Anonymous wrote:The outside temperature isn’t so much a problem, but the sun is. My 2 story house doesn’t have any shade on it. Regardless of the temperature (nearly), my AC runs continuously from 7-10am and 4-7pm if there’s full sun.

Do you have good blinds and close them every day? Not just when the sun is shining on those rooms but all the blinds. This is to stop the radiant heat from coming in off the glass on super hot days. It makes a HUGE difference in energy use and costs.

Anonymous wrote:

Anonymous wrote:My husband and i were just talking about this. He says you can only expect the air conditioner to be 20 degrees below what it is outside. our house is often at 78 during the day.

This is exactly what two different HVAC installers told me. However, it’s been over a hundred several days and my house stayed at the 73 preset temperature….but it ran all day to keep up. My unit was installed in 2020.

I live in AZ. We have 3 units for 4,100 sf.

Set to 74-75 during the day and 67 in the bedrooms at night. Some days when it’s above 110 the acs are slightly above where we set them but not drastically. Other days they cool to where we set them.

Anonymous wrote:The outside temperature isn’t so much a problem, but the sun is. My 2 story house doesn’t have any shade on it. Regardless of the temperature (nearly), my AC runs continuously from 7-10am and 4-7pm if there’s full sun.

A properly sized AC should run continuously on the "design day." It's actually better for them to run continuously, starting is what puts the most stress on the motor and compressor. The sizing should account for solar gains.

The outside temperature isn’t so much a problem, but the sun is. My 2 story house doesn’t have any shade on it. Regardless of the temperature (nearly), my AC runs continuously from 7-10am and 4-7pm if there’s full sun.

Anonymous wrote:We didn’t build a shitty house, so our hvac system is having no problem keeping up.

A shitty house can have an oversized HVAC. It will keep the house cool, just cost a lot more to run than it should. A well-built house can have an undersized HVAC, or the HVAC can be underperforming. It really has nothing to do with the quality of the house.

The question I would ask the OP is whether it's always been this way or just started. If it just started something is wrong with the HVAC. If it's always been this way it was undersized, which is trickier to fix.

Anonymous wrote:

Anonymous wrote:30 yo house with original AC unit set for 78 day and night. normal operation here. 78 with fan is not too bad for us

Do you live in AZ or NV?

Md why?

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:My husband and i were just talking about this. He says you can only expect the air conditioner to be 20 degrees below what it is outside. our house is often at 78 during the day.

He's right. HVAC installers have what's called the "design temperature," which is the hottest outdoor temperature the unit is expected to maintain indoor comfort for. Design temperature for Washington, DC is 92F.

I don’t know if this is correct. All ACs are designed for 95 outside temp. All of them

I love the certainty of "all of them."

Most home HVAC systems aren't in fact "designed," the installer eyeballs the house, refers to a rule of thumb, checks their gut and then installs what he usually does. It's kind of a nationwide scandal. But if the system is in fact designed, the installer follows the process laid out in the Air Conditioning Contractors of America Manual J Residential Calculation

He uses design temperatures established by the Department of Energy in their publication, "County Level Design Temperature Reference Guide." That publication is available here:

https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/County%20Level%20Design%20Temperature%20Reference%20Guide%20-%202015-06-24.pdf

On page 16 you can see design temperatures for the District of Columbia. It's 92F for cooling and 21F for heating.

Anonymous wrote:We got an energy audit around 14 yrs ago. Our house in 25 yrs old.
Got extra insulation in the attic,
solar attic fans on the roof,
Solar attic fan on the roof of the garage,
new energy efficient windows and doors,
new roof,
Solar panels,
Ceiling fans
Room ACs
Whole house humidifier


Our house is super comfortable. A chilly 71 during summer. And cosy during winter. Recently upgraded to a new HVAC too.

We also have wonderful blinds and I will close them to keep out the sun on hot days. We came from a hot tropical country. We know how to keep the house cool by using fans, closing blinds, and using our landscaping to provide insulation in all seasons.

We got an energy audit around 14 yrs ago. Our house in 25 yrs old.
Got extra insulation in the attic,
solar attic fans on the roof,
Solar attic fan on the roof of the garage,
new energy efficient windows and doors,
new roof,
Solar panels,
Ceiling fans
Room ACs
Whole house humidifier


Our house is super comfortable. A chilly 71 during summer. And cosy during winter. Recently upgraded to a new HVAC too.

Anonymous wrote:We didn’t build a shitty house, so our hvac system is having no problem keeping up.

OP. My house was built in 1939. I guess that automatically makes it shitty?

PP re: service. The A/C is 4 years old and the furnace is only two months old. Company said the vents are very slightly oversized but nothing egregious. They suggested we have the vents cleaned. But otherwise said the units are correctly sized and air filter is clean, and that it’s hard to cool older homes without as much insulation when it gets this hot. Anyway, it’s good to hear others experiences. We keep the house at 75 but 80 feels stifling to me.

We didn’t build a shitty house, so our hvac system is having no problem keeping up.

Anonymous wrote:30 yo house with original AC unit set for 78 day and night. normal operation here. 78 with fan is not too bad for us

Do you live in AZ or NV?

Anonymous wrote:My husband and i were just talking about this. He says you can only expect the air conditioner to be 20 degrees below what it is outside. our house is often at 78 during the day.

This is exactly what two different HVAC installers told me. However, it’s been over a hundred several days and my house stayed at the 73 preset temperature….but it ran all day to keep up. My unit was installed in 2020.

We have ours at 69-72 no issues, 8200sf house built in 2019

Yes. Custom built home with properly sized Trane units. On days with 95 plus temps units run longer but there is no struggle.