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Had to do a double take because I swear I [just saw this question asked](https://www.reddit.com/r/AskElectricians/comments/1dnk6m0/minisplit_wiring_requirements/). Looks to be the same manufacturer as that post. 20A breaker & 12 AWG wire are fine here.
There is absolutely no requirement to be professional electrician to answer here.
Many make up credentials and boast wild opinions with impunity.
The misinformation is deep and thick here. Enjoy.
You’re correct sir. 200% for short circuit protection I.e. fuses and breakers.
150% for overload protection.
I’m sure the NEC says something convoluted and you need a math degree to figure out depending on conduit size and wire runs along with whether it’s solid or stranded and if it is stranded, how many conductors in a given diameter.
Don't want to violate the UL Listing it doesn't have! As a UL MTR and QM I'm usually picky, but if it doesn't state a specific fuse class then it's not giving me any fuse requirements and any OCPD is fine. The manual might, but I'll bet $50 it specifically says an HACR breaker is acceptable if you dive into it. Things like VFDs will list specific fuses necessary to incorporate them into a UL 508A assembly, but if you're not Listing the assembly then you have a range of OCPD options. Our panel A/Cs say "Max fuse" on the nameplates all the time, then specifically mention in the manual that any HACR breaker is acceptable. Any HVAC equipment in the last 25 years I've seen that needs specific fusing for drives has to incorporate them internally to be Listed.
[The installation manual](https://d3l66gvjdr7rqw.cloudfront.net/Templates/32505/myimages/user%20manual_1700151736908.pdf) doesn't clarify much.
It also doesn't seem to have been written in English very well.
It doesn’t say it requires a fuse on the nameplate, just a MAX 25A fuse. Even a 20A is still fine. If the nameplate said MINIMUM 25A then you’d be required to use a 25A breaker and still could use 12Awg
From the NEC 2023 Handbook, commentary on 430.7(D)(1):
>Section 110.3(B) requires listed or labeled equipment to be used and installed in accordance with the manufacturer's instructions accompanying the equipment or marked on the nameplate. The nameplate marking for the maximum ampere rating of the branch-circuit short-circuit and ground-fault protective device may limit the type of protective device to a fuse by stipulating "fuse" without reference to a circuit breaker. A circuit breaker located in a panelboard, switchboard, or similar distribution equipment is permitted to supply the equipment in which the fuses are installed.
It says MAX OCPD 25A…a 20A would still be fine at 17A even with startup on these units which have VFD’s usually. If the unit trips a 20A then there’s either a low charge or compressor issue.
The long answer is that the wire is being protected by overload protection built into the AC and motor, and the breaker is sized based on the surge current of the motor. In an industrial setting electricians often size wire based on motor overload protection, but when dealing with AC units all of those calculations are already built in and you basically follow the nameplate.
Is that max saying that 20 amp isn't enough, or is it saying that it shouldn't have a breaker larger than 25A because that would not provide sufficient protection for the wire?
Their saying the max amps that it will draw under under normal operation is 17amps. So you need a wire to handle that.
Then it says max fuse, 25amps. This is the max draw that it will pull upon start up for the motor inrush. This only lasts a second or two, so you need a breaker this size so it doesn’t trip every time you turn the AC on.
At the end of the day, nameplate rating trumps all.
No this is the largest size of over current protection that the manufacturer will allow. A 20A breaker is both acceptable and would generally also be your first choice. If it trips the breaker then you can try to order a 25A breaker. Many suppliers don't carry 25A breakers.
This is the correct answer ! if you do the math calculation on the unit amperage it’s really only 12.5 so the 150% Rule is already factored in with the 17 amp listing, a lot of people ignoring this and 95% of people responding in this sub currently as well !
A 25A breaker will do more harm to this unit then good in a low charge or compressor malfunction scenario
Exactly. People seem to just be making stuff up here. Every time an A/C is on this subreddit people start giving answers that are so wildly different and in some cases wrong that it makes this community look bad. If someone comes here looking for an expert's advice and gets 6 different answers they're probably not going to feel comfortable with any of the answers and we as a community haven't actually solved anything.
You're correct except the motor inrush is like 76A. You will definitely exceed 20A but there is a trip curve for the breaker that allows a temporary peak within a certain time on the curve. Curve can be found from the MFR. https://www.se.com/us/en/product/QO120/mini-circuit-breaker-qo-20a-1-pole-120-240vac-10ka-plug-in/
I understand what you are saying, but what I don't understand is why the use of the word max is used in that rating. The term normally means not to exceed, but doesn't preclude something smaller. Can you further explain? Thanks.
