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You'll Shoot Your Eye Out!
Picture of MaThGr82
posted
My house is 20 years old now and the HVAC system is getting replaced this spring before I enter the hot, hot AZ summer again. I've gotten my quotes, done a lot of homework, but am now down to one last thing I can't decide. Should I go with the two speed compressor for the AC compressor. I'm hoping some of you with experience with a single vs. double can chime in here as to what the real life implications are in comfort and airflow in the house.


Background on what I'm looking at.

A 4 ton, 17 seer two stage vs. a 4 ton, 16 seer 1 stage system.

I'll be getting the Reme Halo Air cleaner, modifications to the ductwork with an additional return in my master bedroom. Currently only have one 20X30 with a 16" pipe leading to the plenum.

Manual J's ranged anywhere from 44K to 60K in BTU's so the 60K would indicate a 5 ton, but I've been in this house with a 4 ton for 12 years and don't run out of cooling capacity so I'm having a hard time with the 5 ton.

One contractor is saying 5 ton, 2 speed and another is saying 4 ton with a single speed (or two if I want it he said).

Thoughts, everyone?

Question:
Single stage or or two stage AC Compressor?

Choices:
Single
Dual stage

 
 
Posts: 6251 | Location: Peoria, AZ | Registered: October 09, 2003Reply With QuoteReport This Post
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No idea. What is the cost difference between the two options? If you don't mind me asking.
 
Posts: 429 | Location: Pearland, Tx | Registered: June 22, 2011Reply With QuoteReport This Post
Unflappable Enginerd
Picture of stoic-one
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I'm not sure how much benefit you would get from a 2-stage in AZ. The main advantage to 2-stage is reduced electrical start-up consumption when the temps are more moderate because you get less cooling AND less frequent starts. I suppose if it's sized correctly the 2-stage would save you money during spring and fall and break even in the summer, just a guess. 2-Stage really seems to provide more advantage in an area with more moderate temps and higher humidity(read middle south/ATL-ish weather).

As mentioned, what is the cost difference? What would you consider a reasonable ROI time-frame?


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Posts: 3601 | Location: Headland, AL | Registered: April 19, 2006Reply With QuoteReport This Post
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Picture of cparktd
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I just had units quoted from the local AM STD dealer. He said they just started putting a 2 stage comp in the mid level 15 seer unit. (on the next ones he orders) He even called his dealer thinking the info he got was a mistake. He said it was a great deal and highly recommended it. Thanks to some forum help I got mine running perfectly again so I won't be buying right now but I did like the idea of a 2 stage compressor, especially here with high humidity. I don't think the extra investment for the 16 seer worth the difference.


his quote differences vs seer.

14 seer + $0 . Base reference
15 seer + $600.
16 seer + $2000.



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Posts: 1682 | Location: Middle Tennessee | Registered: February 07, 2013Reply With QuoteReport This Post
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I'd go with the 2 stage if the costs aren't crazy as it would keep humidity down better, and you have such a large swinging heat load between, day and night and summer/winter.

I would go with American Standard personally. Rheems are junk. I've had several recent ones that have been nothing but trouble as well as some property manager friends.
 
Posts: 15568 | Registered: June 12, 2005Reply With QuoteReport This Post
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My opinion is the cost savings of "efficiency" gained at the expense of complexity and reduced reliability do not pay for themselves.

Single stage fixed displacement compressors (no variables), fixed speed blowers (only speed change by wire taps, no varispeed controls), 80% natural gas furnaces, and no heat pumps. Simple and reliable beats complex high efficiency stuff in the long run, simply because it lasts longer with fewer repairs, which more than offset the claimed energy savings.
 
Posts: 1596 | Location: Indiana | Registered: December 28, 2004Reply With QuoteReport This Post
You'll Shoot Your Eye Out!
Picture of MaThGr82
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quote:
Originally posted by Mikito:
No idea. What is the cost difference between the two options? If you don't mind me asking.


About 1K difference.

I'm not concerned about the energy efficiency as that will take care of itself...I'm replacing a 20 year unit after all.

