Need help with final decision

[jtrammel]

I think it's 70% in first stage. The only one that is half is trane's xl20i bc it has 2 seperate compressors for high and low.

[Zomby]

I think it's 70% in first stage. The only one that is half is trane's xl20i bc it has 2 seperate compressors for high and low.

Thank you sir!

I "really" think 2 ton is the way to go. I just talked to a buddy who has the same size house as me (1500 s/f) layed out very similiar and he found out he has a 3 ton and the contractor told him to go with a 2 ton.

[jtrammel]

My house is ~1300 sq ft with a 2 1/2 ton ac and it is oversized, I have to run a dehumidifier in the summer bc the ac doesn't run long enough to keep the humidity down. I'm in upstate South Carolina with a summer design of 92F. I did a load calc and it came out to 20k btus, a little over 1 1/2 tons and I know of some problems I can fix to bring the calc down a little more.

[RyanHughes]

Net capacity on low can be as much as 75-80% of total capacity depending on the match-up with the unloading scroll compressors used in most 2-stage units. That's why you don't want to go with a 3 ton if that's not what the space requires. On low, you'd already be at a bit over 2 tons capacity, and you wouldn't achieve the long runtimes in low as desired for comfort.

[BaldLoonie]

Just remember that those furnaces quoted aren't meant for 2 stage A/Cs. If you go that route, you should get the variable speed models.

[jtrammel]

Just remember that those furnaces quoted aren't meant for 2 stage A/Cs. If you go that route, you should get the variable speed models.

X2

[Zomby]

My house is ~1300 sq ft with a 2 1/2 ton ac and it is oversized, I have to run a dehumidifier in the summer bc the ac doesn't run long enough to keep the humidity down. I'm in upstate South Carolina with a summer design of 92F. I did a load calc and it came out to 20k btus, a little over 1 1/2 tons and I know of some problems I can fix to bring the calc down a little more.

That is why i am sold on going with the 2 ton. On the initial load calculations, all three contractors said the current 3 ton was too much. Even though 2 of the 3 recommended 2.5 tons, I am convinced from reading these posts the many they are afraid to "undersize".

Net capacity on low can be as much as 75-80% of total capacity depending on the match-up with the unloading scroll compressors used in most 2-stage units. That's why you don't want to go with a 3 ton if that's not what the space requires. On low, you'd already be at a bit over 2 tons capacity, and you wouldn't achieve the long runtimes in low as desired for comfort.

Just remember that those furnaces quoted aren't meant for 2 stage A/Cs. If you go that route, you should get the variable speed models.

Yes sir, the proposal from both Trane and Bryant is for a 2 stage variable speed 97% gas furnace.

[54regcab]

1587sqft in Oklahoma and 2 tons is more than enough for the design temp of 96. AC will keep house @ 75 with a 100 degree outdoor temp but runs all the time to do it. Sizing is right on the money, house is much more comfortable during low load conditions because the smaller unit runs more often.

[Zomby]

1587sqft in Oklahoma and 2 tons is more than enough for the design temp of 96. AC will keep house @ 75 with a 100 degree outdoor temp but runs all the time to do it. Sizing is right on the money, house is much more comfortable during low load conditions because the smaller unit runs more often.

Thank you for your input. I am 90% convinced to go with a 2 ton unit. Like mentioned, I think just having a new system will help alot.

[BaldLoonie]

Ignore me, the warning about the wrong furnaces is for a different thread! Shouldn't have posted after 2 shots of rum last night

[dan sw fl]

So what would your suggestion be from what you have seen me post? 2 ton single stage or 3 tom two stage? I would sure appreciate your opinion!

Definitely a 2 ton IMO (with ~20,000 BTU/Hr sensible cooling load)

A few caveats..
Home will be maintained at ~20'F less than outside.

At > 78'F indoor temperature, the cooling capacity of the system actually increases.

A dry heat is expected in mid-Missouri at > 95'F, so the air handler will operate at a higher Sensible Heat Ratio (SHR) inherently providing
slightly larger capacity to cool the supply air.

> 98'F in mid-Missouri should be much less than 2% of the time / significantly < 170 hours per year.
i.e. 20 days per year for 6 hours a day.
Worst case IMO One might expect 80'F inside for up to 15 days for 4 hours in these days of climate change.
- use a fan for 100 hours per year if need be.-

Those are the weather, equipment and homeowner interaction possibilities.

So, I would go with a 2-ton because I very much like Ithe other 2,500 + cooling hours to be
close to 40% Relative Humidity at ~76'F
which can be achieved with run times of > 10 hours per day.
.... without having the utility as the designated charity.