All breakers have a time curve and will handle inrush to varying degrees. Regular 20a breaker probably won't trip. These are packaged units so they are designed to work with what people have and 25A exists but isn't common. Theoretically yes 20A breaker could be insufficient but it wont be. If it was that isn't a safety concern either.
In this case, yes. Single AC condensors (and similar single-motor loads) are allowed to use larger breakers on wire than would be normally allowed for branch circuits.
NEC Section 240 gives you overcurrent protection ratings of many conductors and circuits, but it also refers you to Section 430 for motor circuits.
Table 430.52 tells us that an instant trip circuit breaker that is protecting the circuit between that breaker and the motor can be rated as high as eight times the motor's running current. In the case of an air conditioning condenser, the running current might be 16 amps. It would be labeled as "FLA", or "Full Load Amps". From that, you would drive the MCA, or Minimum Circuit Amps. That's the smallest size any part of the circuit feeding that AC condenser can be sized. What size conductors at 125% of their full load, so 125% of 16 amps is 20 amps. 12 gauge copper is adequate for this circuit.
The name plate on the AC condenser will also tell you what the manufacturer expects for its MCA.
In most commercial and residential circuits, that 12 gauge copper must be protected with a 20 amp breaker. However, on a circuit that is only feeding an air conditioning compressor (or similar single-motor load), the breaker can be sized 800% of that 16 amps in the aforementioned example to accommodate inrush current during motor startup. There are also other limitations, but in this example, it wouldn't be against Code to put that 16 amp motor on a circuit that is wired with 12 gauge wire, and fed with a 60 amp instantaneous-trip breaker. The motor in the condenser has its own fuse and/or thermal overload protection in case the motor starts drawing too much power, but not completely shorted. The breaker is only there to protect the building and wiring from a true short circuit.
Is the MCA always 125% of the FLA?
I guess there is somewhere that says motors must have integrated overload protection? Still seems risky if you somehow got a motor without it.
> Is the MCA always 125% of the FLA?
Generally, yes. There are sometimes some specialty systems that don't follow that rule, but those need to be approved by an engineer, and are usually in specialized environments. The only one I have seen in person that I can remember was a submerged sewer pump that used undersize wire purely due to cost (we're talking very large wire here), and it was going to be constantly submerged in water (sewage, but it's 95% water). I remember that one specifically because the design called for 2-awg SO cord feeding submerged 100 HP 480v motors, and SO cord with 3 current-carrying conductors is rated to 80 amps. The design called for the motors to be on flexible cords for vibration resistance, and cords larger than 2 awg are custom-made, and ridiculously expensive. The motors drew around 90 amps at full load, which is about the limit for 2 awg in conduit or open air, but SO cord is significantly derated.
Apparently, it was cheaper to get an engineer to certify it than it was to buy larger flexible cord. They were planning for the future (government contracts tend to do that), so the installer provided the rest of the SO cord on a reel to the city so it would get lost in a maintenance yard and rot away in the sunlight until it was needed, at which point the city would scramble to get more when a pump needed to be replaced...as government does.
False. Says MAX fuse, not MIN fuse. 25A breakers aren't common. Many suppliers simply do not stock them. 20A is both acceptable and generally all that's needed.
Agreed! If marginal, up size the conductors, not because the code requires it ( which it doesn’t in this case) but because the unit may be replaced in a few years with one that has a 21 amp ( or higher) rated load!
To all you people saying *"use #10 in case they replace the unit in the future"*..what the actual fuck? A) Do you have any clue how long air conditioning systems last? B) Where do you draw the line with all this "future proofing" bullshit? Do you run 6/3 to a 20A 240V wall oven just in case they put in a bigger one some day? Do you run #4cu to a 150' deep well, just in case it runs dry and they have to dig 400' next time? Where does it end?
I wish the fuck I had run #4 Cu to both my Garage and my Barn 25 years ago… now I am balancing loads very carefully to avoid burning up the 8’s that I Did install….
A feeder is a different story IMO since you really never know the loads. This certainly is a case where bigger is better.
I am referring to branch circuits for exact known loads.
