AC replacement Qs -- please advise

15 years ago

Hi folks,

My AC just conked out and IÂm looking for some advice. The compressor is dead and the unit is at least 20 years old, so replacing the unit seems prudent. ItÂs either 2 or 2.5 tons (label is hard to read); repair person recommended replacing it with 2 tons (based on square footage), Trane 13 SEER, R-22. Quoted $3100 to replace unit, coil, & line set (he left a message; didnÂt specify the model #, so IÂll have to track that down on Mon). Other HVAC people (Carrier, Bryant, and American Standard reps) will be coming in for estimates early next week and I want to be sure that IÂm prepared for those visits. Here are my questions for you:

1. We have 2 AC units (and 2 furnaces) Âfor the east and west sides of the house. Do we need to (or is it advantageous to) replace both of them? The west AC still functions, though the tech needed to add some freon and it still didnÂt seem to be cooling the house that well afterwards (but maybe thatÂs just because the East AC was gone and the two sides of the house are not separated by walls or doors?). It looks very old, but itÂs not identical to the east unit so it could be a little newer (or older!); it must be at least 15 years old (how long weÂve been in the house).

2. ShouldnÂt I be insisting on R410A rather than R22?

3. I gather from reading this forum thatÂat least for furnacesÂitÂs important to do a load calculation rather than estimating based on square footage or size of the unit being replaced. Is this necessary for AC, too? And do load calculations for AC take basements into account? The contractor who based it on square footage said the basement was irrelevant. [East side has full basement (half finished, half unfinished) below. West side has partial basement (finished) and car garage below.]

4. Do the AC units have to be matched somehow to the furnaces or does any AC system work with any furnace? E.g., can one pair a high efficiency AC system with a low efficiency furnace? We have split systems, but our current gas furnaces are very old and certainly arenÂt high efficiency.

5. Assuming one could afford it (IÂm afraid to think about the price), is it necessary or advisable to replace the furnaces along with the AC units or is it OK to just wait until one or more of the furnaces dies and deal with it then? They are Magic Chef units and my guess is that they are 25 years old. As far as I can tell, they are running OKÂ

Sorry to ask so many basic questions, but IÂm new to the world of HVAC and worry about being taken advantage of or doing something stupid. Thanks in advance for your help.

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Comments (7)

ryanhughes
15 years ago
1. I would make sure you are getting a matching coil with the air conditioner.
2. I would recommend R-410A. You're replacing the lineset anyway, so it makes sense to future proof.
3. Basements typically add little to the cooling load. A load calculation is certainly the best thing to do. Him disregarding the current unit's size and guessing off of square footage is bad practice and could leave you uncomfortable.
4. Air conditioners and their matching coils are independent of the furnace. As long as you have the proper airflow out of the furnace, you should be okay. Note that higher efficiency A/C's above 14 SEER have a difficult time getting their rating without a variable-speed furnace blower.
5. I'd have the furnaces checked out to make sure the heat exchangers aren't cracked and emitting poisonous CO gas at the very least at that age.

Good luck.
carol08
Original Author
15 years ago
Many thanks! Very helpful. One more Q: How would I go about having my furnaces checked out? Not to be cynical and suspicious, but if I ask the folks who are bidding on the AC replacement to check the furnaces too, might not some of them be motivated to find furnace problems? E.g., Is a cracked heat exchanger something I could see if it were pointed out to me? I don't know if it's relevant, but I have CO detectors in the house and they haven't detected anything amiss...
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ryanhughes
15 years ago
That's why it's important to get a contractor that you trust to look at your equipment. Sometimes special tools are required to find small cracks in the heat exchanger. I'll let someone more familiar with furnaces comment on this. I do know that at 25 years old, they're getting up there. I have a heat pump, so I'm not a furnace expert. Good luck with finding a good contractor.
carol08
Original Author
15 years ago
Thanks. It seems clear from everything people say on this forum that getting a good contractor is critical. I wish I knew more about making sure a contractor was good...I have a Bryant guy coming in who was highly recommended by a neighbor, and I've been checking Angie's List and Consumer's Checkbook. I've also been looking for people who are NATE-certified. There seem to be relatively few of those (i.e., many companies that are very popular around here and have been working in the community for decades have no NATE-certified technicians). Is NATE certification not an important criterion for choosing a HVAC contractor? Are there other things I should be looking for instead?
ryanhughes
15 years ago
You're on the right track for finding the right companies. While NATE is a good indication of them being a good company, I'm not sure if I'd automatically assume that makes them a good company. I would keep asking for personal references. Let us know the outcome of the quotes so that you can compare them.
carol08
Original Author
15 years ago
Will do. Thanks very much.
nycareerpro
15 years ago
If you are in the NJ area, you should definitely try out Browns Heating & Cooling for any air conditioning repair or even if you ever need new installation. They came highly recommended and now I won't use anyone else. They are a company you can trust that does not overcharge and does great work!

Here is a link that might be useful: Browns Heating & Cooling

AC replacement Qs -- please advise

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AC replacement Qs -- please advise

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