If the "cooling was a little weak", it's also a possible sign that the AC unit was oversized, not undersized. Recent studies have shown that, even when following the industry standard (ACCA Manual J), most residential AC systems end up being oversized. Unfortunately, even when a contractor uses the manual (and it's good that yours did because many do not), they often "round up", recommending an even larger unit than the manual would suggest, "just to be safe". For an understanding of why you don't want an oversized AC (besides the obvious fact that it costs more), go to http://www.proctoreng.com/articles/bigger.html and http://www.proctoreng.com/articles/better.html.

Ask them what their load came out to (in BTU's). The sizing is extremely important. If the contractors said to go up to a 4-ton, then you should do so (if feasible--see below) if their calculations say so. The others likely just went by the old size.

Replace the lines to meet the manufacturer's requirements and to be safe with the new refrigerant. Ruud is good stuff but I don't recommend that unit--go with an R-410a unit (all systems quoted are R-410a except the 24ACR and the UAND).

What is the model number on the furnace? You can't put just any A/C on any old furnace--you have to make sure it will be compatible. Avoid the 15 SEER options--you won't get the 15 SEER without a variable speed blower.

With that said, I'd... actually, I wouldn't go with any until you can confirm what is compatible with your current furnace. What kind (make and model) is it? You ideally want one with a 4-ton drive to go with a 4-ton unit. The last 2 quotes look good, but who knows if 3.5 tons is enough? Ask both how much SEER you will really be getting. Don't expect 14 SEER with the XL14i without a variable speed blower.

Good luck. Need more info before I can further advise you.

Hi, Tom, Ryan. Thx for your feedback. I will check out the article that you recommend.

According to one contractor, his calculated load is 48000 BTU.

I checked the unit up in the attic. The current coil is RCBA-4882GG21. The furnace is UGPH-10EBRJR. All Ruud.
Which AC unit will work well for this furnace? Thx for any help you can provide in selecting the cental AC that works best for me.

Thanks for the model numbers. A 4-ton should be fine for that furnace if the installers set the air speed correctly.

Is this unit for an upper level? Do you know the rough square footage? If their load comes to a 4-ton unit, there is really no debating that, but the fact that the load was exactly 48,000 BTU/H is a bit suspicious unless he rounded.

The motor in that furnace being a PSC, I don't see any reason to go with any of the 15 SEER options as 15 SEER is likely unachievable without an ECM motor. I would go with one of the setups that uses R-410a and involves new lines (this would rule out the Ruud UAND and Carrier 24ACR). Carrier, Ruud, Trane or Lennox should be fine--brand isn't really important here. I would confirm with those who are quoting 3.5 ton units why they are quoting this size so you can compare apples to apples.

Thx. Ryan. I think the contractor rounded up to 48000 because he did tell me while he was doing the calculation on the laptop that the result was between 3.5 and 4T and he rounded up to get 4T. Some contractors didn't do the calculation and just looked up the existing unit to figure out the size for the replacement. My house has a two-story foyer and family room. The replacement is for the upstair unit in the attic. The family room is opened to the kitchen. So a lot of the heat in the summer goes to upstair and the unit has to handle the extra heat from downstair. The upstair area is about 2100 sqf. There are quite a few large large double hung windows facing east, south, and west. The contractor also considered the double story foyer and family room. The foyer is 170 sqf. The family room is 323 sqf. The upstair hallway overlooks both the foyer and the family room. The return of the upstair unit is in the hallway.

Okay. Only 1 return? You're definitely going to need some ductwork modification in my opinion. I would not be surprised if the poor airflow is what killed the other unit. I'd check the heat exchanger for cracks, too. If this is the case I hope every contractor mentioned something about it... Take care of this before proceeding; you don't want to kill the next compressor. The ductwork is probably in the attic so this isn't going to be a problem.

There are actually other returns. The main one (the largest one) is in the hallway. A smaller one (half the size of the main return) is in the master bedroom. I also added a return in two of the 3 remaining bedrooms (these two faces south-west) because the rooms are not cooling properly; it helped some after I added the returns in these two rooms. The last room has no return because its door opens to the part of the hallway where the main return is. It is also facing north and the room seems to heat and cool ok. Do you think with these returns are sufficient? Is the 4 ton the right size for the sqf of the upstair area and the two-story foyer and familyroom? Thx.

Sounds like you have sufficient return air. Poor airflow can strain the compressor, so that's why I asked. Square footage is just one factor in determining size--windows, insulation, etc. play a roll as well. What is your location? 3.5-4 tons "sounds about right." Too big and you may have poor humidity control, so proper sizing is important. Did any contractor look at the ductwork? Most importantly, which contractor did you like the most? Are the Carrier bids from the same guy? I think R-410a + a new lineset would be a good decision for you. Take for example the Carrier Comfort 13 A/C (24ACA3). According to Carrier, the lineset size is 7/8 vapor and 3/8 liquid. (See http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/24aca3-2pd.pdf.)

