ac (split unit) rating of overcurrent device ?

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paul hesson

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A technition has wired a branch circuit for an ac split unit. The nameplate on the unit says it draws 21 amperes. He has used # 12 rmx cable and put it on a 25 amp.ckt. bkr. Is this the correct size overcurrent protection device as referenced in table 310-16* to 240-4 (g) and then to art. 440. ?
 
Re: ac (split unit) rating of overcurrent device ?

It could be.

You would need to know the minimum circuit ampacity and the maximum overcurrent protection listed on the unit to be sure.
 
Re: ac (split unit) rating of overcurrent device ?

Acceptable practice is to wire for min. and fuse for max.
While on this subject of a/c`s when the data plate says for instance min ampacity 19 amps. and max brkr size as 35 amps.What is the general concecsus ? Do we have to fuse at the max size which in this case is 35 amps or can we use a smaller breaker lets say a 30 amp.bkr.Is there a code reference in regards to this. ?
 
Re: ac (split unit) rating of overcurrent device ?

Do we have to fuse at the max size which in this case is 35 amps or can we use a smaller breaker lets say a 30 amp.bkr.Is there a code reference in regards to this. ?
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You can set your OCPD anywhere between the minimum circuit ampacity and the maximum overcurrent device. Although it may have starting issues if the minimum were 19 amps on a 20 amp OCPD.
 
Re: ac (split unit) rating of overcurrent device ?

I use the max size allowed. That way if it trips, the HVAC service tech cant say the electrician installed too small a breaker. ;)
 
Re: ac (split unit) rating of overcurrent device ?

The reason I asked this is that the inspectors in this area determine that when the manufacturer lists a max bkr. size That size must be installed.They will tag it for under sized OCPD since the manufacturer lists a specific amperage as a max. bkr size.
Imo as long as we stay within the listed amperages on the data plate we are code compliant.True if we go to low then on start up it more than likely will trip but the inspectors use manufacturers instructions ( data plate ) as the rule.Max. size + what will be installed.
 
Re: ac (split unit) rating of overcurrent device ?

Your inspectors need to understand the concept of minimum and maximum.
 
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