A/C system reconfiguration

[Grimas 671]

Got a 2 story house with an original 5-ton unit (20+ years old) and a 3-ton (3 years old) for the upstairs.  Every summer I struggle keeping the upstairs cool - set to 75 but thermostat shows 79 at 5pm.  Been fighting this for a few years and looking for suggestions/options...

16" of installation blown in a few years ago but didn't make much difference.  Insulated cover on attic entrance.  Relatively steep roof with ridge vents (and soffits cleared to ensure no blown-in insulation covering them).  For the windows facing south and west, shades/curtains closed.  In the upstairs game room with vaulted ceilings, the 2 ducts were replaces with "high capacity" vents to allow for greater flow.  Attached garage roof that gets late afternoon direct sunlight has reflective barrier sprayed on it while the remaining house has mature trees blocking afternoon sun.  Ceiling fans up upstairs rooms constantly running and all room doors open during the day.  \

I haven't installed solar attic fans (yet) as with the steep roof and ridge vents, attic air should be circulating decently as designed.  (I actually stuck a high capacity fan in the attic at some point a few years ago that was point upwards to help with circulation but that didn't seem to make a difference either...)

Was listening to home repair show on Saturday and a caller made a comment that made sense but I hadn't considered before - the 5 ton should be cooling upstairs and the smaller unit should be cooling downstairs  (duh - hear rises...).  Would it make sense to get someone to change the ductwork to have the ducts from the 5-ton unit to send air upstairs and the 3 ton downstairs?

Asked my AC service company if they could test the flow out of each vent to see if I have the system "balanced" and to adjust the dampers if needed and they said they don't do that and I need to get an "engineering firm" to do it...  I just think they don't want to deal with it so anyone got suggestions in Houston area who might do this? Not sure where to go next/what to try next... Looking for suggestions...

[Parliament 14372]

Are both AC units in good repair?  Filters, fans, charged up?  Seems odd that more insulation made no diffence.

Does rhe ground floor stay good and cold?  Like it doesn't need all 5 tons?

Might wanna consult with a contractor to check things out and do some math.  HVAC is complicated, and this board is too busy solving other problems.

[UT_OB1 2227]

8 tons seems like a lot for any normal sized house. 

[Grimas 671]

1 hour ago, Parliament said:

Are both AC units in good repair?  Filters, fans, charged up?  Seems odd that more insulation made no diffence.

Does rhe ground floor stay good and cold?  Like it doesn't need all 5 tons?

Might wanna consult with a contractor to check things out and do some math.  HVAC is complicated, and this board is too busy solving other problems.

Biannual service just done 2 weeks ago and all working good (other than the 15 year old capacitor that went out this weekend).  Downstairs can hold 73 with no problem (mentopausal wife and sorry, no pics). Filters all changed every 3 months, all duct work in attic suspended (not sitting on the installation) and no leakage in any of them per test last year...  Front entry is 2 stories so any heat from downstairs from downstairs goes up both the stairs and the entryway.

UT_OB1 - 8 tons is the normal for most of the 2 story houses in the neighborhood.  

When you say contact a contractor - I assume you mean an HVAC one?  (Just wondering what to search for...)

[Parliament 14372]

Yeah, a contractor who can can do load calculations and such.

[66BUFF 2574]

Stick frame?  How many SF on each floor?

[Grimas 671]

5 hours ago, 66BUFF said:

Stick frame?  How many SF on each floor?

Yea, stick frame. 2500 sq feet downstairs, 1400 upstairs.

[66BUFF 2574]

6 hours ago, Grimas said:

Yea, stick frame. 2500 sq feet downstairs, 1400 upstairs.

Breakdown of tons per floor looks correct. You need an HVAC contractor to do load calcs.  

[Fastbreak 3996]

wasn't there someone on here with an HVAC company?  I am in need also for some guidance for my condo in Austin.

[deadshank 24653]

9 hours ago, Fastbreak said:

wasn't there someone on here with an HVAC company?  I am in need also for some guidance for my condo in Austin.

@T’Boo Ted Marshall

[Jkwellborn 6877]

What is a high capacity register? Sounds like bullshit to me. Properly sized duct work accounts for the pressure to get enough air into the room. Just putting a bigger boot and vent in does Jack shit unless the duct coming to it will have enough air behind it in the first place.

[statsman 5502]

I guess you’ve already checked into planting crepe myrtles (cheap, fast growing trees) on the side with a lot of solar exposure? 

[Grimas 671]

12 hours ago, statsman said:

I guess you’ve already checked into planting crepe myrtles (cheap, fast growing trees) on the side with a lot of solar exposure? 

Southern and western side of the house getting all the sun on ground floor is the attached garage which stays pretty cool (foam insulation on the garage doors that used to take a beating with the setting sun.  The attic above the garage has the radiant barrier sprayed onto the under roof and it does make a difference in that part of the attic.

Not gonna get any relief from crape myrtles on that side of the house unless they are 30 feet tall and i only have limited space to plant anything due to the property width...  ( Previous neighbor pulled out some 20' tall plants on his side of the fence to widen his driveway...)

[T’Boo Ted Marshall 2741]

[mention=479]T’Boo Ted Marshall[/mention]

Apologies. For some reason I’m not getting notifications when tagged.
I’m in DFW but @Spaulding Smails is in Austin.

[dmtx 159]

any updates on this?

My downstairs ac is cooling down to 70 w/o issue with these 105 degree temps. My upstairs ac was having issues cooling down below 73 at 105 degrees outside. I turned on my attic fan and insulated attic door, no issues cooling down to 72 (havent tried to go cooler). Using the infrared temp gun, prior to fan, I believe the air coming out of the duct was 63 or 64 degrees. Now its at 58-60.

[T’Boo Ted Marshall 2741]

So you have no issues.