...AND MORE AIRCONDITIONING QUESTIONS

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Author Message   Bob K Supporter Username: Bobk Post Number: 10955 Registered: 5-2001 Posted on Thursday, March 16, 2006 - 7:52 am:        We are looking into central air and a couple of questions arise: 1. Do the high velocity mini-duct systems make a wooshing or humming sound? 2. One of the contractors we are talking with uses Amana products. I know they make reasonably good refrigerators, but this is the first time I have heard of them making central air units and air handlers. Their warranty is excellent btw and the SEER is 15. Any experience with these units here?   HOMMELL Citizen Username: Hommell Post Number: 52 Registered: 11-2005 Posted on Thursday, March 16, 2006 - 8:17 am:        1. If installed correctly, no. See, for example, http://www.unicosystem.com/. Go with a company that knows how to do it (may cost more than some of the others). Also, because the air handler is typically suspended in the attic, it does not vibrate the house. 2. I believe the high velocity units can only use 12 SEER (they were excepted from the 13 SEER rule - see http://www.unicosystem.com/seer_info/13SEER-Rules.pdf). No experience with Amana. Only Trane and Carrier - both top quality. Good luck.   SOSully Citizen Username: Sullymw Post Number: 1185 Registered: 5-2001 Posted on Thursday, March 16, 2006 - 9:09 am:        I had a 14 SEER unit in my previous house. Excellent product I always hear the air in a high-velocity installation   SO1969 Citizen Username: Bklyn1969 Post Number: 235 Registered: 7-2004 Posted on Thursday, March 16, 2006 - 9:54 am:        We have whooshing on the first floor (air handler in basement, pushing air up) but very little to no whooshing on 2nd floor/3rd floor (do hear the air handler if near it).   Bob K Supporter Username: Bobk Post Number: 10960 Registered: 5-2001 Posted on Thursday, March 16, 2006 - 2:51 pm:        Thanks for the information. I think we will probably end up going with a conventional system.   Travis Citizen Username: Travis Post Number: 374 Registered: 6-2004 Posted on Thursday, March 16, 2006 - 6:55 pm:        Bobk, I got CAC installed when I should have done more homework. I think now the system is there, I at least have something to work with as I try to replace it piece by piece. Some of the things I've learned: 1. Retrofit installations are always flex duct. Flex duct in general is garbage, and installation of flex duct is usually hack work. Flex is much less efficient than tin and even less efficient when installed with lots of kinks etc. I am bit by bit replacing flex with solid duct. 2. There was no mastic applied in the installation, so it will leak. 3. Almost always the handler goes in the attic, to save space. This is a big energy loss, the air-conditioned air is going through R4.2 ducts (R6 with new code) when you must have between R30 and R50 insulation on your attic floor. Does that make sense? Even worse, you have condensation problems with warm moist outside air condensing on the air handler (which is poorly insulated, no-one will pay for a properly insulated air handler). After doing my research, I plan to bite the bullet and insulate my roof deck (after having had ridge and soffit vents put in a couple of years ago....). 4. What I've heard about HV is that it is hack-proof. But AC installers will try to talk you out of it because they don't know how to do it. In any case it seems to me it has all the disadvantages of flex duct except it requires less space. 5. Make sure your installer does Manual/J and Manual/D calcs. Demand to see the calcs. Find out what they're assuming about your house. Oversizing is very common and results in the system shutting down before it has properly dehumidified the house. 6. Retrofit has a single return instead of a return in every room. Don't leave any doors closed while the system is running or you may build negative pressure which will draw in moist outside air. If you're lucky, you've got transoms in your old house. 6. Insulation is real important for reducing the load on your AC system. But there is also a danger of condensation soaking insulation e.g. in walls. This is why I dread turning the system on. The conventional building science says put a VB on the outside, which of course is the wrong place for winter, so current thinking appears to be some kind of vapor retarder with the ability to dry in either direction. I think the best options are foam insulation in the walls or dense-pack cells, but former requires a gut job and the latter is not possible if your house has no building paper.....   SO1969 Citizen Username: Bklyn1969 Post Number: 239 Registered: 7-2004 Posted on Thursday, March 16, 2006 - 7:37 pm:        Travis thanks for sharing. Not sure I got all that but had been wondering about spray foam insulation on the underside of roof deck in unfinished / unconditioned portion of attic where air handler is housed - is that what you're doing? Our house has ridge vents, but no soffit vents.   Jgberkeley Citizen Username: Jgberkeley Post Number: 4490 Registered: 5-2001 Posted on Thursday, March 16, 2006 - 8:14 pm:        BobK, 4 years ago we had an Amana 14 SEER unit installed. I am still amazed at how quiet the compressor is, the cost of the operation and the quality of the system. If you want to pop over and look at it, call me, 973 953-0781. Later, George   Travis Citizen Username: Travis Post Number: 375 Registered: 6-2004 Posted on Thursday, March 16, 2006 - 8:29 pm:        SO, I expect to insulate the entire roof deck. Here are some pointers: http://www.buildingscience.com/designsthatwork/cold/profiles/boston.htm http://www.buildingscience.com/resources/roofs/default.htm The big worry is moisture build-up in the attic in winter, the argument for venting. Basically the house absorbs moisture during the winter months and lets it out in spring and fall. So fixing sources of moisture (sump pits with no covers, basement floor with no VB) and introducing some kind of mechanical ventilation will all have to be part of the equation.   Bob K Supporter Username: Bobk Post Number: 10968 Registered: 5-2001 Posted on Friday, March 17, 2006 - 4:23 am:        Travis, thanks for the information. In our case the air handler will be going behind a knee wall in a finished space and the main distribution duct will be metal. The air handler will have a drip pan to handle any condensation issue. I don't think there is any practical way to avoid using flex ducting in the walls, but I see your point. George, thanks for the information.