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How to increase AC efficiency?

3,088 Views | 30 Replies | Last: 1 yr ago by P.H. Dexippus
redline248
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1:07a, 8/6/23
AG
Is it best to set a temp and leave it alone? Or use programs to set different temps at different times of day?

Is there an optimal method for setting 2 units, 1 for upstairs and one for down? Meaning should one be set at a different temp than the other?

Is it beneficial to have ducts cleaned or serviced? How would one even know if they are a problem?

All doors open or close off rooms?

Everything works fine, just wondering if any tweaks will help things run or save a few dollars over time.
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Whoop Delecto
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6:33a, 8/6/23
AG
Outside units in the shade with good airflow area around them? Filters clean? Clean outside units' fins with water spray from top to bottom.
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terradactylexpress
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7:57a, 8/6/23
Man I miss the eco zapp guy
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terradactylexpress
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7:58a, 8/6/23
What's you insulation/window situation look like?
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redline248
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8:29a, 8/6/23
AG
Units are shaded most of the day except afternoon. I change filters regularly.

I think the insulation is pretty solid. Not sure about windows, but people are always knocking on my door trying to sell new ones.
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TriAg2010
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In reply to redline248 • 8:53a, 8/6/23
AG
redline248 said:
Is it best to set a temp and leave it alone? Or use programs to set different temps at different times of day?


You will use less electricity if you program thermostats for warmer temperatures during the hottest times of day.
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tgivaughn
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10:54a, 8/6/23
AG
Shade all windows & HVACs, esp. East-West, even if solar screen need to be stapled up when not wintertime.

Get used to 79-80F, best if your system can keep RH below 45%

Outside doors/windows used seldom, consolidate trips in-out

More attic insulation, esp. over ductwork (not the HVAC unit)

Fewer guests, power useage, steamy washes/showers/baths

Add box fans to problem rooms

Swim suit/beach attire
Ten words or less ... a goal unattainable
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clobby
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In reply to Whoop Delecto • 11:46a, 8/6/23
AG
Whoop Delecto said:
Outside units in the shade with good airflow area around them? Filters clean? Clean outside units' fins with water spray from top to bottom.


This, my unit wasn't keeping up. Did these two things and back to working great. Our neighbor has a cottonwood tree and our dryer vent comes out by the unit so it was getting clogged.
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MrJonMan
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4:06p, 8/6/23
AG
I need to clean my outside unit been over a year
Lone Star Pest Control Service, Inc. Call for special Pricing!
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TruService HVAC
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7:37p, 8/6/23
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When is the last time your unit was serviced? The best thing a homeowner can do without any special tools or training is to wash the outside units coil real well with a garden hose and spray nozzle. Do not use a pressure washer. Shut the unit off at the breaker and spray all sides of the coil watching the water going through the coil until it's clear. Start at the top and go side to side and then down. You'd be amazed at the differences a clean condenser will make.

Last year our ridiculously ignorant government shared an image of a tent over a condenser as a means of helping your AC. Newsflash, that's the worst thing you can do for it. AC condensers don't care about sun exposure, they care about air flow. Keep your bushes trimmed at least 18" away from the AC, don't let branches grow across the top of it, don't mow with the discharge facing the unit, wash it out once or twice a year.

Right now every AC is working over time to keep up. If you can afford the electricity usage and desire comfort try to tighten the away and home delta or leave it on one temp all day.

Ventilate your attic. Ridge vent is a joke and should be outlawed. Get some turbines or better yet a powered attic fan. Adding insulation is a last resort in my opinion as it makes most attics impossible to navigate when needing to repair a duct or such that's not on a walkway.

It would be very remiss of me if I didn't say to call your trusted hvac guy and the system serviced.
If you're within the Brazos valley you can call us and we'd be happy to make your AC run at its best.

Ask any questions you may have.

Tru Service
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MrJonMan
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In reply to TruService HVAC • 10:11p, 8/6/23
AG
Funny you mention ridge vents….I've always wondered how well they work. I have 2 regular static vents as well, the large round ones.

