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Fuse or Breaker to protect Heat Pump

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    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
    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

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      #3
      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

      Comment


        #4
        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.

        Comment


          #5
          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

          Comment


            #6
            About fuses on HVACR Gear

            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

            Comment


              #7
              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.

              Comment


                #8
                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...

                I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

                Comment


                  #9
                  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 2017 NEC unless otherwise noted

                  Comment


                    #10
                    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!

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