Looks like it's time to replace my AC, coolant leak somewhere.  Had it filled last summer and now no coolant/frozen lines.  The heater and blower are good.  So that begs the first question - do I replace just the AC and coils or the whole system including gas heat and blower?  System is 16 years old, the AC is the only thing wrong and no complaints about heating.

How about brands?  I'm good with spending more to get more quality/reliability, less noise and efficiency, home is about 6400 sqft but this main unit only does basement and 1st floor.  I've heard good things first hand about Carrier, seems like Trane quality has been going down for a while when they used to be very good.

And lastly - what about variable speed blower fans and compressors?  The blower is quite loud and right underneath the bedroom so if I do go with a total replacement I'd prefer a higher end one I would think.

Thanks in advance, going to get three different installers to quote but would like to know when I'm getting snowed.

IMHO, you need multiple units for zone heating/cooling.

There are 3 units and thermo stats but this is the main one that moves the most air. It's all very open and high ceilings.

im 23 yrs a hvac guy....having typed that and being a trane dealer,90% of the lonhevity can come down to proper sizing/installation.you can take a "lesser" brand and get good life/perfoprmance out it as long as its sized and installed properly.there are tons of pirates in my trade,so beware who you you buy from.also there is no single system that can cool that many sq ft alone.outside of setting a commercial unit outside your home.

also if your anywhere near louisville,hettinger and schuck used to be the best around there and won many trane achievement awards.

Maybe just reload the freon - and press on for now...

Thanks for that. I'm in Louisville so I'll have them out. This unit is only servicing 4000 sqft. The ducting could be improved IMHO.

I figure if I'm going to drop the coin for this I want it done right. Very right which is why I'm curious about replacing the whole thing vs just the AC.

This. 99 percent of systems are designed like a piece a runny dogshit.

Op. How old is this unit? Unless i missed something there are quite a few steps in between "my freon leaked out" and "i need a quote on a new one".

I sell off brand units, mostly comfortmaker and a few goodman, and my units usually outperform the high end just bc i can design a legit setup and dont skimp on unit size. 99 percent of my work is industrial chillers for dairies though. We sell carrier to the dairies bc they are the cheapest and work well if you design it right.

Did that last August.  I don't have to do immediately because of weather which is why I want to spend some time and research to figure out what's really the best long term option.

16 years. Coolant replaced in August of last year. I appreciate the industry knowledge and know the difference unit needs to be sized properly. A sales guy is coming to give me a quote. Sales doesn't equal engineering.  

1 ton per 400 sq feet minimum, residential units only go to 5 ton

Well fuck me then.

I've never really had any complaints about the cooling of the current unit in question. But I'd love to know how to set the three thermostats properly for max effectviveness.

If you think you might want to try to skate by for a few more months, I've used this in my 16 year old system until I was ready to replace.

http://www.amazon.com/Nu-Calgon-4050-06-Nu-Calgon-Easy/dp/B005DTLM1O/ref=pd_sim_indust_3?ie=UTF8&refRID=1KWDG79S7H5C1KWJ80HK

It worked for an entire summer.

I opted to replace my system with one that uses the new 410a freon. It's also way more efficient than my old system. My electric bill dropped $20 a month.

I'm not a HVAC expert, I am in the construction industry and that figure seems wrong to me.  I've had 3.5 ton covering 2,000 SF with zero issues from performance to efficiency.  OP, you may have to go to 2 systems or a split system to properly & efficiently cover 4,000 SF.  Most homes at 4,000!SF have at least two zones.  Homes in your size range should be 4 zones.

I have a Trane XL16i Air Conditioner that was installed a couple of years ago.

It is a 5 ton cooling 4,600 square feet of house in Kansas. We average about 17 days of 100+ days per year. This Trane cools it well. It is comfortable everywhere in house. And, our electric bills dropped about $60/month in the summer.

One of the best purchases that I have ever made.

Plug the hole?

87% derp.

american standard/ trane, carrier, lennox. in that order

get a variable speed heat pump with a variable speed air handler. rule of them when sizing an ac system, do a manual j heat load calculation. you can easily cool 4000 sq feet with a 5 ton system if the load is correct, you will have conditioned space above or next to the zone so you have less heat gain on the space

Listen to this guy. My thoughts exactly.

Thanks a bunch.  I'll grill the installer about sizing and make sure they've actually done some calculations on it rather than "you had a 4 ton unit so we'll replace it with the same size".  I actually don't know the size of my current main one yet.

Thanks for the help fellas.  I'm getting a Trane 5 ton AC dual-compressor unit (his calcs called for 4.4), variable speed blower/furnace and humidifier.  All for 11k.  Had multiple quotes.

The installer told us what we already knew - our duct work/design is bad.  But he didn't try to sell any of that and said we could always change some of that if we wanted.

After walking around the house and measuring his comments were straight - "Builders think they know how do HVAC, they don't - you've got problems with only a single return on the first floor...2k feet and only a single return <facepalm>"

My goal is the system can actually condition the air even humidity.  I want the blower running 24x7 efficiently to compensate for the bad duct design.

Interestingly he said our furnace was too big.  135k BTU and he's taking it down to 110k BTU. - reason being the single return = the far side will never get any heat because of short run times.  Thermodynamics says he's right.