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Simon Gruber
Houston Astros Fan
Member since Mar 2017
589 posts

New Construction HVAC
Getting ready to start building soon and starting to research HVAC brands and models. Got a few questions.

Is 2 stage or variable speed worth the extra cost? I have read that not only are they more expensive up front they can be less reliable over the life of the unit.

What is a good seer rating that gives you good efficiency vs up front costs?

House will be 2,650sq ft living. Looking at Lennox, Trane, carrier. Open to other brands if they offer comparable warranties. Located in southeast Louisiana.


Hamma1122
Member since Sep 2016
13912 posts
 Online 

re: New Construction HVAC
16 SEER Trane


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60
Stellytiger
LSU Fan
Arnaudville
Member since Aug 2015
494 posts

re: New Construction HVAC
Trane variable speed all the way


Simon Gruber
Houston Astros Fan
Member since Mar 2017
589 posts

re: New Construction HVAC
quote:

Trane variable speed all the way

How much?


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gumbo2176
Member since May 2018
9224 posts
 Online 

re: New Construction HVAC
I'll address the duct work. I will not put flex duct in any house I own and will always go with metal duct work in round pipe insulated with the foil backed wrap insulation.

All it takes is one rat or squirrel to get into your attic and decide they want to tear into your flex duct to use for bedding and you will be dumping your A/C and heat in your attic.

I did that kind of work many years ago and ran into that very situation several times.

I did my own duct work back in 93 in my current house and the duct work is still good with no issues. No flex duct, no fiberboard plenums or return air-----all metal ductwork for the win.


Simon Gruber
Houston Astros Fan
Member since Mar 2017
589 posts

re: New Construction HVAC
Speaking of ductwork, I noticed some installers hang the ducts and keep them from resting on insulation/joists. What’s the benefits of this?


gumbo2176
Member since May 2018
9224 posts
 Online 

re: New Construction HVAC
quote:

, I noticed some installers hang the ducts and keep them from resting on insulation/joists. What’s the benefits of this?


Metal round pipe, when installed, should be screwed together and taped at each joint which falls at 5 ft. lengths.

Hanging them is not only done for aesthetics, but to support the joints to prevent potential sagging over time and facilitate a nice smooth flow of air.


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slinger1317
Houston Astros Fan
Northshore
Member since Sep 2005
4459 posts

re: New Construction HVAC
Trane Variable Speed. Very worth it.


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poochie
LSU Fan
Houma, la
Member since Apr 2007
4364 posts

re: New Construction HVAC
I have about the same square footage, blown in fiberglass insulation, single story on slab. I have a 4ton 18 seer variable speed trane with gas heat. Moved in April 2020. This unit is efficient AF.

My average combined power & gas bill is $129, highest being feb21 at $144, lowest being may21 at $89.

ETA: My hvac quote was just under $20k for reference.
This post was edited on 7/21 at 7:57 am


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TheBoo
USA Fan
South to Louisiana
Member since Aug 2012
3314 posts

re: New Construction HVAC
quote:

I noticed some installers hang the ducts and keep them from resting on insulation/joists

Mine are like this and last time a crew came out, when we were trying to get my airflow balanced between rooms, they hung them to straighten them out. They stated that the ups and downs over the rafters has an impact on airflow.


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USA
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notsince98
Missouri Fan
KC, MO
Member since Oct 2012
14497 posts

re: New Construction HVAC
Variable systems are much more complicated and less reliable. Just replacing the control board is crazy expensive and a common repair. None of my good HVAC contractors up here recommend variable capacity AC systems. Variable capacity gas furnaces are much more reliable but they still recommend avoiding those too.

2-stage is nice but if you get an HVAC company who knows how to design duct work, even 2-stage can be a bit of a waste.

Right now I'm running a single stage AC in a 2-zone setup. When only one zone is calling for AC, the blower runs at 70% of the speed. This is keeping my humidity around 40-42% and that is with high outside humidity (dewpoints in the 70s) and not being super hot so my runtimes are not near as long as when the temps are over 92F.

So even with single stage equipment you can hit high SEER/EER ratings like 17/13 and save a lot of equipment costs while still getting very good humidity control if you get a variable speed blower and setup the controls properly. If you have a 2-story home, the duct work is the most important part to get it right.
This post was edited on 7/21 at 8:58 am


ds_engineer
Mississippi St. Fan
South Mississippi
Member since Dec 2014
157 posts

re: New Construction HVAC
Look into the new Bosch systems.For new construction, check into the bosch geothermal HVAC unit.

Otherwise, get the Trane and opt for the 2-stage fan with the internal dehumidifier if possible.


