A/C out - need to decide on new system NOW!! Opinions please

[rhb4321]

Hello all, I've been researching new HVAC system for one of the zones of my home in Dallas, TX. Good thing, as my AC went out today, so will likely replace unless it's a cheap fix. Current equipment is 3.5 ton, 15 years old, 10 SEER, R22.

Did a load calc for the area and it came out at just over 3 tons (39,581 BTU heat gain). Please look at systems proposed and let me know which you would recommend, given that system 2 is about 15% more than system 1. Could also go with a comparable Rheem system for about the same as system 1.

Both systems would include same install details including all new duct work, but use existing line set.

Liked both contractors, and both come highly recommended, so would be comfortable with either. Thanks in advance for your thoughts, as I'll likely need to pull the trigger on this in the next couple of days.

System 1 - 3.5 Ton
WESTINGHOUSE 3.5 TON 14.5 SEER SYSTEM (41,500 BTU COOLING)
- CONDENSER M# FS4BE042K
- HIGH EFFICIENCY COILS, M#C5BHX42CB
- 96,000 BTU FURNACE, M# FG6RA07216B
MANUFACTURER'S WARRANTIES: 10 YEAR ALL PARTS, PLUS WESTINGHOUSE "QUALITY PLEDGE"WESTINGHOUSE 3.5 TON 14.5 SEER SYSTEM (41,500 BTU COOLING)

System 2 - 3 Ton
Carrier two speed condensers model # 24ANA748A003.
Carrier variable speed two stage 80 % afue furnaces model # 58CVA090-1-16.
Carrier tin plated indoor evaporator coils model # CSPHP4812ATA.
Carrier Infinity controls model # SYSTXCCUID01-B.
Carrier EZ-FLEX merv ten rated filters model # EXPXXUNV0016.
Warranty:
Ten year parts and labor extended, ten year compressor part and twenty year heat exchanger part warranty.

[cem-bsee]

did the contractors do a load calc?
did you account for RH?
did you show your calc to contractors, so they could catch errors?
have you been comfortable when old system was running?

[aircooled53]

Hello all, I've been researching new HVAC system for one of the zones of my home in Dallas, TX. Good thing, as my AC went out today, so will likely replace unless it's a cheap fix. Current equipment is 3.5 ton, 15 years old, 10 SEER, R22.

Did a load calc for the area and it came out at just over 3 tons (39,581 BTU heat gain). Please look at systems proposed and let me know which you would recommend, given that system 2 is about 15% more than system 1. Could also go with a comparable Rheem system for about the same as system 1.

Both systems would include same install details including all new duct work, but use existing line set.

Liked both contractors, and both come highly recommended, so would be comfortable with either. Thanks in advance for your thoughts, as I'll likely need to pull the trigger on this in the next couple of days.

System 1 - 3.5 Ton
WESTINGHOUSE 3.5 TON 14.5 SEER SYSTEM (41,500 BTU COOLING)
- CONDENSER M# FS4BE042K
- HIGH EFFICIENCY COILS, M#C5BHX42CB
- 96,000 BTU FURNACE, M# FG6RA07216B
MANUFACTURER'S WARRANTIES: 10 YEAR ALL PARTS, PLUS WESTINGHOUSE "QUALITY PLEDGE"WESTINGHOUSE 3.5 TON 14.5 SEER SYSTEM (41,500 BTU COOLING)

System 2 - 3 Ton
Carrier two speed condensers model # 24ANA748A003.
Carrier variable speed two stage 80 % afue furnaces model # 58CVA090-1-16.
Carrier tin plated indoor evaporator coils model # CSPHP4812ATA.
Carrier Infinity controls model # SYSTXCCUID01-B.
Carrier EZ-FLEX merv ten rated filters model # EXPXXUNV0016.
Warranty:
Ten year parts and labor extended, ten year compressor part and twenty year heat exchanger part warranty.

\
System 2 = Is a 4.0 ton NOT 3.0 ton.
Get the Carrier and hurry before your 1000.00 rebate expires on June 30,2008.

[nvr2old]

Westinghouse in my oponion would be considered a builders model or second tier product. The weather is a little cooler do a little more research. Highly recommended referrals usually mean he has best price or he's a nice guy they don't automatically translate to top quality.

[Milk man]

Don't oversize the equipment. Looks like you need a three ton and nothing larger by your calculations.

You oversize and you will have equipment short cycling with bad humidity control.

[bmathews]

Go with the 3 1/2 ton anything. As far as oversized, it would be so marginal, it wouldn't effect anything. Not only that. I'm 3 hours south of you and its hitting 100 degrees regularly. Your old one was a 3 1/2 ton and your load calc came out somewhere in between. You would have short cycling and possible humidity issues if you went to a 5 ton, probably even a 4. Doubtfully a 3 1/2. Talk to your contractor, they will guide you along.

[beenthere]

The Carrier is a 4 ton 2 stage 50/100 compressor. So in first stage it should have roughly 2.4 ton capacity.

How did your old 3.5 ton handle the cooling load over the years. Did it struggle sometimes, or did it cycle on and off on your normal hot days.

If it stuggled, he the Carrier 2 stage. If it cycled, the Westinghouse 3.5 ton.

[rhb4321]

I actually did the load calc using HVAC-Calc and the pre-loaded settings for Dallas, TX, then had the contractors validate it. As to comfort, it struggles a bit during the hottest days, but I'm convinced that is as much my spaghetti duct work as it is the unit. When I do this, I'm going to re-locate the unit to make more direct duct runs; that's included in the pricing.

Any concerns over the reciprocating compressor in the Carrier?

[beenthere]

No, its a good compressor.

So your increasing to a 4 ton then.

What did the load calc say for sensible, and latent load.

[rhb4321]

Here's the HVAC-Calc design conditions and summary report for the zone in question:

Design Conditions: Dallas
Indoor: Outdoor:
Summer temperature: 72 Summer temperature: 105
Winter temperature: 70 Winter temperature: 20
Relative humidity: 55 Summer grains of moisture: 93
Daily temperature range: High
Sensible Gain: 36,222
Latent Gain: 3,359
Total Gain: 39,581

I did not use any "safety margin", just went with the Dallas settings from CALC.

Think the Carrier is a better system, but worried about over/under size with it, as the Infinity doesn't have 1/2 tons......

Final wild card thought: what about the Westinghouse IQ? This is the most lived in part of the house, so might consider spending more to ensure comfort.....

[beenthere]

The IQ, may be a better choice for you. It should mod down to what you need under most of the load conditions you'll have.

[sparksandfan]

The traditional load in Dallas has been a design of 100*F. 105 is high as a design temperature unless it is a year like 1980.

You show a sensible of 36,222. This is a load, and not an equipment selection. When you match sensible to sensible, you may find that a 4 ton equipment is closer, if 105* is the design point. That's why the question of were you content with your 3.5 ton.

When the outside temp goes over 95, then you have to derate the outside unit. When the inside is 72 and not 80 then you have to adjust the evaporator. Minor adjustments to be sure, but Manual J is only a beginning point for equipment sizing.

[rhb4321]

Oops, posted the one where I DID use a "safety factor". The one using CALC design conditions was a "bit" lower, but still in the "which way do I go" range.

I am interested in some of the comments regarding the Westinghouse system, as AHRI lists Carrier as the weaker EER and Btuh of the two. I realize that the controls are different, but couldn't I get the same dehumidifying effect with a variable speed furnace and Honeywell VisionPro stat? Still trying to learn what's what......