A/C contractor quotes - need to evaluate

[kck]

Hi all, I posted here a few days ago to try to figure out fair pricing on some A/C work. (Main problem is a leaky evap coil, but due to

10-year age am considering a compressor also). I have been getting some quotes since then, and while I am getting a better handle on how the dollars start to fall, I am still not sure whom to follow as advice conflicts between the four estimates I got. Some advice/info from them, for example:

1. I don't need more than 2 tons (which is what I have now), but others are saying I need 2.5 and even 3 tons. (the latest guy said that one should roughly estimate as a quick and dirty that one 8" duct equals aprx .5 tons of supply capacity. We counted and there are 6 of these plus one 4 incher. He is returning tomorrow to take more specific measurements.) Note that some years after the home was built a basement was finished out with one 8" supply.
2. 13 SEER is ok and in many cases the way to go. Current is 10 SEER, about 10 yrs old. (I understand 13 is now the minimum).
3. Freon (R22) is still preferable to Puron (410?) due to the latter's unproven nature and as yet not assured supply.
4. Rheem/Ruud (I understand these are the same) are lower priced than, for example Trane, but not significantly lower in quality. The last guy stocks the first but can get any brand the customer wants.
5. Replacement of copper lines (aprx 40 foot run). This is the part with the greatest variance. The Trane guy said upgrade to 2.5 requires no upgrade of my current lines (which are 3/4 and 3/8). The first Ruud guy said the 2.5 unit *will* require upgrade. The second Ruud guy said no, but I could if I wanted to (aprx 0). He said a nitrogen flush and vacuum should be sufficient, no charge by him).

So, although I am trying to compare apples to apples, it turns out some of those are McIntosh, some are Granny Smith, and some may be just spoiled.

Any help sorting the truth from salesmanship is much appreciated!

[Craig Robison]

I live in Memphis. Dang hot in the summer. When we bought this house it had an old (probably original) 2.5 ton unit which bit the dust the second summer we were here. My heating and air guy said that he usually figures 1 ton for every 400 to 500 square feet of living space, I'm sure this varies depending on where you live. My house is about 1800 sq/ft so I went with a

4 ton unit (R22). The brand is Goodman (I don't know anything good or bad about them). My electric bill actually went DOWN because the old unit was not working right and ran all the time so I don't actually know how much more electricity I am using. Although it seems that a bigger unit is going to cool faster and therefore run less... At any rate, I can swing meat in this house now even on the hottest of days which is fine with me. I am from up north and can't stand the heat. TWO big down sides to the upgrade

1. The old line set for the 2.5 ton unit was not enough for the 4 ton unit and had to be replaced. I believe he told me that the biggest unit the old line set would support was a 3 ton.
2. The old A/C was on a 30amp circuit with 10 gauge wire, again not enough, so I had to run 8 gauge via a 40 amp breaker.

Also, you need to make sure that your furnace blower can move enough air to support the upgrade. Otherwise you will end up packing ice on your coil... Not Good. The Upside: because we had to run electrical and plumbing, I was able to move the compressor from one end of the house to the other, and tuck it back in a corner out of sight and far away from the master bedroom so I don't have to listen to it run at night. I am no expert but it seems that I hear a lot of people say that Freon is going to be around for a while yet. There was a definite cost difference in the Puron vs. Freon comparison and the guy who did mine said he did not think that Puron was worth the extra money. Give it another 10 years and the price will come down as it becomes the norm.

For the new A/C, new coil, and new line set the cost was $2014. I did the electrical... Hope this helps

[buffalobill]

[Dr. Hardcrab]

If none of those contractors did a Manual J, you need to send them packing.

For someone to say that you "may" need a 2.5 or a 3 Ton, they sound like they are just guessing. If they put a 3 ton in and you only need a 2, you are going to have problems. Plus, the ductwork might not be sized properly to handle anything other than what you have now.

Find someone to size it correctly, THEN you can decide ob the least important thing: The brand.

[Joseph Meehan]

kck wrote: ...

That does not sound like anyone did their job. A Manual J calculation will tell you exactly what size you need. Guess work is not good work here. The wrong size (too small or too large) is not a good system at any price. After the Manual J is done it sounds like a Manual D will need to be done to determine the ducting required. If a contractor is not doing these, pass on to someone who does.

This is just one example of why the contractor is far more important to the quality of the job than brand of the equipment you choose.

[Bob]

Definitely stay away from R-410A (Puron), not only because it has problems, but because you MUST change the refrigerant lines. In my area, changing the refrigerant lines usually means ripping out drywall and sometimes half of the kitchen cabinets. If they're easy to change, then go with new lines. If you go with an R-22 system, you can usually use the same refrigerant lines (unless you have a compressor burn out). The installer can evacuate the lines to make them as good as new. Rheem/Ruud specs give a normal recommended tubing size. Next to that, they give a BTU capacity multiplier for different size tubing. A typical multiplier of .99 for the next smaller size tubing would mean that a 24,000 BTU unit will produce 99%, or 23,760 BTUs.

