed on or near the furnace that were supposed
to save you money on your gas bills by periodically cycling the electric
valve in the furnace that delivers the gas to the burners. The savings never seemed to materialize
and it could also cause acidic condensation issues and poor drafting
issues. These also need to be
removed or at least electrically disconnected. (As an amusing asides, I once ran a call where a gas company
technician had shut off and “red-tagged” the furnace because it was
“short-cycling”. The short-cycling
was actually the device doing what it was designed to do – cycle the
burners on and off.)
thermal flue dampers. These were
typically cylindrically shaped stainless steel housed devices installed in
the galvanized flue systems of furnaces and some water heaters. These devices had metal “fingers” in
them that were supposed to close off the flue system when
the furnace wasn’t running. When
the furnace came on, the heat would cause the fingers to “automatically”
open to allow the flue gases to travel through and go up the flue
pipe. The problem was that the
fingers would bind/stick in the closed position and not allow the
flue gases to exit. These
devices should either be removed and replaced with galvanized flue pipe,
or the guts should be ripped out of them, leaving only the stainless steel
housing. NOTE: These are NOT the
ones with the electric motor boxes on the side. Those are MOTOR OPERATED – not THERMAL flue dampers.
electronic pilot re-lighters.
These were just a bad idea.
They’re somewhat similar to the “trick birthday candles” you can’t
blow out. As soon as the pilot is
extinguished, the automatic pilot re-lighter automatically senses the absence
of a pilot flame and starts to spark until it senses that the pilot has been
relit. These are NOT electronic
spark ignition systems. These
were installed on only standing pilot furnaces (the ones
where the pilot is always on).
Here’s why they’re dangerous in my opinion. And I know for a fact that they are,
because I spoke to a gas man who got blown across the room because he
didn’t understand how that system worked.
If the thermostat is calling for heat and you turn the gas control
knob from the on position to the off position, the pilot
light and the burner flames both go out.
But like the gas man, if you then immediately turn the knob back to
the on position, the thermocouple device is still hot and will immediately
allow gas to flow into the burners BEFORE the pilot light
is relit. A very large volume of
gas enters the chamber and when the pilot finally does light, you
have a fairly good size explosion.
And you’re at the epicenter
of it (like the gas man was). If
you’re having a problem with frequent pilot outages, the cause of the
pilot outages needs to be diagnosed and corrected, rather than
installing one of these re-lighters.
The standing pilot system can also be converted to an
electronic spark ignition system as well (which will save on gas usage
too). I realize that gas company
technicians are not furnace technicians.
But it also occurs to me that they know at least as much about
furnaces as the average homeowner.
And it scares me that a homeowner could easily make the same
mistake the gas man made.
(horizontal upflow) cooling coils with very narrow condensate tracks
running under them to catch the water.
The manufacturer of this coil learned fairly quickly what a
disaster this coil was. These very
narrow troughs clogged up with gunk and water would run down into the
furnace. And you could not
clean the face of the coil either.
A/C units with horizontal condensers where the coils were facing
upward. Hail storms would often
flatten the entire face of the coils.
Imagine how a car radiator would fare if you laid it out
horizontally in a hailstorm, and you’ll get a pretty good mental picture
of the carnage.
A/C units with one piece vertically configured condenser with the hot air
exhausting out of the upper of the part of it on the same side as the
inlet air. These used a
double-shafted (expensive) condenser fan motor with 2 squirrel cage
blower wheels. The hot, exhaust
air would get sucked right back into the condenser inlet. As a result, the A/C system had to run
much longer and work much harder to cool the house.
refrigerant hoses running from the outside A/C unit to the indoor cooling
coils. They leaked like a sieve.
flue pipes on some of the older furnaces with really hot flue gases.
The plastic gave out causing dangerous flue gas leaks.
thermostats with little battery operated clock motors in them. Many of these even had proprietary
batteries that ran the clock motor.
