How long does it take your a/c to cool off your house? (heat pump, contractor)

[Zippyman]

Originally Posted by Bummer

WOW, JaredC . . . I bet your Electric Bill is a whopper.

The 4 Ton Heat Pump in my 1450 SqF Slump Block Home (North facing with a fully exposed West facing wall) will drop the temperature at least 5 degrees in less than 30 minutes.

How old is your A/C and when was the last time it was professionally serviced?

4 tons on 1450 sq foot is waaaaaay oversized unless the system was designed to reach the set-point with all of the windows and doors open. Comparing that to a 2000 build is apples and oranges - a 2.5 ton would likely be oversized in a 2000 build. A slump-block home would have very little if any attic or wall insulation & single-pane windows, as well as an entirely different level of air-infiltration.

I run a two-stage 4 ton on my 1560 sq/ft house that has lots of energy upgrades, but that's knowing full well that I'm doing it with the specific intent to go below the (proper) set point of 76 degrees (I prefer 68 degrees!), and the two-stage compressor spools down to 2.75 tons on low-demand days so I'm not setting dollar-bills on fire when my energy bill comes. More tons = more amps = more $$.

[Hal Roach]

Haven't they heard of inverters in Phoenix. Mine runs at 33/66/100....there is no bang or light dimming when the thing starts up.

[jlawrence01]

Originally Posted by jaredC

Hello everyone. I know it's a very broad question, but I'm genuinely curious to know. Today we got back from our vacation to San Diego ( oh god, the weather was fantastic!!). We kept the house at 85 degrees. Our house was built in 2000 and is 1400sf, single story. We face south and north with houses on our east and west. I set the temp to 78 at 1pm today. It is now 8:30 and it is just barely getting to 81 degrees. In 7.5 hours our inside temp went down only 4 degrees. We routinely change the filters each month. I'm considering putting in a maintenance request with our property manager but I was looking for insight on whether or not this sounds normal. I know it has been hot here, so maybe this is normal.

Up until yesterday, we had not run the air conditioning this year as we are at a higher elevation (3,000 ft).
When i arrived home yesterday, it was about 90F in the house. It took about 2-3 hours to get the house back to 82F. Our HVAC dates to 1981.

[Ponderosa]

Get it checked, but I bet there is nothing wrong. As Zippy said above, there is a lot of thermal mass in a house, the walls, furniture, floors, etc that have to be cooled to the set point. I have noticed that on a miserably hot day, my unit will not do a lot more than a degree or two per hour in the heat of the day. it'll do much better after the sun goes down and really well when it is dark and cool in the wee hours. When people get 5 degrees and such their unit is likely oversized. They cycle a lot and use more electricity in the long run than a properly sized one. Oversized is the the rule in Phoenix.

We come and go quite a bit in summer. To deal with the re cool issue I bought a Honeywell thermostat that can be programmed via the internet. I kick it up to a higher hold and then bring it down back on schedule in the morning before we come back. That may not be an option if you are in a rental but your landlord might not care if you pay for it.

[jaredC]

Originally Posted by Zippyman

Lol, I'd do it & I'm a former landlord, but I did it without my tenants needing to ask - got a much better price from my a/c guy when I could just give him five addresses to check on a day when he wasn't swamped. It's a tax-deductible maintenance expense for the landlord & a way to reduce emergency service calls - the a/c guy can look for scorched wires, swelling capacitors, smoked contactors & intermittent fan motors when it isn't 112 out, plus he's less-likely to get a "my a/c bill was $700 because the system was over/undercharged" call..

Ok. I'll update this thread when/if I hear from my landlord. Also, at around 10pm last night, the a/c finally managed to get to the set temp of 78.

[jaredC]

Originally Posted by Bummer

WOW, JaredC . . . I bet your Electric Bill is a whopper.

The 4 Ton Heat Pump in my 1450 SqF Slump Block Home (North facing with a fully exposed West facing wall) will drop the temperature at least 5 degrees in less than 30 minutes.

How old is your A/C and when was the last time it was professionally serviced?

Dang!! 5 degrees in 30 minutes?! It took our a/c like 8 hours to go from 85 to 80! Also, our summer bill is around $300-$350.

Ph, our a/c is around 17 years old I'm assuming. The house was built in 2000, it's the original a/c and the last time it was serviced was around 2 years ago. My landlord is borderline slumlord, so I don't expect him to pay for someone to come out and look at it.

[jaredC]

Originally Posted by Hal Roach

I used to set my as on 86, when I went to work, 3 ton in a 1200sf condo, with cathedral ceilings...I would get home at 15:00 and it would be 80 in less than 20 minutes. Now I have a 16 SEER 1.5 TON and I just turn it off when I leave. 341 sf condo cools to 80 in less than 20 minutes, on a record hot day on the edge of a jungle. Facing north seemsvto pay a big dividend, even in the tropics.

Is your outdoor unit running all this time? That will mean you are low on refrigerant., because it was stolen or leaks, and you are now burning out your compressor.

Yes. Our a/c was running continuously, for nearly 10 hours to get to the desired 78 from 85 degrees.

[jaredC]

Originally Posted by Hal Roach

Without anything more than a thermometer...here is a test...the vent closest to the intake should be 25f colder than the air at the intake..which is going to be very close to room temp. If it can't do that then further testing is needed...but one thing is certain: if your outdoor unit is running conti uosly; you will get a whopper electric bill.

I have that mpower. We used $10 in electricity yesterday. Remember, we got home at 1pm. So from 1pm to to 10pm we used probably $8 in electricity. Probably explains why our electricity usage is around $350, on average, in the summer.

[adventuregurl]

My AC maintenance guy was here working on mine on Monday of this week. I'm in the Verde valley so it's not as hot, but it was VERY hot on Monday.

My temp inside was up at 86 due to a brown out Sunday night that messed with my unit and after fixing it and installing a new part he said not to expect it to get back down to 80, where I generally set it, until after the sun goes down. He said in this heat it's just not realistic even to expect a 4 degree drop.

OP, unless you were away for a really long time you might have been better leaving it.

[Zippyman]

Originally Posted by jaredC

Yes. Our a/c was running continuously, for nearly 10 hours to get to the desired 78 from 85 degrees.

FYI, running continuously on a 110+ day with a huge cooling load isn't a bad thing. Running continuously on an 85 degree day might be.

Like I said before, getting the "energy efficiency tune up" is in your best interest - if the a/c unit is leaking or out-of-spec, a contractor using the utility's diagnostic form and test methods gives you well-documented data that would support a "stick-a-fork-in-it" diagnosis- in court if necessary.

A repair order from a typical a/c guy isn't going to have the documentation necessary to give you the leverage you want to force a repair/replacement on a landlord that's trying to duck out of it. "Unit is old, recommend replacement" isn't going to be good enough. You need actual measurable data - airflow, amp draw, intake & outlet temps, outdoor temp, etc, along with a tech that documents his findings well. There's a data-plate/chart on the unit in most cases that shows the correct readings - you need a couple paragraphs of findings vs. a couple sentences.

The patient isn't dead until the doctor fills out the correct form in triplicate. You need an Arizona licensed contractor & preferably a NATE-certified technician. This is good practice for being a future homeowner - don't be bashful about asking for clear documentation & a real diagnosis in writing before they even roll a truck to your house. If they aren't willing to break out all of their fancy hvac toys & document how they use them properly, any diagnosis they come up with is worthless. Be FIRM.