I ran a 60 foot line from a main panel to a sub panel in the living quarters of our metal building, I opted for the mobil home feeder that had a 100A rating, it is aluminum, but that feeder cable is a pretty good price.
I also ran 220 feet of 4/0 from my meter panel out by the road to my main panel, also was a feeder cable, good for like 300A, direct burial but I put it into a 2" conduit for some additional protection.
That stuff was a little over $4/foot, still a good value, all things considered
Technically you can do a 25 amp breaker with 12 gauge wire because of special hvac code.
I would do a 30 amp breaker with 10 gauge wire with a 25 amp fusible disconnect at the unit.
This gives you the ability to upsize the condenser/heat pump in the future without new wiring and you can up the fuse to 30.
You must love spending other people's money.
Even if you did run #10. Just use a 25A breaker and a non-fused disconnect.
Why spend on unnecessary fuses
How much cost is that? In California we have to do a fused disconnect anyways, so there is no coast difference there, there is no cost difference in the breaker, so it’s just the wire. 56 cents a foot vs 1.02 a foot. On a 50 foot run the upcost is 25 dollars. GTFO.
Honestly. People are saying 12 is safe, but up gauging by 1 size is never a bad call unless you're worried about cost. Hell if it'd aluminum you'd need 10 anyway.
I’d honestly just pull a set of #10’s to it. It’s easier to swap out a breaker than change a set of feeds. Also, if they upgrade unit in future, unless it enormous it’s already set up.
NEC 440.6(A)
The air conditioner's nameplate should be used to determine the size of the disconnecting means, branch-circuit conductors, and the branch-circuit short-circuit and ground-fault protection.
Basically the manufacturer is responsible for specifying gauge and overcurrent. Many time these wire gauge can be set to running amperage while breaker is oversized to account for the crank load, since the crank load is often capable of spiking higher than the gauge maximum, but not for long enough periods to cause heat buildup.
Minimum ampacity of 17 amps qualifies for 12 gauge for running loads (margins already factored in) while overcurrent is 25 Amps.
One of the few and rare times you can use the incorrect breaker size legally.
It's a 20 amp breaker with number 12 wire.
It's just over 12 lamps on the compressor and just over half a amp on the discharge fan
It says maximum capacity 25 in which case you would need number 10 wire but it is not necessary
Minimum circuit amps -17
That means 20amp breaker exceed 80percent rule
So go with 25amps
For 25amps need atleast 10wire because 12 wire work till 20amps
Thank you! Finally someone who can read the ampacity table.
#12 is rated for 20 amps max and the most you can use on a 20 amp circuit is 16 amps. 80% of 20.
This label clearly says 17 amps. Will 1 amp cause an issue. Probably not but if you’re installing to code, you automatically upsize to the next wire size meaning #10.
The label also says 25 amp fuse max. Use a 25 amp breaker.
Depends, you using Romex or then/thwn? NEC limits 12 awg to 20 amps, but the exception is made when feeding motor load, then you may use the listed ampacity of the wire. We also must factor the distance of the run as well.
20A/12g is fine for this application it gives min/max 20A is right in the middle on a normal length run.
if you use max , 25A use #10 You can never go wrong jumping a longer run up a gauge.
I would run 10ga wire for 2 reasons. If it's a long run back to breaker then for voltage loss. If it's short then the material cost isn't a whole lot more (far less than labor); in the event a larger unit was installed and needed more than 20A, you have 30A available easily.
Then with 10ga wire installed, you can choose to use a 20A or 25A breaker, and no local fuse, or a 30A and use a local fuse at the local disconnect.
20A breaker and 12ga wire would work though, as the cheapest solution.
12Awg is absolutely acceptable. The 80% rule is not for specific use single equipment. A lot of people get this mixed up. As long as the unit etc. is under 20A load then you can use 12Awg
There are other rules (125%) for AC equipment and motors, but that’s a different story and would allow you to install a 25A breaker if needed
The 80% rule has nothing to do with what kind of load is on it? It has to do with nuisance tripping as a breaker may trip at 85% of its rated load on continuous current. I have a 50A that trips at 43A running a kiln after about 45min.
The 80% rule is for multi outlet branch circuits, Not Feeders…the only 214 rules that need to be followed are the 125% with NO correction factors OR 100% full nameplate INCLUDING correction factors (heat, VD etc)
I used to get tripped up on this in the past but still utilized it correctly most of the time, while also oversizing a couple feeders as well along the way.
