Air Conditioner MAX Breaker Size.

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stickboy1375

stickboy1375

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Litchfield, CT
This was just an observation, but looking at the nameplate, the minimum circuit ampacity was 19.5 amps, and the maximum breaker or fuse size was 20 amps. Shouldn't the maximum OCPD be 25 amps? Or was this just a design decision by the manufacture?
 
I have seen alot of this lately. Remember the 19.5 already has the 125% built in and with the high efficiency of these units I wonder if there is very little inrush current on these units. That is my guess anyway. Nec allows us 175% but not if the nameplate doesn't. I wonder if there are no thermal protection in these units- I thought there had to be tho...
 
Dennis Alwon said:
I have seen alot of this lately. Remember the 19.5 already has the 125% built in and with the high efficiency of these units I wonder if there is very little inrush current on these units. That is my guess anyway. Nec allows us 175% but not if the nameplate doesn't. I wonder if there are no thermal protection in these units- I thought there had to be tho...
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I took the 19.5 and subtracted the 125%, then multiplied that number by 175%, thats how I came up with the 25 amp breaker...
 
stickboy1375 said:
I took the 19.5 and subtracted the 125%, then multiplied that number by 175%, thats how I came up with the 25 amp breaker...
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440.22 states we can use 175% of the motor rated load current or branch circuit selection current. The branch circuit selection current is 19.5 so I believe you could use that time 175%
 
Dennis Alwon said:
440.22 states we can use 175% of the motor rated load current or branch circuit selection current. The branch circuit selection current is 19.5 so I believe you could use that time 175%
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yep, just as long as we don't surpass 225%... getting back to it, the unit was a split unit... I was just curious why they held back on the maximum breaker, i doubt the motor doesn't contain overload protection built in...
 
I stand corrected. That small of a unit would not need a soft start, but I would still guess it to be a scroll compressor. Scrolls typically compress in 6 small pockets rather than one stroke like a reciprocating and require smaller motors.
 
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