2 Different Outside Condensors = problem?

[augmendoza]

We recently had a our upstairs a/c unit stop blowing cold air. The a/c company told my wife that we needed a new condensor for our upstairs unit. She agreed and allowed them to install a 3 ton, 15.75 SEER American Standard unit [at a nauseating price . . . don't get me wrong, I am not shirking responsibility, I agreed over the phone while at work and felt helpless because of the stifling Houston, Texas heat.] They told her that we would soon need to replace the downstairs outside unit as well as the attic-based evaporator that is connected to the newly-installed upstairs condensor unit [they said that it would eventually damage the new condensor if not replaced.]

The downstairs outside unit makes a strange noise when it turns off; the only analogy I can think of is that it sounds like what happens when you suck liquid up a straw without having your mouth completely over the straw [jeez, I feel dumb just writing that . . .]

I have found several on-line retailers of a/c components; the one that I am interested in has Rheem systems [in the case of the outside unit, the price of the unit that I am leaning towards - 2.5 ton/13 SEER - is about 70% lower than what we paid to have the other installed.] My idea is to purchase the unit and find a local contractor to install it as well as a new evaporator purchased from the same online sources.

Questions:

*Would having two different outside units that sit side-by-side be a negative if I decided to sell the house [I have mixed feelings about how this would look]? Is this possibly in violation of some type of code or agreement? Am I being penny-wise but pound-foolish to try to purchase these components on my own?

Info: Live in Houston, TX. House is 2975 sq/ft.

[TigerDunes]

augmendoza

Some observations, opinion, and questions.

How many sq ft of conditioned air living space for upstairs and downstairs?

Is new outside condensor unit for upstairs an AC unit or HP unit? What is the model number? Was it same size as unit it replaced? Don't guess, make certain.

What is make,model,size, and age of air handler for upstairs?

You will never achieve the rated efficiency of new AS unit with a mismatched system. I would think about replacing the air handler for upstairs first.

As far as having an AS outside unit for upstairs, and another brand for downstairs, this is really just a matter of aesthetics. It may not be pleasing to the eye but it is done all the time. I would not think this is against code but codes vary and you could call residential building inspector for your area and verify. I would prefer one manufacturer.

I would also have a Manual J heat/cool load calculation performed by a professional and reputable dealer for verifying and correctly sizing equipment.

Be careful about purchasing HVAC on internet particularly on how that might affect Mfg equipment warranty. I know the prices are sometimes attractive-just cover all your bases. If any problems develop, you may be left out on the limb. Weigh all possibilities.

As far as sound of downstairs outside unit, has it always made this noise or is this something different than previous summer season. Did you ask your installer about this noise when upstairs unit was being replaced?

:)