You would set these little pins in the appropriate position for the
time you wanted the temperature to change. But they’d typically get stuck in the wrong position.
that pulsed the combustion system.
Big recall due to flue gas leakage. The design was abandoned.
(Lots of them still out there and working okay though).
hot surface igniter and flame sensor in furnaces. The hot surface igniter also served as
a flame sensor. It didn’t work
out, and the conversion kit to convert the furnace into a conventional
design cost an arm and a leg.
efficiency, high voltage electronic air cleaners that caught fire when the
high voltage arced and ignited the plastic inside them.
washing, high voltage electronic air cleaners. These were monster size boxes, almost as big as a
furnace. They had water and a
drain system plumbed to them. They
actually washed out the cells. I
only saw 2 of those – the electronics were fried years before in both for
that sprayed water into the ductwork.
No explanation necessary.
efficiency A/C system made in the early 1980’s. Very few of these were sold (luckily). The contraption I saw was about 5 feet
tall and 4 feet square, and this was merely the smaller 2.5 ton
version. It had a little tiny fan
motor up in the top, and a tiny little compressor down in the bottom that
looked lost in that expansive area.
The problem was that the volume of refrigerant in the system was
over 15 pounds and the little reciprocating compressor just couldn’t
handle it. So they ate compressors
for lunch. I did a warranty
compressor replacement on one of these, but only under the condition that
I would add numerous devices to ensure the survival of the replacement
compressor. The system lived a
long, happy life after that, and was extremely efficient by early 1980’s
standards. These were only made
for one year for obvious reasons.
control in the outside unit that varied the speed of the condenser fan
motor as the temperature varied.
These controls had a very high failure rate.
layer, sealed, permanent “washable” furnace filters. You can’t wash the middle layer
out. Dirt continues to accumulate
in that uncleanable center layer until it finally kills the system
airflow. One of these I’ve seen
had another “novel idea” – a round, plastic whistle in the middle of
it. The whistle was supposed to
whistle at you through the ductwork when the filter became restricted and
needed to be cleaned. (Dirt
plugged up the hole and it never made a peep). The whistle also protruded out a ways, and it would get
caught and pulled apart when you inserted or removed the filter through
the filter slot, leaving a big round hole for dirt to go through the
“water assisted cooling device” for outside A/C units. These spray water on the outside unit’s
condenser coils on demand to help it work more efficiently. Not a bad idea if you use distilled
water. The problem is that the
mineral build up can mess up the heat transfer through the condenser by
insulating it. When this occurs,
it can’t remove as much heat. Then
you have big problems, especially if you can’t remove the scale – without
damaging the condenser. Air cooled
condensers aren’t designed to be used as waterfalls.
made/treated filters. Some
disposables have this feature and some of the permanent ones have it
too. It’s supposed to give you
better particle trapping efficiency.
These are supposed to create like a “static cling” effect when the
air moving through the furnace filters causes the fibers to move
around. So the dust particles will
supposedly be captured more efficiently.
The problem is that in literally no time at all, a fine coating of
dust covers them and disables/insulates the static field. You still have filtering, but you lose
that extra amount of filtration afforded by the electrostatic. ASHRAE (our rating standard) prohibits
the filter manufacturers from including the slightly higher initial particle trapping rates in the filter’s
MERV (particle trapping efficiency) rating for this reason.
filter sprays. You buy this in a
spray can. It makes the surface of
the filter tacky/sticky. It’s
called a “tackifier”. Same problem
as the electrostatic methods – it doesn’t work once the dust covers
it. But at least if you’re
industrious enough, you could keep taking the filter out and respraying it
from time to time.
