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AC, Calculate your Actual SEER

Discussion in 'Environmental Discussion' started by Celtic Blue, Jun 19, 2009.

  1. jayman

    jayman Senior Member

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    I decided to diversify
     
  2. Celtic Blue

    Celtic Blue New Member

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    Well, that 9.2 calculated SEER seems to be real enough. The unit started having some trouble cycling on at times (every once in awhile it would bump the compressor several times before it kicked in.) Finally, one of the posts on the compressor terminal block burned off last week. That was fixable, but after listening to it start and shut down my AC man agrees that the compressor is not long for this world, so we won't be doing the evaporator coil swap is no longer an option. We discovered that somebody had already put a beefy new capacitor on it in the past few years...another sign that it was "rode hard and put up wet." So now it looks like I'll be replacing the whole shooting match. Can't say it is a surprise in a 15 year old unit.

    The good news is that I've been doing a much better job of managing the HVAC, windows, shades, fans this summer to minimize AC use--plus my insulating, duct sealing, and window/wall ceiling haven't hurt either. A cool July helped, but usage was half of what I expected in a normal June and so far in what has been a normal hot August. I effectively used no AC in May and with luck, won't need it in September's billing period either.

    So a new SEER 14 AC would be another nice improvement over this sub-10 system, but I doubt any of the higher SEER, dual compressor systems would be worth the money even with the rebate.
     
  3. hill

    hill High Fiber Member

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    For what ever reason not yet understood by me , the AC guys say the new SEER 13 or 14 minimum they'll sell us now, has to actually be higher ... like a SEER 16, unless we replace the whole shebang ... furnace blower, etc. The killer for us is the SIZE of these extra high numbered SEER pigs (they're HUGE), and we are really pressed for room.
     
  4. jayman

    jayman Senior Member

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    I'd hold off on that until you get your ductwork situation fixed. If the ductwork, especially at the e-coil, is improperly sized, you're throwing good money away for nothing. You'll never get good performance out of a new system if the ductwork is way too small

    If you have to bust out a lot of gyproc to get to the ductwork, that is going to be a major job. However, if you intend to do so, then you can properly seal and insulate the supply side, and seal the return side

    That means every seam, using the aluminum foil tape. They make duct insulation with a silvery side to it, or you can just do it yourself if you're handy that way

    Another option is heavy drinking, but I leave that for more advanced DIY home fixer-uppers

    Sealing and insulating ductwork is also very important for heating performance. You don't get as cold as I do in winter, but you still get "real" winter conditions

    If you wish, I can take some photos and post them on my Photobucket page for you to view. Let me know


    If you just replace the outdoor condenser unit, and leave the furnace and indoor evaporator coil the same, that could be true.

    If you read the fine print on the SEER performance claims the manufacturer posts, that's with a properly matched system: outdoor condenser, indoor e-coil, ductwork, and air handler

    The highest-rated A/C condensers are huge as they have a lot more coil surface area to be more efficient. The lower rated units will cool just as well, but use more power in the process

    I went with highest SEER rated system, not to save money. In my climate, it's highly doubtful I would ever see a ROI. I went with a Bryant Evolution matched system for COMFORT

    With a two speed outdoor condenser, a matched e-coil with Thermal Expansion Valve, and a variable speed furnace fan, I can program the system for priority dehumidification

    In my climate, the summers are brief, but very damp. A single speed A/C does a poor job of controlling humidity, especially on cooler days, unless you really freeze the house.

    I can use a comfy setpoint, like 76 F, the outdoor condenser will run on its lowest speed. The furnace fan will also run at the slowest speed, you hardly feel any cool air coming out the registers. It will average around 3 amps system total, call it 400 watts

    However, at that lowest/slowest speed, the e-coil drain is constantly running with water. It's very effective as keeping the house properly dehumidified

    Its up to you whether you want to spend 40-60% more for a top of the line system. If you live in a climate that also requires a lot of heating in winter, the comfort factor and efficiency are there too. Unless the temps are -30 F and colder, my furnace will almost always be on low fire
     
  5. Celtic Blue

    Celtic Blue New Member

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    Might be the pairing with the existing air handler that they are looking at. Or it could be that they mean in order to get get the tax credit which starts at 16 SEER. Or it could be that they are referring to 13 EER which is about 16 SEER. (Sort of like comparing different kinds of octane measurement, EER is the efficiency at 95 F ambient.)
     