CORIMA
LAFAYETTE
Member since May 2014
396 posts

re: New Construction HVAC
Trane Variable speed systems, VX18, XV20 have been sold to the public since 2014. Installed in test homes years before that. Yes, more expensive and complicated. If you value comfort, variable speed is the answer.


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lsujro
LSU Fan
north of the wall
Member since Jul 2007
3466 posts

re: New Construction HVAC
quote:

Right now I'm running a single stage AC in a 2-zone setup. When only one zone is calling for AC, the blower runs at 70% of the speed. This is keeping my humidity around 40-42% and that is with high outside humidity (dewpoints in the 70s) and not being super hot so my runtimes are not near as long as when the temps are over 92F.

So even with single stage equipment you can hit high SEER/EER ratings like 17/13 and save a lot of equipment costs while still getting very good humidity control if you get a variable speed blower and setup the controls properly. If you have a 2-story home, the duct work is the most important part to get it right.


I have a single stage a/c system and have been trying to look into converting to or adding a 2 stage for this exact reason. Can you give more insight on your setup? I want the ability to run more frequently (or constantly) at a lower speed and a ramp up as needed. Does anyone know if it's possible to add this to an existing system? My a/c is only a year old but was pretty cheap


CrawDude
LSU Fan
Baton Rouge
Member since Apr 2019
3252 posts
 Online 

re: New Construction HVAC
A lot of good information provided by other posters. The expensive high SEER variable speed inverter systems are all about comfort, with luck you’d recover the higher initial cost in energy saving before the unit needs to be replaced. If I was to install one, it would be in a new construction house.

Two stage systems though a little more complex than single stage systems, are more in line with the simplicity of a single stage unit, and most of the year should operate in stage 1 (lower stage) with energy cost savings which should allow you to recoup the higher initial cost before replacement.

Another option is to consider a single stage unit, simplest and less expensive of all, and apply some of the $ savings and couple it with a whole house dehumidifier to control humidity and add comfort during the shoulder seasons of spring and fall when the HVAC is not calling for cooling but outdoor humidity is still high leading some high humidity discomfort in the house.

I like the idea of rigid ducts compared to flex duct - certainly more expensive. Duct work and sizing is every bit important as the equipment in proper HVAC function and efficiency.

If you go with a variable speed drive system, be sure you have a whole house surge protector installed plus a separate surge protector for the HVAC to protect those expensive circuit boards in the unit.

Lastly, all major brands are comparable, Trane/American Standard, Carrier/Bryant, Rheem/Rudd, … more important than the manufacturer is the quality and expertise of the HVAC installers and technicians.
This post was edited on 7/21 at 4:24 pm


Cracker
Montana Fan
in a box
Member since Nov 2009
13204 posts

re: New Construction HVAC
No on the variable speed the ecm will crap the bed it’s 1200.


gumbo2176
Member since May 2018
9224 posts
 Online 

re: New Construction HVAC
quote:

I like the idea of rigid ducts compared to flex duct - certainly more expensive. Duct work and sizing is as every bit important as the equipment in proper HVAC function and efficiency.



This in a nutshell. I did a lot of residential and commercial A/C ductwork installations and all in Joval metal round pipe for the supply and 26 gauge shop formed and insulated supply and return plenums. The absolute best way to go for ductwork.

It was pretty much universal to run each register with 8 in. round pipe as the supply line and for longer runs, we'd run 10 inch round pipe and use a wye to reduce it to two 8 inch lines.

Often bathrooms or small utility rooms would only get 6 in. supply lines since the rooms are so much smaller.


Commercial work was a good bit different since it required a lot of shop made ductwork for a "trunk line" and from that we'd take off the round pipe to supply the registers.


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notsince98
Missouri Fan
KC, MO
Member since Oct 2012
14497 posts

re: New Construction HVAC
quote:

I have a single stage a/c system and have been trying to look into converting to or adding a 2 stage for this exact reason. Can you give more insight on your setup? I want the ability to run more frequently (or constantly) at a lower speed and a ramp up as needed. Does anyone know if it's possible to add this to an existing system? My a/c is only a year old but was pretty cheap


What is your furnace or air handler?


notsince98
Missouri Fan
KC, MO
Member since Oct 2012
14497 posts

re: New Construction HVAC
quote:

No on the variable speed the ecm will crap the bed it’s 1200.


I have had 2 systems with variable speed ECM blowers and have had no issues in 15+ years of total usage.

ECM variable speed blowers are only at risk with undersized ductwork. If the ductwork can properly handle the required CFMs, ECM blowers are very trouble free.


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11
lsujro
LSU Fan
north of the wall
Member since Jul 2007
3466 posts

re: New Construction HVAC
I have a gas furnace. Is that what you mean? I'm not great with hvac terminology


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