I've been doing some research in preparation for next year when I will
be replacing my gas furnace and a lot of people seem to mention that
the make of the furnace doesn't matter as much as the quality of the
installation ... but what exactly does that mean?
The furnance comes preassembled from the factory more or less so it's
not like the contractor is building the thing. How can a poor
installation ruin a good furnace? What makes it a poor installation?
Are we talking about the preparation part of the installation, like
getting the correct size (BTUs), proper chimney size, correct vent
sizes, etc. ... or are those persons refering specifically to the
installation part ... what can go wrong during that part?
P.S. The more technical the information you provide the better ...
Well I have seen plenty of systems the wrong size (too cold/hot).
And I have seen plenty of systems where one or more rooms are colder or more
hot than the others.
And then plenty of systems where it may be very cold around the outside
walls, and the problem with this is that the return ducts are located on
inside walls in each room (to save money on duct work I suppose).
*But* I have seen most modern commercial high-rise buildings which have very
good systems all around. Every room perfect temp.!
"Harry Muscle" wrote in message
However, since this is a remove and replace situation, will any of the
points you mention really apply? The house is prefectly comfortable as
is right now, it's just that the existing furnace is 35 years old.
The reason why I posted this question is that the comments I've read
about the installation being most important are usually part of answers
to persons just like me ... replacing a furnace, not a brand new
installation. I can understand a brand new installation where all the
duct work needs to be run, etc. That's a lot more planning and more
chance of things going wrong like you mention. But what can go wrong
when you're basically swapping in a newer furnace.
I have seen situations where the air flow was more than the old unit and the
duct work was not modified - caused problems. If same BTU, same air flow,
then this will reduce a lot of potential problems.
Then could be problems with a newer high efficiency unit. Old venting for
exhaust gases might not be right. Also venting for fresh air might need to
Then new code regulations may apply and modifications may need to be made to
bring everything up to code.
Old thermostat may have problems with new unit.
And of course do they know what they are doing? Know codes, wiring, etc...
"Harry Muscle" wrote in message
Not going to get techincal, but I will go to the extreme. Not trying to be
funny, but think about it:
Do you have a neighbor that has a 14 year old kid. Good! Tell him you will
pay him $100 to hook up your furnace.
There! You're all set....
What about the electrical, sheet metal and other plumbing connections?
I assume you did your manual calculations, for capacity and for air flow.
You know how to calculate the volume that your duct work can handle right?
What makes it a poor installation? Your kidding! What can go wrong,,,,, gee
the list is almost endless.
If your changing exact model numbers and the same manufacture then you MAY
have an easy go of it.
Lastly a qualified,licensed installer warranties the installation and
equipment. Most of the mechanical manufactures I know do not sell to
homeowners and will not warranty anything directly to an home owner.
Endless list...... Can you offer at least the first few entries to give us
In the OPs situation perhaps installation and features/efficiency are more
balanced in importance.
In a furnace replacement, at least some sheet metal will need to be
bent/formed to interface the new furnace to the old ducts. Naturally, here
is a place where workmanship can matter. Lead time can be effected too if
they need to go to a third party shop for sheet metal or can do it on site
in the back of the truck.
Furthermore, you may have chosen a furnace with different features which
must be accounted for. Building codes may have changed over the years so
what was done then may not be acceptable now. A good installer will know
this as second nature but a green guy might just swap things over 1 for 1
not knowing an upgrade was required.
Newer model furnaces have complicated control systems and sensors not found
on older models. It may not be obvious to a new owner or green installer if
something is set marginally wrong and the procedures for adjusting those
things may not be obvious. Reading the manual and calling tech support can
help but you need to know when you need to do that.
IMO the make, features and efficiency are most important while you choose a
model but the installation is most important when choosing a
dealer/installer. Since most dealers sell limited models and brands, You
will need to find the optimal point between these two factors. I would say
that if a dealer can answer your question satisfactorally, then use him.
Absolutely right. They are both important. I would just add that
reliability/longevity is also important for brand choice.
We did this about a year ago, and had about six or seven companies quote the
job (I know conventional wisdom is 3, but we just kept going until we felt
we had the right combination). You want a good installer, sure. But if the
equipment fails in 5 years the quality of the response you get will have
more to do with the manufacturer than the installer. And of course, a
reliable brand will be less likely to fail in the first place. The
installer we chose spoke authoritatively about the reliability/quality of
the equipment he was recommending, which gave us confidence in both.
There were some other responses and I'm going to add mine.
You hire a gent to install the furnace. It is 'preassembled', but does he
really know the right way? Does he know the local codes? Does he know that
brand A has a certian quirk the brand B dosen't? Does he service it and
know how to work on it if and when it goes bad?
Installation generally means two or three guys more interested in getting
off work than anything else. This means they'll take whatever shortcuts
they can and not really care about what they might do to your house, either
cosmetically or functionally.
We replaced our furnace and A/C a couple of years ago with similar units and
if I wasn't home and asking questions I would have had some pretty ugly
hackery done to my house, including fresh air vents where I didn't want
them, wiring where I didn't want it and a water heater moved(!) where I
didn't want it. All of what they would have done was for their convenience
in getting in and out as fast as possible.
As far as the specific equipment goes, generally that's decided pretty
easily by the sales guy who checks what you have and how well it works vs.
what he wants to replace it with. I agree that it's pretty largely a
drop-in replacement, but *how* its dropped in is what matters.