- I know
I’m going to catch some flack over this one. But sometimes you just gotta. Not all my colleagues agree with
me on this. AIR CONDITIONER
COVERS. I’ve seen some MAJOR
disasters occur when the system got turned on with the cover on
it. That can really mess up
your unit when it happens. Don’t’
think it can’t happen. You
could be the only person who knows that cover’s on there. So if you have a house-sitter while
you’re on vacation or you’re in the hospital, etc. it can happen. And an electrical malfunction can also
turn the outside unit on without the thermostat even being turned to the
cool position. Obviously you could
turn the A/C breaker off when you put the cover on it, but if you don’t
remember to turn the power back on to many units 24 hours in advance, they
can be damaged the first time you turn them on. I saw a setup at a customer’s house once that was pretty
ingenious. The lady had a piece of
screen with a couple of 2 by 4’s on each end laid over the top of the
unit. So if it did come on, the
air could at least move through the screen.
replacement silicon nitride hot surface igniters for replacing OEM silicon
carbide igniters. I understand
that some of these designs work better than others. But the first and second long, skinny,
stick shaped models I tried only worked for 8 days, and 2 weeks,
respectively. These were
supposedly “appropriate replacements” for the silicon carbide igniters I
was replacing. For those of you
that don’t know, silicon nitride igniters typically last a lot
longer than silicon carbide igniters. But most silicon nitride igniters are being powered
with only 70 volts, whereas the typical silicon carbide igniters
are being powered with 120 volts.
But the manufacturer of the after-market replacement silicon
nitride igniters claimed that their design would allow the use of their
igniters in a 120 volt circuit.
But I found that both of the ones I had purchased split down
the middle from the combined heat of the flame and the extra voltage that
makes them run much hotter in a 120 volt vs. a 70 volt power
environment. After discussing this
later with some friendly competitors, I learned that I got out lucky. They had purchased dozens and had
experienced the same issues I did.
drop-in replacement refrigerants for R22 systems. Some of these come with a penalty of
less BTU output of cooling power from the A/C system.
“home improvement store” pleated furnace filters. These can literally destroy your
furnace and A/C unit. The
restriction to airflow is unbelievably high, and to make matters worse,
the frames are extremely flimsy.
They end up warping and allowing dirt to pass around them, which
can damage your system. I’ve seen
several of them turn into sails and end up getting stuck in the blower
motor, where they can wreak all kinds of havoc. See the furnace filter tutorial page for more information.
gas control valves. We jokingly
refer to them as “dumb valves”, especially when they don’t work
properly. These are gas control
valves that actually contain a processor. These have a history of problems.
humidistats. This is a really neat
concept. Hopefully they’ll get the
bugs ironed out someday. The
humidistat has a processor that automatically adjusts the humidity setting
for your furnace humidifier as the outdoor temperature changes. I’ve seen a lot of problems with these
systems. Granted, some of them
were not properly installed per the manufacturer’s instructions. But others were and many still
failed. The remote (outdoor)
sensors fail a little too often for my liking.
thick electronic air cleaner filters.
These just don’t have enough surface area to be effective.
steam humidifier systems. This is
another fantastic concept. But
like anything else, it’s a better idea to wait until they iron the bugs
out, especially all that racket when they vibrate the ductwork they’re
mounted to and the water leaks.
And they’re extremely expensive units too, typically costing up to
5 times as much as a conventional humidifier. I saw one brand that actually cost ten times as much
as a conventional unit. But when
they’re properly installed, they can humidify your house using a small
fraction of the water used by a conventional humidifier.
damper controlled residential zoning systems. When properly installed with good quality components and adequate
ductwork these systems have a lot of potential for people unlucky
enough to have only one system for a large 2 story home that really should
have been built with 2 systems. So
far I’ve been sorely disappointed, having only seen damaged equipment and
poor performance, typically much worse than you’d see with a 1 system
configuration without the zoning installed. The problem is usually that there just wasn’t enough duct
capacity to support the dampered zoning system, and no easy ways to add
more. So you’re left without much
to work with when configuring the zoning system. There are numerous workarounds, but the extent to which they
can be applied is limited in scope when the duct capacity just isn’t
there. The A/C system and furnace
both need x amount of airflow per minute moving through them. And they aren’t happy campers when they
don’t get it. They’ll voice their
disapproval by rewarding the energy companies and/or repair companies with
more of your hard earned cash.
