Second floor Attic AC vs Install Honeywell Wireless 4 Zone System

[DJSTONES]

My home is 22 years old located in Chicago. The house is approx. 2500 sq. ft and has a 4 ton ac unit. I have had several experts in to solve a problem I have had since the house was built.

Common Problem:
In the summer during hot weather, above 90, we live in the basement. The temperature is around 72 in the basement, first floor goes up to 77 and upstairs, depending on the room, is 82-84 when the temp is above 90. The ac never shuts off. They all said that the HVAC system is in good condition and would consider other alternates instead of replacing the system at this time.
We are looking at this problem now because our 4 kids are old enough to start complaining that it is to hot to sleep on the 2nd floor.
I have had 2 different approaches:
1) Install Honeywell 4 zone wireless system
2) Install a smaller ac unit in the attic and run additional ducts to the 4 bedrooms upstairs from the attic unit.

I have been trying to educate myself about both solutions but I have been unsuccessful finding information or reviews about these 2 solutions. I am hoping someone can give me the pros and cons of each solution so I can make an educated decision.
Thank You in advance for your help.

[DJSTONES]

What type of problems would I be running into?
I am trying to understand the 2 systems and that would help me make a good decision.

[DJSTONES]

I have had them do what you mentioned.
The AC unit is probably working like a 3 ton at this point in it's life. I have a good 20 degree difference between the pipes coming out of the ac and into the house. The underside of the coils needs to be clean so I know that we can improve the performance. The refrigerant was checked and is fine.
The unit is slightly oversized for the house.
I know it has to be the duct work choking it off since I have had contractors come in to "balance" the airflow in the ducts and there was no change.
The house is contemporary, open design which did caused them do route the ducts a certain way since there are not many walls to run duct work into.

[DJSTONES]

ResponsibleHeat,
Thanks for the explanation. I understand what you are talking about. Would I have the same result if I added the second unit in the attic also?

[DJSTONES]

mchild,
Thank you for your input. I will have the contractor do those calculation.

[DJSTONES]

I am confused.
-Is an AC unit protected if it is put into a Hot attic with standard Fiberglass batts?
-What about the use of Honeywell Zone system?
Thinking logically, air takes the path of least resistance. If certain ducts were closed the air would be forced to go elsewhere. The 1 stage unit will still be operating at 100% but putting the air where it is needed.
- Thinking about the second AC in the attic, wouldn't the first response from Responsibleheat about zoning hold true? The original unit now would be oversized and would not be as efficient of reducing the humidity since it would not be on as long?

So what am I missing?

I thank you for all your responses and it brings up other questions.

[k-fridge]

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[glennac]

You might consider opening your return air ducts at the ceiling level in the basement and let it go free air return from there to your unit assuming your unit is in the basement. This would allow you to close off your supply vent in the basement during the summer and allow more to go to the two floors above.

You also should consider putting a large grill on either side of the basement door to allow more return air flow since a lot of times the return air ducts are two small. Now open the ducts in the 2nd floor wide open and choke off the first floor a little and see if that helps before spending the money on a zoned system and definitely before you install duct work in your hot attic. I have my home set up like this. Try that out and if it doesn't work then go to a zoned system. 4 tons should be enough for your house.

Now free air return would be good rather or not you go zoned. That helps ventilate your basement summer and winter. In the winter of course you would open up your registers in the basement, modulate them on the first floor and basically close them off upstairs. That is my advice.

One HO in College Park wanted to heat and ac his basement. He had supply and return ducts in all the rooms. I just opened up all his returns to the basement and took the return ducts and made them supply ducts for the basement to be used in the winter. It worked perfectly. Thank you very much

[BaldLoonie]

Most of the time, not cooling the 2nd floor is due to insufficient ducting to that floor. Zoning often won't help. Also if just 1 zone is calling, you could short cycle the A/C on freeze protection or if the panel doesn't have that, freeze up the A/C. Zoning is best done if the duct system was designed with that in mind.

A small system in the attic would give you the best comfort upstairs.

And we have add these to homes with zoning!!!

[DJSTONES]

What happened to all the posts I had?

[glennac]

Read post 7

[BaldLoonie]

I had a nice chat today with a guy who HAS ZONING and a very hot upstairs. We verified all dampers working and open. As I pointed out to him in weather like this with both zones open all day, it is like a single zone system. The cooling goes mostly downstairs due to insufficient ductwork to upstairs. He's going to try leaving the downstairs set pretty high to force more air upstairs to see if it helps.

[thes]

Most of the time, not cooling the 2nd floor is due to insufficient ducting to that floor. Zoning often won't help. Also if just 1 zone is calling, you could short cycle the A/C on freeze protection or if the panel doesn't have that, freeze up the A/C. Zoning is best done if the duct system was designed with that in mind.

A small system in the attic would give you the best comfort upstairs.

And we have add these to homes with zoning!!!

agreed!