Bad Duct Installation in New Home

[KingQA]

Hi Everyone,

I am in need of advice. I live in CA, and I bought a new model home a few years ago. I had issues with my HVAC split system a few weeks ago. My home is two levels at a total of 2500 sq ft. My AC Heating is a 5 ton unit, which you all know produces 2000 cfm, but I only have one 20 x 30 return of 1200 cfm on the second floor. There is no return on the first floor and it gets very humid at night. It's going to be impossible to have a return on the first floor now.

Do I have any grounds of making my home builder install a second return? Is there a construction standard on how duct work is installed? What facts can I use to back up my claim?

Thanks for your assistance.

The King

[pwg11386]

A return on each level is code in NC. Don't know about CA though. A single 20x30 return grill on a 5 ton is disgraceful. Its doing more than killing your efficiency, it's killing your unit.

[catmanacman]

I doubt its the lack of a 2nd return causing your high humidity generally speaking low airflow causes ac units to be great dehumidifiers ,I suspect the problem is 5 tons of ac for 2500 square ft on a newly constucted home I would demand the load calculation that they used to backup the reason for such a large air conditioner

[KingQA]

I really am going to need more help on this one. My home builder told me that they aren't obligated to put in the 2nd return, and the numbers of CFM are just "speculation." I did ask for the load calculation for my home, and I was told that it's proprietary information.

Any thoughts on how I should approach this now?

[catmanacman]

I really am going to need more help on this one. My home builder told me that they aren't obligated to put in the 2nd return, and the numbers of CFM are just "speculation." I did ask for the load calculation for my home, and I was told that it's proprietary information.

Any thoughts on how I should approach this now?

In other words they don't have one because they guessed at the size , I don't see how it would be proprietary it's not like it can use it for other houses . Or on the other hand maybe they have a one size fits all load calc and there fore that's the problem. I thought in the great state of Cali they had to summit a load calc with the application for a permit . Any how they are shams

[btuhack]

You will rarely if ever see a return for each floor on a tract home in California. That argument is a dead end. Architects won't allocate any room for the duct work and soffit to conceal, and buyers would rather blow their mechanical budget on non-comfort items such as granite and tile.

What's the story with your neighbors systems? Are they sized similar to yours? What happens with continuous fan operation?

Let the great return location debate begin.

Any thoughts on how I should approach this now?

Go see what the builder submitted to the city Building Dept for your house, they may still have records

[MM#7]

how about getting a whole house dehumindifier?????

[KingQA]

I think I'm SOL. Apparently there is a 4 year statute of limitation to file a claim against a contractor in California. My home is a model home so it was built more than 4 years ago. It's a shame that some contractors are allowed to get away with horrible workmanship.

[jimj]

I think I'm SOL. Apparently there is a 4 year statute of limitation to file a claim against a contractor in California. My home is a model home so it was built more than 4 years ago. It's a shame that some contractors are allowed to get away with horrible workmanship.

You may want to check on that with the registrar of contractors. If you are the first to live in the home that rule may not hold true!
California has whats called title 24 and a load calc has been required for years, the statue of limitations I believe is seven years for construction defects as far as filing suit.

[precision hvac]

Model homes typically have oversize units to compensate for doors opening & closing all day long, no window coverings or shade & large people loads. I wouldn't be surprised if the non model in your floor plan uses a 4 ton.

[fisher01]

When was the Notice of Completion filed? Sometimes builders hold off filing those until the hold is sold. The 4 years would start from that date.

[skippedover]

Sometimes it's just more cost effective to play the hand you're dealt. In this case a long legal battle still won't improve your comfort and it'll likely cost you more to litigate than it would to fix it. So here are my limited suggestions:

A. Have a qualified and competent company give you a proposal to replace the existing system with a properly sized system, naturally using Manual 'A'. Also have them check the duct system to see if any modifications need to be done.

or

B. Have a qualified and competent company give you a proposal for a whole house dehumidifier that will operate independently of the cooling system. This would relieve your high humidity issue at lower cost than replacing the AC system and when it does come time to replace the AC for other reasons, then you can address sizing at that time. And you can keep the WHD too.

