The big problem is getting the duct system, registers, return air filter sizing, large enough to accommodate a 3-Ton system.

Check your home for energy efficiency improvements & then do a free load-calc.

Due to ductwork & other factors, I would NOT go to a large 4-Ton; go for what an honest load-calc & sizing calls for.

Here is a link that might be useful: Free Online Whole House Load-Calc

But we would be having the ducts registers & returns all replaced with either installation so I am not clear on what you are saying. We did have a load calc done by the Carrier person who recommend the 3 ton system. Thanks.

Then go with the 3-Ton system; far too many don't get the duct system & return air filter areas sized right...

What size system are you replacing, both furnace and AC?

Two entirely different levels of HVAC quoted between the Trane and Carrier. Plus the obvious size difference. Big difference between 3 ton two stage and 4 ton single stage.

You have actually seen a copy of the load calc in writing on the software letterhead? What design temps were used?

On the Carrier system quoted, you want the Infinity controller, no substitute would be acceptable.

IMO

I am having trouble following the price quote for the furnace, AC, coil, and thermostat installation. The prices seem high.

The attic insulation should be at least R30. The Carrier dealer is doing the right thing by basing his size on the upgraded insulation.

It is difficult to comment on the quotes for the new duct work. It involved a lot of labor in a hot attic.

You should use the Infinity controller with the quoted Carrier equipment. There have been mixed reviews about the Nest thermostat. There are better thermostats available for about the same money.

Had a 3rd company out today who said we need a 5-ton variable speed system & he is recommending Rheem as he says there have been issues with Trane. His quote is somewhere in the neighborhood of $15-16K. This is crazy.
This does not include electrical or insulation.

And he kept saying that ours is not a normal install - that it is not a retrofit which is most of their jobs - more that a modified new construction to reduct whole system in attic. Doesn't give me a whole lot of confidence in them having the expertise to do the job.

The Carrier dealer who did the did load calc sort of showed it to me but would not give it to me. He said he based it on 103 degrees outside and either 74 or 76 inside.

What is the difference between 3 ton 2-stage & 4 ton single stage?

I need to make a decision soon as this impacts our ability to do other projects before move-in but I am so confused.

How do 3 companies give you 3 different sizes?

Thanks

I will ask the same question as before.

What size are you replacing, both furnace and AC?

If you don't know, you need to find out.

You have a decision to make and really can't make until you have the documented specifics on the load calc.

You currently have not moved in?

IMO

The first post above references existing 2-ton system.

Considering how hot it can get in Dallas, isn't 3 tons a little low for 2,273 sq. ft.? Although, 74ðF also seems low for an indoor target temp at 103ðF ambient. I have 5 tons for 2,350 sq. ft. about an hr west of Houston.

We have been told by 2 people that we are replacing 2 ton Trane & a 3rd said 2.5 ton Trane 14 seer both of which appear to be marked 2001.

We are replacing furnace & A/C.

We have not moved in yet.

Our inspector did not point out to us that the existing system was undersized.

We were there today for a good part of the day & had thermostat set at 74 & it was ok but the master & back bedrooms were not cool.

Thanks.

Pls...size furnace.

The idea that the back bedrooms including master are warm need to be evaluated by dealer for specific suggestions for improvement.

For Texas, your overhead insulation in attic needs evaluation.

Where is ductwork system located?

Post back.

IMO

The reason many think it takes a 5-Ton to cool is that the 5-Ton, due to undersized & leaking ducting & too small return air grilles & filters, may only be delivering around 3-Ton to the rooms.

If the calc that says 3-Ton is correct & the install & design engineering is done right it should handle the heat-load.

You can always do things to reduce the heat-gain of your home...!

"Our inspector did not point out to us that the existing system was undersized."

Just a lowly homeowner here, but how would the home inspector know accurately whether your old A/C was too large or too small? He or she might observe that the unit was not keeping up with demand - something you could do just as well on your own.

From one homeowner to another homeowner, the pros are trying to give you help here but you seem to be fighting them. When they ask a question, inevitably the question has a direct bearing on the issue at hand!

This post was edited by saltidawg on Sat, Aug 2, 14 at 20:47

I am trying to answer as best I can. I am not trying to be difficult, I was just not expecting having to face this major expense right after closing. The real estate market in Dallas is crazy & we were on a time limit to buy a home. Most homes have multiple offers as did ours & we had a short option period. I realize no one forced us to buy this home but I am just frustrated that 3 top rated companies are coming up with different recommendations. The system currently in place is working but if we are not going to be comfortable & it is undersized I'd rather bite the bullet now & replace before we do other work & paint before moving in.

