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Thread: 2 stage, multiple condenser system question.

  1. #1
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    2 stage, multiple condenser system question.

    We have a 40 year old R22 Trane 44 ton condensing unit cooling 12K foot building 6 damper controlled zones serviced by single AHU with 2 staged evap coils.

    System is still operating fine, but the renter wants to shut off AC to 9K foot of the building and wants more efficient A/C for the remaining 3K feet office space which is served by 3 zones. The current condenser system does a pump down to off when the staging solenoid valves are closed, so we have liquid waiting at the inlet of the solenoid valves at the evap.

    Yes, we have dampered off the 3 zones serving the 9K square feet, but the condenser still draws about 75 amps at running under no load, and 85 amps servicing a load.

    Question is this. Could we put a 5-10 ton condenser unit as a first stage on this system so the 44 ton unit does not startup unless we have a demand load. This could be a manual switch or a pressure/temperature controlled system. We do not want to change out the complete system (yeah it is past life we know) because they building use possibly changing in the future and the 44 tons may be required. We have already installed a VFD on the 15hp blower motor to reduce running cost and air flow.

    Any advice or direction where I could get input on this type of application?

  2. #2
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    I'm thinking something like a parallel system. All new and stand alone. Then turn off the existing unit, but leave everything in place. Heck, depending on how the offices are laid out, could even be a heat pump mini-split system.
    I do a triple evac with nitro to remove non condensables.

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  4. #3
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    Thread Starter
    Quote Originally Posted by BBeerme View Post
    I'm thinking something like a parallel system. All new and stand alone. Then turn off the existing unit, but leave everything in place. Heck, depending on how the offices are laid out, could even be a heat pump mini-split system.
    Thank you, we are considering this type of application but just wondering if there is any standard of practice out there for the original idea. As R22 5-10K condensers are available and low cost.


    Sent from my iPad using Tapatalk

  5. #4
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    Really have to be on site to see what's there.


    Quote Originally Posted by 23F5% View Post
    Thank you, we are considering this type of application but just wondering if there is any standard of practice out there for the original idea. As R22 5-10K condensers are available and low cost.


    Sent from my iPad using Tapatalk
    I do a triple evac with nitro to remove non condensables.

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  7. #5
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    Quote Originally Posted by 23F5% View Post
    Thank you, we are considering this type of application but just wondering if there is any standard of practice out there for the original idea. As R22 5-10K condensers are available and low cost.


    Sent from my iPad using Tapatalk
    What's his short term / long term goals?

    Are those 5 - 10 Ton systems rated commercial?

    Sounds like a cheap slum lord!

  8. #6
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    Thread Starter
    Closing thread. LOL Cheap slum lord!

    Actually we have 12,000 sf building all serviced with the 44 ton unit. But now will only be needing to service the office space, about 3000 sf.

    We determined to install split units to service office and leave main system in place unmodified. The splits will consume less energy than AHU blower alone and can be easily removed in the future should the building return to its original service. 1 month summer electric will pay for the splits. ;-)

    Thanks for your input.


    Sent from my iPad using Tapatalk

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