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  1. #1
    Join Date
    Sep 2002
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    12,661

    Can I run a compressor on low speed all the time?

    And here I am thinking of a 50/50 TS compressor.

    That way I could size the low speed for cooling only and the two stage operation for heating.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,748
    no reason why you could not lock out high speed for cooling.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,174
    You can.
    How well it will dehumidify is the question though.

    The compressor is 50/100. But your indoor coil is sized for the 100% capacity. So, in low stage cooling, you will be at 60% or so. And the latant ability is not good on a large coil with low mass refrigerant flow.
    So you will need to watch your blower control.
    Or, get a whole house dehumidifier also.
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  4. #4
    Join Date
    May 2007
    Location
    Naples, Fl
    Posts
    889
    Two air handlers perhaps? A progressive Lennox contractor here use to do it.

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,470
    Quote Originally Posted by beenthere View Post
    You can.
    How well it will dehumidify is the question though.

    The compressor is 50/100. But your indoor coil is sized for the 100% capacity. So, in low stage cooling, you will be at 60% or so. And the latant ability is not good on a large coil with low mass refrigerant flow.
    So you will need to watch your blower control.
    Or, get a whole house dehumidifier also.
    Call 911! There is a teddy bear in WI lying on the floor in shock. Thanks, anyway. Regards TB
    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"

  6. #6
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Quote Originally Posted by beenthere View Post
    You can.
    How well it will dehumidify is the question though.

    The compressor is 50/100. But your indoor coil is sized for the 100&#37; capacity. So, in low stage cooling, you will be at 60% or so. And the latant ability is not good on a large coil with low mass refrigerant flow.
    So you will need to watch your blower control.
    Or, get a whole house dehumidifier also.
    Hmm. Then what's all the hype about great dehumidification in low stage? Is it because it runs longer and with a lower fan speed? That's my guess. I understand what you're saying, so it must be the longer run time.

  7. #7
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by RyanHughes View Post
    Hmm. Then what's all the hype about great dehumidification in low stage? Is it because it runs longer and with a lower fan speed? That's my guess. I understand what you're saying, so it must be the longer run time.
    While the fan speed is lower, check the CFM/ton. Probably very close to second stage.
    AM

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,174
    Quote Originally Posted by RyanHughes View Post
    Hmm. Then what's all the hype about great dehumidification in low stage? Is it because it runs longer and with a lower fan speed? That's my guess. I understand what you're saying, so it must be the longer run time.
    The better dehumidification is from the longer run time in first stage. And if the unit is oversized, you don't get that long run cycle that you need.
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  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,174
    Quote Originally Posted by teddy bear View Post
    Call 911! There is a teddy bear in WI lying on the floor in shock. Thanks, anyway. Regards TB
    He's designing and building his own units and system.
    He is going to grossly over size his heat pump.
    There is no way it will remove enough moisture.
    So a dehumidifier is the only way.

    What he's doing would be more headache then its worth, in Joe home owners house.
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  10. #10
    Join Date
    Sep 2002
    Posts
    12,661

    It just struck me while poring over spec sheets -

    If I use a single speed compressor heat pump, I come up short on the heating side for this area, and will eventually have to add heat by alternate means. Generally electric resistance.

    So then I thought: how about a two speed compressor? The low speed capacity could be sized for the cooling load, and the high speed heating performance would be available for heating. Which would tend to minimize the use of the resistance.

    It was just a thought. And who else can I ask if not you? <g>

    It may all come to nothing now as no one will sell me the TS compressors out-right anyway.

    I used to propose that people installed two heat pump systems - for the exact same reason - one as the back-up to the other. Plus; the redundancy of having two complete systems for AC.

    I only got two takers in twenty five years and both houses are gone now. Well, only one is physically gone. The other had the systems ripped out by a new owner before I could get to them.

    The contractor they called had no idea what it was and so condemned the whole install with: we've never seen this and no one in their right mind would ever work on it - you need a whole new system. This despite the fact that it worked great for years before they showed up.

    We used to alter the stage one unit every year.

    What a great guy the original owner was. He had a game room in his house that was probably 1000 square feet by itself. Always reached into his pocket and paid the bill in hundreds with a generous tip. Plenty of times he said: I've got to run. Help yourself to whatever you want in the kitchen, just lock the door when you go. Thanks!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,174
    You should have got benny to get you one before he went into biz himself.

    You could contact hvar r us 2, he should be able to get you one.
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  12. #12
    Join Date
    Apr 2001
    Location
    Camel City, NC
    Posts
    6,233

    PHM

    How bout a copeland scroll that can unload to approx. 65% and stack Rheem coils shown for 4 or 5 ton applications?
    Be safe not fast. body parts don't grow back

  13. #13
    Join Date
    Sep 2002
    Posts
    12,661

    3 ton two-speed versus 2 ton single-speed

    Rheem 3 ton 16.5 SEER HP - two speed

    35,400 total cooling
    1 - 25,800 = 19,350 / 6450 latent
    2 - not used for cooling

    1 - 24,000 @ 47 / 14,900 @ 17
    2 - 33,400 @ 47 / 21,400 @ 17

    ============================

    Rheem 2 ton 14 SEER HP

    24,200 total cooling - 17,700 / 6500 latent

    22,600 @ 47 / 14,200 @ 17

    So according to the ARI matches I lose slightly on the humidity side but I gain 50% on the heating side by using the 3 ton instead of the 2 ton.

    Is that loss enough to make an issue do you think? Am I missing anything important here?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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