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Old 07-04-2012, 03:04 PM   #1
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Novice - AC cools only half house


Our home is one story, shaped like a rectangle. Installed new 5 ton unit, on top of roof, common placement in AZ. Square footage is 2471. 2/3 of house is cool and comfortable. Down the hall about 1/8 of house, 2 bedrooms and 2 baths, is 6-10 degrees hotter than other end of house. I know there is a problem somewhere. Either the duct work has a problem or the unit was purchased undersize for our square footage. Original installer no help. Where is the logical place to start and what steps to take to eliminate possible causes?

2nd question. Why is it, in our building codes, AC units are supposed to be selected using a number of factors, but all AC people I have talked with says no one uses the software and everyone bases unit size on square footage. Why is the building code ignored?

Thanks for any suggestions.


Last edited by beads4me; 07-04-2012 at 03:15 PM.
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Old 07-04-2012, 04:13 PM   #2
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I have been reading posts and realize I did not put enough info in my original post.

House is one story. We remodeled and installed new AC 5 ton unit.

Sq footage is 2471.

House is rectangle shaped. 2/3 of house gets cool. Remaining 1/3 does not.

I checked the attic but am not sure what to look for. After some research I think there are several things to check. The installer is not talking to us so he is no help.

Can someone suggest a list and what order to do things in?

I know, after reading on this site, that the problem could be any number of things. A leak in duct work. Duct work not installed to the best. AC unit undersized.

The rest of the house cools just fine so I am guessing the AC unit itself is not the problem. If we turn the thermostat to 65 degrees the entire house cools off. Except the 2/3 is cold enough to keep dead bodies (ie CSI) and the 1/3 is just comfortable. If we up the thermostat to 76 or 78 the 2/3 end is comfortable (not to cold) and the 1/3 end is hot as all get out. 80+ degrees.

Given this can someone suggest where to start and an order to check items by?

We are in the process of filing a ROC complaint against GC. I need to know if the AC installer screwed up and did not do things the way they should have been done. He is refusing to help.

Thanks. I appreciate all the people who donate their time and experience to answer questions, such as mine, thanks.

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Old 07-04-2012, 05:09 PM   #3
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1. measure cold air temp at the 1/3 side register, compare it to the 2/3 side cold air temp. are they the same ?
2. Is the 1/3 side register cold air flow weaker than the 2/3 side air ?
3. Other physical differences, like face West, bigger windows, less house insulation, etc.

Last edited by clocert; 07-05-2012 at 12:37 AM.
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Old 07-04-2012, 09:55 PM   #4
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Code is ignored where it is not enforced, and when inspections are not done.

Most likely your duct work is under sized.
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Old 07-04-2012, 09:56 PM   #5
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Merged threads.
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Old 07-05-2012, 01:16 AM   #6
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Quote:
Originally Posted by beenthere View Post
Code is ignored where it is not enforced, and when inspections are not done.

Most likely your duct work is under sized.
We are constructing a complaint against the GC for numerous reasons. He won't account for the spending of our money; the work was mostly substandard and he did not finish the job. The AC contractor will get his own complaint - he has refused to address the problem.

Would you suggest I consult a legitimate AC company - get their opinion on the system? Or will they be biased at the potential job and say what they think I want to hear? Or

where do i start with the duct work? I am tiny in size and short to boot. I have no problems moving around in the attic. I can't stand but I can get all the way to the far side. Do I measure the diameters? And should any of it be laying on the attic floor? All of it is bright shiny silver looking - does that mean it is not insulated?

I am very ignorant but at the admin hearing I need to sound like I know what I am talking about - and actually I want to know what I am talking about. Chances are real good that the judge will not be an expert on any part of home remodeling. The person who does their homework should get the remedy they are after.

Does it matter that the AC unit is on the roof outside? I forgot to mention that.

thank you. Gail
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Old 07-05-2012, 01:30 AM   #7
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What kind of thermometer do I need to measure the coldness? I remember the AC installer came by and held a regular outdoor thermometer up the vent and measured the coolness that way. he told me the air was so many degrees cold. In spite of my ignorance I knew or rather saw the BS. And it didn't matter how cold the air is coming out of the vent - the room was not cool. And do I hang string or something from the vents to judge the amount of air blowing? Sorry to ask such simple questions but I don't want to assume.

I know the front room on the hot side is facing north and has a average size window. It is the hottest room in the house. I have installed heat blocking curtains but that hasn't helped. This room has two windows - one facing north and the other is on the east side. Oh and the GC installed the windows, for some unknown reason he used some sort of yellow foam stuff around the windows. We didn't see him do this but whatever he used it for it makes no sense. I would guess he didn't cut the opening right or the window simply didn't fit and he used that foam stuff to fill in the gaps. I am grateful it doesn't rain in Phoenix to speak of.

this house was built in 1957. I can't tell you about the insulation. I do know the attic only has the kind that is spread on the floor - and it seems to be displaced in a lot of places. I am sure that is from the AC installer not bothering to put stuff back after his work.