I've also gone back and forth on adding insulation or a powered vent. Not sure which is better
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JP76
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In reply to TruService HVAC • 10:48p, 8/6/23
Turbines are inefficient and create hot spots. Powered fans use 5-9 amps and will run up to 20 hours a day in peak summer temps. They also work well to pull conditioned air back into the attic. Solar fans dont move as much air and most work very poorly after about 3-5 years.
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JP76
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In reply to MrJonMan • 10:54p, 8/6/23
Depends on your location and how much insulation you currently have in the ceiling joist. In BCS I have done a few that were around r11-13 and we blew in to achieve ~R38 and the difference was night and day.

I like to start with attic venting first. I have been in numerous attics and seen a lot of bad set ups. Too few lf of ridge vent, decking that was covered with felt and had ridge vent, decking that was barely cut back and had ridge vent. Also you have to make sure you have enough intake in the vents to make it function properly
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Picard
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12:07a, 8/7/23
AG
Put mini splits in your attic

Also walk around naked when possible

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MrJonMan
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In reply to JP76 • 7:14a, 8/7/23
AG
So your negative comments about powered vents are exactly why I haven't added them.

Insulation is r16 (I believe) but house was built in 2001, so if would be whatever the required amount was then. We've been here 10yrs and never added any so likely all original.

We have soffit vents all the way around the house. Ridge vents were install in 2017 with new roof, they run the entire length of the 2 ridges but it's nothing crazy. They also left the round static vents in as well
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sts7049
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7:19a, 8/7/23
AG
I'm no expert but I thought if you had ridge vents you don't want to have gable circle vents on the sides because they compete with airflow. ridge pairs with soffit.
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CapCity12thMan
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7:22a, 8/7/23
AG

Quote:
Ridge vent is a joke and should be outlawed

paging Infinity Jason
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TruService HVAC
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In reply to JP76 • 8:12a, 8/7/23
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Okay so we have to agree to disagree but you validated my reasoning of why I hate ridge vent. I can count on one hand the number of times I've actually seen it installed properly. Way too many times I see ridge vent from outside but when I go in the attic I see decking clear to the peak. Not to mention all these 1400sqft houses with 8-12 total feet of ridge.

I don't think powered fans pull the amp draw you mention but I'll check the next time I'm in an attic with one. I'd guess they pull about 1-1.5 AMPs at full load. I will validate your point that if the house does not have adequate soffit intakes that it could pull cool air from the house. On my house, I installed an attic hatch zipper cover and installed a 115v powered fan on my roof and it dropped my attic temp by over 30 degrees.

I think we both can agree on this though, anything from HVAC systems to ridge vent are only as good as the people that installed it and the knowledge that they have on what product to use where.

Tru Service

JP76 said:
Depends on your location and how much insulation you currently have in the ceiling joist. In BCS I have done a few that were around r11-13 and we blew in to achieve ~R38 and the difference was night and day.

I like to start with attic venting first. I have been in numerous attics and seen a lot of bad set ups. Too few lf of ridge vent, decking that was covered with felt and had ridge vent, decking that was barely cut back and had ridge vent. Also you have to make sure you have enough intake in the vents to make it function properly
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P.H. Dexippus
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In reply to TruService HVAC • 10:14a, 8/7/23
AG
Quote:
Detailed simulations suggest that the heat transfer in an attic to a residential building interior in mid-summer is dominated by radiative gains from the hot roof decking directly to the insulation surface. This mode of heat transfer is more effectively limited by 1) increased attic insulation, 2) a truss-mounted radiant barrier or 3) a white reflective roof surface that limits solar gain to the attic structure.
"Trying to solve the heat gain problem in your attic by using a fan is like lying out at the beach with a fan blowing over you and thinking you're not going to get a sunburn."