In your situation, if the 50A breaker is tripping at 43A after 45min then you likely have a worn out breaker or an issue with the equipment. A 50A breaker shouldn’t trip at 43A after a year of use lol
The 80% rating on breakers isnt an NEC thing. It's a manufacturers thing. Standard breakers are 80% rated for 3hrs of continuous load. You can specifically buy 100% rated breakers in larger frame sizes.
https://www.se.com/us/en/faqs/FA109750/
I see now it is an NEC thing. Continuous loads (like lighting) require a 1.25 multiplier. This is same as the 80% defined by manufacturer. They don't both apply, they are the same.
The 80% rule is NEC for branch circuits, having multiple outlets and or lighting. That’s where and how we use the 180 VA per outlet calculation to get 16 A on a 20 amp max circuit and 12 A on a 15A…
but if it’s for a specific device or equipment, it’s technically a feeder which the 80% rule doesn’t apply, you would go to either 125% without having to do any correction factors for VD, Temp, etc. or you can do 100% of the full load after calculating VD, temp, etc.
215.2A1 covers feeder, however, its just the conductor, not the OCPD.
210.19A1 for branch, same rules, except there's an exception for 100% rated OCPDs don't require 125%. I don't understand the 2nd Exception.
Manufacturing standard is OCPD rating +-20%. That's what originates this requirement of 215.2A1 and 210.19A1, the +20% side of the breaker. But there's still a nuisance side of the -20%. NEC isn't going to concern itself with that, as it's not a casualty risk.
Correct, the nameplate will dictate the OCPD but then you’ll have to go back to verify if you’re allowed to use that OCPD on the current wire size.
Which in some instances will allow 12awg on a 30A breaker for some specific AC equipment
Depending on how far the unit is from the breaker you may need to account for voltage drop, although it's unlikely this will affect the wire size for the given load. Also make sure you use a HACR type breaker or mfg equivalent
Hmmmm I thought 20 amp breaker is at 80% rating, so 16 amp constant? Unless you get a 20 amp continuous rated breaker, but why not just run a #10 and put in a 25 amp breaker and not worry. Breaker protects the wire installed is what I was taught, but I am in Canada and may differ from the States
Minimum ampacity is 17A. That means you need at least a 20A breaker and 12ga wire.
Max breaker is 25A. That means even if you use 10ga you can’t use a 30A breaker. So there’s really only one thing to do here. There’s no point in using 10ga unless you imagine switching to a bigger unit in the future. In either case a 20A breaker is in your future.
The inrush can be up to 76A, so even with an HACR breaker you can push the trip curve and come home to find it's hot as balls inside because you tripped the breaker by not allowing any inrush headroom. Why ask for problems?
Typically an inverter drive will have a lower inrush, but the drive manufacturers typically still recommend significantly upsized OCPDs. Power bumps can drain then rapidly recharge caps under a flying restart, for example. Typically less but not always none.
Your thought process is wrong.
Use 12ga wire AND use 25A breaker.
Walk away knowing you performed safe and a code compliant installation without spending more of the client's money than was necessary.
If you’re in Canada even #14 would be compliant at 75° C. Real question is how long is the wire run and with which size can you achieve 3% or better voltage drop under load ?
Though with a shorter distance, the incremental cost to jump up to 10AWG is less as well. I'd put 10AWG on a 25A breaker. That would allow a system change in the future to swap the breaker out to up to a 35A without changing out the feeder.
Canada is so much more permissive. I ran 14/2 on a 15a dp breaker for my 18k ceiling cassette mini split and that’s totally fine. You can also go as high as 25a dp and 4800W on 14/2 for heating circuits. I’m going to do a 4000W (2k main area plus two bedrooms at 1k).
So many wrong answers.🤣
You need a fused disconnect with 25A fuses (could use 20A, but don't) and 12awg wire. You can feed this fused disconnect with 10awg on a 30A breaker.
10
Breakers should only be continuously loaded to 80 percent of their rated amperage.
Thus a 20 amp breaker should only be loaded to 16 amps. This thing is going to draw 17 amps. Thus you need a 25 amp breaker. No. 10 wire is rated to 25 amps.
25 amp breaker, 25 amp wire. Guaranteed good to go.