I appreciate your suggestions. I will make a list of any factors that might interfere with the AC and measure the air temp.
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Old 07-05-2012, 04:10 AM   #8
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You should be able to find an HVAC contractor that will evaluate and fix your system.

If your duct work is flex duct, it should be suspended, and not resting on the floor. If its sheet metal, it may be lined, with insulation.
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Old 07-05-2012, 06:39 AM   #9
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Sounds to me like duct issues. You're not delivering sufficient quantities of air to the spaces that are warmer. Duct systems can be sized and installed to deliver the correct amount of air to your rooms, and those rooms should be adequately cooled.

Our industry uses a concept known as "Manual D" to determine the size ducts which should be run to the room. This is a defined process, and if followed correctly will result in deliver of adequate cooling and heating to your rooms.

We also use "Manual J" to determine the size system needed to cool your home. If done correctly, this will accurately determine the size of HVAC system needed for your home.

To me, the next step would be to find a contractor in your area who will provide you with the Manual J and Manual D details for your home. If you're going to court over this, you're going to have to have something other than fodder from internet postings .

You also asked about insulation and such. Overhead insulation has a significant impact on cooling loads, so you must be sure to properly insulate the home. If you have a space with no overhead insulation then you would be very hard pressed to cool it, no matter how much air you deliver to that room.

Note too that with larger, sprawling homes sometimes it's better to install 2 smaller units to handle the space independently. Of course, that's a decision that your (hopefully competent) contractor could discuss with you after you get the jacklegs off the job
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Old 07-05-2012, 09:02 AM   #10
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WELCOME TO THE WORLD of HVAC IN PHOENIX!!!!!

in answer to your question about building codes...There always has been too much building and not enough inspectors, so thing slip and then they become standard practice.

as to substandard work, this is due to the building booms and untrained labor. I can tell you that just last week, I was working with a large large hvac company on an installation of an evap cooler. The guys who were installing it, had no clue about flex duct (ie no 181ul approved tape, no screws, no mastic). Took the 6 return trips to fix my punch list of code violations and bad workmanship issues.

now, as to your issues, I would be happy to take a look at your system this weekend. I do not do work on systems, I do not have anyone to recommend do the work on your system, but I would be happy to share my education with you, so that you can be more informed. only cost would be a cold pepsi....

I suspect, without looking of course, that your return is way undersized for a 5 ton. I suspect that the flex duct was not pulled tight and that plenum boxes were used where WYE's should be used. I suspect that your ductwork is in the attic and that it needs more insulation... I also suspect that a blower door test would find that your home is not well sealed..

How do I know this... experiance from helping others and general knowledge of building in PHX... Am I an expert, nope, but I have experiance and teaching (30 years ago at my grandfathers knee)

I will bet the free pepsi your going to give me, that the static pressures are very very high in you duct system and that your registers are very restrictive...

so the offer of an education is there if you would like.

bob in phx. (mesa really)
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Old 07-05-2012, 09:33 AM   #11
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It does seem like you have some major ductwork problem. It maybe both the return air (air that comes back to your ac unit) and your supply line ( the ducts that supply the cold ac air) maybe undersized or not properly layed out.

Check this pdf file from NAIMA and compare how they advice in installing flexducts and see how your ducts are installed.

http://www.naima.org/insulation-reso...keywords=ah116

You click on the download link ...just scroll down a bit.

Take some pics and post them here. Maybe the forum can point something out and lol see if Bob can help you too. Thats nice of him.
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Old 07-05-2012, 01:07 PM   #12
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I would be thrilled to present you with a whole six-pack of cold pepsi - although Bob your price for experience and a willingness to share is on the low side J

I did not mention that the ductwork is in the attic - I assumed that all ductwork is in attics. The duct is flexible - I guess pliable and some of it is on the floor in the attic. I do not know about "plenum" boxes - don't know what those are but you can show me. Any time you could come by would be great. We have no plans. That is partially due to hubby dealing with diverticulitis, on IV antibiotics to prep for surgery in early August and the end treatment of thyroid cancer. He's been healthy his entire adult life and he hits 54 and wham. He gets sick coming and going. He is pretty much confined to the master bedroom. The attic entrance is at the cool end of the house in my office.

Can I send you an email with phone, address etc? I am not sure if I can do that from here but I'll look.

Gail
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Old 07-05-2012, 01:15 PM   #13
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Let me put together a one time use email address and we can get together maybe friday(after 4) or maybe saturday (before 11 or so, cause its hot!!)

bob in phx.
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Old 07-05-2012, 02:26 PM   #14
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Any time is good. Whatever fits your schedule. After 4 or before 11 is good. I know the earlier the better at this time of year. Is there anything I should do beforehand? The space is clear to open the attic door and extend the stairs. There is no light in the attic itself but I have a portable flood light I carry into the attic with me. Of course light comes through the attic openings as well.

Gail
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Old 07-05-2012, 08:53 PM   #15
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Don't forget to post back here, we would like to know the results.

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