Replacing A/C system--two stage or single stage,also which brand?

[mtrot]

Hi all. I am looking at replacing my 20+ year old A/C system which consists of a 10 SEER compressor and gas furnace. The house is single story, with about 2850 square feet. The location is East Texas.

I have two quotes so far, and another contractor is coming tomorrow for another quote. It seems the most used brands around here are Trane and Lennox.

First of all, is there any brand out there that is better enough than Trane or Lennox that I should definitely seek out a dealer for a quote?

Secondly, I am an audiophile and listen to a lot of music, as well as movies, and I like my house as quiet as possible. Also, unfortunately, my furnace closet is located in the hallway right by the family room where my audio system is. When my current furnace fan is running, it sets up a veritable roar that obscures a lot of the music.

Where this may be an issue is that with the two-stage units, the furnace fan(admittedly at a quieter level) will end up running for longer periods of time than a single stage model. I can't decide if I'd rather have the fan running longer but quieter, or if I'd like it better for the fan to run on full for a shorter time and then turn off. Bear in mind that the new furnaces will be significantly quieter, even on full speed, than my current fan. Also bear in mind that during the 105 degree summers we have here, any A/C system is going to be running at full capacity from about noon till 8 to 10pm.

What experience has anybody had with the two stage units? How long does the system run continuously when in cooling mode? Does it shut off much, or mostly run?

It appears I can obtain a 14 to 15 SEER with either the single stage or the two stage system.

Thanks for any input!

[universaltech]

Shopping for a company is just as important with shopping for a brand.

[mtrot]

Thanks, yes I am researching local contractors as well. Can anybody provide any insight on my equipment questions? Thanks much.

[HVAC/Stud]

First have the contractor perform a Manual J, and show it to you. This will find out the heat loss, heat gain and latent heat load.They can then size the unit. Check ductwork, don't install a new unit on poor ductwork. Check return air, very important.

Any brand will work as long as its installed IAW ACCA standards and the manufactors guidance. Go with best warranty on brand.

Having the AHU in living space is poor design, not much you can do about that. Move to crawl space or attic?

Two stage a/c are way to go, if sec stage load matchs Manual J.

I'd go with two stage or a modulating gas furnace, var speed blower(first check ESP on duct work. If high SP on duct work noise will be a problem).

Have your contractor find a furnace that has the lowest decibles. In-shot burners are loud.

Its your system and your money, be informed and hold the contractor's feet to the fire.

Good luck,
STUD

[mtrot]

First have the contractor perform a Manual J, and show it to you. This will find out the heat loss, heat gain and latent heat load.They can then size the unit. Check ductwork, don't install a new unit on poor ductwork. Check return air, very important.

Any brand will work as long as its installed IAW ACCA standards and the manufactors guidance. Go with best warranty on brand.

Having the AHU in living space is poor design, not much you can do about that. Move to crawl space or attic?

Two stage a/c are way to go, if sec stage load matchs Manual J.

I'd go with two stage or a modulating gas furnace, var speed blower(first check ESP on duct work. If high SP on duct work noise will be a problem).

Have your contractor find a furnace that has the lowest decibles. In-shot burners are loud.

Its your system and your money, be informed and hold the contractor's feet to the fire.

Good luck,
STUD

Thanks, both the Trane contractor and the Lennox are quoting 10 years parts and labor. I went on a HVAC review site, and Lennox is about the lowest rated major brand. Trane and Carrier are rated higher, but still have tons of horror stories of poor reliability. Will look for low decibels on furnace. Still not sure if I want a two stage system.

[HVAC/Stud]

If you anything demand a Manual J and check static pressure on duct work.

STUD

[mtrot]

I received another quote(Trane) yesterday, and the contractor said he could do a manual J, but he did not see the point because the system is already a 5 ton and to increase the tonnage would require two zones, which would be prohibitively expensive. Also, all the contractors stated 5 tons AC should be plenty for a 2850 square foot home.

One nice thing about this fellow is that, as we checked the duct work in the attic, he noticed that the duct that goes to the master bedroom was partially disjointed and leaking air, which could be the problem with not enough cooling in the master bedroom, and which is an easy fix. The other contractor who went in the attic did not notice this.

Also, can anybody comment on what percent of time(on cooling) that the system will run if I go with a two stage compressor and variable speed furnace? I have read as much as 80% of the time.

[precision hvac]

Doesn't sound to me like you are a candidate for a ECM VS furnace IMO. Run times will be long.
I'd go with something like the Rheem 95 AFUE single stage w/ PSC motor. Model RGRC & have them vent it out using a concentric vent kit. Totally sealed doors & all sounds of combustion are out your roof now.

[udarrell]

This is only what I'd do in your situation.

Eastern TX doesn't tell us if U live in the dry area say in Dallas area, or in a more humid area near say Houston.

I'm betting the 5-Ton condenser is probably achieving around 4-Ton of cooling due to an insufficient duct system for 1800 to 2000 required CFM airflow. It is very very rear to have a 5-Ton residential setup with a duct system that supports that tonnage.

First even in your climate area, 2850-sq.ft home should be retro'ed to allow 712.5-sq.ft., per ton of cooling, or a 4-ton A/C or heat pump.

I would have a Home Energy Efficiency Rater/Audit performed & do the retro-fit work so a manual J would call for a 4-Ton system; efficiency will be greatly improved.

What that does is allow you to set the blower for as low as 1400-CFM, or 350-CFM per ton of cooling. That will greatly reduce the noise factor & if in a humid area the longer runtimes will reduce indoor humidity & provide a higher SEER efficiency due to less on/off cycling.

Doubt I'd go for a two-stage cooling system; I'd install a programmable t-stat with a setting for longer off-time settings. Depending on outdoor conditions the setting can permit variant temp off/on swings the suit u comfort-wise.

The amount of blower motor runtime does add to the electric bill; a PSC 5-Ton blower will pull around 14.5-amps; a 4-Ton PSC motor around 8 to 9-amps.

Because of the long cooling runtime, I would want an efficient DC blower motor...

Work with your local contractors & make your decisions accordingly... :.02:

[mtrot]

I ended up going with a Lennox system, XC16-060 two stage outdoor unit, SL280V-110 furnace, ADP coil, ComfortSense 7000 t-stat. They shot me a phenomenal quote, which includes 10 years warranty on parts and labor. I could not see going with either of the two Trane quotes because they were significantly higher and did not offer a two stage compressor.

The three installers, who seemed very professional, just left, and I obviously can only comment on the heat mode, but it is definitely quieter, even on the high fan speed, than the twenty-something year old Day and Night unit on the heat mode. It may need to employ somewhat longer run times in really cold weather because the air temp out of the registers is not as hot as with the old furnace. The old furnace was a 125000 btu, which I am told is way more than needed for this climate. I was assured that 110000 btu was plenty for East Texas.

I guess I won't know about the efficacy on Cool mode until next spring.