Where do you live that a new house 2600 sqft needs 5 tons of cooling? Little insulation?

You cannot expect a 5 ton to do much better if they don't do anything to the ductwork. Might even make matters worse. Lineset size likely needs changing as well.

Also, post model number of your current furnace. Needs to have a 5 ton blower in it. Not all do.

Yep - I'm going to go with ryan is implying - that the problem is something other than being undersized.

What kind of problems are you having, where do you live and how old is your house? Also, do you have a lot of west or south windows? Vaulted ceilings?

bnun

while you may have won a legal battle, that was probably easier than correcting problems/issues you have with your HVAC.

first off you need an independently performed Man J and D for correct sizing of both HVAC and ductwork. I certainly would not rely on the dealer.

the following should be said.

1.on two stories, you will get much better comfort with two systems than one.

2.if you stay with one system, then you should go with zoning controls.

3.and if no zoning controls, then you need at least a manual damper control to adjust supply air between the main and second floors.

ductwork has to be sized and designed for the CFMs it is supposed to carry and that includes adequate returns for both floors.

and BTW, you can't achieve the high eff ratings from AmStd's Allegiance 15 AC without a var speed blower from your furnace. An 80% eff furnace for NJ is a dinosaur.
As Ryan mentioned, refrigerant lineset will likely need to be replaced and blower rating size of furnace has to match the size of AC condenser.

Sorry for your trouble.

IMO

bnun

sorry I may have been thinking of another post.

what is your location?

IMO

Thanks for the feedback so far. I'll try and answer most of your questions.

I live in Atlanta, GA. My home is 2 stories, but one-half of the home is a large living area with high vaulted ceilings (starting at 12 ft, peaking around 20-22 ft). The main living area has a good bit of windows and faces West, so it gets blasted by the afternoon sun. I currently have a Westinghouse 3 ton 10 seer zoned unit. My home is new, built in 2005, I moved in May 2006.

For the Spring and Fall months we stay pretty comfortable, but during the Summer and Winter my system cannot keep up. As long as 1 zone is calling at a time, things go ok. But when it gets really hot and both zones require cooling, the temperatures start rising quickly.

I called in the installing HVAC company within the warranty period (12 months), but they would not help me. I brought in 4 other companies to run load calculations and they all came to the same conclusion that my home requires 4.5 to 5 tons. I also have issues with a lack of returns and the number and placement of my vents. For example, the hottest area in my house is only cooled by two tiny vents that make very long runs right against the roof deck. By the time what little air comes out, its basically room temperature.

The other HVAC techs directed me to the Secretary of State, so I filed a complaint. The Sec of State found in my favor and now I'm dealing with the HVAC company's lawyer to see how they are going to fix the system. Since they admittedly installed my original system without doing a load calculation, I'm concerned they will only want to scam me again.

The Sec of State had the original HVAC company come out to run a Manual J on my home and their calculations agreed that my home would need a 5 ton unit.

Obviously, based on my home's layout, the best solution would be a 3 ton for the main floor and a 1.5 to 2 ton for upstairs. Unfortunately, that would be very expensive for me to do and since the installing company is being made to fix the system for free, they want to upgrade the existing setup (1 system, zoned) without the additional expense of running new duct work in my basement for the main floor.

My main concern having these guys back in my home is that they will not properly upgrade the duct work so that the required CFMs are reaching each room. I was considering bringing out a 3rd party to run a duct test once they finish their work.

- On top of upgrading the compressor, other items that would need to be upgraded would be the: lineset, furnace, air handler/blower and duct work?

I really appreciate any help. This has been a long process and my current system has been so overloaded that its is about to give out. Last night the system froze up so badly that there was a 3 inch wide line of condensation on my bathroom mirror where the lineset runs up the wall.

bnun

what size/mdl furnace?

ductwork to second floor runs through a chase/closet?

you have zoning controls now? if so, what mdl?

add new evap coil to your list.

don't mean to be reptitive, but you need an independently performed Man J and D for correct sizing of both HVAC and ductwork. I certainly would not rely on the dealer. if you have to pay, then pay. you want it right and this is only way.

again sorry for your trouble.

TD

Thanks TD, I'll make a note for an evap coil.

I'm not sure what size my furnace is, but its made by Westinghouse. The zoning controls are made by Honeywell and can handle up to 4 zones.

The furnace is in my attic, so all the ductwork down through the ceiling.

bnun,
I wrote a long message but the short story and the correct fix is better zoning. They should break up your home in 4 properly designed zones using proven zoning and air conditioning and heating equipment.

What temperature do you set your thermostat?

classicdave,

Right now we keep the thermostat at 76, but it really can't hold that past 1 or 2pm. My wife would prefer closer to 74, but right now, she'd be happy with 76.

I think zoning could be an improvement. My main floor thermostat is back in a hallway, so in the afternoon, the main living area is usually 3-5 degrees warmer.

bnun,
You really need to look into having more zones.
This is the simplest, fastest most efficient way to get your home comfortable by using what you have now.

Even though I'm not a fan of honeywell zone boards
You already have a honeywell zone board that can handle up to 4 zones correct?
so I would recommend using the 4 zones the board offers. The contractor that did the zoning should have thought of this and every contractor that told you to file a claim against the a/c contractor should have recommended this. To me you got a barrel full of monkeys running around pointing fingers and no one has a clue how to solve your problem other than slapping a bigger sized system in and to me that is sad. But as a contractor I know we are not equal so getting the right contractor matters.

back to your problem,
Having two zones with a 3 ton system when a manual J is calling for 5 tons, this is where the problem is.
If a Manual J recommended a 5 ton system for your whole home then a 3 ton system with 2 zones definitely will not cool or heat your home on extreme temperatures when both zones are calling for the whole house to be cooled or heated.

Having only 2 zones your home will more than likely call for both zones at one time, like it is doing now.
If you break up your home to 4 correct zones there is a less likely hood that 3 or 4 zones will be calling at one time. There is also a greater chance that a zone will satisfy faster when it is smaller. This will then force the air to go to a zone which needs more cooling and heating.
Most of the time only one zone will call followed by 2 zones and occasionally 3.

The reason why I asked what you like your thermostat to be set at is a question I ask before before I perform a Manual J
for example
The manual j rates cooling btu's need for when it is 90F outside it can reach a temp of 75F - 15 degree difference.
So if you want it colder than 75F when it's 100F outside you may not get it. That is why a manual j is a guide not an end all.

So you say 74 then if it were me I would make sure I manipulated the Manual J so that the house could cool to 70/72F on 100F day.