What I would do is call the 3.5 ton people back and tell them you want to know why they chose that size. You ideally want to be comparing all 4-ton units or all 3.5-ton units.

Ryan, thx for your help. The two contractors that did the manual J calculation have gone into the attic to check out the furnace and the evaporator unit, the insulation, and the condition of the duct work. They also measured the area of the windows upstair. So I think they have considered the factors that you indicated. I am in central NJ. So humidity can be bad in the summer. The Carriers were proposed by two contractors, one did manual J calculation, but the other one didn't. But I did tell the contractor that didn't do the calculation that I was thinking about getting a larger unit, and I think that is why he proposed the 4T configurations.

I would forget about these:

Ruud UAND042JAZ and RCFAHM4821, use existing lines $2950
Carrier 24APA5-48-3 and CNPVP4824,use existing lines, $3875
Carrier 24APA5-48-3 and CNPVP6024, new lines, $5670
Carrier 24ACR3-48-3 and CNPVP4821, new lines, $4757

There is simply no reason to invest in a 15 SEER system when you MAY NOT be getting 15 SEER due to having no variable-speed blower. I don't think there is any ARI data for your match. You MAY be able to get 14 SEER (but I doubt from the Trane due to not having a v/s blower). I would look at R-410a setups (this goes with the new lines I recommended), and the 24ACR3 and UAND use R-22. Maybe you can get a price on a R-410a Ruud. Rheem/Ruud is a good product line.

I would consider these if all contractors can agree on one size (which appears to be a 4-ton unit according to the load calculation, presuming one was truly done--did you see him using a computer or piece of paper to calculate this?):

Carrier 24ACA4-48-3 and CNPVP4821, new lines, $5529
Carrier 24ACA3-48-3 and CNPVP4821, new lines, $5143
Trane 4TTX4042 and 4TXCB048BC3, new lines, $5206
Lennox XC14-042 and CX34-49C, new lines, $4596

Hope this helps and isn't too confusing. At least you'll be making an educated decision.

Ryan, thx so much for your time and info. This really help me a lot. I have talked to the contractor that quoted me the Ruud to get me a quote on the unit that uses R410a. He said that he will get me the info tomorrow. I will let you know once I hear back from him.

As for the 4 units that you recommend, I will need to get in touch with the contractors tomorrow to see if they can give me quotes on equivalent sized units so that I can do some comparison. I agree that it is hard to compare 4T vs 3.5T units. Do you have any idea what the price difference is between 4T and 3.5T units, given the same brand?

One contractor did the calculation with a laptop; he seemed to be the more thorough one. He went up to the attic to check out the condition of the existing unit, ducts, and insulation. He did measurement of all the rooms, checked orientation of the house to verify which is the south side, and measured all the windows. He is also the one pointed out the extra load coming from the 2-story foyer and family room load. He is the one that proposed the 4T Carriers.

The other contractor that also did the calculation was not as thorough, but he was also using a laptop.

The Trane and the Lennox are proposed by a contractor that didn't do the calculation. He was basing it on the existing unit size. His company was the one that put in the hard start kit last summer. They gave me credit for the repair on the new unit.

You're welcome!

"Do you have any idea what the price difference is between 4T and 3.5T units, given the same brand?"
-Minimal. Maybe a few hundred.

"One contractor did the calculation with a laptop; he seemed to be the more thorough one. He went up to the attic to check out the condition of the existing unit, ducts, and insulation. He did measurement of all the rooms, checked orientation of the house to verify which is the south side, and measured all the windows. He is also the one pointed out the extra load coming from the 2-story foyer and family room load. He is the one that proposed the 4T Carriers."
-This sounds like a competent contractor. Ask him if he really thinks the 15 SEER units are really worth it as you don't have a v/s blower.

"The Trane and the Lennox are proposed by a contractor that didn't do the calculation. He was basing it on the existing unit size. His company was the one that put in the hard start kit last summer. They gave me credit for the repair on the new unit."
-While he didn't do a calculation, many don't, though it is important to do. The fact that they are giving you credit says good things about the company.

I'll wait for word back from the contractors to see what they say.

What state do you live in? Is it a hot climate, such as Florida? This will play a role in your sizing and efficiency requirements.

Hi, Ryan. I live in NJ, which can be very humid in the summer and can get into the 90s.

I talked to the contractor that did the calculation. He said that the calcuated load is 3.77, and he rounded it up to 4T for the quote. He said that if a 3.5T is put in, he can only gaurantee that indoor temperature can be maintain at 75 degree when the outside temperature is 87 degree or less. Does this make sense to you? I am not familiar how much temperature drop to expect. He also explained that the 24APA5 will not get me 15 SEER; that configuration only provides 14 SEER and 12 EER. I looked back at the quotes and it did state that; I some how missed it (too much data to look thru). He explained that he quoted that configuration becausee it will meet the electric company rebate requirements on SEER and EER ($300 rebate). He seems to be very honest and straight forward with me and his quotes are very detailed, much better than all the other quotes.

