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  1. #1
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    HVAC question 2 stage or single

    I live in northern NJ and am interested in installing a new central air system (first time). Many contractors have given us estimates that include 2 stage systems and are saying this is the way to go. Do we need a two stage in NJ?

  2. #2
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    Two stage, like most other higher efficiency equipment, is mostly about comfort and lower energy bills...

    Two stage offers these options:
    They are more comfortable in 'swing season' (Spring and Fall)...
    They tend to control indoor humidity better during cooling season...
    They tend to handle the really HOT days of summer a bit better...
    And if they are installed properly (installation is more important than brand); they use a bit less energy.

    Now is it worth the extra $$$...
    That depends on how much the added comfort means to the occupants of the building.

    Some folks do not care...
    Some folks do care...

    Each person has to determine what 'value' means to them... and act accordingly.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  3. #3
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    Thanks for the quick reply. We were concerned that the more costly 2 stage would mean more costly repairs if something went wrong. One contractor told us because our house is a small cape cod (1100 sq ft) that it would be a waste of $$

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  5. #4
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    What size a/c is in the home now? Is over-sized?
    In addition to the cost and increased complexity, consider that on low speed the air flow is less which may change distribution of the conditioned air. This changes the temperature in the farther reaches of the system.
    A properly sized and setup a/c is most effective, generally.
    Like posted, multi-speed is slightly more effective at humidity control. Yet during low/no sensible cooling loads, no dehumidification is possible.
    If you want real humidity control, get the single speed a/c and add a small whole house dehumidifier, like the Ultra-Aire 70H. You will have 50%RH even when the a/c is off and its raining outside.
    Keep us posted on your results with whatever you install.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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  7. #5
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    This would be a new installation; we've been using window a/c's in the past. Our home is a two story cape cod with 1100 sq. ft. total This process is SO confusing and we don't want to make the wrong choice.

  8. #6
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    Since you mentioned it is a two story... this changes a lot... might want to provide lots of details!

    Two story buildings rarely are the same temp (sometimes as much as 10D difference) between up and down levels... if the lower is part basement (in the ground) the issues are worse.

    Might look into zoning or two systems or a multi-head mini... or there is gonna be a temp difference between up and down.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  9. #7
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    It is a cape cod. Main floor 912 sq. ft. 2 bedrooms, living room, bath, kitchen. upstairs attic & 1 finished bedroom (guest room) we hardly ever go up there. There is a full basement that's partially finished. House has plaster walls throughout and there is a fan in the attic. Let me know if there's any other info you need. Up till now we used a 10,000 btu window a/c that did the entire main floor comfortably. Town has us listed as 1 1/2 story

  10. #8
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    Quote Originally Posted by doydoy View Post
    It is a cape cod. Main floor 912 sq. ft. 2 bedrooms, living room, bath, kitchen. upstairs attic & 1 finished bedroom (guest room) we hardly ever go up there. There is a full basement that's partially finished. House has plaster walls throughout and there is a fan in the attic. Let me know if there's any other info you need. Up till now we used a 10,000 btu window a/c that did the entire main floor comfortably. Town has us listed as 1 1/2 story
    Thank you for posting in detail.

  11. #9
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    You didn't mention if you are planning to replace your furnace at the same time. Two-stage A/C usually requires a variable speed air handler to be fully effective.

  12. #10
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    No, we are not replacing our furnace. We have steam, radiator heat. The quotes included a variable speed air handler. Can anyone just tell me if a 2 stage is silly for our size home and area of the country (Northeast New Jersey)? I see a lot of them installed in VERY high humidity areas like Florida or Georgia.

  13. #11
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    Quote Originally Posted by ga-hvac-tech View Post
    Two stage, like most other higher efficiency equipment, is mostly about comfort and lower energy bills...
    No, staged or variable equipment is ONLY about comfort. In certain stages they are NOT efficient (not as efficient as a "regular" single stage unit of equipment)

    2 stage may be used if the load requires the lesser amount and a regular single stage unit cannot be obtained because it does not exist.
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"
    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

  14. #12
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    Given the information you provided:

    Two stage units come in even tons only... so you would be getting a (nominally) 24K BTU AC unit...
    Which will operate at low stage of nominally 16,800 BTU's (note these BTU ratings depends on ductwork and installation).

    OTOH... a 1.5 ton AC unit is nominally 18K BTU's capacity... so the two stage would have a lower setting for mild days...and lots of reserve capacity if you had a HOT summer.

    Bottom line... it is a comfort choice. If you want to spend some extra $$$ for better comfort (translates into better temperature and humidity control)... then go for it.

    My opinion: If you have been getting by on a window shaker... the improvement with ANY central system (assuming it is installed correctly)... is gonna be significant.

    We try to not give out clear answers... due to the forum policy of no DIY information...
    However we do try to explain things so folks can understand.

    The reason this forum, which is directed at professionals in the industry (yeah, I know, Google brings it up in searches... nothing we can do about that)... allows consumers: Is so consumers can find better quality contractors. There is a 'find a contractor' feature in this site... might look for someone in your area.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  15. #13
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    Quote Originally Posted by doydoy View Post
    Can anyone just tell me if a 2 stage is silly for our size home and area of the country (Northeast New Jersey)? I see a lot of them installed in VERY high humidity areas like Florida or Georgia.
    Here are my thoughts as a homeowner living very close to to you with a similar climate. Four years ago I replaced an aging single stage 3-ton system with a 3-ton two stage Carrier Infinity system. My electric bill has gone down significantly, and the home is more comfortable than before. Most of the time the system runs in the low stage, even if it is over 90 degrees outside. Running in that low stage, the cycles are longer which results in better humidity control. That lower humidity is what makes the home feel more comfortable at the same temperature.

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