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  1. #1

    staging heat pumps

    I've recently taken over service at a local catholic church and school. They are remodeling the caffeteria and it has three split 5 ton heat pumps that i've moved but have not started up yet. I was thinking about staging them so they could save a little money when room wasn't being used which is a bout 70% of the time. If i wanted two of them on first stage and the other on stage two could I do this by running off of one 75 or 100 va transformer or should I go about this differently. I've never staged three systems before so I want to make sure the control side won't get overloaded.

  2. #2
    Join Date
    Dec 2006
    Location
    Middle Tennessee
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    11,347

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    Quote Originally Posted by buddylee View Post
    I've recently taken over service at a local catholic church and school. They are remodeling the caffeteria and it has three split 5 ton heat pumps that i've moved but have not started up yet. I was thinking about staging them so they could save a little money when room wasn't being used which is a bout 70% of the time. If i wanted two of them on first stage and the other on stage two could I do this by running off of one 75 or 100 va transformer or should I go about this differently. I've never staged three systems before so I want to make sure the control side won't get overloaded.

    i would go with at least 40va per system for a total of 120va

    you could parrallell two 60va x-formers, or three 40va x-formers, just make sure you phase them properly!



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  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    How were they originally controlled.
    Does each HP have electric aux heat.
    How lose to each other are the air handlers.
    Will it cause stratification if only 2 are running.
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  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    How were they originally controlled.
    Does each HP have electric aux heat.
    How lose to each other are the air handlers.
    Will it cause stratification if only 2 are running.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #5
    Each was controlled by its own stat.
    Two have auxillary heat.
    They are suspened approx. 15 feet apart so I was thinking about using the two on the ends as first stage and the one in the center as second stage and as heating is not really an issue i was going to wire the auxilary only as emergency.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    I would do it a little different.

    An unoccupied cafeteria doesn’t need a lot of cooling for most of the year, when its not occupied.

    I would use an IAQ thermostat. Set up the 2 outer units as stage 1 and stage 2. Then hook a delay timer that if stage 2 runs for 15 minutes, the third unit comes on.
    This would give them economic operation when not occupied, and keep the humidity down while under a low sensible load.
    The IAQ is quick enough that it will bring the second stage on quick enough when people/students come in for lunch.
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