Minimum current ampacity

[AC\DC]

Got a Mini Split with a minimum current capacity of 23 and a Max overcurrent protection of 25 I installed the number 10 and I put it on a 20 amp breaker Inspectir saying I have to put it on a 25 because it states that and I just said that’s the maximum he’s trying to say since the minimum current capacity is 23 that I have to match that or go be above

 

[AC\DC]

He agreed that it doesn’t pose an issue in NEC, but he says I have to follow the nameplate rating which I believe I am because it says maximum overcurrent which I’m good and then minimum current capacity which I meet

 

[LarryFine]

I agree with you, if the units start reliably.

 

[infinity]

Got a Mini Split with a minimum current capacity of 23 and a Max overcurrent protection of 25 I installed the number 10 and I put it on a 20 amp breaker Inspectir saying I have to put it on a 25 because it states that and I just said that’s the maximum he’s trying to say since the minimum current capacity is 23 that I have to match that or go be above

I agree with the inspector. 20 is below the minimum circuit ampacity.

 

[AC\DC]

Well minimum circuit ampacity is for sizing the wire not the over current protection device
Straight from manufacturer

Recommended Fuse/Breaker Size (Outdoor) A 25

Key word recommended

 

[AC\DC]

I agree with you, if the units start reliably.

Yep starts fine

 

[curt swartz]

I also agree with the inspector. Minimum means everything in the circuit must be rated for at lease 23 amps.

 

[AC\DC]

I also agree with the inspector. Minimum means everything in the circuit must be rated for at lease 23 amps.

Then they would not say maximum- they would just say 25

Either way manufacture said there is no minimum so I am following there name plate

 

[curt swartz]

Either way manufacture said there is no minimum so I am following there name plate

Your first sentence.
Got a Mini Split with a minimum current capacity of 23

I have never seen a name plate that said minimum current capacity but most of us assume you mean minimum circuit ampacity (MCA).
The label is required to show an MCA.

 

[Master Nater]

i also have to agree with the inspector. i believe the words you're trying to say from your name-plate is "Minimum Circuit Ampacity." i have never seen "current capacity" on a nameplate. and that means your entire circuit has to be rated for at least 23 amperes. not 20.

as for the maximum OCPD, yes, you can go no larger than 25a. but must be larger than 23a. is there any chance you could post a picture of this nameplate to verify? frankly, i'm surprised the two are so tight on ratings. pretty rare. but not impossible.

the easy fix is to simply go to the hardware store, and get a 25a 2p breaker. my shop carrys them for just these instances. whether we like it or not, they are required.

 

[don_resqcapt19]

Well minimum circuit ampacity is for sizing the wire not the over current protection device

It is for sizing the circuit and no matter what size the conductor is, a 20 OCPD cannot supply a 23 amp load.

210.22 Permissible Loads, Individual Branch Circuits.
An individual branch circuit shall be permitted to supply any load for which it is rated, but in no case shall the load exceed the branch-circuit ampere rating.

 

[Dennis Alwon]

The reason the breaker doesn't trip is that the load is 18.4 amps--I assume as 125% of that is 23 amps. However that 18 amps is still more than the 80% of a 20 amp breaker, since this is continuous load you need a 25 amp overcurrent protective device. What's the big deal just install a 25 amp breaker and be done with it.

210.20 Overcurrent Protection.

Branch-circuit conductors and equipment shall be protected by OCPDs that have a rating or setting complying with 210.20(A) through 210.20(D).
(A) Continuous and Noncontinuous Loads.

Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the OCPDs protecting the branch circuit shall not be less than the noncontinuous load plus 125 percent of the continuous load.
Exception:
Where the assembly, including the OCPDs, is listed for operation at 100 percent of its rating, the ampere rating of the OCPD shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load.

 

[tortuga]

The reason the breaker doesn't trip is that the load is 18.4 amps--I assume as 125% of that is 23 amps. However that 18 amps is still more than the 80% of a 20 amp breaker, since this is continuous load you need a 25 amp overcurrent protective device. What's the big deal just install a 25 amp breaker and be done with it.

