Attic AC System Recommendations


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Old 04-28-19, 08:20 AM
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Attic AC System Recommendations

First off I have hot water baseboard heating in my house with two zones off my boiler. Each zone is controlled with a NestE thermostat. I'm ready to put an attic AC system in and have installed all the duct work in the addition and just about to start with the existing house. Here are my questions.

  1. This will be for just AC, installed in attic
  2. Need two zones
  3. Goodman, Carrier, what other brands?
  4. Can I install the air handler and condenser and have a pro come and charge it with freon?
  5. Air handler in attic, condensor outside, what other components
  6. Is this called a split system?
  7. Can I run a fan/filter to clean the air in the house without AC running? Is that an added fan I need to put into the system?

I'm trying to save money on this house and got estimates from 8-15k for 3 and 4 ton units. I can buy a 4 ton goodman unit for around $2500 https://www.acwholesalers.com/Goodma...--/p75363.html

install in myself, ductwork, etc. Any suggestions?
 
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Old 04-28-19, 08:26 AM
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First, you’ll need to run manual J, manual S, and manual D to determine unit size, select the unit and design the ductwork.
Manual J-heat loss and gain
Manual S-unit selection
Manual D-duct design (used with room by room manual J)
Your duct design will have to be very good to get a zoned system to work. Multistage equipment is also recommended.
You can’t just buy whatever tonnage you want and get the system to work.
 
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Old 04-28-19, 08:38 AM
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Thanks for replying, the 4 ton is what was recommended on 2 of the 3 estimates I received. One estimate recommended a 3.5 ton as a good and the 4 ton as better. Its a small house and I trying to split the ac into one section of the house and the other with the two zones. There's duct work in almost every room of the 1700 sq foot home. Anything will be better than window AC units, so I don't want to over complicate things and just want AC to blow out of the ducts I installed out of my attic.
 
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Old 04-28-19, 08:43 AM
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You don’t need 3.5 or 4 tons for a little 1700 sq ft house.
Manual J will show what’s needed. I wouldn’t trust the quotes.
A lot goes into blowing cold air. There’s a science to this trade. Especially if your zoning.
What size ducts did you install? How many supplies? How many returns? What material are they constructed from?
 
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Old 04-28-19, 09:01 AM
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Is there manual J calculator you prefer to use or online that's free to DIYers?
 
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Old 04-28-19, 09:06 AM
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This is a free version. The information put in must be spot on.
Crap in=crap out.

HVAC Load Calculation - Maunualj - Whole House Loadcalc

You'll still need a room by room manual J, which this one doesn’t do.
 
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