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frankleibo 09-05-2011 04:18 PM

AC Overhaul Recommendations
 
I live in a 2 story home approx 2400 sq feet. Currently, the home has a 3 ton GE AC condenser that is 32 years old and original to the house. Inside there is a Carrier gas furnace (80% efficiency). The AC system was installed prior to a 500 sq foot addition (in law suite) so originally the 3 ton system was sized for a 1900 sq foot home. On the second floor (approx 600 sq ft) there is only one return in the hallway (return size is approx 19" x 12") and there are no return in any of the bedrooms. The duct work in the attic is a 10" x 10" fiberboard duct with 5 flex duct runouts to each ceiling vent feeding the upstairs rooms.

The system cools the first floor well. Second floor is miserably hot in the summer. In the winter the heating is OK for the most part with some cold spots in the house. I live in southern NJ near Atlantic City.

I have had several contractors come out and give quotes. No one has done a manual J calculation. Based on HVAC size estimators a 4.5 ton system should heat and cool my house sufficiently. My goal is to put the right system and not just do what is easiest for the contractor. None of the contractors have addressed the fact that the 3 ton is likely undersized for the house. Instead here are some of their approaches


1. Contractor 1: Put a 1.5 ton system to heat/cool only the back in law suite (500sq feet). Replace the 3 ton unit with a new one. Returns in all the upstairs bedrooms. Never addressed any other duct work issues. Keep current Carrier furnace. Price : $7800

2. Contractor 2: Put a 1.5 ton unit to heat/cool upstairs. Returns in all bedrooms and new ductwork in attic. Replace 3 ton condenser unit with a new one. Keep current Carrier furnace. Price: $10K

3. Contractor 3: Replace 3 ton unit with a new 3 ton Carrier R-410a unit. Flush my current coil (its a dual coil). New ductwork in attic and return in bedrooms. Some other odds and ends. Price: $6800

So, what do you make of these options and what do you think of my approach of starting from scratch and going with a 4.5 ton (or appropriately sized system)?

hvactech126 09-05-2011 04:30 PM

contractor 2 is probably closest to what you need done, however, you will never know for sure without a manual J being done. I don't think your approach of a 4.5 ton unit is correct. I think you need 2 systems.

REP 09-05-2011 07:09 PM

One;your house has nevern been sized prooperly for a HCVAC system.
It seems that the contractors want your job (meaning your money) but they don't want to work for it.
Selling equipment without a manuel "J" went out the window 15 years ago.Cost of fuel is just too expensive to guess at what you need.
Two;you need returns in the bedrooms and possibly more downstairs as well.Without a manuel "J" you can't get a manuel "D" for duct sizing.
If you end up with a new duct system tell the contractor you want the flex sized properly and installed to manufactuerer 's specs.It is totally differant than hard pipe sizing and installing correctly is a must.there is probably an install sheret in every box of flex.
Because of the way things used to be sized UI would believe that the 3.5 tons was way oversized to begin with.
Its your money and your comfort for the next 20 years,demand a real manuel J. and D.


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