Fuse or Breaker to protect Heat Pump

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Empire96

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Baltimore , Maryland
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?
 
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.

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Empire96 said:
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?
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Based on what you have told us, I think the fuses are not compliant. It appears this unit is requiring a breaker for OCP.
 
Empire96 said:
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?
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. 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.
 
About fuses on HVACR Gear

About fuses on HVACR Gear

Empire96 said:
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?
Click to expand...


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.

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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.
 
Empire96 said:
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?
Click to expand...

Do you have a photo of the nameplate?
 
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