[dan sw fl]

Ignore me, the warning about the wrong furnaces is for a different thread! Shouldn't have posted after 2 shots of rum last night

Confusing thread are you? ... easily done EVEN without Any Rum.!..!!

Simply get tired in the evening and thoughts become a bit less clear.

[papa_jo]

My house is ~1300 sq ft with a 2 1/2 ton ac and it is oversized, I have to run a dehumidifier in the summer bc the ac doesn't run long enough to keep the humidity down. I'm in upstate South Carolina with a summer design of 92F. I did a load calc and it came out to 20k btus, a little over 1 1/2 tons and I know of some problems I can fix to bring the calc down a little more.

i am in death valley cola town sc. I run a 3 ton unit and after installing new windows this year I can go to a 2 ton unit, also new doors front and back

[Zomby]

Ignore me, the warning about the wrong furnaces is for a different thread! Shouldn't have posted after 2 shots of rum last night

Ha! I kinda thought I mentioned that both furnaces were variable speed.

[Zomby]

Definitely a 2 ton IMO (with ~20,000 BTU/Hr sensible cooling load)

A few caveats..
Home will be maintained at ~20'F less than outside.

At > 78'F indoor temperature, the cooling capacity of the system actually increases.

A dry heat is expected in mid-Missouri at > 95'F, so the air handler will operate at a higher Sensible Heat Ratio (SHR) inherently providing
slightly larger capacity to cool the supply air.

> 98'F in mid-Missouri should be much less than 2% of the time / significantly < 170 hours per year.
i.e. 20 days per year for 6 hours a day.
Worst case IMO One might expect 80'F inside for up to 15 days for 4 hours in these days of climate change.
- use a fan for 100 hours per year if need be.-

Those are the weather, equipment and homeowner interaction possibilities.

So, I would go with a 2-ton because I very much like Ithe other 2,500 + cooling hours to be
close to 40% Relative Humidity at ~76'F
which can be achieved with run times of > 10 hours per day.
.... without having the utility as the designated charity.

Well I just talked to the contractor and he told me he would do anything I wanted but he said he was extremely apprehensive installing a 2 ton unit. He said he trusted his calculations that originally called for a 2.5 ton. But since the Bryant Preferred 127A doesn't come in a 2.5 ton, he bumped it up to 3 ton instead of dropping to 2 ton.

He reasoned that since it was 2 stage it would keep the house cool no matter what kind of summer we had.

So confusing.............

[Zomby]

The sales rep for the contractor just emailed me this: (1) Bryant up to 16.50 SEER 2.0 Tons 2 Stage Air Conditioner w/ Puron Model 127ANA024000

(1) Bryant Vertical Cased N-Coil with Factory Installed TXV - Tin w/ Furnace Install Model CNPVP3017ATAx

(1) Bryant 96.3% AFUE 60000 BTU Two Stage Variable Speed Gas Furnace Model 986TA42060V17

(1) Bryant Thermidistat Programmable Digital (System) Model T6-PRH01x

(1) Bryant $125 Mail in Rebate

(1) $200 (power company) Incentive Included in Price for 95% Furnace

(1) $600 (power company) Incentive Included in Price for Air Conditioner

(1) $80 (power company) Incentive Included in Price for Motor

(1) 10% Discount for Friends & Family Included in Price

[jpsmith1cm]

leaker2

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[54regcab]

Not surprised, contractors have been forever scared of undersizing. This is why we find so many oversized units installed. A 2 ton single stage would suit you well. You need to determine the cost difference once rebates are applied.

IMHO if utilities REALLY wanted to save peak demand they would simply limit the peak power of the unit relative to square footage of the house. Peak demand occurs on those days it's over 95 outside in most areas. EER is about the same for a 15 or 21 SEER unit. A smaller unit would reduce utilities peak demand by using less power during peak conditions then allowing the unit to do the catching up during off peak times.

The 60K furnace is overkill for your house, a 40k is more than enough.

[catmanacman]

Just have the trane guy install a 3 ton 20i with a xc 95 furnace and you will have the extra on the hot days

[Zomby]

Not surprised, contractors have been forever scared of undersizing. This is why we find so many oversized units installed. A 2 ton single stage would suit you well. You need to determine the cost difference once rebates are applied.

IMHO if utilities REALLY wanted to save peak demand they would simply limit the peak power of the unit relative to square footage of the house. Peak demand occurs on those days it's over 95 outside in most areas. EER is about the same for a 15 or 21 SEER unit. A smaller unit would reduce utilities peak demand by using less power during peak conditions then allowing the unit to do the catching up during off peak times.

The 60K furnace is overkill for your house, a 40k is more than enough.

The cost difference between the 2 ton and the 3 ton is $600.