New Unit Trouble (condensation, pics/specs included)

[sweatinit]

First time posting here at HVAC-Talk although I have used your site last year when my then landlord told me my A/C unit was fine, I did some research on here and he eventually had it fixed (saved me about $50 a month on the electric bill as the return air supply was 1/3 the size it needed to be)
So again thanks to those that post and reply on here, it is a great resource especially for those of us who are not experts in the field and need some sound 3rd party advice.
So here goes.

Pictures at the bottom of the post I also attached the Installation guide I got from Amana if anyone needs to check a spec or if anyone is looking for the manual for a Amana ARUF363616BA and stumbles into this thread.

Problem: Newish (11month old) Amana System (model # ARUF363616BA) is condensateing profusely when I turn the temp below 75-77.

Unit Location / Details: Unit is in an attic, there is ventilation to the outside and it is on the 3rd story of a house in NE Florida, so it gets HOT up there. I purchased this home 7 months ago and before purchasing it the person who rehabbed and sold the house had a new Amana 3 ton system put in, the previous unit was a 2.5ton and had gone belly up.

Question: I have been told by the company that installed it (they came out and had a look at it after I let them know about the problem) that the issue was warm air intrusion that we found when looking at the system, there was a crack in the flex tube intake about the size of a pencil eraser that was patched. The problem is that the unit is still condensateing on the bottom of the unit and filling up the emergency drain pan even after that small hole was patched. After I let them know the issue was still occurring they said the next step would be to replace the flex tubing in the attic and go from there.

My Theory: So after crawling around in the attic, calling Amana and getting them to send me a copy of the instruction/owners manual, and doing some reading on these forums here is my thoughts and I would love to know if you think I am close, way offbase, or just missed the mark.
Flex Tubing. The flex tubing in the attic is old, about 1/3 of is was replaced when they put the new system in, but the other was left, it is about 22 years old and there are some small leaks in it that I have tried to patch. The unit is still under the 1yr installation/parts warranty, is it not standard to replace flex tubing that is old/damaged when installing a new unit?
Return Air. Alright so according to my Amana installation manual (model # ARUF363616BA) I need between 375-425 CFM per ton for my unit to have the proper air supply to run multiply that by 3 tons and I got 1125-1275 CFMs needed to run the system, the distance from the return opening to the unit is about 18 feet and it makes 2 90degree turns before reaching the unit, it is also a 12inch return. Looking around the site it looks like in rough numbers for a short return a 12inch duct will return about 600cfm, a 14inch about 900cfm and a 16inch about 1400 cmf on a short return, am I wrong to assume that 18 feet with 2 right turns is not a short return and my unit may be starved for air? The company that put it in said that 12 was more than enough and a 14 would not give me enough static pressure for the unit.

So the unit is sweating like crazy and that is the overview and my thoughts, I would really appreciate some feedback and any suggestions as far as what I should have done, this unit was the only thing new with this house and the 1 thing I thought I would NOT have to worry about (replaced the roof, hot water heater, windows, etc.) but such is life.
Thanks again for your comments on this thread and the great resource that these forums are.


Overview of the system, please bare with me I pasted 3 pictures together so you could see the entire unit so it looks a bit odd but should give you an idea of the layout, keep in mind from the return air source (on the far right, another picture of it below) to the far left side of the unit were the air intake is is approximately 15-18 feet.



Air intake/return source, as you can see this is a 12inch intake which should give me about 600CFMs about 1/2 of what the 3 ton system needs (please let me know if I am incorrect)


In the attic this is were the return air comes through that 12inch flex tube pictured above, is it just me or does that kind of bend take my 12inch return down to a 9-10?


Alright there you have it, I hope this is a decent first time post, I think I followed all the rules and hopefully someone has a little time to let me know their opinion on this. I am a big DIYer but electrical work and HVAC units are something I leave to the pros, just not sure if this particular pro has my best interests in mind seeing as I am still under warranty.

Thanks again,

Tom

[Gunnery Sergeant Hartman]

You would need at least 3- 12" returns for proper return airflow...

[gasser65]

You need a new contractor that knows what a p trap is and knows how to properly size and install flex duct.

[sweatinit]

I checked the outside drain pipe and the ptrap seemed properly attached, what should I tell this guy when he comes by and tells me that the single 12inch return is sufficient? Does the flex tubing seem to be installed incorrectly?

[ZiLLaCooL]

12in flex will only flow around 625cfm,(on a good day)this is not taking into account,length,friction loss,bends,kinks,ect..........................at the very least it needs to be 16in if not 18in.Seriously though,you need to find some1 that knows what their doing.

[sweatinit]

Thanks for the input so far, I feel as if I am stuck with this company as it is still under warranty, would you recommend that I confront the company with an improper installation ask that they add another return at no cost. Or eat it and find someone else to do the work? I would assume the lack of proper return would damage the compressor as well as increase cooling and heating bills correct?
Any suggestion if I get the ole "we have been working on HVAC units here in town for the last 20 years and a 12inch return is plenty" speech? I feel like I need to backup my claim that they installed the system incorrectly although as the consumer I really should not have to.

[bill88]

Since you bought the home from someone who "flipped" the house the HVAC contractor worked for him not you. Having said that, you will more then likely have a very difficult time geting them to revamp the duct system at no cost.

It is not standard to replace the duct system when replacing equipment although many times thats what should be done. It all depends whats in the quote.

As already stated, I would get quotes from some reputable contractors to correct the problem.

[sweatinit]

It seems like just about everything else in this house I am going to have to eat it and am out of luck, if anyone else has a suggestion let me know. Having thrown this system together I will definitely not be paying this company any money having done what I would consider a sloppy job putting this system in. Putting a system in with duct work that would cause the system to run inefficiently and possibly cause harm to it kind of blows my mind.

I guess my last question would be do I have any recourse here? It seems like if a system was installed in such a way that it would not function correctly and could damage the unit and the house that I should at least expect the installing company to work with me.

[m kilgore]

I feel for your situtation but lets look at this from another point of view. The HVAC contractor was working for the house flippers. More than likely they did what was asked of them. If they gave a price with all of the ductwork changes included they most likely would not have gotten the job. Not that this is right but in this day and time it is what it is. I always put duct changes as a option on my proposals so the owner can look at the replacement costs apple to apple with other contractors. Then I really stress doing the duct changes and have got several jobs that way.

If I were you I would be more angry with the house flippers as it sounds like you have more than one problem with the house. In my opinion any recourse would need to be with them.

If the HVAC contractor tells you that 12" is enough then I would find one that you trust and will do the job properly. The duct looks like a mess on your job.

[sweatinit]

That all makes quite a bit of sense, can you tell me (a layman) why the duct work looks bad?

[sweatinit]

The owner is coming back on Thursday to "get to the bottom of this" and I wanted to know what I was getting into as far as profressionalism and wanted to be prepared, great advice so far, many thanks. If anyone else has a suggestion please let me know and I will keep those who care posted.

[pacnw]

since you have the install manual, see what the minimum required airflow is.

ask them to bring along the duct calculator to show you the max flow for FLEX duct.

ask the install company to measure the airflow.

I think you will find that the flow is WAAAAAAAAAAAAAAAY short.

[m kilgore]

From the pictures I can't tell you about sizing but I can say that flex duct has a high friction loss when it is strait. With all the twists and turns I see the airflow is being cut down dramaticaly. It dosn't look like there was much planning in the installation of it.