  6. Celtic Blue

    Celtic Blue New Member

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    The restrictive e-coil has to be changed as part of any upgrade so that's not an obstacle. The current system is R-22 and the new system will be R-410a. I stuck an anemometer in the ductwork and was surprised at how much flow I was getting despite the current narrow e-coil. It was near what spec would suggest. With a variable speed blower and knowing that I'm already in the ballpark, there shouldn't be a problem.

    I doubt that I'm going to bust all of it open as it would be far too many surfaces in the house. Instead, I've targeted whatever I can get at, and whenever I break into something new I seal anything I can reach. I did quite a bit reaching up through registers into the duct runs. (Lots of GE silicone II...about 6 tubes so far.) I've been replacing, sealing, and insulating legs when possible. I got rid of a major condensation problem a few weeks ago by replacing a 4" bathroom run with insulated flex duct. Sealed and wrapped another multi-jointed, very leaky, 7" round run in insulation and wrap. Finally the utility room is running the same temp as the surrounding level during cooling season.

    The major thing left related to the ducts are condensation issues (garage ceiling to bedroom above, two long runs) and balance issues (two new registers needed in the one corner on two floors, and one new return needed on the lowest level.) Right now I'm trying to figure out how to do them all in one fell swoop so that I do the sheetrock, mud/tape, and paint all as a single project. Much rides on things I can't see until I begin demo...

    The other major frustration is that I probably need to punch a bunch of holes in the walkout wall to check for insulation in 4 rooms. I have a sinking feeling I won't find much as the builder seems to have been allergic to the stuff even though this area was "finished living area" as originally built.

    The Catch 22 is that once I start making holes I pretty much have to refinish/repaint even if I find insulation. I already know of several voids so the question is one of degree.

    The special foil duct tape is not particularly tacky, so I try to reduce my reliance on it, preferring to cinch ends tight with a long piece of cable tie where possible. I've been told the tape works acceptably if you use a heat gun on it.

    I reserve that for the clean up phase...or when an unexpected "gotcha" hits. Some of my best/most innovative ideas have come from those less than sober moments. The key is evaluating them once one is sober again. Great projects arise like a phoenix from the ashes of failure.
     
  7. jayman

    jayman Senior Member

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    Good to hear

    Silicone sealant works fine to seal gaps/seams. Mastic works good too, and is better suited for larger gaps

    I've been in unfinished basements here, with bare ductwork, on a humid summer day with the A/C roaring away, and the ductwork had a sheen of condensation, occasionally dripping onto the bare cement floor below.

    And they wondered why they had mold in the basement!

    Of course, left unchecked, you're setting yourself up for a serious case of mold. That alone would motivate me to properly fix the problem

    That's the way it always is. I've been known to begin the heavy drinking once I had the gyproc busted out, because of what I found behind the gyproc - the Point Of No Return

    Haha, he was "allergic" to the insulation. But I bet he wasn't allergic to the money he charged on the assumption the insulation was actually put in

    If you're handy with gyproc, it's more of a question of your time involved. If you had to pay somebody to do that sort of work, it would be cheaper to throw a match to the house and walk away

    One option to consider for insulation is that isocyanurate foam stuff. Some of it is DIY, most is professionally applied. The biggest advantage is much better performance compared to batt, as the foam also functions as a moisture barrier too

    Hmm we must have access to better stuff in Canada. That foil stuff I use, it's damn near impossible to remove if you make a mistake and miss the seam.

    Ah, that's the part I'm missing
     
  8. Johnbear

    Johnbear New Member

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    Can anyone here say for sure whether an old-style spin-the-disk meter measures volt-amps or measures actual watts.








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  9. hill

    hill High Fiber Member

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    Watts. In kilowatts, per hour. That's why it's called a kilowatt meter:


    [​IMG]

    So the above reads 72,666 kilowatt hours.

    Or, if solar panels are running the meter backwards, it'd be 27,335 kilowatt hours of surplus generated.
     
  10. Celtic Blue

    Celtic Blue New Member

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    I read that as 72664 (not quite 72665).
     
  11. jayman

    jayman Senior Member

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    Don't forget that dreaded Kh factor multiplier