View Full Version : New AC / high velocity
07-15-2005, 08:58 AM
Total newbie to AC systems. Where should I go for basic overview of issues, terms, ratings, etc? We are looking at putting AC into second floor addition currently under construction. Only window units currently. Should we put AC only in upstairs (bedrooms) or put in first floor as well. We don't use AC all that much, prefer open windows so won't need cadillac system. Neighbor suggested high velocity system. Worth it? Issues, comparisons with traditional? Heat is hot water radiators so no central air option. Basement is open ceiling and room for air handler but also attic space. Chicago suburbs. 1800SF cape cod house. Thanks!
07-15-2005, 09:23 AM
High velocity systems are typically used for installs where you really can't run normal ductwork...like old houses where you don't want to tear out walls/put in soffits to hide the ducts. HV systems are typically more expensive too. Since you're under construction, you can run the ductwork for a non HV system now...no?
07-15-2005, 09:51 AM
I can run the traditional ductwork now in the new construction in the second floor but the first floor is closed up. I could get to it, though from the basement below. I was wondering if the HV would be quieter or more efficient to offset any higher cost. Also, we are open to the possibility of installing AC only in the upstairs (new construction) and not messing with the cost of the downstairs. We can always use a window unit or 2 to supplement the upstairs. Comments?
07-15-2005, 11:41 AM
HV is less efficient and probably not as quiet as a well designed standard system. Since cold air falls, few vents will be needed on the first floor. Often you can go down through 2nd floor closets with a few runs and the first floor will be fine. I would go with an attic system covering the 2nd floor and pop a couple to the first floor. I think you'll be fine.
07-15-2005, 11:54 AM
Is an attic system any different (i.e. is the equipment different because it is in the attic) or is it just a different location for the air handler? Thanks.
07-15-2005, 04:47 PM
I've designed about 30 of these systems(Unico) and they are not diffused air but aspirated air that mixes with the air in the house so there are no hot*/cold spots in the house. And the system is quieter than a conventional system and it takes about 1/2 the time and space to put one in, plus he fact that you can probably do the first floor from the attic also and depending on sq footage maybe just one system!
07-15-2005, 04:51 PM
Also because of the air moving in aspiration effect instead of diffusion it is a more efficient system and dehumidifys 30% more!!
07-15-2005, 07:37 PM
If you have enough room in attic I would use conventional system having central return on second floor ceiling, a supply in each room on second floor and utilising closets on second floor, try to get three 8" supply to first floor ceiling.
( 600 to 700 cfm)
I have done this many times in existing homes that have hydronic heat, and it has worked extremly well.
07-15-2005, 07:43 PM
Spacepak is a nice spendy system- every one I've done is a success with the HO, but you can't humidify or filter the air with it, which you could with a conventional ductwork system.
07-15-2005, 07:49 PM
not to mention the wear on the compressor and ofm from constant starting and stopping, due to the freeze stat.
08-05-2005, 01:03 PM
I've gotten some bids now. The system that seems to meet our needs is an airhandler in the attic with ducts running to each of the 4 upstairs bedrooms. This requires a 2 ton size. Two of the bidders suggested upping to 2.5 ton and placing a vent over the stair well to allow some more cold air to go downstairs and help cool the main floor. (Again, we are using the AC primarily to cool the bedrooms and will supplement the main floor with window units if needed.) Also, 1 bidder installs Lennox but said we could save a few bucks with a Westinghouse system. The other bidder uses Ruud/Rheem. Are these good ideas? Comments? Thanks.
Craig in Chicago suburbs
08-05-2005, 01:06 PM
Makes sense to me. Since cold air is going to fall anyway and cool the downstairs, I would go to the 1/2 ton larger size and an extra outlet over the stairs.
Lennox is OK, don't buy the Merit cheapo series. Westinghouse & Rheem are fine too.
08-05-2005, 01:13 PM
I you have access to the ceiling of the first floor for suppy and return registers, you might consider including it in your system and zoning your first and second floor separately. That way, you can get rid of your window units and still open the windows downstairs if you like.
Just a thought...
(Oh, and if you're going the Lennox route the HS26 is a very nice mid-range condenser. The HS29 is similar but lower SEER -- 11 vs. 13).
08-05-2005, 01:22 PM
Thanks for your replies -- very helpful. The Lennox is the 11 SEER model; the payback on the 13 would be too long since it is not used except on the 20 or so hottest days of the year.
08-05-2005, 01:58 PM
Originally posted by farns
The Lennox is the 11 SEER model; the payback on the 13 would be too long since it is not used except on the 20 or so hottest days of the year.
Good choice then. I think the 11 and 13 SEER units use the same compressor anyway for 2.5 ton and larger units -- the 13 just has a larger coil,
08-10-2005, 12:21 PM
After tweaking the design and matching our budget, our contractor is now suggesting a Weather King condenser (model 10AJB030A01) and WK air handler (model 17AHJ11502C01) on the grounds that WK is the same as Ruud but with a different name plate. He is offering a 5 yr warranty on parts and labor for the WK to match the Ruud. Any red flags? Thanks.
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