User Tag List

Page 2 of 2 FirstFirst 1 2
Results 11 to 15 of 15

Thread: Evap coolers

  1. #11
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    39,614
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by 624 View Post
    I’m Just a electrician, so after Researching on line and finally getting the nameplate of motor it says locked rotor amps 85, so do I size my breaker for 80 or 90 amps, or do I size it to table 230. 152 at 2.50xFLA@12.4=31amps.
    That is what the "magnetic" is about in "thermal-magnetic" circuit breaker. Most will hold for a few seconds at 6-8 times the rating, this is what allows motor starting and some other high inrush applications to work without nuisance trips.

    As mentioned 35 is the max code allows as the general rule, I earlier mentioned I have seen 10 HP motors that work just fine on 15 amp breakers. Most of those were I-Line type FA breakers (FWIW) All depends on conditions at the install and the actual trip curve of the breaker.
    I live for today, I'm just a day behind.

  2. #12
    Join Date
    Sep 2009
    Posts
    1,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    High efficiency motors have a lower impedance, higher starting current. There were code letters for starting current that went up. For example you could upsize to 175% time delay fuse for a high locked rotor code letter, to get it to hold with the high efficiency motor.

    It seems there's a lot missing from the given information. 10 hp is big for an evap tower fan but not so big if it's an entire package unit. It's not clear what equipment is being wired. 10 hp in a tower fan is a big blade. You want to be able to ramp to speed and modulate speed with demand.
    Lasciate ogne speranza, voi ch'intrate

  3. #13
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    39,614
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by __dan View Post
    High efficiency motors have a lower impedance, higher starting current. There were code letters for starting current that went up. For example you could upsize to 175% time delay fuse for a high locked rotor code letter, to get it to hold with the high efficiency motor.

    It seems there's a lot missing from the given information. 10 hp is big for an evap tower fan but not so big if it's an entire package unit. It's not clear what equipment is being wired. 10 hp in a tower fan is a big blade. You want to be able to ramp to speed and modulate speed with demand.
    Which increases likelihood of it being VFD driven, and then there is no starting surge as severe as across the line starting has.
    I live for today, I'm just a day behind.

  4. #14
    Join Date
    Sep 2009
    Posts
    1,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Well, trying to say this in a gentle way, breaker and fuse size for a motor load is one of my tells.

    50 hp of evap tower fan points to a sufficiently large installation to have field and factory engineering, along with inhouse facility engineering. It's a lot of people and a large capital project. It does not make sense that there would be no plans and specs. What is on the plan for starter or drive. No drawing would be another tell.
    Lasciate ogne speranza, voi ch'intrate

  5. #15
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    39,614
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by __dan View Post
    Well, trying to say this in a gentle way, breaker and fuse size for a motor load is one of my tells.

    50 hp of evap tower fan points to a sufficiently large installation to have field and factory engineering, along with inhouse facility engineering. It's a lot of people and a large capital project. It does not make sense that there would be no plans and specs. What is on the plan for starter or drive. No drawing would be another tell.
    You don't do farm work do you?
    I live for today, I'm just a day behind.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •