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Old 06-26-2008, 08:23 AM   #1
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The first floor of my home was completely renovated last year. New insulation, new walls, new ceiling, new hardwood floors, new windows, new HVAC system, including central air. The house has forced air heating. A separate ac unit was installed on the second floor. Therefore the ac system is two zone. The first two floors have between 1400-1600 square feet. The house is hot and uncomfortable on the first floor when there is a family gathering of 10 or more people. At those times I set the AC for 60 - 65 degrees early in the day, but it stays around 70-72. The second floor cools down to whatever the setting is (even 60 degrees) in and hour or two, and that floor has poor insulation (new windows, but not new insulation). The first floor takes 4-5 hours and it only once got down to 60. Usually it only cools to around 70.
1. How long should it take to cool down the first floor?
2. Shouldn't a new system get down to 60 degrees if I'm expecting a large number of people?

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Old 06-26-2008, 02:01 PM   #2
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it also depends on outside temp

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Old 06-26-2008, 06:20 PM   #3
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The 60 degree projected temps you're looking for seem unrealistic. I don't think the unit is up to that task. Did you specify a projected temp when the system was designed?
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Old 06-26-2008, 10:09 PM   #4
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No, I didn't know enough at the time to specify anything. How cold should a forced air system get and how much time should it take?

Let's say the temperature is going to be 90 degrees outside and I turn it on in the morning, before it gets hot.
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Old 06-27-2008, 12:04 AM   #5
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The AC's ability to cool the house depends as much on the home's insulative properties and the duct system design as it does the unit's ability to cool. If the ductwork is improperly sized or has excessive or insufficient amounts of outlets, you'll never get the potential out of the HVAC system.

With an outdoor temperature of 90 and a house full of people, 60-65 degrees seems like an unrealistic expectation in most homes. If you achieve it, the unit would run 24/7.

My AC is able to keep the house about 18-20 degrees cooler than the outside temperature in the summer without running constantly. So if it is 90, I can keep it 72 without breaking the bank. That's my house though...It is 50 years old and only has mediocre insulation and poor windows...New AC though.
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Old 06-28-2008, 10:41 PM   #6
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The company that installed it returned yesterday and said that the rear damper was not adjusted correctly and "fixed it." Today I ran a test. It was 77.9 degrees outside and 80 degrees inside at 6:46 pm. That's when I turned on the first floor ac. The one upstairs has been set at 70 degrees all day.

Now it's 10:29 pm (15 minutes less than 4 hours) and it's 73.9 outside. The inside temperature is 78 degrees. It's been at 78 degrees since 7:54 pm.
To recap:
From 6:46 - 7:54 (about 1 hour) the temperature on the first floor of the house went down 2 degrees.

From 7:54 - 10:29 (about 2.5 hours more) the temperature has not changed.

My second floor AC (where insulation is awful) will go down 10 degrees in 2 hours!

So far, in the last year and a half the company that installed the two systems:
recharged the freon (or whatever the coolant is) twice
retaped the ducts
fixed a damper

It's still not cooling well.
What is the next step? Every time I call they make me feel as though I'm expecting too much from the system. They never even apologized for the problems so far. They make me feel as though I don't get it and they did a great job. I'm very frustrated.
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Old 06-28-2008, 11:02 PM   #7
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whats with the re-charge twice call them back and get a nitrogen pressurized leak check on the first floor unit....your freon charge is your tonnage that cools the floor if that charge is leaking(especially over a winter sitting)your tonnage starts to change.did they find a leak from the original install the charge should be original never replaced or aded to on a TIGHT piped up system.who's paying for the freon and time...good leak check there goes for 8 hourspressurize it run the piping and condenser evap chech and finally a 2hour RE-VAC with a 2 hour standing test to verify a tight system.......just say to them.... you want a 300 PSI nitro leak check and then AFTER the leak is found.... you want a 250 MICRON vacuum held for 2 hours before freon is re-charged they will.......hammer and haw on that takes time and do not let them bill you for anything.

Last edited by biggles; 06-28-2008 at 11:12 PM.
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Old 06-30-2008, 06:17 PM   #8
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Thanks for your responses....

The leak was on the original install. Does that mean it will never run right?
My second floor is poorly insulated and they installed a separate new system for that floor. That AC has no problem cooling down to 60 degrees quickly, no matter how hot it is outside.

I spoke to the company, again, today and asked for a supervisor to come out and check things out on the first floor ac system. They told me the temperature should only lower by one or two degrees per hour. Is that right? How long should it take for the ac to cool off the first floor of the house?
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Old 06-30-2008, 06:27 PM   #9
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You gave me a lot of info all at once and I'm not sure I've got it all right...

I should tell them that:
1. I want a 300 PSI nitro leak check (what is that, anyway?)
2. I want a 250 vacuum held for 2 hours before freon is recharged (what does this mean and why do it for 2 hours before freon is recharged?)

You also said that it NEVER should leak on a TIGHT piped up system...why not? I need to be able to speak to the guy intelligently, so I need to get some education on this.

You also said to get an 8 hour pressurized leak check. Is that either one or two above, or is this different?

You said then they should run a piping and condenser evaporation check.
Is this the same as one or two above??

Thanks for your time and patience helping me out.
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Old 06-30-2008, 10:00 PM   #10
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the tech will show up not knowing were the leak is(you have one)he has to recover the exsisting freon left in your system.now he will introduce nitrogen and raise it up to 300 PSI...now he has to check all the piping from the evaporator out to the condenser while the unit is under this pressure.might be a quick find or take 2 to 3 hours depends.say he finds a leak he has to ZERO out the test pressure and repair the leak with a torch.then he will hookup a vacuum pump and run it till he sees 250-500 MICRONS and it holds for 2 hours...then the unit is considered TIGHT and will take a recharging and NEVER leak again..it is all time if he bum rushes thru the leak checking and throws a charge in there is still a leak...that 250-500 MICRONS is proof it is fixed if he doesn't do a VAC test it is all a "circle jerk"
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Old 06-30-2008, 10:20 PM   #11
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thanks for taking the time to explain...let's see what happens
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Old 07-14-2008, 11:41 AM   #12
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I'm having a problem with central air it's started to run constantly when temp. is at a set temp. it won't stop had freion put in was low a little . Does, this mean I need a new thermostat next??? what to do.
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Old 07-14-2008, 03:40 PM   #13
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Quote:
Originally Posted by annette01 View Post
I'm having a problem with central air it's started to run constantly when temp. is at a set temp. it won't stop had freion put in was low a little . Does, this mean I need a new thermostat next??? what to do.
I would start a new thread
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Old 07-14-2008, 05:07 PM   #14
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Each person puts out about ~100w, so I guess you can use this to tell how much more BTUs you need removed for this thing to work right.
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Old 07-15-2008, 06:07 PM   #15
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Quote:
Originally Posted by Ron6519 View Post
I would start a new thread
Ron
Hi! Ron thanks for answering not knowing alot about ac problems not sure to do with a thread besides sewing

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