Is quote 3 for a 120KBTU furnace? That is twice the size you would need for the LA area.

I highly doubt you need a 5 ton condenser? Load calculations based on square footage almost always results in over sized equipment. You need to find a contractor who will do a proper load calculation.

Where specifically are you located? I would like to look up the outdoor design temperatures.

@tigerdunes: One of the contractors said the current condenser looks to be 3/3.5 ton but it isn't easily accessible to check. Our furnace is the original from 1976 and most of the specs are too faded to read.

@mike_home: I'm in Santa Clarita, CA (91354). The Quote 3 contractor did a load calc that he says came in at 4.25 ton cooling requirement, but he thinks ductwork may be designed for 3 tons max. (I have the full report but it's Greek to me.) We're hoping to replace some or all of the upstairs ducts, but the downstairs will need to wait. To be honest, I'm not sure about any of the furnaces, but the spec sheet for the Quote 3 furnace says:

1st Stage Input BTUH: 78,000/1st Stage Capacity
BTUH 74,880/2nd Stage Input BTUH: 120,000
/2nd Stage
Capacity BTUH (ICS): 115,200


Quote 3 contractor said, "The American Standard single stage furnace with the 16 SEER condenser does not quite meet 16 SEER. To meet a verified 16 SEER we would need to use their variable speed furnace."

Side questions:

1) we're leaning toward a two stage condenser (variable just doesn't seem worth the extra expense) but have quotes for single stage. Any advice how to determine best choice?

2) living room has 14 ft ceiling but plan to put in a ceiling fan for circulation. Upstairs much warmer in summer too, again planning ceiling fans to help. Wondering if should consider 2 zone system? It's an extra $2K. Could probably swing with the single stage condenser but probably not with two stage.

also, we have no attic/ceiling access due to a horrible design oversight, so options are expensive and limited for replacing ductwork/insulation.

The design temperatures in your area are about 35 degrees in the winter and 98 degrees in the summer. Were these the temperatures used in your load calculation? The indoor temperatures are usually 72 degree for winter, and 75 degrees in the summer. Those numbers can be adjusted if you like it warmer or colder.

"The Quote 3 contractor did a load calc that he says came in at 4.25 ton cooling requirement, but he thinks it may be designed for 3 tons max. "

Can you explain what this statement means?

Is contractor 3 picking a furnace that will achieve a SEER 16 rating? Do you need SEER 16 to meet a minimum allowable efficiency? It is a bad idea to oversize equipment just to meet a paper rating. I have serious concerns about a contractor who would propose such a large furnace in such a mild climate. It is highly doubtful your duct work could handle a 120K BTU furnace.

"One of the contractors said the current condenser looks to be 3/3.5 ton but it isn't easily accessible to check".

If the current AC is able to keep the house to your desired temperature in the summer then why are you increasing the size? The second floor temperature problems are most likely due to duct problems and not condenser size. Where is the condenser located that makes it so difficult to access? Are you going to fix this access problem so the condenser can be serviced in the future?

Zoning the second floor would be a good option assuming the contractor you are using is good at zoning. If you go with zoning then I would think a 2-stage AC would be a better option. A single stage could work but the contractor has to put in some type of bypass when only on zone is calling for cooling.

The design temps used on the load calc (outside/inside): winter (42/70) and summer (97/75). The condenser is on a flat roof in the back of the house. It can be accessed for servicing but wasn't something I could get at easily on my own to check size.

As far as original equipment size, I can have my husband climb up tomorrow to try to find a serial number and see if we can confirm the tonnage. It keeps the house relatively cool (we keep the thermostat around 76-78 most days), but not really cold. The ducts are smaller, 5-6" if I'm properly reading the sketch Contractor 3 made, which is what I think he meant when he said the house may be designed for 3/3.5 tons max.

As far as Quote 3, that contractor originally quoted us Carrier equipment: a 16 SEER two stage 4 ton Carrier condenser (24ABC748A003) paired with a two stage 4 ton furnace (59TP5A080E2120) for $11,940. He said that he could get a comparable American Standard quote, but it's not a brand he typically reps, and he sent us Quote 3. The Carrier furnaces he quoted us are smaller, so I'm not really sure why the American Standard isn't. We didn't press him for more info yet since we've realized we're in over our head and need some outside advice.

The 16 SEER is arbitrary based on the fact that we've been looking at quotes for various SEER (13-21). We've ruled out the high end as too expensive for the energy saving but the 16/17 SEER models seem to offer a decent savings compared to the price difference for a 13 SEER.