Some of the commonly used, manufacturer recommended workarounds
result in decreased BTU output and/or decreased efficiency.
type humidifiers. These have a
motor that turns a media wheel through the same water, i.e. no water flows
through them and goes down the drain to keep gunk and mineral
accumulation at a minimal level.
They use a float mechanism, similar to the ones found in a toilet
to maintain the water level at a specific height in the humidifier. But just like toilet floats, the float
ultimately fails to shut off the water.
So the tank overfills until the water reaches the overflow hole
and (if you’re lucky) runs out a
drain hose. When that happens,
water goes straight down the drain 24/7, like a toilet that keeps
running. If the hose clogs, the
water goes into the ductwork and sometimes the furnace and rots them out,
before ultimately ending up on the floor.
But at least the humidifier is getting purged of some of the built
up stuff when that happens. Very
few of us in this business have installed these type units. Most of them we see were sold through
department stores or home improvement stores. We on the other hand typically prefer the “flow through”
models where all the water drains out of the humidifier via gravity when
the furnace turns off. And that’s
the type most of us have on our own systems, because we don’t
need to “drum up” business at our own house.
hair media, permanent, washable filters.
These aren’t really made of hog’s hair – they just look like
it. These are better relegated to
use for “door mats” to wipe your shoes on than for air filters. They are just too limp to maintain
their shape, because they have no frame around them. So they tend to curl up around the
edges and let all the dirt bypass them.
So if you have one of these in your system, replace it with a real
furnace filter. Then cut the hog’s
hair one into the shape of a hog and put it on your stoop.
humidifier water panels, AKA humidifier filters. This product is so bad that the results are almost
comical. Humidifier water panels
typically reside in a vertical position inside the furnace humidifier and
are honeycomb shaped. So the water
dribbles into the top of them and runs down through them via gravity in
diagonal back and forth downward paths.
These are typically made of thin, flat aluminum with a “wetting
agent” applied over it. The home
improvement stores are now selling these cheap replacement models that
have paper attached to a honeycomb shaped, extremely thin wire
frame. So what happens when you
keep running water over paper? The
paper goes bye-bye. You look
in there and you see what looks like a partially decomposed skeleton of a
frame made of trash bag tie wires with the paper stripped off them. So the water coming in the top of the
humidifier just falls directly to the bottom of the humidifier without evaporating. But where did the paper GO? I found the answer to that question
immediately when I saw a humidifier leaking water, because the drain hose
coming out the bottom was plugged up with PAPER. It wouldn’t be so bad if they at least
stated on the box that they were paper. Some tell you that you should change them twice per
heating season. They just don’t
tell you why they should be changed twice instead of once per
heating season. Being a
somewhat artistic person, I can think of one good use for these. You could create a paper sculpture by
controlling the rate of water flow into the top at varying rates from side
to side. So it’s artwork created
by the process of removal over time – like woodcarving or sculpting. Then you could paint them and sell them
as “water panel art”. Paper has
its uses. It just doesn’t work
well in some applications involving water, which is why we don’t see much
Hat” flue caps. The last thing in
the world we want to happen to our flue gases coming out of the flue on
the roof is for them to be forced back down the flue pipe by the
wind. This can cause the flue
gases (containing carbon monoxide) to come out of the appliances inside
the house. At the very least, it
will blow out the pilot or cause nuisance lockouts on newer
equipment. Oddly enough, the Roman
Hat flue caps were designed to prevent that, but more often
than not, they cause it.
