4 ton replacement estimate

chbweberJuly 22, 2011

I am looking to replace a 10 year old 12 seer 2 ton unit that services about 5/8 of my house, mostly upstairs. I have a 2 ton unit downstairs that services the area adequately, but the upstairs unit is almost never adequate. It was installed by a prior owner and evidentally undersized.

My contractor tells me my house is a heat trap (he's probably right there--brick, sharp angles, ventilated somewhat poorly) and he recommends a 3.5 ton or 4 ton, some additional ducts, enlarging some existing ducts and a second return for the upstairs. He is quoting me about $9750 after rebates for a Carrier 2 stage, 4 ton 16 seer unit with all the bells and whistles in terms of programmable thermostat and humidity control. And about $8600 for a 3.5 ton Carrier single stage 16 seer.

I do trust his judgment about the size of the unit, and I'm going to be there for another 15 years and don't mind paying for comfort. He's losing me a little because he won't breakdown the equipment cost and labor cost in his estimate and I smell a rat there. I lived in another house installed and serviced by my guy so I know his work is quality.

Sounds too expensive though. Thoughts, comments? Thanks.

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Cb weber

What is your location?

What size living area for upstairs system?

Ductwork for upstairs is located in attic?

Has a load calculation been performed and given to you in writing to confirm dealer's opinion on sizing?

To be clear, this is a HP system you are replacing and is proposed?

More questions here than have been answered.

Have you sought a second opinion?

It is difficult for me to believe if going up in size to a 3 1/2 or 4 ton system, then your complete ductwork system would need replacing.


    Bookmark   July 22, 2011 at 1:59PM
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Long Island, NY

Not a heat pump. The living area upstairs is about 900 sq feet, but the upstairs unit has three ceiling ducts that also service downstairs rooms, which are also serviced by floor ducts. If I counted that additional downstairs space, I would probably be more like 1300 sq feet. The upstairs flexible duct work is located in attic space.

The dealer did not do any complicated math in sizing and he did not give me a load calculation in writing.

    Bookmark   July 22, 2011 at 2:13PM
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In general contractors do not break down labor and equipment costs. This is very common in this industry. You should get a breakdown of all the model numbers of the equipment. I think asking for break out of the duct work is a fair request, but you may not get it.

Is the quote for a condenser, and fan coil? If yes, then the price seems high, but it is difficult to judge since there is some cost for the duct work modification.

Going from a 2 ton to 4 ton unit is a big increase. You have to be assured it is being properly sized. Having a single stage system which constanly short cycles is not good. If you get a two stage unit, then you have the issue of it constantly running in the low stage. It would be comfortable but wasteful.

You also need to make sure your duct work can handle the air flow of a 3.5 or 4 ton air handler. Have the contractor explain how he has calculated the additional return sizing. He should not be using rules of them on any sizing.

I also recommend getting quotes from other Carrier dealers. I find it helpful getting additional contractors opinion on how they would solve a problem. The solutions and prices will vary.

    Bookmark   July 23, 2011 at 10:50AM
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I had a mess of a system with 3 ton indoor coil, 2.5 ton outdoor unit and fan speed set for 4 ton into ducts sized for 2 ton! Air flow was noisy with temperature extremes whenever the system came on in room immediately above HVAC unit and poor flow to far end of house. Ducts need to be twice the size for a 4 ton as for a 2 ton. This is a very big deal--must find space in ceilings or wherever to run the much larger ducts. Depending on locations, may need to rip out and replace ceilings. Avoid any contractor that wants to increase size of A/C without this ductwork. The result will be a disaster. If there are too few end registers, additional tear up work may be needed.

Easiest solution is to try to fix "heat trap" if possible. Make sure attic is properly vented if you have an attic. An attic fan can save a lot of energy and cut heat load. If windows are not low-e glass, window replacement may make sense.

If your contractor is doing all the right ductwork, the quote seems LOW. I rang up a far higher bill in fixing my house. Of course, a big parameter is the extent of ductwork replacement needed and how accessible the space is for new ducts. The main return duct on a 4 ton system needs to have a 300 sq inch internal cross section for optimal performance. From my experience, even experts doing proper Manual J calculations come up with very different numbers on sizing, so best to go with a two stage system since it will run closer to right more of the time. Oversized means run stage 2 more, undersized means run stage 1 more. This is much better than single stage which if oversized switches on and off excessively wasting a lot of power and wearing out components faster.

    Bookmark   July 24, 2011 at 1:27PM
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