Hi all, I posted here a few days ago to try to figure out fair pricing
on some A/C work. (Main problem is a leaky evap coil, but due to
10-year age am considering a compressor also). I have been getting some
quotes since then, and while I am getting a better handle on how the
dollars start to fall, I am still not sure whom to follow as advice
conflicts between the four estimates I got.
Some advice/info from them, for example:
1. I don't need more than 2 tons (which is what I have now), but others
are saying I need 2.5 and even 3 tons.
(the latest guy said that one should roughly estimate as a quick and
dirty that one 8" duct equals aprx .5 tons of supply capacity. We
counted and there are 6 of these plus one 4 incher. He is returning
tomorrow to take more specific measurements.) Note that some years
after the home was built a basement was finished out with one 8"
2. 13 SEER is ok and in many cases the way to go. Current is 10 SEER,
about 10 yrs old. (I understand 13 is now the minimum).
3. Freon (R22) is still preferable to Puron (410?) due to the latter's
unproven nature and as yet not assured supply.
4. Rheem/Ruud (I understand these are the same) are lower priced than,
for example Trane, but not significantly lower in quality. The last guy
stocks the first but can get any brand the customer wants.
5. Replacement of copper lines (aprx 40 foot run). This is the part
with the greatest variance. The Trane guy said upgrade to 2.5 requires
no upgrade of my current lines (which are 3/4 and 3/8). The first Ruud
guy said the 2.5 unit *will* require upgrade. The second Ruud guy said
no, but I could if I wanted to (aprx $250). He said a nitrogen flush
and vacuum should be sufficient, no charge by him).
So, although I am trying to compare apples to apples, it turns out some
of those are McIntosh, some are Granny Smith, and some may be just
Any help sorting the truth from salesmanship is much appreciated!
I live in Memphis. Dang hot in the summer. When we bought this house it
had an old (probably original) 2.5 ton unit which bit the dust the second
summer we were here. My heating and air guy said that he usually figures 1
ton for every 400 to 500 square feet of living space, I'm sure this varies
depending on where you live. My house is about 1800 sq/ft so I went with a
4 ton unit (R22). The brand is Goodman (I don't know anything good or bad
about them). My electric bill actually went DOWN because the old unit was
not working right and ran all the time so I don't actually know how much
more electricity I am using. Although it seems that a bigger unit is going
to cool faster and therefore run less... At any rate, I can swing meat in
this house now even on the hottest of days which is fine with me. I am from
up north and can't stand the heat.
TWO big down sides to the upgrade
1. The old line set for the 2.5 ton unit was not enough for the 4 ton unit
and had to be replaced. I believe he told me that the biggest unit the old
line set would support was a 3 ton.
2. The old A/C was on a 30amp circuit with 10 gauge wire, again not enough,
so I had to run 8 gauge via a 40 amp breaker.
Also, you need to make sure that your furnace blower can move enough air to
support the upgrade. Otherwise you will end up packing ice on your coil...
The Upside: because we had to run electrical and plumbing, I was able to
move the compressor from one end of the house to the other, and tuck it back
in a corner out of sight and far away from the master bedroom so I don't
have to listen to it run at night. I am no expert but it seems that I hear
a lot of people say that Freon is going to be around for a while yet. There
was a definite cost difference in the Puron vs. Freon comparison and the guy
who did mine said he did not think that Puron was worth the extra money.
Give it another 10 years and the price will come down as it becomes the
For the new A/C, new coil, and new line set the cost was $2014. I did the
Hope this helps
"My heating and air guy said that he usually figures 1
ton for every 400 to 500 square feet of living space, I'm sure this
depending on where you live. "
So a typical 2500 sq ft house should have a 5 1/2 ton unit? Doesn't
something seem very wrong with that?
Guys, thanks for all replies so far. Bob, there are 6 8" ducts and one
4". That sounds to me like about 1250 CFM, correct?
Some nfo which has now become more relevant...In the original home, 10
years ago, there were actually 4 ducts. When I bought I thought I would
need an extra supply in the main living space and asked for it in the
negotiations. The builder, blast his bones, added it without warning me
of the consequences.
Then, a couple of years ago, I added another 8" in the basement.
So it looks like perhaps the original 2 ton was slightly undersized but
not by much, while today, I just might actually need a 3 ton? Am I
reading the data right?