The make up air drawn in by powered attic vents is often from the living space. You'd be better off air sealing and insulating.

https://www.energyvanguard.com/blog/The-1-Reason-Power-Attic-Ventilators-Don-t-Help
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will.mcg
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In reply to TruService HVAC • 11:24a, 8/7/23
AG
Should my inside unit sweat profusely? It's in a closet that I believe is well insulated. There is a "water line" stain about an inch or two surrounding the unit's bottom.
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TruService HVAC
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In reply to will.mcg • 12:06p, 8/7/23
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Don't want to hijack the original post but the short answer is no. Start a new post with a picture if you would and I'll try and solve your puzzle. Take a picture of the closet ceiling where the duct goes into the attic as well.
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tgivaughn
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12:48p, 8/7/23
AG
Ridge & soffit vents must be working well IF
not a foamed attic

This system is no longer debateable
ref: The Money Pit radio show & its experts,
http://rb.gy/j8twa
among others, even Construction Science college courses
Ten words or less ... a goal unattainable
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will.mcg
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In reply to TruService HVAC • 1:12p, 8/7/23
AG
Thanks. Will do this evening.
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JP76
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In reply to TruService HVAC • 8:55p, 8/7/23
Perhaps it dropped it by 30 degrees because it was pulling 70-75 degree conditioned air into the 150 degree attic ?

Next time your are in the attic with a functioning exhaust fan, take your infrared thermometer and shoot the insulation around the light fixtures in the ceiling.


The older fans used to pull about 8-10 amps
The newer ones I have seen have been around 5-7. About the same as the newer hvac blowers now draw.
Personally I have never seen a ac or solar fan last longer than 5 years in BCS. Have removed numerous on refroofs and added ridge vent. If not enough ridge I add square static vents to hit the required intake amount.
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JP76
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In reply to MrJonMan • 9:28p, 8/7/23
Here is a calculator to give you a general idea for minimum intake and exhaust needed

https://www.gaf.com/en-us/for-professionals/tools/ventilation-calculator
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Ag13
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In reply to TruService HVAC • 12:51p, 8/10/23
AG
TruService HVAC said:
When is the last time your unit was serviced? The best thing a homeowner can do without any special tools or training is to wash the outside units coil real well with a garden hose and spray nozzle. Do not use a pressure washer. Shut the unit off at the breaker and spray all sides of the coil watching the water going through the coil until it's clear. Start at the top and go side to side and then down. You'd be amazed at the differences a clean condenser will make.
Had a question for you specifically on this. Just moved into new house and having some issues with the 2 A/C units. Had an HVAC guy come out and he topped off refrigerant but also told me the units were extremely dirty and that they could be cleaned with chemicals and such for ~$185/unit.

Before he came I had actually hosed them down a bit like this post said and they were indeed extremely filthy (based on the brown water that was coming off it). Guess they still are dirty though.

Question is whether or not using chemicals to clean is a common and useful practice? Guy said it should be done every 2-3 years. In my previous house, I had HVAC maintenance done 2x a year and they would always spray it down for me so spraying with a hose is all I know. Never had heard of the chemical clean. Not too expensive, but not exactly cheap.

Also while you're here - any thoughts on solar shields for west facing windows? Brutal sun on giant windows seems to be at least part of my issue right now.
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aggiepaintrain
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1:11p, 8/10/23
AG
Does anyone have a insulation company recommendation company in B/CS. I have no interest doing this myself.
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JP76
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In reply to aggiepaintrain • 10:02p, 8/10/23
Foam ? Blow in ?
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aggiepaintrain
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In reply to JP76 • 10:13p, 8/10/23
AG
blow in
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Whoop Delecto
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10:19p, 8/10/23
AG
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P.H. Dexippus
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In reply to Whoop Delecto • 10:34p, 8/10/23
AG
You don't need coil cleaner for the outdoor condenser coil IMO, just use the water hose. Coil cleaner is geared towards cleaning the indoor evaporator coil, which is harder to access and not easily washed out unless removed.
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