I would think that an inspector who told us he has inspected 17,000 homes in DFW would have given us a heads up that a 2 or 2 &1/2 ton mismatched system would be undersized for a close to 2,300 SF home,

The ducts are located in the soffits below the attic (as was apparently done in the 60's in these homes) running in a t-shape down 2-hallways perpendicular to each other,

The quotes I have received are to install all new ductwork in the attic so we can at some point knock out the existing ductwork & soffits & raise the ceiling height in the 2 hallways to that of the rest of the home.

The all new duct work is approx $2,500-$3,500 of the quotes I have mentioned (although we would still have some cost even if we retrofit) .

This would be done if we installed a 3, 4 or 5 ton replacement system including furnace, coil etc.

I just have a hard time understanding how a 3 ton system would cool a 2,300SF home.

I have attached a copy of the floor plan that the Carrier dealer created. He would not give me the load calc. We also requested an additional supply in the MBR and they will be installing a 2nd (additional) return.

Thank you.

I personally would go with the 3-Ton Carrier; as I stated previously, U can always do things to your home & the duct system to increase the ability of the system to handle the heat-gain.

Then the main thing is the quality of the install.

The installed performance should be tested by the Technician; if not then U take the temp of the nearest diffuser; @50% Relative Humidity the temp-drop should normally be around 19 to 21ðF. U must know the INDOOR humidity...! Low cost at a hardware or other retail store.

If U know the CFM of airflow multiply it times say 20 * 1.1 is 22 * say 1200-CFM is 26400-Btuh sensible, if 75ðF in the home * 1.25 is 33,000-Btuh total.

That is about what a decent functioning 3-Ton will produce.
Then there is the checking of each duct run to see how much CFM & sensible Btuh is 'actually' being delivered to the rooms.

The Tech can use other methods to check the systems performance.

Before doing anything else; U ought to check the performance of your existing unit...!

Here is a link that might be useful: WAYS You Can Check HVAC Performance & Reduce HOME ENERGY USE & Equipment Costs

Interesting the last company that came out yesterday called and said they did not want the job. This is the one that said they usually did retrofits & this would be a difficult job for them. I guess best they declined if they did not think they could do a good job but how do I know I am finding someone who is an expect at installing new ducts, etc in a 1964 home? Thanks.

Here is my deal on sizing ducts; scroll 'way-down' until you get to the 2nd chart. Sized for a heat pump as well as an A/C.

However, they should do the sizing based on an ACCA Manual D; that is the best way to get everything right.

Make sure all the joints are sealed with mastic & it's properly insulated.

Here is a link that might be useful: Duct sizing

The hardest part for a homeowner is determining if the HVAC contractor can do the job correctly. You have to interview the contractor as a employer who is interviewing a candidate for a new job. Ask a lot of questions and figure out if the answers are correct or at least make sense to you.

I like the fact the Carrier dealer wants to put in the proper size AC. I am a little suspicious about his load calculation. The design temperature for Dallas/Fort Worth is 99 degrees. You stated he used 103 degrees with an indoor temperature of 74 or 76. I find it a little hard to believe a 3 ton condenser would be able to cool a 2273 sq. foot 1964 ranch with duct work in the attic. I realize the attic insulation and duct work will be upgraded, but I still think the AC could be undersized. I would want to review the load calculation carefully before signing a contract.

I spoke to the Carrier person again today and he confirmed verbally to me that when he first walked into our house the thought 4 ton but that we do not have a lot of windows & they are not big windows except for in LR & that the load calc came out to 2.8 using 102 degrees & cooling to 75 degrees.

So if we do new ductwork, put insulation in atti that 3 ton will do it.
He said if we are only thing of staying in the house a few years to go with 2 speed otherwise he'd recommend variable speed.

He said satisfaction guaranteed & that if he is wrong they'd replace with a 4 ton. I would certainly ask for that in writing.

He also told me Carrier no longer offers extended warranty on labor so our choices are either: 1) use them - labor free if we have service agreement or 2) get 3rd party labor extended warranty.

He said none of the manufacturers are offering 10 year labor anymore. Is this true?

Thanks.

I have been told by my dealer that Carrier is no long offering the 10 year labor warranty. I am not sure if this is true for all manufacturers.