He gave me new quotes for 3.5T units. He worked pretty fast; much faster than others (I haven't heard back from the Ruud contractor yet). You are right about the price difference between 3.5T and 4T units, only a few hundred dollars. One configuration stands out is 24ACA4-42-3 and CNPVP4821; this combination provides 14 SEER and 12 EER, which qualifies for the rebate of $300. The final price is $4961. Compared to the equivalent 4T unit (24ACA4-48-3 and CNPVP4821), this is a saving of $560. However, this only provides 40500, compared to 46500 of the 4T unit, cooling capacity. Is he correct that 40500 will only provides 87 -> 75 temperature drop? 12 degree drop seems to be small. Can I get away with the 3.5T unit? I need some help on doing this trade off.

The new 3.5T Carrier is comparable with the Trane and Lennox units. The Lennox unit is attractive also since it is the lowest price. However, I don't know if the quoted efficiency is valid or not. The contractor states in the quote that it is a 15 SEER configuration and it qualifies for the electric company rebate of $400. This contractor will do all the paper work for the rebates and I only pay the total after-rebate price.

So now I am still undecided, 3.5T or 4T? Please help!

By the way, what is the difference between SEER and EER? Why does the electric company cares about both numbers? Which matter more in terms of saving electricity?

I have narrowed down the contractors down to 3. One quoted the Ruud. One quoted the Carrier. One quoted the Trane and Lennox.

Ruud contractor: 1 yr labor, 5 yr parts and 5 yr compressor

Carrier contractor (certified Carrier contractor and did load calculation): 10 yr labor, 10 yr parts, and 10 yr compressor

Trane and Lennox contractor: 5 yr labor, 5 yr parts, and 10 yr compressor

It is tough to make a decision.

Thx for your help.

"By the way, what is the difference between SEER and EER? Why does the electric company cares about both numbers? Which matter more in terms of saving electricity?"

The electric company should care about SEER and EER, you should because you are paying the bills.

Energy Efficiency Ratio (EER) = system cooling btus / compressor power draw in amps at 95F laboratoty conditions. A system with a higher EER will always be cheaper to run than a system with lower EER. EER of 12 is great, higher is better.

SEER = EER x fudge factors. SEER is geared to lower summer outdoor conditions. 66% of the weight of the SEER calc is at 67F, 72F, and 77F outside temps. Less than 7% of the value of the SEER calc is at 95F and 102F (the higher end of the temp range). SEER is a BS number.

Take care.

Since I believe you said the 3.5 ton wasn't working well for you and one contractor calculated 3.77 tons, I'd go for the 4 ton unit as recommended by the Carrier dealer. It sounds like you have found a contractor you are pleased with.

Any information from the Lennox, Ruud or Trane dealers regarding sizing and efficiency?

Regarding the temperature drop, I can't tell you for sure, but if your unit can't keep up due to a lack of capacity, this makes sense. I'm sure he determined this with his calculations by using outdoor and indoor ambient temperatures.

Hi, Gary. Thx for the info on the SEER and EER.

Hi, Ryan. I have not heard back from the other contractors yet about the Lennox, Trane, Ruud. However, I was able to find the info on the ARI web (the Carrier contractor told me about the URL). This is very useful web site where I can find a lot of info in terms of efficiency and capacity of all the configuraitons.

The calculated load is 3.77T, or 45240 BTU.

The Lennox has 14 SEER and 12 EER, but only 41500 BTU, which is 3724 BTU short.

The Carrier 24ACA442A30 and CNPVP4821 has 14 SEER and 12.5 EER, but only 40500 BTU, which is 4740 BTU short. So if I go with Carrier, I will need to go to 4T units.

The Ruud UANL042JAZ and RFCLHM4821 has 13.00 SEER and 11.75 EER, but only 42500 BTU, which is 2724 BTU short. Do you think 2742 BTU is small enough that I can use this? I think the cost for this configuration is pretty low; I am waiting for the contractor to get back to me on this one.

Hi, guys. I just want to give you an update on my central AC project. I finally went with the contractor that gave the most detailed estimation and also did the heat load calculation to figure out that I needed a 4T AC. I decided to go with the Carrier 24ACA3-48-A003 and CNPVP4821 for a good compromise between price and efficiency. I would not be able to recoup the extra few hundred dollars that I paid up front for the higher SEER units. The final price that I paid is $4885 (I got 5% off for paying with check instead of credit card). This also includes a nice TP-PAC18 Edge programmable thermostat. The contractor did the installation today. He put in new lines (3/8 for liquid and 7/8 for vapor) on the outside of the house going from ground up to the attic. He also had to install a couple of extra things due to the vertical seperation is more than 20'. The job is pretty nice and clean. This installation also includes Carrier extended warranty for 10yrs, part and labor, on everything. Pretty nice. I guess now I have to wait till the first hot day to see how well this work. Thx for everyone's help.

