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10&12 SEER to 13 SEER +

happened to "basement model" furnaces?


  • Empire_2
    Empire_2 Member Posts: 2,343
    Cased coils are Huge!!! Thoughts

    I am very concerned that the change over to 13 + SEER A/C units and the elimination of 10 and 12 Seer units leave little room to install the A-coil. They are huge... Add on installations leave me with upcomming head aches. Any thoughts?
  • Wethead7
    Wethead7 Member Posts: 170
    larger coils

    The new a/c units do have larger coils, but most new furnances
    are much shorter. You might be undercutting yourself not replacing everything. A/c only may need to replace the air handling unit. We like to upgrade to ecm units, they are much quiter most of the time.

  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    One issue

    One issue that I forese arising on a regular basis is the increased inefficiency of the air distribution system on the newer, higher efficienicy units. Remember that a piece of equipment is not the system and that the system is comprised of all of the components, not only the 13 SEER condensing unit and/or air handler.

    Here's my concern about the air distribution system.

    Qite often, vertical space is limited, especially when an "A" coil is mounted on top of an existing furnace. And, as you mentioned, the newer coils are larger, reducing the clearance space above the equipment for adequate and properly sized ductwork.

    It is important to remember that you cannot expect the system to operate properly if there is nowhere for the air to go.

    I was just in a house with my students, the owner of which gave me the opportunity to use her home to conduct a complete Manual J and Manual D on the heating/AC system. The supply plenum coming off the furnace as 22 inches by 22 inches by 18 inches high. The MAIN TRUNK LINE measured 13 by 8 inches and was butt connected right into the side of the supply plenum. Gee... I wonder why there's insufficient airflow? Hmmmmmmmmmm

    Now consider the possibility (which is going to be a reality in the very near future) when she replaces her undersized 2.5 ton system with a new, 13 SEER 4-ton system which will service her existing home as well as the extension she is putting on the home.

    The first and most dramatic suggestions I can make are three in number and they are (1) Add turning vanes to the supply and return elbows. (2) Add turning vanes to the supply and return elbows. And finally (3) Add turning vanes to the supply and return elbows.

    By choking the supply air we are increasing the total equivalent length of the air distribution system (TEL) and decreasing the amount of available static pressure (ASP). A poorily designed supplu plenum elbow can have an equivalent length of over 85 feet, whil a properly sized elbow with turning vanes can have an equivalent length as small as 10 feet.

    So although the quarters may be getting a little cramped with the newer equipment, think about the air distribution system as well. You'll be glad you did.
  • John Mills_5
    John Mills_5 Member Posts: 935

    One thing I've had trouble beating into our salesmens' heads is not selling the brand you want to push but push the brand that fits the application better. One brand we have now is 51 1/2" tall, any furnace, any coil. Another can have 44" in just the furnace and some cased coils add another 24" so 68". I'm trying to convince the guys that look at the job and if the short furnace & coil will deliver better performance in a short basement, push that one. The installers are tired of trying to squeeze tall equipment in not to mention the damage to the performance. And of course the days of 17.5" tall coil boxes even from this vendor are over.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Buffalo, NY

    Basement height is usually around 7 to 8' if you're lucky. I have often pondered usuing a horizontal application, but now I would end up with even more head bangers. I guess I have no choice but to ask the home owner to raise the house another foot or so:)...I don't have a problem with the higher eff. but this is the govs answer to reducing the total load on the power grid. Guess who pays for it,...We do.
  • Tom_35
    Tom_35 Member Posts: 265
    Physical room for furnace and coil--

    I'm in Arkansas and basements are almost non-existant here. Most of the older homes that are going to need change-outs have furnaces and coils in closets---either in the home or the garage. Most of these closets were tight for space originally, and the new systems will not fit. We have had to make changes where the furnace only is in the closet and the plenum is then run up into the attic, hits a rectangular elbow, which then hits a horizontal coil. A supply air plenum is then installed and new duct hook-ups are installed on the plenum. Obviously this is much more expensive in that we now have emergency drain pans and float switches to add, new supply hook-ups, more rectangular duct, and labor as opposed to a simple transition that was used in the past with evaporator coils that were smaller.

