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Thread: hey refer guys

  1. #14
    Join Date
    Jan 2004
    Location
    mass
    Posts
    538
    I would run as 2 separate systems but with 1 defrost time clock shutting down both units. You could set up with 2 separate time clocks and have no issues. But if the clocks were not in sync the potential exists for a unit to be running while the other is in defrost.

  2. #15
    Join Date
    Jan 2006
    Location
    DFW Metroplex
    Posts
    4,910
    Ok...I'll kick at the cat once here too.

    If the compressor did not have issues, I would gut one of the condensing units and just use one thermostat, solenoid and defrost timer to control both units.

    But - since you will potentially be requiring your customer to invest a significant amount of $$ to repair the compressor anyway, I would just sell a system that is matched and designed to work properly for the box in which it is installed.

    They way I figure it, customer can spend a chunk of money and still have a piece of crap, or - he can spend a little more money and have a properly designed system......

  3. #16
    Join Date
    Nov 2005
    Location
    so cal
    Posts
    176
    Quote Originally Posted by Airmechanical View Post
    ok went to the job tonight (last call) walk in cooler (beer)

    its the first time i ever been to this job

    it has 2 mismatched evaps, a 2 fan evap with a 1 h/p cond. and a 3 fan evap with a 2 h/p cond.

    2 different stats for the same cooler

    cooler is 25 wide x 8 length x 7 foot ceiling,

    anyway the 2 hp comp. has wasted valves and its old, i am gonna replace the condenser

    i am probably gonna wire a relay to turn both compressors on and off at the same time thru 1 controller

    maybe i will slap a 1 minute delay between both stages for $hits and giggles

    or is there a different way anyone else would do it?

    my second thought was turning one stat (the bigger condenser) a few degrees lower than the other

    what option would you guys use, and can you see any advantages or disadvantages one way or the other


    .
    i would run 2 stats and stagger them so the units dont come on at the same time and prevent in rush current. also i would not give access to adjust the stats or turn off the fans so that customer or vendors cant mess it up. a delay would also work tho. 2 time clocks adjusted to defrost @ the same time

  4. #17
    Join Date
    Aug 2005
    Location
    Tampa
    Posts
    105
    Quote Originally Posted by Airmechanical View Post
    ok went to the job tonight (last call) walk in cooler (beer)

    its the first time i ever been to this job

    it has 2 mismatched evaps, a 2 fan evap with a 1 h/p cond. and a 3 fan evap with a 2 h/p cond.

    2 different stats for the same cooler

    cooler is 25 wide x 8 length x 7 foot ceiling,

    anyway the 2 hp comp. has wasted valves and its old, i am gonna replace the condenser

    i am probably gonna wire a relay to turn both compressors on and off at the same time thru 1 controller

    maybe i will slap a 1 minute delay between both stages for $hits and giggles

    or is there a different way anyone else would do it?

    my second thought was turning one stat (the bigger condenser) a few degrees lower than the other

    what option would you guys use, and can you see any advantages or disadvantages one way or the other


    .
    Having spent 2 years in a design office let me try to pass on what the senior engineer told me about this situation.
    There are 2 evaporators (1x 1HP and 1x 2 HP rather than one large 3 HP) spaced out to get a better airflow around the cooler.
    I'm guessing that the cooler has glass doors for customers to take there chosen beer, and a door for staff to enter to restock the shelves from the back.
    I was told that in a 3 HP load, that it’s best to have a 1 HP unit closest to the "staff entering door", and the 2 HP away from the staff door. The reason being, that when the staff door is propped open for loading reasons, that the 1 HP unit is there to cool the incoming heat from the open door. The 1 HP unit t'stat should be set at the same temp as the 2 HP unit, to stop it from running 24/7, but will start earlier once the staff door has been opened, and in doing so saves on running costs.
    That’s how I was told to size and design them, but it does not mean I was told correctly.
    Knowing this, I would leave the unit with one t'stat per unit, because of running cost reasons.
    You want me to do what, with that thing!!!!!!

  5. #18
    Join Date
    Sep 2007
    Location
    Balto, MD.
    Posts
    200
    Quote Originally Posted by fl_dude View Post
    Having spent 2 years in a design office let me try to pass on what the senior engineer told me about this situation.
    There are 2 evaporators (1x 1HP and 1x 2 HP rather than one large 3 HP) spaced out to get a better airflow around the cooler.
    I'm guessing that the cooler has glass doors for customers to take there chosen beer, and a door for staff to enter to restock the shelves from the back.
    I was told that in a 3 HP load, that it’s best to have a 1 HP unit closest to the "staff entering door", and the 2 HP away from the staff door. The reason being, that when the staff door is propped open for loading reasons, that the 1 HP unit is there to cool the incoming heat from the open door. The 1 HP unit t'stat should be set at the same temp as the 2 HP unit, to stop it from running 24/7, but will start earlier once the staff door has been opened, and in doing so saves on running costs.
    That’s how I was told to size and design them, but it does not mean I was told correctly.
    Knowing this, I would leave the unit with one t'stat per unit, because of running cost reasons.
    I agree! No sense reinventing the wheel.
    I've woked on the same setups in beer coolers and flower shops both with the display doors. One thing that helps with keeping the temperture controls more even is mounting the sensing bulbs in a well full of oil, or glycol. Has some advantages over sensing air temp.

  6. #19
    Join Date
    Sep 2002
    Posts
    13,153

    I would never go to a single unit -

    What they now have is a Much better setup.

    Light loads / winter time - run one unit. High loads / summer time - both units come on. Stage the stats at about 33 and 35 degrees for beer.

    AND . . . if a unit fails they are not screwed because they have the redundancy of the remaining unit. That is a biggie!

    I try to talk all walk-in customers to go with multiple units for that reason.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  7. #20
    Join Date
    Jan 2007
    Location
    maine
    Posts
    790
    Quote Originally Posted by Poodle Head Mikey View Post
    What they now have is a Much better setup.

    Light loads / winter time - run one unit. High loads / summer time - both units come on. Stage the stats at about 33 and 35 degrees for beer.

    AND . . . if a unit fails they are not screwed because they have the redundancy of the remaining unit. That is a biggie!

    I try to talk all walk-in customers to go with multiple units for that reason.
    Thats if there sized properly.. I went on one of these the other day one unit was going off on LP.. ambient temp was in 30s and couldnt keep box at temp

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