I'm only concerned about comfort and airflow really. Like stoic-one said, I'm thinking about going with the 2 stage since I'll be able to have it run more often in the shoulder seasons in AZ...like October to April...May to July, it'll be on full blast anyways Smile
 
Posts: 6251 | Location: Peoria, AZ | Registered: October 09, 2003Reply With QuoteReport This Post
You'll Shoot Your Eye Out!
Picture of MaThGr82
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quote:
Originally posted by jimmy123x:
I'd go with the 2 stage if the costs aren't crazy as it would keep humidity down better, and you have such a large swinging heat load between, day and night and summer/winter.

I would go with American Standard personally. Rheems are junk. I've had several recent ones that have been nothing but trouble as well as some property manager friends.


It'll end up being a Trane system...basically the same as American Standard.
 
Posts: 6251 | Location: Peoria, AZ | Registered: October 09, 2003Reply With QuoteReport This Post
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quote:
Originally posted by MaThGr82:
quote:
Originally posted by jimmy123x:
I'd go with the 2 stage if the costs aren't crazy as it would keep humidity down better, and you have such a large swinging heat load between, day and night and summer/winter.

I would go with American Standard personally. Rheems are junk. I've had several recent ones that have been nothing but trouble as well as some property manager friends.


It'll end up being a Trane system...basically the same as American Standard.


I like Trane's. I have one at my house. They're built in the same plant as AS. Some are exactly the same, some the Tranes have different parts. AS is about 20% cheaper.
 
Posts: 15568 | Registered: June 12, 2005Reply With QuoteReport This Post
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quote:
Originally posted by jimmy123x:
I've had several recent ones that have been nothing but trouble as well as some property manager friends.


Well you should get new friends then Smile
 
Posts: 1552 | Location: DFW Texas | Registered: March 13, 2012Reply With QuoteReport This Post
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Picture of henryaz
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We have been replacing our old central ducted units with mini-splits (Trane). This is not a straight apples-to-apples comparison, as they are different types of units. But the mini's are all of the multi-speed compressor variety, and I have noticed that even in the hot AZ summer, the mini's often are running on their lower speeds. I often wonder whether a compressor is running until I get really close to it. And even on low they do a good job of maintaining our preset temps.
 
The way our Trane guy explains it, for a central ducted unit, is you weigh the extra cost for the variable speed against your expected electricity savings over the life of the unit. I believe I would go with the variable speed anyway. They do work well in AZ. Trane has a 10 year guarantee on the compressor.
 
 
Posts: 7554 | Location: South Congress AZ | Registered: May 27, 2006Reply With QuoteReport This Post
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quote:
Originally posted by henryaz:
 
We have been replacing our old central ducted units with mini-splits (Trane). This is not a straight apples-to-apples comparison, as they are different types of units. But the mini's are all of the multi-speed compressor variety, and I have noticed that even in the hot AZ summer, the mini's often are running on their lower speeds. I often wonder whether a compressor is running until I get really close to it. And even on low they do a good job of maintaining our preset temps.
 
The way our Trane guy explains it, for a central ducted unit, is you weigh the extra cost for the variable speed against your expected electricity savings over the life of the unit. I believe I would go with the variable speed anyway. They do work well in AZ. Trane has a 10 year guarantee on the compressor.
 


It really depends on the house and area. I live in south Florida and we see 93f during the summer, then my unit runs a proper amount of time, maybe 60% during the summer during the day. Right now it's 75f out and with my thermostat set at 75f it might only run 5 minutes an hour. If I had a dual stage it would run more in the winter and keep temperature balance better between rooms and humidity.

Granted I got greedy when I replaced it. The 2.5 tom would only keep it 79-80f during the day in the summer st at 75f after I increased insulation to r30. Before 82f. Everyone recommended 3 tons and I went 3.5 tons which is a touch much.
 
Posts: 15568 | Registered: June 12, 2005Reply With QuoteReport This Post
Tinker Sailor Soldier Pie
Picture of Balzé Halzé
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quote:
Originally posted by jimmy123x:
I'd go with the 2 stage if the costs aren't crazy as it would keep humidity down better...