25 amp breaker with 10 gauge wire. You have to factor in continuous load for minimum circuit ampacity, and there can be a spike of in rush current on start up. Maximum fuse already has these factored in. 240.4(D) prohibits 12 gauge wire being protected by a 25 amp breaker
Incorrect, read 440.4(B). 12 AWG on a 25A breaker is absolutely acceptable for an HVAC condenser exceptions. You'll also find in article 440 that the required nameplate already has continuous load calculations factored in at 125% - size wire to minimum ampacity, OCPD to max OCPD.
Wrong on many levels. First, the nameplate takes into consideration a continuous load, add up the compressor motor and fan motor numbers and compare to minimum circuit ampacity. Then go read article 440, 12 on a 25a breaker is a code compliant installation.
**Attention!** **It is always best to get a qualified electrician to perform any electrical work you may need.** With that said, you may ask this community various electrical questions. Please be cautious of any information you may receive in this subreddit. This subreddit and its users are not responsible for any electrical work you perform. Users that have a 'Verified Electrician' flair have uploaded their qualified electrical worker credentials to the mods. If you comment on this post please only post accurate information to the best of your knowledge. If advice given is thought to be dangerous, you may be permanently banned. There are no obligations for the mods to give warnings or temporary bans. **IF YOU ARE NOT A QUALIFIED ELECTRICIAN, you should exercise extreme caution when commenting.** *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/AskElectricians) if you have any questions or concerns.*
Had to do a double take because I swear I [just saw this question asked](https://www.reddit.com/r/AskElectricians/comments/1dnk6m0/minisplit_wiring_requirements/). Looks to be the same manufacturer as that post. 20A breaker & 12 AWG wire are fine here.
Its rovson but yeah it look like the same label
12 gauge wire with a 25 A breaker. Don't use a 20.
It’s very scary that you’re getting downvoted by professional electricians.
There is absolutely no requirement to be professional electrician to answer here. Many make up credentials and boast wild opinions with impunity. The misinformation is deep and thick here. Enjoy.
r/AskSomeGuy*
Lol, most of the frequenters of all these subs are armchair contractors. You can find some wild stuff in construction subs!
You’re correct sir. 200% for short circuit protection I.e. fuses and breakers. 150% for overload protection. I’m sure the NEC says something convoluted and you need a math degree to figure out depending on conduit size and wire runs along with whether it’s solid or stranded and if it is stranded, how many conductors in a given diameter.
Isn’t a breaker also overload protection?
Overcurrent. Overload is closer to the amps used on say, a motor. Breaker sized at like 600 amps for startup will not help and overloaded motor.
No, don't use a 25A breaker. You must use a 25A *fuse*.
Don't want to violate the UL Listing it doesn't have! As a UL MTR and QM I'm usually picky, but if it doesn't state a specific fuse class then it's not giving me any fuse requirements and any OCPD is fine. The manual might, but I'll bet $50 it specifically says an HACR breaker is acceptable if you dive into it. Things like VFDs will list specific fuses necessary to incorporate them into a UL 508A assembly, but if you're not Listing the assembly then you have a range of OCPD options. Our panel A/Cs say "Max fuse" on the nameplates all the time, then specifically mention in the manual that any HACR breaker is acceptable. Any HVAC equipment in the last 25 years I've seen that needs specific fusing for drives has to incorporate them internally to be Listed.
[The installation manual](https://d3l66gvjdr7rqw.cloudfront.net/Templates/32505/myimages/user%20manual_1700151736908.pdf) doesn't clarify much. It also doesn't seem to have been written in English very well.
r/engrish
Yeah, they wouldn't pass a UL Listing without some more work. I didn't see a mention of OCPDs in there at all.
All the best Chinese products get listed by Intertek 😉
[удалено]
When a manual says to not get the machine wet or touch it while barefoot, but it must be installed outside, I tend to question the listing.
Most breakers are HACR rated as you mentioned
It doesn’t say it requires a fuse on the nameplate, just a MAX 25A fuse. Even a 20A is still fine. If the nameplate said MINIMUM 25A then you’d be required to use a 25A breaker and still could use 12Awg
No you don't lol I never use fuse disconnects for AC units. Just a way for the HVAC companies to charge a homeowner $500 if a fuse blows
From the NEC 2023 Handbook, commentary on 430.7(D)(1): >Section 110.3(B) requires listed or labeled equipment to be used and installed in accordance with the manufacturer's instructions accompanying the equipment or marked on the nameplate. The nameplate marking for the maximum ampere rating of the branch-circuit short-circuit and ground-fault protective device may limit the type of protective device to a fuse by stipulating "fuse" without reference to a circuit breaker. A circuit breaker located in a panelboard, switchboard, or similar distribution equipment is permitted to supply the equipment in which the fuses are installed.
