"calhoun" wrote in message
.. .
I want to add central air to my existing forced air furnace. I see many
available kits and it looks pretty straight forward. Any one done this?

Do it daily.
Its not as simple as you might think. And what I am about to say, try to
understand I make a ton of money on DIY kits, so dont think for a second I
am trying to stop you.....
First, ANY kit you buy will have the warranty void the second you install
it. Thats right...in all technicalitys, its void the second you install it.
Second, you wont know this till you call out a tech to find out why in a
couple of years, why the compressors making this awful noise, and it wont
cool, and they ask the important question..where is your invoice, and the
techs name that installed it. You got it....every major maker of AC units
clearly states that a non licenced person can not bring parts in for
warranty.....gets better...if you buy it off the net, you have no place to
go back to if you get a dud unit off the shelf. They dont have to make it
right, since NONE of the major manufacters will allow their dealers to sell
to the public directly off the internet. Its a fast way to get your
dealership pulled.

Second, What size unit did your manual J call for? You stated you are
getting AC, not a heat pump, so you didnt need to do a manual T. Too small a
unit, you wont be happy..too large and you get cold, clammy air thats just
wonderful for mold.
Oh...that would also void the warranty, the part under improper
installation.

Third, Now that you have your tonnage figured, and your airflow of the
furnace you have is ok, and you have made sure that your furnace has the
proper equipment to allow for AC additions on the unit, 2 speed fan and all,
what does your manual D state about your current duct? Normally, straight
heat duct is not large enough for AC. So, you will have to determine using
the proper formula in manual D if your ducts are large enough to supply as
many BTUs to each room and proper velocity of the air to each room to allow
for proper cooling, and no air stagnation.
Your return will normally have to be larger than it is as well, to maintain
the proper face velocity depending on how much free area your current grille
allows for.

Forth. Tools. You have all you need right? Starting with an EPA certificate
that allows you to handle refrigerants. Not FREON, as Freon is nothing but a
trademark name for any DuPont refrigerant. If you cant handle R22, or 410a,
then you cant legally install the unit anyway.
You have nitrogen for purging the lineset, and you have a good oxyacet tank
set right? SilPhos? A micron gauge? A good vacuum pump to go with the micron
gauge? A D_A_M_N good set of gauges, like CPS or the like? A Schrader core
tool? All your Malco stuff? PErhaps you have ductboard, so you will be sure
to insure that no fiberglass enters the airstream when you are done...
After all that, you will need an EPA certified recover tank, and machine,
JUST in case you overdo the charge when you get around to charging to
superheat, or subcool, depending on the type of metering device you order.
Anyone with any sense orders a TEV to put on the evap coil, since it will
offer the best in making sure you are always getting what you pay for, and
in the case of higher SEER units, it will allow you to gain all the SEER
points you paid for.

Fifth: Lineset...you know where to put the oil traps if needed, and your pad
will be the right thickness and size to code.

Sixth, Permits and inspections. In most areas, only a licenced and insured
person can pull permits and ask for inspections, this may vary in your area.

7th- Electrical. You will need to insure that you have a new thermostat wire
pulled from the furnace, to the thermostat, since you will more than likely
have a 18-2 wire pulled, and will need at least an 18-5...perhaps more
depending on the thermostat and options you add on.

8th- Allow me to suggest to you that you get someone that knows what he is
doing, and has the needed tools on hand to insure that you get what you pay
for.

Besides, you will be more than likely getting a Goodman unit, (Janitrol, or
GMC...same stuff) and its garbage from the word go. Their warranty is
clear...no licence, no warranty. Dont think you can not send in the warranty
validation card and get away with it. EVERY make knows when the unit was
last sold, and if you dont send the card in, the supplier is listed as still
owning the unit, and since you have to have a licenced person fill out the
back of their cards, well....again...no warranty.

Dont get me wrong. IF and only if you can get the right tools, know how to
use them, can size your unit correctly to manual J, or T, and size your
ducts to manual D...go for it. There is nothing like knowing you did it, and
it works.
But..
What really sucks is when you do it, and it works, but inst working right,
and you dont know its not working right, and call someone like me out, and
we find non condensables in the unit, or bubblegum welds that have allowed
BBs to make their way to the metering device, and then, all that money you
thought you saved is gone.

I personally LOVE DIY stuff. I HATE telling the person that warranty
coverage has been denied, and that will be $1500 for the repair, and I have
to notate that the ducts still undersized, and no further warranty on the
part will exist after 7 days.

Seriously, (as all this has been) get someone thats licenced, and INSURED to
run the unit. You might pay a bit more now, but you wont be paying later.


Also all the kits, I have seen, use Freon. Any one know of any that use
134A.