He lives in Arizona.


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Posts: 19503 | Location: Out of Jersey, Into Utah | Registered: October 29, 2012Reply With QuoteReport This Post
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quote:
Originally posted by Balzé Halzé:
quote:
Originally posted by jimmy123x:
I'd go with the 2 stage if the costs aren't crazy as it would keep humidity down better...


He lives in Arizona.


Exactly re-enforcing my point.

It's 104-106F in July-Sept, so the unit is properly sized to keep his house cool in the summer. And it probably runs 60-80% of the time during those months and keeps humidity perfect.

BUT there are 5 months where the average temps are highs of 76F-90F where he will be running the A/C, during these months the unit Probably will only run 5-30% of the time (IF it's sized to properly cool when the average temps are 104-106F). During these months the 2 stage compressor will run a lot longer on the just the 1st stage, and will help keep the humidity down AND temperatures more even from room to room. During those months with the current old unit, humidity is probably a lot higher than it should be in the house because the unit doesn't run long enough to remove the humidity.

In a pretty well sealed house, which I would guess it should be, being AZ and all, everytime you take a shower, you introduce a ton of humidity into the house.

https://www.currentresults.com...by-month-average.php
 
Posts: 15568 | Registered: June 12, 2005Reply With QuoteReport This Post
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quote:
Originally posted by Lefty Sig:
My opinion is the cost savings of "efficiency" gained at the expense of complexity and reduced reliability do not pay for themselves.

Single stage fixed displacement compressors (no variables), fixed speed blowers (only speed change by wire taps, no varispeed controls), 80% natural gas furnaces, and no heat pumps. Simple and reliable beats complex high efficiency stuff in the long run, simply because it lasts longer with fewer repairs, which more than offset the claimed energy savings.


I know you stated this is your opinion... but it couldn't be further from the truth.

High efficient systems don't always equate to reliability issues and complex equipment.

'Last longer with fewer repairs' comes with properly sized, installed and set-up equipment.

Higher efficient A/C's and H/P's have larger coils, maybe a two-speed condenser motor, but for the most part, everything else is the same. It's not like one has a hundred dollar flux capacitor, while the high efficient one has a thousand dollar flux capacitor.
*Not like comparing a Model T to a Lamborghini.

High efficient furnaces are not 'complex and unreliable' as many seem to think (Techs included). There's not many differences between 80 and 90%+ equipment.
For example, the main components are often the same:

Blower Motor
Control Board
Transformer
Door Switch
Primary Heat Exchanger
Gas Control
Burners
Ignition System (spark or HSI)
Flame Sensors
Rollout Safeties
High Limits
Auxiliary Limits
Pressure Switches (same with different settings)

Parts designed a little different:

Inducer Assemblies (plastic vs. metal)

Items added for efficiency:

Collector Box (metal box)
Secondary Heat Exchanger (stainless steel and plastic)
Transition Assembly (plastic box)
Drain System (plastic trap with tubing)
*Just materials, no moving parts or electronics added.

Now, when upgrading to comfort featured equipment, you get into:

Two-Stage Gas Controls
Modulating Gas Controls
Two-Stage Control Boards
Two-Speed Inducer Assemblies
Variable Speed Blowers
Two-Stage Thermostats
Communicating Thermostats
*The basic design is the same, you're just swapping 'basic' for 'upgraded' parts.

As for payback, that can be in as little as 3-5 years (Northern States).
Most equipment nowadays have 10 yr. parts warrantees, so it really becomes a non-issue.

**As always, comfort and dependability comes from properly installed/set-up equipment. So locate the best installer/tech in your area.

***And if you 'think' you know more than the guy doing the work, you hired the 'wrong' guy! Trust their recommendations (equipment and sizing), then when things go sideways, they are the ones reliable for making the corrections.




 
Posts: 7354 | Registered: October 15, 2008Reply With QuoteReport This Post
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