Replacing Old Unit...Need advice

[tecboy]

I live in southwest Ohio. Approx 1500 Sq ft ranch, little to no insulation in outside walls. Current system is a Lennox 70% furnace and 2 ton AC unit. AC unit has developed a leak in coils and i do not want to spend money replacing a old undersized unit. I had a Carrier dealer out to access my HVAC needs. According to his numbers i should be running a 3 ton AC unit(numbers actually came out to 2.6 ton). I have a few options they gave me quotes for...All work includes some minor ductwork tweaks including adding a few dampers to balance airflow in house, all necessary electrical work and permits
1. only replace A/C system with 38TZA036 A/C unit(12 SEER) and CC5AXA036 coil )--use existing Lennox furnace
2. replace furnace with Carrier 58MTA080 Performance(93% AFUE) and replace A/C with options in #1 along with a TSTATCCPRH01 thermidistat. )
3. replace furnace with Carrier 58MVP080 Infinity 96(94% AFUE) and replace A/C with Carrier Infinity 18 38TDB036 (15.5 SEER)along with a SYSTXCCUID01 Infinity Control

My questions..I have never priced/shopped HVAC units before.
Is the small increase in efficiency worth the extra money spend for the Infinity series? I wasnt sure if the variable speed furnace and 2 speed a/c motor made that much difference with comfort levels.
If I replace only A/C unit..I cannot go with the higher 15.5 SEER Infinity A/C system. I will spend more money up front by replacing the entire system at once vs A/C only now and furnace later which has me leaning towards replacing the entire system now and recouping some of the cost on immediate tear round energy savings..

Your thoughts on the above are appreciated..

[Edited by tecboy on 05-18-2005 at 09:45 PM]

[chadman]

Did 2 ton work before? If it came out at 2.6 I suggest a 2 and a half ton condensor with a 3 ton coil and add some insulation.

[tecboy]

During peak days in summer..A/C would lose ground temp-wise as the day went along...so i would imagine that the undersized 2 ton was a big part of my problem..
Adding insulation is not possible..Outside wall construction is brick with block backing then firring strips then plaster..only about 3/4 inch space in walls for insulation..not worth the money

[chadman]

What is desired temp during the summer months? Do you set your T-stat and leave it at a constant temp?, or do you try to swing your temp between night and day? A/C is just like having a big dehumidifier. Alot of homeowners do not relize every thing in the house holds humidity carpet furniture ect. I go to houses all the time where people think that they are saving money by shutting the A/C down and opening windows on cool days and nights. The thing yhey do not relize is the humidity that they spent two days removing is all coming back in. I always tell them set it and leave it. The only reason I say a 2.5 condenser and a 33 ton coil is because the more surface area on the coil the more humidity removal. It will not hurt to install a 3 ton condenser, I am just looking for your most efficiancy,and I have not seen the job.

[tecboy]

no problem..appreciate the help..temp during summer is set 74/75...i currently have a honeywell prog thermo that controls everything..during summer..most time zones are prog within 2-3 up or down as i found if i set thermo higher while at work..unit can never cool house back down between 5pm and dark/bedtime...

[amd]

more surface area on the coil the more humidity removal.

Wait...wouldn't that make the coil run warmer, thus reducing latent capacity? (yes, I am referring in indoor)

I thought that coils were oversized to increase SEER/sensible capacity, not improve humidity removal.

[Edited by amd on 05-19-2005 at 12:18 AM]

[chadman]

refering to indoor coil,more surface area on out door condencing coil higher seer

[tecboy]

I was more intersted if the extra cost for the Infinity system as worth the extra $800 i was quoted. I didnt know if the variable speed fans and 2 stage A/C unit actually made that much of a difference. I would also really like to find out what avg installed price ranges the systems should come in at and would post what the bid was but i understand that is a no-no....

[docholiday]

If you only got an 800 dollar difference from 2-3, I would jump all over it.

We dont discuss pricing here, sorry.

[pecmsg]

Even 3/4" insulation will save more then High eff A/C in your area.
If your furnace is over 15 years old then replace both at the same time. Make sure the duct work can handle the higher CFM of a 2 1/2 ton unit.
This is a big investment, Do it right.
90 + heater is worth it. 18seer A/C I dont think so.
Get some more estimates and get back to us.

[dash]

Originally posted by tecboy
During peak days in summer..A/C would lose ground temp-wise as the day went along...so i would imagine that the undersized 2 ton was a big part of my problem..
Adding insulation is not possible..Outside wall construction is brick with block backing then firring strips then plaster..only about 3/4 inch space in walls for insulation..not worth the money


Adding it to the attic has the greater effect on cooling load ,then adding it to the walls.

[dash]

#3

Use the search function on this site ,keyword Infinity,to see what other homeowners think about theres.