[genduct]

I agree with catmanacman and Precision has a really interesting thought on the reason why your unit may be oversized. But to answer your question directly
1.Unit size does have more to do with excessive size and not duct
2. return grill is 600 sq Inches, 300FPM face velocity, so siized right but does air have a path ie transfer duct from a room if door closed?
3. Check, 4 years may be from date when problem discovered. If the builder didn't pull the loads and the code required it then he is never covered by statute of limitations because he never did it right in the first place.
4. Doesn't your state energy law or utility co require a load calc. It is your house you need to see it. Again find out if original permit building drawing required this info.

Check my profile for email and other contact info if you would like to discuss this offline.

Mike

[motoguy128]

5 ton on a 2500sqft new construction home in CA? Yikes. With good windows and insullation, I'm thinking most like 3-4 ton, but you'll need a heat load calculation.

Ideally, if feasible, the best set-up woudl be a 4 or possibly even a 3 ton 2 stage unit and split the upstairs and downstairs into 2 zones.

[motoguy128]

The lowest cost solution might be to just replace the outside condensor unit only with a smaller unit based on a proper load calculation. Having a 5 ton coil on a 4 ton unit is acceptable.

No need to repalce the entire system IMO.

[Shophound]

The lowest cost solution might be to just replace the outside condensor unit only with a smaller unit based on a proper load calculation. Having a 5 ton coil on a 4 ton unit is acceptable.

I doubt that would solve the humidity issues. Most parts of California cool off pretty well at night, so the heat gain to the house can fall off substantially a few hours after sunset. Compared to where I live, when we were hitting 105-108 degrees for daily highs, it often would not drop below 100 until around 9 PM.

OP stated it was a two story house. If the thermostat is on the first level (and I'm assuming there's only one system on this house) this problem alone is aggravated by two factors: summer reverse stack effect AND oversized equipment. The downstairs stays cool more readily due to thermal gradient characteristics of a two story house, meaning the system runs less, thinking there's not much load. The less the system runs, the less it can dehumidify. If the OP pushes the stat colder to get dehumidification, the first floor overcools and then feels clammy.

A whole house dehumidifier might be an option in this case, but it would still leave the OP with an oversized HVAC system. That said, the dehumidifier may allow the occupants to live in higher room temperatures before cooling would be needed. It's just a shame he's in a corner like this.

[teddy bear]

Lets start over instead of offering solutions before we find the problem.
What is the inside temp/%RH?
What is the outside dew point overnite?
How many occupants?
Overnite setting of the t-stat?
On/Off minutes ofcycle time of the A/c?
How much water is the a/c removing during day and at night?
Keep all of the inside doors open as much as possible to provide indoor circulation with pressurization/depressurization.
Extreme coastal climates in CA can have high enough dew points to require supplemental dehumidification. Also occasional wet cool weather may cause indoor humidity problems. When the outdoor dew points are <55^F, adequate fresh air ventilation will maintain reasonable indoor %RH. Keep in mind that occupants add a considerable amount of moisture to an unventilated space. All homes need an air change in 4-5 hours to purge indoor pollutants and renew oxygen. When the outdoor dew point is <50^F, fresh air reduces indoor %RH. When the outdoor dew point is +55^F, adequate fresh air ventilation plus the moisture from the occupants needs several lbs. per hour dehumidification. If the a/c is operating enough, no problem. When the a/c is not operating enough, supplemental dehumidification is needed to <50%RH.
Give us the information requested and we will be able to give some intelligent solutions.
Regards TB

[MM#7]

Lets start over instead of offering solutions before we find the problem.
What is the inside temp/%RH?
What is the outside dew point overnite?
How many occupants?
Overnite setting of the t-stat?
On/Off minutes ofcycle time of the A/c?
How much water is the a/c removing during day and at night?
Keep all of the inside doors open as much as possible to provide indoor circulation with pressurization/depressurization.
Extreme coastal climates in CA can have high enough dew points to require supplemental dehumidification. Also occasional wet cool weather may cause indoor humidity problems. When the outdoor dew points are <55^F, adequate fresh air ventilation will maintain reasonable indoor %RH. Keep in mind that occupants add a considerable amount of moisture to an unventilated space. All homes need an air change in 4-5 hours to purge indoor pollutants and renew oxygen. When the outdoor dew point is <50^F, fresh air reduces indoor %RH. When the outdoor dew point is +55^F, adequate fresh air ventilation plus the moisture from the occupants needs several lbs. per hour dehumidification. If the a/c is operating enough, no problem. When the a/c is not operating enough, supplemental dehumidification is needed to <50%RH.
Give us the information requested and we will be able to give some intelligent solutions.
Regards TB

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