What is the Minimum breaker size required by NEC for #14 Copper wire feeding a A/C minimum 18.5 amp and 25 amp Max over current protection?

[Roger Stevenson]

What is the minimum wire size required by NEC for a A/C mini split system with a minimum 18.5 amp and Maximum 25 amp over current protection?

 

[LarryFine]

Welcome to the forum.

What size wire, of the type (NM, MC, THWN, etc.) you intend to use is rated at 18.5a or better?

We usually don't like to just answer such questions, preferring to teach you how to figure it out.

Added: Is that 18.5a the MCA or minimum breaker?

 

[texie]

Do you mean a MCA of 18.5 and a max OCPD of 25 as stated on the label? If so the conductors could be #14 using 75 degree conductors (pipe and wire) of if using NM cable they would need to be #12 as NM must use the 60 degree ampacity.

 

[LarryFine]

Well, some of us do.

 

[Roger Stevenson]

14-2 nmc!

 

[Roger Stevenson]

Do you mean a MCA of 18.5 and a max OCPD of 25 as stated on the label? If so the conductors could be #14 using 75 degree conductors (pipe and wire) of if using NM cable they would need to be #12 as NM must use the 60 degree ampacity.

Yes 14-2 romex

 

[Roger Stevenson]

Doesn’t #14 Copper have an asterisk and footnote requiring 15 amp breaker maximum and #12 20 amp breaker Maximum and #10 30 amp max?

 

[infinity]

NM cable is limited to the 60° C ampacity which is 15 amps for #14 AWG. Use MC cable or pipe and wire and you can use the 75° C ampacity.

 

[Roger Stevenson]

Welcome to the forum.

What size wire, of the type (NM, MC, THWN, etc.) you intend to use is rated at 18.5a or better?

We usually don't like to just answer such questions, preferring to teach you how to figure it out.

Added: Is that 18.5a the MCA or minimum breaker?

MCA

 

[don_resqcapt19]

Doesn’t #14 Copper have an asterisk and footnote requiring 15 amp breaker maximum and #12 20 amp breaker Maximum and #10 30 amp max?

The * in the ampacity table sends you to 240.4(D), the small conductor rule. The parent text says the rules in 240.4(E) or (G) can override the small conductor rule. The rule in 240.4(G) says that the conductor sizing and overcurrent protection rules in Article 440 apply to air conditioning circuits.

 

[Roger Stevenson]

Yes 14-2 romex

The * in the ampacity table sends you to 240.4(D), the small conductor rule. The parent text says the rules in 240.4(E) or (G) can override the small conductor rule. The rule in 240.4(G) says that the conductor sizing and overcurrent protection rules in Article 440 apply to air conditioning circuits.

So 14-2 Romex is allowed on a 20 amp breaker?

 

[infinity]

So 14-2 Rolex is allowed on a 20 amp breaker?

14-2 NM cable is limited to 15 amps of MCA.

 

[suemarkp]

Yes, if it feeds a motor, HVAC unit, or some of the other exceptions. The MCA would need to be 15A or less though.

 

[infinity]

Yes, if it feeds a motor, HVAC unit, or some of the other exceptions. The MCA would need to be 15A or less though.

That's correct. The MCA would be a maximum of 15 amps but the OCPD could be any size on the nameplate.

 

[Roger Stevenson]

Yes, if it feeds a motor, HVAC unit, or some of the other exceptions. The MCA would need to be 15A or less though.

No the MCA is 18.5

 

[infinity]

No the MCA is 18.5

Then you cannot use #14 AWG NM cable.

 

[LarryFine]

Yes 14-2 romex

No, 12-2 Romex.

 

[LarryFine]

So 14-2 Romex is allowed on a 20 amp breaker?

Only if the MCA was 15a or lower.

 

[Roger Stevenson]

No the MCA is 18.5

Then you cannot use #14 AWG NM cable.

Thank you

 

[Dennis Alwon]

The title and the first post are different questions.

What is the minimum wire size required by NEC for a A/C mini split system with a minimum 18.5 amp and Maximum 25 amp over current protection?

If this is the question then I would say 14 gauge wire is fine with a 25 amp overcurrent protective device. That is assuming it is not nm cable. Since the info isn't given then I would use t. 310.16