These things look like the battle helmets worn by the Romans, hence
the name “Roman Hat”. The idea is
for them to work like a wind vane, and turn the opening where the flue
gases escape in the opposite direction from the way the wind is blowing
from. But the flue system is a
very hostile environment and eventually the Roman Hat ends up permanently
stuck in one position due to corrosion of the pivoting surfaces. And obviously a wind coming from
the direction the opening is facing is going to force the flue gases
backward when that occurs. I’ve
also seen these attached to fireplace flues on the roof as well.
attic ventilation turbines. These
were initially thought to be energy saving devices. But I’ve seen studies indicating that
in many cases, they can cause you to use more energy. And they typically don’t provide as
much ventilation as the standard 8” round attic rooftop vents they replace
when no wind is blowing or when they get stuck and won’t turn. Contrary to popular belief, the primary
reason why codes mandate attic ventilation is to ensure that we don’t end
up with condensation in the attic during the winter. Yes, the attic ventilation does also
provide the added benefit of removing some of the heat from the attic in
the summer. But its primary
purpose is to prevent winter attic condensation issues. If you have inadequate attic
ventilation, the moisture from the living area can migrate up through the
attic as humidity contained in the air in the winter. And when it reaches the much colder
surfaces in the attic, the relative humidity of that migrating air
skyrockets. When it reaches 100%,
it condenses on the building materials in the attic. A properly sized attic ventilation
system prevents this from occurring by creating a continuous flow of air
through the attic, though inlet vents and outlet vents. The problem is, that if the turbines don’t
turn, they provide less of an escape route for the attic air than the
standard 8” roof vents do. So we
can end up with inadequate air movement volume to prevent the attic
condensation from occurring in the winter. And here’s the other totally different problem in either
winter or summer. The
faster the outdoor wind speed is, the faster the turbines rotate. Keep in mind the fact that the inlet
openings where the air enters the attic are a fixed size. The faster the turbine rotates, the
more of a negative pressure it places the attic in, because it can’t move
enough outside air into the fixed size air inlets. Here’s what happens then: A portion of the air from the living
area that you’ve already paid to heat or cool is literally being sucked up
into the attic and forced out of the attic through the turbines on the
roof, running your energy bills up by making the furnace or A/C have to
run longer. Ideally, the attic
should be fairly well sealed off from the living area, but that is rarely
the case, especially in older homes with ceiling mounted can lights,
bathroom fans that terminate into the attic, unsealed common areas between
the living area ceilings and attic floor, etc.
attic ventilation fans. These are
not what we call “whole house fans”.
These are typically fan systems that blow the air out of the
attic. It’s like a powered
version of the rooftop turbines previously mentioned. These units are typically installed
with adjustable thermostats that turn the motor on automatically when the
attic reaches a certain temperature.
And the thermostat is likewise supposed to turn it off again when
the thermostat senses that the attic temperature has dropped x number of
degrees from the setpoint. The
problems here are twofold. First,
they are subject to the exact same problem as the turbines, i.e. they can
put the attic in a negative pressure and cost you more energy
dollars. And secondly, studies
have shown that these fairly large motors use more energy than you save by
getting that heat out of the attic.
But then someone came up with a very clever invention – a solar
powered attic ventilation fan.
The problem was that the initial cost of the unit was so
great, it would take it 20 years to pay for itself in the form of
reduced cooling bills.
filled A/C condensing unit pads that the outside unit sits on. These are very lightweight pads with
some type of foam covered in plastic.
They just aren’t strong enough so they collapse and come apart.
boosters”. These are small, inline
blower systems, typically designed to be installed in a duct serving an
area that is hard to heat and/or cool, usually due to a lack of adequate
duct capacity serving that area.
I’ve seen quite a few of these, but have yet to see one perform
effectively enough to justify the initial cost and the power consumption
over time. It’s typically just a
drop in the bucket improvement scenario.
Greater Kansas City including:
Kansas Kansas City, Kansas
Kansas City, Missouri
2009 Leonard Arenson Heating & A/C
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