Maximum Size Breaker for #12 Branch

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Re: Maximum Size Breaker for #12 Branch

tryinghard,
So when would this scenario become a feeder?
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The only time I would say that the circuit becomes a feeder is when there are multiple load end OCPDs feeding multiple pieces of equipment. I don't think that the addition of a single OCPD at the load end of a circuit ever changes a branch circuit into a feeder.
Don
 
Re: Maximum Size Breaker for #12 Branch

Originally posted by RUWired:
Tryinghard,even if you thought that this is a feeder,your overcurrent protection is then limited to 100% /125% of the load.This would'nt be enough to stop and start the load.This is the reason for the 175% rule.
Rick
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I?m going to get this I swear!! I?m just not quite there yet.

Rick, if the equipment FLA is 14A and this is a branch circuit then the breaker size would be a minimum of 14 x 1.25 = 17.5 / 80% = 22A so a 25A breaker would suffice, is this correct?
 
Re: Maximum Size Breaker for #12 Branch

Originally posted by don_resqcapt19:
tryinghard,
So when would this scenario become a feeder?
Click to expand...
The only time I would say that the circuit becomes a feeder is when there are multiple load end OCPDs feeding multiple pieces of equipment. I don't think that the addition of a single OCPD at the load end of a circuit ever changes a branch circuit into a feeder.
Don
Click to expand...
What if this unit had a fused disconnect and controller (with overload heaters)?
 
Re: Maximum Size Breaker for #12 Branch

What if this unit had a fused disconnect and controller (with overload heaters)?
Click to expand...
That is equipment protection and not branch circuit protection. The only way that OCPD at the load end can make the supply circuit a feeder is where there are multiple OCPDs serving multiple pieces of equipment.
Don
 
Re: Maximum Size Breaker for #12 Branch

Originally posted by don_resqcapt19:
tryinghard,
So when would this scenario become a feeder?
Click to expand...
The only time I would say that the circuit becomes a feeder is when there are multiple load end OCPDs feeding multiple pieces of equipment. I don't think that the addition of a single OCPD at the load end of a circuit ever changes a branch circuit into a feeder.
Don
Click to expand...
Actually it would be 14 x 1.25 = 17.5 so a 20A breaker, is this correct?
 
Re: Maximum Size Breaker for #12 Branch

Originally posted by don_resqcapt19:
What if this unit had a fused disconnect and controller (with overload heaters)?
Click to expand...
That is equipment protection and not branch circuit protection. The only way that OCPD at the load end can make the supply circuit a feeder is where there are multiple OCPDs serving multiple pieces of equipment.
Don
Click to expand...
Okay, wow I see HVAC branch-circuits often listed on feeder schedules.
 
Re: Maximum Size Breaker for #12 Branch

Tryinghard, If this 14 amp fla is including all loads on the equipment;the min circuit amps would be 14x125%=17.5.If this unit has t.o.l protection ;then max brkr would be 14x175%=24.5(25)amp breaker.A disconnect is required at the unit.If the unit requires fuse/hacr protection,then installing a hacr brkr in the panel serving the branch ciruit is good with out the need of fuses.if not then a fused disconnect at the unit is needed.
Rick
 
Re: Maximum Size Breaker for #12 Branch

Originally posted by RUWired:
Tryinghard, If this 14 amp fla is including all loads on the equipment;the min circuit amps would be 14x125%=17.5.If this unit has t.o.l protection ;then max brkr would be 14x175%=24.5(25)amp breaker.A disconnect is required at the unit.If the unit requires fuse/hacr protection,then installing a hacr brkr in the panel serving the branch ciruit is good with out the need of fuses.if not then a fused disconnect at the unit is needed.
Rick
Click to expand...
Okay; the 25A breaker in a remote panelboard is existing and the replaced unit was circuited with #12?s so it must have had T.O.L.?s.

Now the new unit draws 14 FLA x 125% = 17.5A and (with info I have received from Mech. does not require T.O.L.).

The basic rule is #12?s = 20A & #10?s = 30A? but there are exceptions to this basic rule and they are revealed in 240-4(G).

From what I understand from this string of information most, if not all, agree this application qualifies #12?s on the 25A breaker because it is HVAC equipment and 440 parts III, VI, except for me!

Let me attemp to pick up what you may be referancing in NEC, if 440-22(A) does not apply because I do not have T.O.L.?s I then continue on to 440-52(3) & (B)(3) which qualifies the 125% of FLA. If this is not the exception you are referencing I am certainly lost and am curious; what/where in 440 III, VI qualifies the exception to allow #12?s on 25A breaker in my application? If you are correct in your reply to me earlier then the existing 25A breaker needs to be changed to a 20A and the local fused disconnect is redundant. If I am wrong in this thinking how so?

Now back to my scope I have #10's from the existing 25A breaker to a local fused disconnect at the new unit, which will most likely have 20A fuses for the new unit. Again with info I have received from Mech., the author of this change, I can see nothing wrong with my scope.
 
Re: Maximum Size Breaker for #12 Branch

Tryinghard, The mech contractor said it did'nt need t.o.l. because it already is supplied with the unit and or package.The data on the unit has already figured the 125/175% rules.The only ac equipment that does'nt come with t.o.l's(of some sort) are where it is just the pump/compressor by it's self.(no package).Not used to often.If i'm not mistaken,80% of the breakers ampere rating(175% rating) is within the 125% rating of the wire.On a hot summer day/night when that ac unit is cooking,you'll be glad you put the right size in.
Rick
 
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