I'm sure there are some installers that are good as gold, but based on what
other homeowners in my area have complained about, I think they're rare.
Business, as usual, relies on volume and speed.
Harry how bout this - pay somebody to develop the specs, including pipe
layout, sizes and locations for intake and vent - then use your
"Muscle" and install the sucker yourself. I got a quote on a new HVAC
system installed with high efficiency air for around $7K for a 2,400 sf
1 story structure. Some parts of the country have really pricey HVAC
contractors - lots of demand now. At least get a quote from a good
installer/dealer and get an idea of about how much you could save - you
might find out your time is more valuable than your savings on a hourly
Ever see a chimney vented down hill?
Ever see PVC venting that did not drain condensation properly?
Ever see improper materials used for supply air duct?
Wrong gas pressure, or improper gas line size?
Ever see condesate drain from the AC coil improperly and ruin a perfectly
Ever see some one replace a furnace where the old duct work as inadequate
for the new unit, but it was fine for the old unit?
I have seen so much hacked up, shit installs I wish I could do something
myself to keep the crooks from ever doing business again!
There is so many points as to the difference to a good install compared to a
great install it would be impossible to list them all. USUALLY experience
will lend itself to a better install, assuming the installer gives a shit
what his work looks like!
One of the worst installers I have ever seen worked for the same company I
work for! ( No longer!) He knew it all, but in reality know very little. He
would do something wrong and you could show him in the install manual
proving he was wrong, but no, he knew more than the manufacturer!
When I do an install I take a few minutes to go through the manual, even if
I have installed the same equipment before, things change! I check my gas
supply to make sure it is adequate, even on a change out of similar
equipment. I measure duct work to make sure the duct is of reasonable size,
too big or too small is bad. I lay cardboard on the floor in the working
area to catch drips of pipe dope and PVC solvents. I use a level to get
pipes straight and neat. On start up I check amps, gas pressure, temp rise,
blower speed, AC pressures, super heat/sub cooling, and more depending on
what is required. When it is all done, I get a broom and dust pan from my
truck and sweep up the area, perhaps even wash the floor if needed.
I have seen installs where they set the furnace in place, hooked up the gas,
duct, and vent then start it up and run. . Not one test was made to ensure
it was running properly and the install manual is still sealed shut, rolled
up in the furnace.
Hope I can find somebody like you in my town, when I break down and contract
for the furnace upgrade I need, sometime in the next year. Even though I
grew up in the construction business, and basically know what is and isn't
good workmanlike practice for mechnical installations, I dread the prospect
of having to play roulette with the local tradesmen, and walking that fine
line between micro-managing and pissing off a good guy, and staying away on
install day, thereby rolling over for a possible quack. As an installer, how
did you feel about the owner standing there and watching, as long as they
kept their mouth shut and didn't get in the way? (Still getting over a bad
experience with a plumber that came highly recommended, but made stupid
mistakes, and had to be called back twice for followups. I wasn't in the
house for his work, but probably should have been.)
I'm assuming the installation manual comes with the furnace (ie: not
something bought seperately) ... so if I were to read it from cover to
cover would it explain things enough for someone good at handy man work
to understand it and be able to double check that the HVAC contractor
did most of his work correctly? Or in other words does the
installation manual outline the correct gas pressure, gas line size,
how to properly drain the AC coil condensation, how to know if the
existing duct work is adequate, etc.?
The manual will have wiring diagrams, utility requirements, space
It will have nothing about good plumbing practice, local codes, duct
requirements, etc. That varies for each situation so the installer must
know how to do that and do any calculations for sizing and the like. You
won't know if the proper procedure was followed for hooking up the line set
to avoid contamination.
The reason why the installer is so important is because most houses
have crappy installed HVAC, even new ones. A good installer will be
able to properly size, fix ductwork problems, etc. Now if your
existing system is working perfectly and you can buy one the exact same
size and install it yourself, and pay the pros do the startup and fill
freon I say go for it, but that is probably the rere freak exception.
As another example, my house probably now has an oversized furnace
bacause it had no insulation when I bought it, and I insulated it Even
if my system was working perfectly before (it wasn't) I certainly will
want to make sure that any new system is properly sized and can get
proper air flow to every room, etc.
Several years ago we suffered a nightmare of a poor installation of a
furnace. The new oil furnace needed better flow through the chimney
which we found later was partially blocked and we had to have it
cleared and lined.
Furnace also backfired and poor installation of a simple thing like
changing the filter replacement around left an unsealed vent and smoke
went from furnace room throughout house. We had to have the house
cleaned 3 times from the original cracked plenum and the chimney and
backfire problems of the poor installation. Took about a month to
straighten out the mess and insurance which installer had to pay.
Both matter ... if the install is bad though the brand of
furnace wont matter. So install quality is first. also a
good installer will not be selling junk.
Too small or leaky air ducts.. leaks will cost you a fortune,
too small will not provide sufficient heat to rooms farthest
from the furnace..and if you want to add cooling later small
ducts will be a problem.
What makes it a poor installation?
Bad venting can fill the house with carbon monoxide.. thats
fatal, the wrong vent pipe material can cause a fire.
Improperly secured and sealed duct can come apart later.
HVAC contractor/ mech engr since 1741
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