It says MAX OCPD 25A…a 20A would still be fine at 17A even with startup on these units which have VFD’s usually. If the unit trips a 20A then there’s either a low charge or compressor issue.
As directed on name plate. Correct wire based on charts. Common sense. 20a would lead to nuisance trips.
Yo... If you want to go ahead. But I would recommend a 10g for anything over 20a. 14g, 15a, 12g, 20a. Better safe than sorry right?
Wire size is based off the minimum ampacity and fuse off the maximum. #12 with a 25 A breaker is 100% legal and up to code
Aight. I just wouldn't. But that's me. If you want to... MORE POWER TO YA!
Why, please explain?
Article 440 NEC
The long answer is that the wire is being protected by overload protection built into the AC and motor, and the breaker is sized based on the surge current of the motor. In an industrial setting electricians often size wire based on motor overload protection, but when dealing with AC units all of those calculations are already built in and you basically follow the nameplate.
I would kiss you if I could
Says right on the label… max fuse 25.
Is that max saying that 20 amp isn't enough, or is it saying that it shouldn't have a breaker larger than 25A because that would not provide sufficient protection for the wire?
Their saying the max amps that it will draw under under normal operation is 17amps. So you need a wire to handle that. Then it says max fuse, 25amps. This is the max draw that it will pull upon start up for the motor inrush. This only lasts a second or two, so you need a breaker this size so it doesn’t trip every time you turn the AC on. At the end of the day, nameplate rating trumps all.
No this is the largest size of over current protection that the manufacturer will allow. A 20A breaker is both acceptable and would generally also be your first choice. If it trips the breaker then you can try to order a 25A breaker. Many suppliers don't carry 25A breakers.
This is the correct answer ! if you do the math calculation on the unit amperage it’s really only 12.5 so the 150% Rule is already factored in with the 17 amp listing, a lot of people ignoring this and 95% of people responding in this sub currently as well ! A 25A breaker will do more harm to this unit then good in a low charge or compressor malfunction scenario
Exactly. People seem to just be making stuff up here. Every time an A/C is on this subreddit people start giving answers that are so wildly different and in some cases wrong that it makes this community look bad. If someone comes here looking for an expert's advice and gets 6 different answers they're probably not going to feel comfortable with any of the answers and we as a community haven't actually solved anything.
You're correct except the motor inrush is like 76A. You will definitely exceed 20A but there is a trip curve for the breaker that allows a temporary peak within a certain time on the curve. Curve can be found from the MFR. https://www.se.com/us/en/product/QO120/mini-circuit-breaker-qo-20a-1-pole-120-240vac-10ka-plug-in/
I understand what you are saying, but what I don't understand is why the use of the word max is used in that rating. The term normally means not to exceed, but doesn't preclude something smaller. Can you further explain? Thanks.
You could use something smaller (which would be safe) but it may trip before the unit has a chance to fully start up.
They make delayed trip breakers to handle the inrush, if you don’t have one, then you use a 25amp fuse.
All breakers have a time curve and will handle inrush to varying degrees. Regular 20a breaker probably won't trip. These are packaged units so they are designed to work with what people have and 25A exists but isn't common. Theoretically yes 20A breaker could be insufficient but it wont be. If it was that isn't a safety concern either.
Inrush current can be over fuse rating. Please stop posting here.
Could you do a 25A breaker (or fuse) and wire rated for 20A?
In this case, yes. Single AC condensors (and similar single-motor loads) are allowed to use larger breakers on wire than would be normally allowed for branch circuits.
That’s so weird. Isn’t the breaker supposed to be protecting the wire?