    We have used this configuration on new jobs, but the furnace and coil are located in the attic. This is not the best location, but space is a premium on homes and the homeowners are not interested in giving up any more square footage than they have to.

    Tom Atchley
    Ft. Smith, AR
  • JackFre
    JackFre Member Posts: 225
    a very good alternative

    I think with the new regs and the sizes of equipment you are going to see dramatic growth in the mini-split business. I represent Fujitsu in New England, so yes, there is some bias. Having said that, most of Fujitsu's new equipment is inverter based and running in the 16-21 Seer range. The evaporators are getting smaller (18kbtu was 49" long, the new one is 31.5")...and quieter. Also, with the new inverter units you will see small (7-24kbtu) ducted and non-ducted air handlers ('07). That means the transom mount over the closet door is ideal for retrofitting A/C. I think there will be a push to mini-splits for additions. Leave the old system in place and add the m/s. Just as we have seen the push into the European technology for heating I think we will begin to realize that the rest of the world cools in a more efficient manner too! Exciting times, eh!
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Horizontal configuration

    We may also start seeing an increase in the number of vertical to horizontal conversions, espeically in basements that have low clearances.
  • will smith_4
    will smith_4 Member Posts: 259
    I think the emporer has no clothes

    Unless they make it a punishable offense to install a high efficiency condenser without a new evap, and properly designed ductwork (properly sealed, too), the whole swing to higher efficiency is nonsense. New home construction is miniscule compared to existing home numbers. Existing home units are improperly ducted 99% of the time. So will a government agent come out to inspect your duct and then determine whether or not you can get a replacement system put in? Of course not. We will continue to see replacement systems jammed into duct it was not designed for. Overall energy consumption reduction overall-likely negligible. In the case of ductless minisplits to replace existing inefficient ac units, well, those are just expensive window units in my book.
  • jim lockard
    jim lockard Member Posts: 1,059
    How long

    is the cooling season in buffalo NY, 2, 21/2 months max that you need the same SEER machine as FLA or MISS ? Central A/C's in Buffalo suffer more wear and tear in the off season then when they are working. Evaporator coils on gas and oil fired furnaces where during the heating season freon pressures are raised to hundreds of PSI's. While the condensers sit out in low moist temptures all winter and rot. Just my rant. Best Wishes J.Lockard
  • Keith W.
    Keith W. Member Posts: 29

    It seems like the Fujitsu mini-splits I see online are 13 SEER. What are the models of the higher-eff. units? Thanks.
  • Keith W.
    Keith W. Member Posts: 29

    It seems like the Fujitsu mini-splits I see online are 13 SEER or lower. What are the model numbers of the 16-21 SEER units you mention? And/or, links to specs. Thanks.
  • D lux_2
    D lux_2 Member Posts: 230
    but look at the ''good'' we did

    big gov one size fits all . we feel better too
  • JackFre
    JackFre Member Posts: 225
    Sorry for the time delay on response

    The 13 seer requirement kicks in the end of January. As you saw on-line we have only the 9&12k units in the 13 seer for the '05 season. All of the inverter based (up to 21 seer) product will start arriving Jan/Feb '06.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Would like

    I would like to see a catalog, Jack. Could you please send one to me at the office?

    Suffolk County Community College
    Michael J. Grant Campus
    1001 Crooked Hill Road
    Brentwood, NY 11717

    Att: Professor Eugene Silberstein
    Coordinator HVAC/R

    Nesconset Hall Suite N-17

    Thanks, Buddy
  • Keith W.
    Keith W. Member Posts: 29
    What is an \"inverter based\" AC system?

    Does that mean you're using DC motors, or is there something else there I'm missing. And, how sure are you of the Jan/Feb timeline? I might tentatively hold off spec'ing some jobs if I thought a 21 SEER unit was going to be available before long. (I'm a green design/builder, so my clients REALLY REALLY care about these things)

    Thanks, Keith
This discussion has been closed.