My husband like Quote 1 because it's the cheapest but the contractor seemed sketchy. It's a big company and the rep offered us a "great deal" to replace "any accessible ductwork" (which is basically none of the ductwork since we don't have crawl space or attic access and everything in in the walls/ceiling) for $2000 so we could upgrade to a 5 ton unit. We like the contractor for Quotes 2, but the $2400 difference between quote 1 and 2 is off putting. The Quote 3 contractor spent the most time with us and did a load calc at our request, but he seems to better understand the Carrier equipment if he's misquoting the American Standard equipment so badly. This is our first huge decision as new homeowners and it's become so confusing. Since we hope not to replace the AC system for enough 20+ years, we're stressed about getting it right.

For most manufacturers, the size of the equipment is within the model number. If you see an "80", or a "120" within the model number, it usually means the furnace is rated for an input of 80K or 120K BTU respectively. The output BTU is the input multiplied by the efficiency. The load calculation has to be compared to the output BTUs.

I am concerned contractor 3 is quoting a Trane furnace that is 120K BTU. You don't have to be a Trane equipment expert to figure that one out. It is good that he did a load calculation, but then he quotes a furnace that is too big for the duct work to handle. Did you make a recommendation on how that can be addressed?

Contractor 1 should make you nervous. If your ducts are as small as you say they are, then he has no business quoting a 5 ton condenser. He is a salesman working on a commission. His job is to up sell. How it will work is the installer's problem.

Quote #1 with a true two stage thermostat with WiFi if interested and filter media cabinet. This is quality HVAC. What Mdl evap coil. No third party coil permissible, only Trane,AmStd.

80 K 80% furnace with 4 ton rated blower and 4 ton 2 stage AC condenser.

Insist on load calculation as condition of purchase.

IMO

Back with more info: current AC compressor is Bryant model number 561CJ042-F/serial number 3304E17340. If I'm reading that correctly, the 42 on the model number indicates that it is a 3.5 ton and the serial number tells me that it is from 2004.

From your previous posts, I'm taking away:

1. We should consider sticking with a 3.5 ton unit, not increasing to a 4 ton, regardless of the Manual J calculations coming in at 4.25 tons. Is there a downside to having a smaller unit? If we're replacing our upstairs ductwork with newer ones now and expect to replace the downstairs ones in the next 3-5 years when we remodel our kitchen, is there an argument to go with 4 tons if we could have ducts that could handle more capacity? Or is it possible/likely that the 3.5 ton unit could still meet our cooling needs?

2. Our upstairs/downstairs temperature differential is probably better addressed through examining ductwork. We know that there isn't enough airflow into the warmest room (our master bedroom); we're fairly certain that we're losing heat in the upstairs ducts due to leaks or other issues but won't know until we take out the old equipment and/or open up the ceiling to get a look at the existing ductwork Is it possible that making the ducts more airtight and just adding a second vent to increase airflow could address the temperature issue? Or should we more seriously investigate a two zone system? The extra money for zoning is a small stretch, but could be worth it in the long run so trying to be pound wise but not penny foolish.

P.S. Thanks for answering my many questions. We don't have an unlimited budget and there's so much to consider.

The down side of getting a smaller condenser is that you will not be able to maintain a 75 degree indoor temp when it is 97 degrees outside. You may need to increase the condenser to 4 tons, but you have to address the duct sizing. If you don't the duct work will be noisy and you will put stress on the air handler which will lead to a shorter life. You also won't get the full benefit of the larger condenser.

The main duct is one that has to carry all of the air. See if that can be increased in size. What size filter do you currently have? That also has to be sized appropriately. A 4 inch thick filter is much better than a 1 inch. The larger filter creates less air resistance.

Now many returns does your home have? How do you currently filter your return air? I agree if going up in AC condenser size, ductwork needs thorough inspection/evaluation as to ability to handle 4 tons of conditioned air.

IMO

We have two returns, one upstairs (approx. 22" x 10") underneath the furnace platform/closet and one downstairs (approx. 25" x 14") which is just in the wall cavity with no ducting. It has been recommended to us by nearly all of the contractors that we increase the size of the upstairs return.

There is a 20" X 25" X 1" filter at the base of the current furnace. We were offered to add on the American Standard AccuClean system, which would be much larger than a 1" filter and were leaning in that direction.

One furnace question: 80% or 95% AFUE? The more efficient furnace qualifies for a slight rebate but one contractor suggested that the condenser would operate more efficiently with the 80% unit and that gas is so cheap in CA that it isn't worth paying extra for the 95% unit.

Any advice about questions to ask/research to decide if zoning is a good option for us? The extra $2000 starts to strain the budget.

Also, we have a comparable Carrier quote at $11,940 for Outdoor Unit Model Number: 24ACB748A003/Indoor Unit Model Number: CNPHP4821ALA/Furnace Model Number: 59TP5A080E2120. Is Carrier worth considering instead of American Standard? Are there any difference in cost for upkeep/repair? The shady, Quote 1 American Standard contractor claims they cheaper to repair because they allow 3rd party parts vs. Carrier which requires only original parts, but this sounded suspect.