It isn't that simple. The only thing that tells you, is that you have enough
branch ducts, assuming you are correct. Are the 8" ducts made of metal or
flex duct? If they're flex, do they say 8" or did you measure them?
As mentioned earlier Manual J is the best way to determine what you
need. A list of the following helps determine your cooling load
The direction the house faces effects the amount of heat gain at any
given part of the day.
What type of windows
What type of doors
How much insulation is in the walls and in the attic
Slab floor or crawl space
What construction materials on the wall
Your desired set points for cooling and heating
Your location in the United States
Whether your windows have drapes, blinds or nothing at all
How many people
and the list goes on. If you can get all this information to the right
person then they can determine the proper size equipment you need. I
hope this helps.
You got a hack job.
500 square foot per ton is used from Maine to Florida. It is not
anywhere as good as a real load calculation. I have used data loggers
to check cooling capacity and current draw on many units. You don't
get near rated efficiency for about 15 minutes of run time. So if your
unit cycles a lot, common with oversized units, your 10 SEER unit may
only get 7 or 8 SEER. Plus oversized equipment does not dehumidify
well. This is because a piston metering device like a Goodman does not
develope a maximum coldness at the indoor coil for 10 to 15 minutes.
Can you spel M-O-L-D? My 2000 square foot house in Myrtle Beach, SC
has a single 2-ton system that does just fine.
BTW Freon is a brand name, like Ford. There are dozens of different
refrigerants, many made by DuPont under the Freon brand. Equipment
using R-22 (your Freon), can only be manufactured for another 4 years.
R-22 can be made for service use for at another 10 years after that,
although cutbacks in production are required. There is also a fair
amount of used R-22 in storage that can be re-distilled. Prices of
R-22 are going up and prices of R-410a (Puron) are comming down, but
R-22 is cheaper right now.
A bigger unit will not move more air through an existing duct system.
To double the air flow as needed for a unit twice as big as the old one
without changing the duct system requires 8 times the blower horsepower
(the cube of the air flow increase according to the fan laws)
Goodman is a cheap unit. A good unit like Trane or Lennox will outlast
Goodman by about 5-years around here. It may be different where you
live, but will be similiar. Goodman is one of the noisiest units
Does not sound like you got a good deal.
Please don't suggest to other people that they make the same mistake
that you did.
If none of those contractors did a Manual J, you need to send them packing.
For someone to say that you "may" need a 2.5 or a 3 Ton, they sound like
they are just guessing. If they put a 3 ton in and you only need a 2, you
are going to have problems. Plus, the ductwork might not be sized properly
to handle anything other than what you have now.
Find someone to size it correctly, THEN you can decide ob the least
important thing: The brand.
That does not sound like anyone did their job. A Manual J calculation
will tell you exactly what size you need. Guess work is not good work here.
The wrong size (too small or too large) is not a good system at any price.
After the Manual J is done it sounds like a Manual D will need to be done to
determine the ducting required. If a contractor is not doing these, pass on
to someone who does.
This is just one example of why the contractor is far more important to
the quality of the job than brand of the equipment you choose.
Definitely stay away from R-410A (Puron), not only because it has problems,
but because you MUST change the refrigerant lines. In my area, changing the
refrigerant lines usually means ripping out drywall and sometimes half of
the kitchen cabinets. If they're easy to change, then go with new lines. If
you go with an R-22 system, you can usually use the same refrigerant lines
(unless you have a compressor burn out). The installer can evacuate the
lines to make them as good as new. Rheem/Ruud specs give a normal
recommended tubing size. Next to that, they give a BTU capacity multiplier
for different size tubing. A typical multiplier of .99 for the next smaller
size tubing would mean that a 24,000 BTU unit will produce 99%, or 23,760
I don't design the homes, I just have to deal with them. In at least 25% of
the homes in my area, the refrigerant lines are run above the drywall in the
ceiling. There's one development where the horizontal air handler is hung
from the floor joists in the laundry room in the center of the house. You
can't stay in business very long if you insist on replacing the refrigerant
lines. The next guy will insist that you don't have to.
The houses I work in have the units in the attic, therefore access from the
attic to the outside of the house.
So, the answer is yes, I run them across someone's living room ceiling, just
in the attic space, not in the room.
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