NEC Section 240 gives you overcurrent protection ratings of many conductors and circuits, but it also refers you to Section 430 for motor circuits. Table 430.52 tells us that an instant trip circuit breaker that is protecting the circuit between that breaker and the motor can be rated as high as eight times the motor's running current. In the case of an air conditioning condenser, the running current might be 16 amps. It would be labeled as "FLA", or "Full Load Amps". From that, you would drive the MCA, or Minimum Circuit Amps. That's the smallest size any part of the circuit feeding that AC condenser can be sized. What size conductors at 125% of their full load, so 125% of 16 amps is 20 amps. 12 gauge copper is adequate for this circuit. The name plate on the AC condenser will also tell you what the manufacturer expects for its MCA. In most commercial and residential circuits, that 12 gauge copper must be protected with a 20 amp breaker. However, on a circuit that is only feeding an air conditioning compressor (or similar single-motor load), the breaker can be sized 800% of that 16 amps in the aforementioned example to accommodate inrush current during motor startup. There are also other limitations, but in this example, it wouldn't be against Code to put that 16 amp motor on a circuit that is wired with 12 gauge wire, and fed with a 60 amp instantaneous-trip breaker. The motor in the condenser has its own fuse and/or thermal overload protection in case the motor starts drawing too much power, but not completely shorted. The breaker is only there to protect the building and wiring from a true short circuit.
Is the MCA always 125% of the FLA? I guess there is somewhere that says motors must have integrated overload protection? Still seems risky if you somehow got a motor without it.
> Is the MCA always 125% of the FLA? Generally, yes. There are sometimes some specialty systems that don't follow that rule, but those need to be approved by an engineer, and are usually in specialized environments. The only one I have seen in person that I can remember was a submerged sewer pump that used undersize wire purely due to cost (we're talking very large wire here), and it was going to be constantly submerged in water (sewage, but it's 95% water). I remember that one specifically because the design called for 2-awg SO cord feeding submerged 100 HP 480v motors, and SO cord with 3 current-carrying conductors is rated to 80 amps. The design called for the motors to be on flexible cords for vibration resistance, and cords larger than 2 awg are custom-made, and ridiculously expensive. The motors drew around 90 amps at full load, which is about the limit for 2 awg in conduit or open air, but SO cord is significantly derated. Apparently, it was cheaper to get an engineer to certify it than it was to buy larger flexible cord. They were planning for the future (government contracts tend to do that), so the installer provided the rest of the SO cord on a reel to the city so it would get lost in a maintenance yard and rot away in the sunlight until it was needed, at which point the city would scramble to get more when a pump needed to be replaced...as government does.
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False, read max fuse. 25 amp breaker on a #12wire. Downvote this all you want this is the correct answer.
False. Says MAX fuse, not MIN fuse. 25A breakers aren't common. Many suppliers simply do not stock them. 20A is both acceptable and generally all that's needed.
25A absolutely IS common for a real supply house.
I know right? Where does he lives? In a hut? 25 amp breaker are common..
Ordered mine off Amazon lol
This is correct. I just watched the Mike holt video on this yesterday
as long as it is not a very long run. there will be a voltage drop at 17 Amps
Read better.
“Water of proof”
The manual also says to not get it wet or touch it while barefoot...
Run 10 gauge so any future changes will be no worries if it's over this current unit
Agreed! If marginal, up size the conductors, not because the code requires it ( which it doesn’t in this case) but because the unit may be replaced in a few years with one that has a 21 amp ( or higher) rated load!
To all you people saying *"use #10 in case they replace the unit in the future"*..what the actual fuck? A) Do you have any clue how long air conditioning systems last? B) Where do you draw the line with all this "future proofing" bullshit? Do you run 6/3 to a 20A 240V wall oven just in case they put in a bigger one some day? Do you run #4cu to a 150' deep well, just in case it runs dry and they have to dig 400' next time? Where does it end?
I wish the fuck I had run #4 Cu to both my Garage and my Barn 25 years ago… now I am balancing loads very carefully to avoid burning up the 8’s that I Did install….
A feeder is a different story IMO since you really never know the loads. This certainly is a case where bigger is better. I am referring to branch circuits for exact known loads.
Depends on who it's for. If it's my stuff I'll upsize it, depending on how long the run is.
Plus, on hot ass days when the voltage is sagging. Its bad enough for stuff w/o more sag from thin wire.
ive never seen anyone run 12 to a condenser
Just because you’re content with your own mediocrity doesn’t mean that everyone else is.
Mini splits don’t last very long jsyk
12 would be fine for 21 amps as long as it isn't romex
I just did 8ga strand running for the 50ft line in my ceiling to the AC out back. 10ga solid ground though. I'm not made of money after all.