[trader4]

"My heating and air guy said that he usually figures 1 ton for every 400 to 500 square feet of living space, I'm sure this varies depending on where you live. "

So a typical 2500 sq ft house should have a 5 1/2 ton unit? Doesn't something seem very wrong with that?

[Bob]

Nothing against you, but your HVAC contractor is a hack.

[Bob]

For round ducts, 6" is roughly 100 CFM, 7" is roughly 150 CFM, and 8" is roughly 200 CFM. Go around and add them all up, and this will give you the total CFM your ducts can handle, assuming your trunk duct is big enough. You may need to rip out your whole duct system if you go with a larger unit. Rarely have I seen a house require more heating or cooling than it was originally designed for unless there was an addition. Quite often, it will require less BTUs because of new insulation, windows, etc. A 3 ton unit will require ROUGHLY 1200 CFM. If you don't have enough duct work, your system isn't going to operate properly, and might be noisy.

[WM]

No. That's a huge house and most around here have 2 units that total more than that.

[kck]

Guys, thanks for all replies so far. Bob, there are 6 8" ducts and one

4". That sounds to me like about 1250 CFM, correct? Some nfo which has now become more relevant...In the original home, 10 years ago, there were actually 4 ducts. When I bought I thought I would need an extra supply in the main living space and asked for it in the negotiations. The builder, blast his bones, added it without warning me of the consequences. Then, a couple of years ago, I added another 8" in the basement.

So it looks like perhaps the original 2 ton was slightly undersized but not by much, while today, I just might actually need a 3 ton? Am I reading the data right?

[Bob]

It isn't that simple. The only thing that tells you, is that you have enough branch ducts, assuming you are correct. Are the 8" ducts made of metal or flex duct? If they're flex, do they say 8" or did you measure them?

[kck]

They are flex, and I know about the 8" because the contractors verified that, plus I have done some ducting work before and recognize the common sizes.

[Bob]

Then they should be 10" diameter.

[Al Moran]

If someone is designing the size of you r system based on the size of your current duct work then this person is an idiot or a crook. You need to do a "manual J" to size a system correctly. Run from this person.

13 seer or greater is the law. period.

Probably true.

Bullshit, buy a rheem, get rheemed. Trane is top of the line.

This is correct.

This guy is an idiot or a crook. Run.

This is correct.

[JH]

Manual "J" is a great start but it is only as good as the information being entered. In other words garbage in garbage out.

Not necessarily true. R22 is partly preferred because the industry is familiar with the product. Regarding "unproven" it is going to make or brake a contractor if they do not install R410 products correctly.

That is a matter of opinion. I have seen Rhuud/Rheem, Janitrol/Goodman units last as long as Trane. Again many factors must take place for proper installion.

[Stretch]

Craig You got a hack job.

500 square foot per ton is used from Maine to Florida. It is not anywhere as good as a real load calculation. I have used data loggers to check cooling capacity and current draw on many units. You don't get near rated efficiency for about 15 minutes of run time. So if your unit cycles a lot, common with oversized units, your 10 SEER unit may only get 7 or 8 SEER. Plus oversized equipment does not dehumidify well. This is because a piston metering device like a Goodman does not develope a maximum coldness at the indoor coil for 10 to 15 minutes. Can you spel M-O-L-D? My 2000 square foot house in Myrtle Beach, SC has a single 2-ton system that does just fine.

BTW Freon is a brand name, like Ford. There are dozens of different refrigerants, many made by DuPont under the Freon brand. Equipment using R-22 (your Freon), can only be manufactured for another 4 years. R-22 can be made for service use for at another 10 years after that, although cutbacks in production are required. There is also a fair amount of used R-22 in storage that can be re-distilled. Prices of R-22 are going up and prices of R-410a (Puron) are comming down, but R-22 is cheaper right now.

A bigger unit will not move more air through an existing duct system. To double the air flow as needed for a unit twice as big as the old one without changing the duct system requires 8 times the blower horsepower (the cube of the air flow increase according to the fan laws)

Goodman is a cheap unit. A good unit like Trane or Lennox will outlast Goodman by about 5-years around here. It may be different where you live, but will be similiar. Goodman is one of the noisiest units around.

Does not sound like you got a good deal.

Please don't suggest to other people that they make the same mistake that you did.

Stretch

[JH]

As mentioned earlier Manual J is the best way to determine what you need. A list of the following helps determine your cooling load

The direction the house faces effects the amount of heat gain at any given part of the day.

What type of windows What type of doors How much insulation is in the walls and in the attic Slab floor or crawl space Any overhangs What construction materials on the wall Your desired set points for cooling and heating Your location in the United States Your elevation Whether your windows have drapes, blinds or nothing at all How many people Fireplaces

and the list goes on. If you can get all this information to the right person then they can determine the proper size equipment you need. I hope this helps.

[HeatMan]

Since when? I re-run refrigerant lins on the outside of the house if I have to run them.

[Bob]

Do you run them across someone's living room ceiling?