Should I replace duct work & furnace

12 years ago

I bought a one story 1900 square foot house built in '69 last year. Duct work is in the floor, but the air flow is very weak in parts of the house. The heat seems to work ok, but generates a lot of heat around the furnace (seem to be leaks in the ductwork connecting furnace and rest of house). When we try to use air conditioning, air blows, but is not cool. We had several repairman come under our home warranty policy and they say air conditioning is "technically working" even though it doesn't cool the house. We are tired of trying to fix things piecemeal and think we need to just replace part or all of the system. The outside 2 ton air conditioning unit is about 13 years old. The current gas furnace is an entry level Trane, and about 3 years old. A couple of HVAC companies told us they would use the existing duct work, but replace the furnace with a variable unit (Carrier #58CVA070-12, 80% efficient), and that would solve our problem. One company suggested replacing the floor duct work with duct work in the attic (which they said would help air flow), replacing the air conditioner with a 3 ton Carrier (#24ACC624) and the coil (#CNPVP2417) but keep the furnace (which is not variable speed). All of these estimates are in the 6-10k range. What makes the most sense? Replace duct work only, replace furnace only with variable speed, or replace everything?

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Comments (5)

mike_home
12 years ago
My first suggestion is to stop wasting time with the home warranty company. The people they send are typically not qualified when it comes to an HVAC system.

What is your location, and what the typical winter low and summer high temperatures?

It sounds like your current duct work has issues. Does this house have a basement and is the duct work accessible? I suggest it be thoroughly inspected and fixed as needed. The supplies and returns must be properly sized and sealed. Installing a variable speed furnace on a poor duct system will only create more problems.

I think you should try to salvage your three year old Trane furnace. I would rather see you get a matched Trane coil and condenser. If you have the budget, then replacing the furnace and AC would be the best solution. The Carrier furnace you mentioned is the top of the line for 80% efficiency. Depending on your climate you may want to spend to extra money on a 95%+ efficiency furnace. This may qualify you for additional local rebates.
ionized_gw
12 years ago
If your current ducts are inside the house, changing to ducts outside the house (attic) will be a big step backwards. Try not to do that.
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Feli123
Original Author
12 years ago
Thank you for the information. I think you are right about the home warranty company. We have not had good experiences so far, and the companies that have come out always find something to charge for that isn't covered under the warranty. For example, one company came out to see why the air conditioner wasn't working, added Freon (not covered by warranty), and the system didn't improve at all. We are located in Northern Virginia, and so far it is the heat that has bothered us most. The duct work is between the slab and the floor, so it is pretty inaccessible. It looks dirty when we open up the registers, and it is quite possible there might be minor blockages along the way because of root damage etc. I am open to installing new ducts in the attic, but I thought that given that the attic is quite hot in the summer, this might create some other inefficiences. However, if there is a problem with the existing floor duct work, there is almost no way to fix it without tearing up the floors. I was hoping to salvage the Trane furnace, but would it work ok if it were paired with the new Carrier air conditioner(#24ACC624) and the coil (#CNPVP2417) (the company that gave us this estimate doesn't deal in Trane), or would it be better to pay a couple of thousand more and just get the new 80% gas furnace too (16 SEER rating we are told with the new furnace, 14 seer, with just the air conditioning and coil).
heatseeker
12 years ago
Home warranty company "system is performing normally"
Home owner " system does not blow cold air"
Semms to me that Home warranty company is 'performing Normally' as they follow their script.
Installing new equipment will not fix ductwork problem BTW.
mike_home
12 years ago
You need to address the duct system first. If you do not you are wasting your money on new equipment.

A 2 ton air conditioner for a 1900 sq ft 1960's ranch house in Virginia seems undersized. Did the contractor do a load calculation to come up with this size? If no, continue looking for other contractors.

You can connect the Carrier coil and condenser to the Trane furnace. The efficicency rating will be unknown since this it is not a verified match.