User Tag List

Results 1 to 10 of 10

Thread: Fuse or Breaker to protect Heat Pump

  1. #1
    Join Date
    Feb 2019
    Location
    Baltimore , Maryland
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Fuse or Breaker to protect Heat Pump

    We have a heat pump that is 3 phase 208V and the name plate calls for a Max Breaker size of 15A. The circuit serving the heat pump is on a 3P 30A breaker. The Disconnect at the heat pump is fusable. Is it acceptible to install 15A fuses at the disconnect in lieu of changing the Breaker to 15A?

  2. #2
    Join Date
    Dec 2010
    Posts
    1,510
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yes. That is the first OCPD above the heat pump.
    The more they overthink the plumbing, the easier it is to stop up the drain

  3. #3
    Join Date
    Jun 2015
    Location
    NYC, NY
    Posts
    259
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If label on heat pump MOP = 15A, the 15A fuses in disconnect should be ok. Some manufacturers permit you to install only fuses or only breakers.

    Sent from my ONEPLUS A6013 using Tapatalk

  4. #4
    Join Date
    Jul 2015
    Location
    Wilmington, NC USA
    Posts
    793
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Empire96 View Post
    We have a heat pump that is 3 phase 208V and the name plate calls for a Max Breaker size of 15A. The circuit serving the heat pump is on a 3P 30A breaker. The Disconnect at the heat pump is fusable. Is it acceptible to install 15A fuses at the disconnect in lieu of changing the Breaker to 15A?
    Based on what you have told us, I think the fuses are not compliant. It appears this unit is requiring a breaker for OCP.

  5. #5
    Join Date
    Jun 2003
    Location
    NE (9.06 miles @5.9 Degrees from Winged Horses)
    Posts
    11,388
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Empire96 View Post
    We have a heat pump that is 3 phase 208V and the name plate calls for a Max Breaker size of 15A. The circuit serving the heat pump is on a 3P 30A breaker. The Disconnect at the heat pump is fusable. Is it acceptible to install 15A fuses at the disconnect in lieu of changing the Breaker to 15A?
    . Are you sure that is exactly what it says? Usually the problem is the label says Max fuse 15 Amp. That means fuses only. Following that line of thought, Max breaker would mean breakers only.

    Maximum OCPD would mean either fuse or circuit breaker.
    Tom
    TBLO

  6. #6
    Join Date
    Jul 2013
    Location
    Moab, UT USA
    Posts
    304
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    About fuses on HVACR Gear

    Quote Originally Posted by Empire96 View Post
    We have a heat pump that is 3 phase 208V and the name plate calls for a Max Breaker size of 15A. The circuit serving the heat pump is on a 3P 30A breaker. The Disconnect at the heat pump is fusable. Is it acceptible to install 15A fuses at the disconnect in lieu of changing the Breaker to 15A?

    Fuses on a 3 phase line are the quickest way under the sun to destroy a compressor that in many cases could be saved. I have seen it scores of times and the discussion persists. While some so called modern machines have single phase protection, many do not. A breaker can trip, while one blown fuse can cause major and expensive destruction. There are fault conditions that cause those fuses to blow that can happen that do not indicate a major problem with the compressor proper. This is where the trouble starts and why they are an inferior protection scheme from the equipment standpoint. Just the facts from the HVACR side. One would think that the design community would have gotten on the same page as long as this has been going on, but in many cases matters have gotten far worse and the gear keeps getting thinner every year because everything has been $$ monetized. This one simple fact leads to bad Engineering, poor quality systems, and a throw away, " you need a new one " mindset among the population.

    Star
    Microwave Radiation Dangers should be openly discussed

  7. #7
    Join Date
    Feb 2016
    Location
    Illinois
    Posts
    1,458
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by oldsparky52 View Post
    Based on what you have told us, I think the fuses are not compliant. It appears this unit is requiring a breaker for OCP.
    Agreed. It’s likely that the manufacturer wants to eliminate the possibility of single-phasing introduced by using fuses.

  8. #8
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,833
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    I just looked at the manual for a Trane 3 phase unit we have here, it says "Max. Circuit Prot. Device .... 15A". It doesn't distinguish between a CB or fuses. Most commercial units (which is where you will find 3 phase versions) come with Phase Loss protection now.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  9. #9
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    27,496
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Empire96 View Post
    We have a heat pump that is 3 phase 208V and the name plate calls for a Max Breaker size of 15A. The circuit serving the heat pump is on a 3P 30A breaker. The Disconnect at the heat pump is fusable. Is it acceptible to install 15A fuses at the disconnect in lieu of changing the Breaker to 15A?
    Do you have a photo of the nameplate?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  10. #10
    Join Date
    Nov 2007
    Posts
    983
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by infinity View Post
    Do you have a photo of the nameplate?
    That, is the best question I have seen so far. Makes others answer straight to the solution!

Posting Permissions

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