On some brands of panels the 25, 35 and 45 amp breakers might be non-stock items (here in rural back woods Oregon) especially if you need a twin or quad, so unless HVAC person gets me the correct info in advance and I can order it might be a return trip of a hour drive for correct breaker.

 

[kwired]

All those that say the overcurrent protection must also be no less than 23 amps please tell us which code section confirms this.

MCA is minimum circuit ampacity- it applies to ampacity of the circuit conductors.

Overcurrent protection is a different issue and is covered by a different code section.

When it comes to 90.2 (A) and practical safeguarding of persons and property, so what if this overcurrent device trips because you selected a 20 amp instead of a 25 amp? It still protected the equipment and conductors from overcurrent which could otherwise lead to other hazards.

 

[AC\DC]

manufacture say recommended- not mandatory— he saying I have to follow naw plate and I am

 

[Master Nater]

All those that say the overcurrent protection must also be no less than 23 amps please tell us which code section confirms this.

MCA is minimum circuit ampacity- it applies to ampacity of the circuit conductors.

Overcurrent protection is a different issue and is covered by a different code section.

When it comes to 90.2 (A) and practical safeguarding of persons and property, so what if this overcurrent device trips because you selected a 20 amp instead of a 25 amp? It still protected the equipment and conductors from overcurrent which could otherwise lead to other hazards.

dennis alwon already did that. read above.

 

[kwired]

dennis alwon already did that. read above.

210.3 sends us to art 440 for this application the general rules in 210 don't necessarily apply if 440 addresses a particular topic. MCA and MOCP are definitely things covered in art 440.


From what I see here, minimum setting only has to be capable of carrying starting current. If OP has an inverter driven compressor, it likely will start on a 15 amp breaker. Though it may not be such a great idea to use that in case it would ever draw maximum rated current for any extended time, as it is likely over 15 amps but probably less than 20 which would make a 20 more practical than some want it to be. I admit I generally would install the 25 in most cases. I'd put in a 20 in a pinch but may intend to replace with the 25 when practical to do so.

 

[AC\DC]

I could correct it — but I don’t want to cause I don’t need to

 

[Master Nater]

210.3 sends us to art 440 for this application the general rules in 210 don't necessarily apply if 440 addresses a particular topic. MCA and MOCP are definitely things covered in art 440.

View attachment 2582225
From what I see here, minimum setting only has to be capable of carrying starting current. If OP has an inverter driven compressor, it likely will start on a 15 amp breaker. Though it may not be such a great idea to use that in case it would ever draw maximum rated current for any extended time, as it is likely over 15 amps but probably less than 20 which would make a 20 more practical than some want it to be. I admit I generally would install the 25 in most cases. I'd put in a 20 in a pinch but may intend to replace with the 25 when practical to do so.

210.3 only sends you after conductor sizing requirements on a/c and refrigeration equipment in 440.6, 440.31, and 440.32. there's nothing in 210.3 about OCPD.

i gotta agree with dennis. 210.20 applies for OC protection requirements. and 20a breaks that code.

110.3(B) also still applies. so it has to be at least 125% of the continuous duty loads but can't take it beyond 25a (to 30a) because of the manufacturer nameplate.

 

[Master Nater]

I could correct it — but I don’t want to cause I don’t need to

i used to take a continuing education class with an old-school master electrician by the name of fred bender. the guy was the president of the electrical board in the state of nebraska. he was an incredibly well-versed and super-intelligent guy.

one year, he did a motor class and was pretty spot on when someone asked him about what OCPD to install on a motor when we were given the possibility of a 250% on an inverse time breaker. he said, "which one do you install? you install the biggest one you can. why not? do you think the 40a breaker will clear slower than a 25a breaker on a short circuit? nope. do you think the breaker will protect the motor, in the event of overload? NOPE. there's no reason not to put in the biggest one that the code allows."

overlooking the possible price difference, it was hard to disagree with his logic. he was right. the breaker will still function in the event of a short circuit, and protect the insulation on the conductors. and the overload/VFD settings that provide the OL protection are the only things gonna protect the motors, if they go into overload.

the only reason i see not to go to the 25a is just stubborn pride. but, i get it. i've been there too.

have a good night.