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watersda 07-10-2007 02:10 PM

HVAC for 2nd Story Addition?
I am in the process of designing a 2nd floor addition to my 1500 sf ranch. The current forced hot air, gas furnace is in the basement. I plan on having it replaced with a new Trane with central air. Will I be able to have one unit to heat/cool the 1st and 2nd floor? Can I have the duct work extended up through the 2nd floor into the attic and branch off to the seperate rooms from there? Or, will I have to have 2 seperate HVAC units, 1 for each floor? I am estimating $10-15K, am I in the ballpark?
Any comments/suggestions would be appreciated.

CraigFL 07-11-2007 05:37 AM

After owning several 2 story homes and ranches, I prefer two seperate units for two story homes. There are air flow/mixing problems with two story homes that are easily overcome by two units. And... if one unit goes out, you always have a backup.

subcoolman 07-20-2007 07:58 AM

As with many other things in life, "It depends". I'm new here (first post), but I've been in the HVAC industry for over 10 years.

Whether air will reach the second story of your addition really depends upon proper ductwork design and sizing. If the ductwork is sized, designed, and installed properly there is no reason why this wouldn't work for you, but most Residential HVAC installers don't want to take the time and/or effort to do this.

Find a "good" HVAC Contractor, perhaps even a light Commercial one, and ask them to do a ductwork sizing analysis and layout for you. Then, install the ductwork as sized- no cutting corners.

Proper design can make a world of difference.

glennjanie 09-10-2007 09:43 AM

Hello Watersda:

It looks like you and Subcoolman are both new to the Forum; Welcome to both of you. Can't you just picture Subcoolman with his mask, cape and a big S on his tee shirt. A timid little lady with her hands folded, saying "My Hero".

I personally vote for Subcoolman's answer for your problem; he has covered the bases and knows what he's talking about. Cooling two levels is a challenge for an A/C man but most of them know they can do zone heating and cooling by proper duct sizing and regulating dampers or by using two systems. Naturally the single system is the lower price.


watersda 09-21-2007 07:54 AM

I had 3 local trane dealers come to give me qoutes. 2 of them did, 1 came and looked at the job, but ended up blowing me off for the quote. The 2 that did were very close to each other. 1 qouted XR12 Central Air units with the old refrigerent. I asked him to reqoute with the same model #'s I got from the other dealer and they were within $800 of each other.
The concensus was 2 seperate units.
1st floor: Replace downstairs furnace with high efficiency trane (95%) and a 2.5 ton trane XR14 central air unit, extend a few ducts. ~$8000
2nd floor addition: 80% eff. trane furnace in attic, all new ductwork, 2 ton XR14 central air unit. ~$12,000

~$20,000 total, installed. Seems reasonable?

glennjanie 09-21-2007 11:05 AM

Hello Watersda:
Call your neighborhood Carrier dealer(s) and ask them the same questions and ask for bids. If any HVAC contractor talks about any flex duct, take him off your list and ignore his bid.
It is not that big a deal to use one unit for both floors with zoned duct work and the single unit will be less expensive to buy and more efficient to operate. Some dealers have a computer program to design the system for them and can do a magnificent job for you. The $20,000 bid is far out of line.

gwliston 10-03-2007 08:18 PM

$20,000 - ouch! Get more quotes.

I've had several houses - ranch and 2 story - in places with similar climates to Schenectady. I've never needed a separate AC for the upstairs. You're adding 1500 sq ft or less, right? So, total squares will be 3000 or less. That's not too much to ask from a single furnace/AC unit. Once it's installed, a little trial-and-error experience will tell you how to set the dampers for the heating and cooling season.

When you're looking around, I suggest that you don't get "target fixation" on a particular line or model. Unless, of course, you like spending money. My guess is that you should be able to get one monster system for less than $10K, and two smaller systems for less than $15K. The $20K quotes may actually be the right deal for you, but you need to be sure.

'nuther Glenn

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