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Thread: Swapped circuits on RTU?

  1. #1
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    Swapped circuits on RTU?

    Any issue with having an RTU with the circuits swapped. Each compressor/stage is 5 ton so identical output.

    Just wondering if I am missing something as I don't see how it would be an issue?

    Thanks!

  2. #2
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    Controls & safeties ?

  3. #3
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    Thread Starter
    I'm saying simply swapping Y1 and Y2. Safeties/contactors would remain on their respective stages.

  4. #4
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    Can affect latent capacity depending on coil arrangement.

  5. #5
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    So what about the evaporator draining condensate down on to a inactive lower coil ?

  6. Likes heatingman liked this post.
  7. #6
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    Some standard small tonnage units use stage 1 to control condenser fans. Economizer won't work.

  8. #7
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    Open forum, so we are very limited.

    If in a jam and need to get a circuit to run as the lead circuit in a system, then you must take everything into respect. Your the one standing there in front of this mystery unit, we are just the numb-skulls imagining what you may be talking about.

    Give us a make and model, and we can probably be a tad more specific on things. I will add that you have been around since 2012, I would apply for PRO where we can get down and dirty, not just shooting blanks in this open forum.

  9. Likes CHAINIK liked this post.
  10. #8
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    Quote Originally Posted by ehsx View Post
    Can affect latent capacity depending on coil arrangement.
    Quote Originally Posted by VTP99 View Post
    So what about the evaporator draining condensate down on to a inactive lower coil ?
    Quote Originally Posted by hvac69 View Post
    Some standard small tonnage units use stage 1 to control condenser fans. Economizer won't work.
    What ehsx and VTP99 are talking about is that usually with a 2 stage unit, the evaporators are set up so that 1st stage is the bottom half of the coil. If you swap things around so that only the top half gets cold, humidity will evaporate into the air stream as it drips down the inactive lower part. If the unit is an old junker and/or you are just needing to do this temporary to get them by for a while then go for it. Just be aware that it won't dehumidify as good after the swap.

    Hvac69 makes a good point too. Make sure the condenser fan(s) still come on after you are done and/or things won't get screwed up if it tries to economise.
    If at First You Don't Succeed, Skydiving Is Not for You.

  11. #9
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    What are you going to do with the economizer? If you just swap the Y1 and Y2 at the thermostat terminal strip, you’ll have an economizer that doesn’t work. Which you may be able to rewire. And depending on the unit, it may be anywhere between pretty simple to a nightmare or impossible. Swapping circuits after the economizer output may be the better way. Again, depending on the unit. But then you may run into other issues like stated above about evap coil configuration causing RH and condensate issues.

    Is this just a temporary “get ‘um some sort of cooling for a couple weeks” thing?

    BTW, customers have a way to turn on you with jobs like this. “You never told me I would have humidity issues” “You never told me I ran the risk of condensate blowing past the coils, down the ductwork and ruining my $10,000 Xerox machine” “You didn’t tell me I wouldn’t have a working economizer”. “You never told me you were going to rewire the entire control circuit if my unit”

    Document everything first and get signatures.

  12. #10
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    Thread Starter
    Quote Originally Posted by ammoniadog View Post
    What ehsx and VTP99 are talking about is that usually with a 2 stage unit, the evaporators are set up so that 1st stage is the bottom half of the coil. If you swap things around so that only the top half gets cold, humidity will evaporate into the air stream as it drips down the inactive lower part. If the unit is an old junker and/or you are just needing to do this temporary to get them by for a while then go for it. Just be aware that it won't dehumidify as good after the swap.

    Hvac69 makes a good point too. Make sure the condenser fan(s) still come on after you are done and/or things won't get screwed up if it tries to economise.
    Confirmed my thoughts. So can be done in a pinch with minor issues. Nothing going to blow. Thank you!

  13. #11
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    Thread Starter
    You smart man. This is true. Definitely common to see fans wired on stage 1 contactor. Thanks for you insight.

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