Hi, guys. I just want to give you an update on my central AC project. I finally went with the contractor that gave the most detailed estimation and also did the heat load calculation to figure out that I needed a 4T AC. I decided to go with the Carrier 24ACA3-48-A003 and CNPVP4821 for a good compromise between price and efficiency. I would not be able to recoup the extra few hundred dollars that I paid up front for the higher SEER units. The final price that I paid is $4885 (I got 5% off for paying with check instead of credit card). This also includes a nice TP-PAC18 Edge programmable thermostat. The contractor did the installation today. He put in new lines (3/8 for liquid and 7/8 for vapor) on the outside of the house going from ground up to the attic. He also had to install a couple of extra things due to the vertical seperation is more than 20'. The job is pretty nice and clean. This installation also includes Carrier extended warranty for 10yrs, part and labor, on everything. Pretty nice. I guess now I have to wait till the first hot day to see how well this work. Thx for everyone's help.

I need help with the purchase of a HVAC. I have no idea what I am doing.
I got a price on a
Trane Air Handler 2TFE3025A1DOSA
Trane TCONT802 XL Series 3H-2C,
Trane XL15i Condenser

The price includes setup in the attic with install overflow condensation pan, primary and secondary condensate pipe, Final Conn, replacing the duct work, install insulated sheet metal return, Filter Grille and supply return air plenum. The price quote is $9233. I could get the Trane XL14 for 8,479.

The contractor went up into the attic to check the space, he looked at both the inside and outside unit. He showed me what the system will look like.

My current system is a Payne AC PA10TAJA224 with a 1973 furnace. The Payne unit is 4 years old. I do not know how well the unit is because of the old furnace. So there is a possibility I do not need the outside unit.

My house is a 800 square foot one story townhouse with 2 bed, laundry, bath, LR, DR, and kitchen in Los Angeles.
I appreciate all and any help that anyone can give me. Thanks Deb

Deb,

Couple of things came to my mind that I recommend going over with your contractor:
-Why R-22 units versus R-410a units? This is the refrigerant type--R-410a is the new refrigerant
-Why the compact air handler? Do you have a tight space in the attic?
-How was the unit sized? My guess is by going off the old size of the system--this isn't really the best way to do it. Ask him to do a load calculation--2 tons for 800 square feet is a lot if you ask me (they make 1.5 ton units)--if you were you having difficulty dehumidifying or had to set the thermostat low to cool effectively, an oversized unit could be why

I think you're close to having a great system, but you should consider a few changes and ensure proper sizing. The price isn't way out of the ordinary (I think LA is a bit high), but it is a bit higher than I'd expect (this depends on the circumstance, but I'd expect around $8k).

Danny.

You got a Comfort 13, the lower end of the Carrier brand. Performance is mid and Infinity is high end. Not that it's a bad thing, just letting you know.

That match-up with 24ACA348 condenser w/CNPVP4821 coil is:
46,000 btu cooling, 13 SEER, 11 EER. ARI# 793485.

That should be a nice improvement over your old 10 SEER system. I'm guessing a 15 - 20% improvement in your cooling bills.

Best to you.

Here is a link that might be useful: American Refrigeration Institute

I think the Comfort 13 is a fine system. I'd consider the base/builder 25HBA/25HBR units lower end. I'm not sure how much of that efficiency he'd get on a standard blower. The Comfort 13 was a good decision in my opinion--not sure how much SEER he'd get with a Performance (likely not 15). Sounds like you did it right--new lineset, new indoor coil, and new outdoor unit.

Thanks for the information. The space is small. The Payne unit has never worked properly. I would have to turn the thermostat to 60 degrees in order to get some relief from the heat. Again I do not know if the furnace is working properly. It is the original when the unit was built in 1972.

Is R410 a good think? They were saying something that I will need a HERRS inspection? What is generally the cost. They stated that if the unit failed they would reimburse me. But they will make necessary repairs. Should I go with this one, or get other estimates. Does it sound good? Thanks for the information. YOu are a big help....
Deb

I have no idea what a HERRS inspection is--R-410a units are put in often. I prefer it for future proofing.

I'm confused--by unit, do you mean the furnace? That furnace is old, and it's really time to replace it in my opinion (however, it appears you're getting a heat pump system--see below).

I'm even more confused because the parts you listed are part of a heat pump system--no furnace involved. The outdoor unit provides both heating and cooling, and you have an indoor blower called an air handler.

I'd keep looking for another bid or two.