replacing air conditioner

[liz charmin]

Our home which is about 13 years old has 2 separate “air conditionering” systems: one for upstairs and one the downstairs. Both are approx 2 ton. We believe the air conditioner for the upstairs must be replaced and we really don’t know much about this subject. It consists of a dual or split system—outside is the condensor/compressor/airconditioner (different companies and sites use any of these words in reference to it) , and indoors, in the attic is the evaporator also called the refridgerant coil. So, the real question we have is, is it necessary to replace the evaporator in the attic? This , at present, seems to be working. There are many, many companies listed in the phone book and know one we know has any recommendations as to who to call so we are on our own. We are considering Home Depot but they only use one company in the Atlanta area and this company only installs Trane. We will not be living in this home for too many more years. Thanks Liz

[LazyPup]

My first question would be, why do you believe you need to replace the unit you have?

To answer our question, yes you can change either the condensing unit (outside unit) or the evaporator unit (inside unit) independant of the other, providing that the replacement unit is properly sized to match the opposite end.

To put it in perspective, think of the two units in the terms of a car pulling a trailer. The car only knows the weight of the load its pulling, and the trailer only follows were the car pulls it. The car is pulling a trailer, but it wouldnt matter if it was a utility trailer, a camper or a boat, it is simply a specific load. In turn, the trailer don't care if its pulled by a Ford, Chevy or a Toyota, so long as the hitch is compatible and the vehicle has the horsepower to handle the load.

The outside condensing unit works independantly to pull hot refrigerant back through the suction line, compress and condense it and return it by means of the liquid line. The evaporator in turn receives high pressure liquid refrigerant and converts it to low pressure gas which is then returned via the suction line. Both systems work independant and are only interconnected by the two refrigerant lines and a low voltage thermostat signal cable to tell the outside unit when to turn on. And just as the car didnt care what kind of trailer, or the trailer didnt care what kind of car, the indoor and outdoor units can operate perfectly well even though they are different brand names, However, The outside unit is the power unit and it must be perfectly matched to the load to maintain balance. A 2 ton evaporator coil requires a 2 ton condenser and both systems must be designed to use exactly the same refrigerant. They must also be the same type of unit, whether it is a heat pump or a straight cool unit. (Before I get into a long winded argument with someone, Technically it is possible to mix a heat pump unit with a straight cool unit, but in the end, it will only operate in straight cool mode.)

Before you make any changes there are some factors that must be consideered. As i stated before, the question is, why are you contemplating changing the unit. If it is not cooling the space adequately we must then determine if the system is operating to its proper specifications. Did it properly cool the space when it was new? Has their been any additions to the living space that would increase the working load?

If the unit is not working up to specification you would then need to determine why. Perhaps the unit could be properly serviced to restore it to proper operation and no major equipment change would be necessary. If the cost of restoring the unit exceeded an economical break point then it might be best to change whichever section is not performing adequately.

On the other hand, if there has been significant changes to the living space that would increase the working load, then it would be necessary to re-calculate the demand load and replace both the indoor and outdoor sections to upgrade to a larger system.

[drifter12]

I agree with lazypup. Why change something that has been working. By replacing something simple a great deal of money can be saved.

[HiltonTech]

"We believe the air conditioner for the upstairs must be replaced "
"we really don’t know much about this subject"
Being you don't know much about the "subject" how did you come to conclusion that your unit needed to be changed out?, did a tech inspect the unit and was it him that said it needed to be changed out?
If the unit is cooling the home why change it?, unless as you said you weren't going to be living there to much longer and thinking of the resell value


HiltonTech