Appropriate breaker and wire size for ductless mini split?

[Huy Huynh]

I recently purchased a ductless mini split and am trying figure out the correct breaker and wire size. Currently I have a 220v, 30 amp breaker with 10 AWG Romex.

The electrical characteristics for my LG ductless mini split are as follows:
MOP 35 amps
MCA 23 amps
Cooling rated amps 17.55
Heating rated amps 17.55
Compressor 17.3 amps
Fan 0.25 amps

If I'm reading article 440 correctly, my wiring needs to carry at least 23 amps, while my circuit breaker must not exceed 35 amps. Is a 30 amp breaker with 10 gauge wire appropriate for my system?

Thank you for any help you can offer me.

Huy Huynh
Madison, AL

 

[iwire]

I recently purchased a ductless mini split and am trying figure out the correct breaker and wire size. Currently I have a 220v, 30 amp breaker with 10 AWG Romex.

The electrical characteristics for my LG ductless mini split are as follows:
MOP 35 amps
MCA 23 amps
Cooling rated amps 17.55
Heating rated amps 17.55
Compressor 17.3 amps
Fan 0.25 amps

If I'm reading article 440 correctly, my wiring needs to carry at least 23 amps, while my circuit breaker must not exceed 35 amps. Is a 30 amp breaker with 10 gauge wire appropriate for my system?

Thank you for any help you can offer me.

Huy Huynh
Madison, AL

It would likely be fine.

I would use a 35 amp breaker with 10 AWG or even 12 AWG, that is allowed for this type of application.

 

[texie]

I recently purchased a ductless mini split and am trying figure out the correct breaker and wire size. Currently I have a 220v, 30 amp breaker with 10 AWG Romex.

The electrical characteristics for my LG ductless mini split are as follows:
MOP 35 amps
MCA 23 amps
Cooling rated amps 17.55
Heating rated amps 17.55
Compressor 17.3 amps
Fan 0.25 amps

If I'm reading article 440 correctly, my wiring needs to carry at least 23 amps, while my circuit breaker must not exceed 35 amps. Is a 30 amp breaker with 10 gauge wire appropriate for my system?

Thank you for any help you can offer me.



Huy Huynh
Madison, AL

If you are using a pipe and wire method and assuming 75 degree terminations, you could use #12 THHN/THWN as it has an ampacicty of 25@75 degree and use a 35 amp breaker.
If you are using NM you will need to use #10 as you must use it at the 60 degree value. Still use the 35 amp breaker.

 

[Huy Huynh]

If you are using a pipe and wire method and assuming 75 degree terminations, you could use #12 THHN/THWN as it has an ampacicty of 25@75 degree and use a 35 amp breaker.
If you are using NM you will need to use #10 as you must use it at the 60 degree value. Still use the 35 amp breaker.

So is a 35 amp breaker a requirement? I interpreted the code as saying MOP was the maximum size breaker I could use. Ultimately, if my wiring is sized to my breaker, shouldn't I be fine so long as my breaker is 175% of a 17.55 amp motor-compressor rating?

-Huy Huynh
Madison, AL

 

[iwire]

So is a 35 amp breaker a requirement?

No, it is a choice, you could use a 25 amp breaker.

A 30 will likely be fine but I would still use a 35 to prevent any call backs if it does happen to start hard.

35 amp breakers are not hard to get.

. Ultimately, if my wiring is sized to my breaker, shouldn't I be fine so long as my breaker is 175% of a 17.55 amp motor-compressor rating?

Again, maybe ... even likely but there is no down side to using the max breaker size with a smaller conductor. The motor overloads in the HVAC unit will protect the conductors from overload.

 

[JFletcher]

I'd use the 35A breaker with 10ga wire, especially if it's not a super short run or there may be ambient temps over 40*C.

 

[Saturn_Europa]

I'd use the 35A breaker with 10ga wire, especially if it's not a super short run or there may be ambient temps over 40*C.

Correct me if I am wrong, but I thought 240.4 D limited #10 to 30 amp breakers.

Is there an exception for this in article 440?

 

[iwire]

Correct me if I am wrong, but I thought 240.4 D limited #10 to 30 amp breakers

It does for many circuits but we need to read it completely.

240.4(D) Small Conductors. Unless specifically permitted in
240.4(E) or (G), the overcurrent protection shall not exceed
that required by (D)(1) through (D)(7) after any correction
factors for ambient temperature and number of conductors
have been applied.

When we look at 240.4(G) we find that overcurrent protection for HVAC equipment is handled by parts III and VI of article 440.

 

[Saturn_Europa]

It does for many circuits but we need to read it completely.



When we look at 240.4(G) we find that overcurrent protection for HVAC equipment is handled by parts III and VI of article 440.

Got it. Thank you for the correction

 

[dionysius]

I recently purchased a ductless mini split and am trying figure out the correct breaker and wire size. Currently I have a 220v, 30 amp breaker with 10 AWG Romex.

The electrical characteristics for my LG ductless mini split are as follows:
MOP 35 amps
MCA 23 amps
Cooling rated amps 17.55
Heating rated amps 17.55
Compressor 17.3 amps
Fan 0.25 amps

If I'm reading article 440 correctly, my wiring needs to carry at least 23 amps, while my circuit breaker must not exceed 35 amps. Is a 30 amp breaker with 10 gauge wire appropriate for my system?

Thank you for any help you can offer me.

Huy Huynh
Madison, AL

We assume that this is single phase?? I am curious to know the tonnage and sq footage to be cooled/heated?? What is the cost of such a unit?? What size air handlers?? I need one myself. Any info will be appreciated.