Confused about new HVAC units
I'm having 3 quotes on replacing our units. The old ones were a 5 ton and a 2 ton units. However, each company is quoting me differently. First one is 5 and 2.5 ton units, Second is 4 and 4 ton units, third is 5 and 3.5 units. They are suppose to have done the J Calc? using 75 F indoor temp when outside is 94 (we're in FL). They are all quoting the Trane XR15 (15seer) units. Not sure which one I should sign the contract with??? Our house is 2 stories, first floor about 2500 sqft, second is about 2200 sqft with lots of windows and high ceilings. Any suggestions?
Did your current 5 ton and 2 ton units keep the house cool? Was the humidity comfortable?
If the answer to both of those questions is yes, then you need to find new contractors. All of them are wanting to put larger systems in. If they put in a larger system are they putting in larger ductwork? If not you will have an issue.
How did they do their Manual J Loac Calcs. Did each measure all your windows and walls and input data as to what types of windows and how much insulation in walls, ceilings, slab/floor etc? If they just counted registers none of them are correct.
How many sq feet is the home, what type of construction is it(insulation windows etc). How have the current systems been performing.
The 5 ton on main floor seems large to me. The 2 ton seems small to me. Without seeing the home, I would suggest 3.5 ton downstairs and 3 ton upstairs. FYI, 3 tons is 36,000 btu.s Most "3 ton" units deliver 2.75 tons Duct work for downstairs will/should be large enough for 3.5 tons, but upstairs needs evaluated.
Last edited by Kevin Weaver; 12-18-2012 at 04:03 PM.
Reason: added more
As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84
Without seeing the house, or knowing more information it will be hard to say for sure, but here is my take on what you posted.
Originally Posted by jetsetter
“The old ones were a 5 ton and a 2 ton units”.
First quote is for a 5 and 2.5 ton units: This seems in line with what you have currently with some improvement with the cooling.
Second quote is for a 4 and 4 ton units: This would concern me because of the amount of supplies and returns in the system. That is double the system on one, and a ton smaller on another, not good either way.
Third quote is for a 5 and 3.5 units: This would concern me because of the amount of supplies and returns in the system as well, you are adding 1.5 ton of cooling, that's a little much.
If I understand your post correctly, you have a 4,700 sqft home. Are the other two guys going to do any new duct work (be it reutrn or supply)?
You said 2nd floor had high ceilings and lots of windows. Since heat tends to rise and the attic is at the second floor, it may require at least as much as first floor. Also the bedrooms may be on second floor. My wife likes a cold bedroom. Manual j should determine correct size.
~700 sq feet of Single Pane windows ... gets you about 6% of the answer.
Originally Posted by jetsetter
Built in 1982 ( or _ _?) gets you another 4%.
_ The 6th one says 3.5 ton and 2 ton,
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
I'd say 4 tons up/2 tons down sounds about right. A load calculation would give closer numbers. As others have said DELIVERED capacity depends largely on ductwork. Most system don't' deliver their rated capacity.
Are you doing heat pumps or gas heat?
We bought the house from the bank and don't have prior knowledge of its performance. I did ask them if my current ductwork is large enough and all said fine. They are going to have all new wirings because we're changing from propane gas to heat pumps. Only the contractor with 5 and 2.5 tons quote asked about windows, raised floors and insulation. the others just used sqft in county records and counted registers. Thank you for your reply.
Originally Posted by SkyHeating
Heat pumps. They were telling me the downstair had the 5 ton unit but I looked at the ductwork it's quite small, tucked between floors with one section smaller becuase the structure beam in middle of the house then gets bigger again. There were three small returns for the main floors. Upstairs had 6 returns because all bedrms.
None wants to change the ductwork even its black inside. They insist if to replace it will still be same size but will cost $. They also insist that I change all the grills, there were two different kinds and can't be adjust to achieve energy efficiency. I never heard that before! That's $.
Two companies wants to eliminate a return tucked under our raised main floor that's on the other side of the house. We have so many questions????
Last edited by beenthere; 12-19-2012 at 05:54 AM.
I would think 3 down and 3.5 up.
Downstairs requires a LOT less cooling than upstairs. Like 1/2 or even 1/3 the amount per square ft. Most of the downstairs load will come from internally generated heat and humidity. You will get some through the west windows, a little from the ceiling that isn't covered by the upstairs.
In winter upstairs requires very little heating, a heat pump big enough to handle cooling should get you into the 20's for heat before the aux strips are needed. For downstairs a lot more heat is required.
Here in Florida, summer is brutal with heat and humidity. There really isn't winter season here. We get cold spells a few times but never below freezing. Our house is facing North, East side is shaded but West side faces afternoon sun. We took out windows on west side of house so it will help with cooling downstairs. The raised floor is insulated. There is one room downstair not covered by upstairs but the rest are.
I don't know how I can tell if the air handler for upstair was for the 5 ton or was it downstair handler. The old units were stolen.