Evaporator Coil has to go, does the condensor also has to go?

[Nadia_Mayl]

Hi all,
I hope I'm posting in the right forum, if not, please excuse me. We are trying to figure out what to do about our AC unit. We live in Houston, TX, high humidity and lots of heat! Our house was built in 2003. A few weeks ago AC started leaking through the emergency overflow pipe, the condensor unit has also been making a high pitch 'beep' sound, and I think it has also been getting louder; so we had a tech come out and check it. Here is what he says:
-Evaporator Coil is completely rusted (true, I saw it) and needs to be changed.
-Our unit is undersized, our house is 2600sq. ft. and we have a 3.5 ton condensor to a 4 ton evaporator coil and a 4 ton furnace. Two thermostats, one upstairs, one downstairs.
-The leak is due to clogged pipes (which he fixed).
He recommends changing the whole unit to a 14 SEER (which would include coil, condensor, piping, and drip pans.
Our questions are:
- If we change the evaporator coil, do we have to change the condensor as well, or can we keep the old one?
-Does it make sense that a 3.5 ton condensor is not right for a 4 ton coil and 4 ton furnace?
-He didn't do a load calc (is that what it's called), should I absolutely have them do one before selling me a machine?
THANKS so much for your help!

[ibis1]

Nadia,

There are several pros on here that service your area. Hopefully one will come along and offer to evaluate your situation. Good luck! ibis1:LOL:

[samtheman]

How could he determine that the system is ungdersized without doing a load calc (trick question, can't be done) It is common for a coil to be a half size larger than the condensing unit, it's usually a factory approved match. It is normal for a coil of that age to show some rust on the steel plates at the ends of the coil. Has the system been cooling the house? Did he have to put any refrigerant in the system? For right now, I would say do NOTHING but get some more information

[sktn77a]

Sounds like you need a new coil! But the condenser is only 7 years old so you could get another 7-10 years out of it. Get a second opinion as to whether it is bad also. I would use the prior cooling performance a guide to sizing. If the old unit doesn't cool your house adequately, it is probably undersized. If it cools the house just fine, then it is probabaly correctly sized. A heat load calculation would confirm this but prior performance is important too.

[dash]

First I'd look at a "tax credit" system, up to $1500.00 ,if you can qualify with your furnace.

That aside, if you can factory "match" a new coil with the existing outdoor unit,you are good to go,other then you think it's under sized.


I say think it is,because if the duct system is undersized , the system will produce less sensible btus,so the duct system can prevent the equipment from producing full capacity. A load calc. will tell the capacity needed.

A little confusing,but hope this helps!

[beshvac]

Is it working now?

The condensate drains were clogged and are now ok and no more leakage from emergency drain?

If its only rusty looking and it works....who cares?

[RyanHughes]

3.5 tons may not be undersized. Dash makes a good point about the ductwork. A load calc will tell for sure--anything else is just an educated "guess." Not unusual for a 4 ton coil/furnace and 3.5 ton condenser. The max you could go to would be 4 tons (likely), and with your ductwork, may not do much good at all.

[udarrell]

First, do a manual J load calc., then do everything possible to reduce the heat-gain.

Then, a manual D on the duct system & airflow should be done; make it super efficient.

I sincerely believe with the above actions properly performed in the proper sequence, that your present 3.5-Ton with the 4-Ton A-Coil with excellent airflow ought to easily do a perfect efficient cooling job for you. - Darrell