I ran a 60 foot line from a main panel to a sub panel in the living quarters of our metal building, I opted for the mobil home feeder that had a 100A rating, it is aluminum, but that feeder cable is a pretty good price. I also ran 220 feet of 4/0 from my meter panel out by the road to my main panel, also was a feeder cable, good for like 300A, direct burial but I put it into a 2" conduit for some additional protection. That stuff was a little over $4/foot, still a good value, all things considered
Smarty mcsmart smart right here. This dudes thinking.
No. That's not how this works. 😂
Yes, it is
Exactly. Thank you!
Run #6 to allow for future changes. 👍🏻
I was going to post this. Most of these people are hacks, masters of the minimum at best.
I was thinking the same thing.
Both are fine, you just have to meet the 17A minimum. The breaker can be bigger than the wire due to special HVAC wiring rules.
Technically you can do a 25 amp breaker with 12 gauge wire because of special hvac code. I would do a 30 amp breaker with 10 gauge wire with a 25 amp fusible disconnect at the unit. This gives you the ability to upsize the condenser/heat pump in the future without new wiring and you can up the fuse to 30.
You must love spending other people's money. Even if you did run #10. Just use a 25A breaker and a non-fused disconnect. Why spend on unnecessary fuses
A lot of unnecessary cost just to have the ability to upsize in the future. Imo
How much cost is that? In California we have to do a fused disconnect anyways, so there is no coast difference there, there is no cost difference in the breaker, so it’s just the wire. 56 cents a foot vs 1.02 a foot. On a 50 foot run the upcost is 25 dollars. GTFO.
Agreed. Just use a 2 pole 25 and an AC pullout disconnect.
That's silly.
Why?
Honestly. People are saying 12 is safe, but up gauging by 1 size is never a bad call unless you're worried about cost. Hell if it'd aluminum you'd need 10 anyway.
How far is the run?
25 amp breaker, 12awg wire. They do the math for you!
I’d run 10 for future upgrades if it’s not cost prohibitive
12 is fine
#12 wire with 25 amp breaker. Anyone else suggesting something else has absolutely no idea what they are talking about.
EXACTLY!!! You're being down voted by morons.
Do you know
12/2 would be good for 100 ft but also 10 gauge is better incase future units require more amperage as others said. **Edit spelling error*
33,222a as essay re Q
I’d honestly just pull a set of #10’s to it. It’s easier to swap out a breaker than change a set of feeds. Also, if they upgrade unit in future, unless it enormous it’s already set up.
D3 calculation
#12 is good for plenty of distance even with the table D3 calculations.
3/4-ton cooling for 12.7 amps seems high even for 115v. That’s like a medium size room. For a lot of power usage.
25A breaker (2 pole of course) and 10/2 wire would pass code here in Florida
#8 wire would also pass 🙄
12 is fine unless it’s any distance away
Is it less than 150ft to your electrical panel????
NEC 440.6(A) The air conditioner's nameplate should be used to determine the size of the disconnecting means, branch-circuit conductors, and the branch-circuit short-circuit and ground-fault protection. Basically the manufacturer is responsible for specifying gauge and overcurrent. Many time these wire gauge can be set to running amperage while breaker is oversized to account for the crank load, since the crank load is often capable of spiking higher than the gauge maximum, but not for long enough periods to cause heat buildup.
Minimum ampacity of 17 amps qualifies for 12 gauge for running loads (margins already factored in) while overcurrent is 25 Amps. One of the few and rare times you can use the incorrect breaker size legally.
As an apprentice, thanks for typing this out. I learned something new today. Do you know the requirements (if any) for overload protection as well?
It's always stated as the maximum fuse rating on the equipment
It's a 20 amp breaker with number 12 wire. It's just over 12 lamps on the compressor and just over half a amp on the discharge fan It says maximum capacity 25 in which case you would need number 10 wire but it is not necessary
10
20amp breaker 12 gauge If it’s over 100 feet away then put #10
Minimum circuit amps -17 That means 20amp breaker exceed 80percent rule So go with 25amps For 25amps need atleast 10wire because 12 wire work till 20amps
Thank you! Finally someone who can read the ampacity table. #12 is rated for 20 amps max and the most you can use on a 20 amp circuit is 16 amps. 80% of 20. This label clearly says 17 amps. Will 1 amp cause an issue. Probably not but if you’re installing to code, you automatically upsize to the next wire size meaning #10. The label also says 25 amp fuse max. Use a 25 amp breaker.
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12
How long is the run from the breaker box to the equipment? Could decide if 10 is needed over 12.
10awg/25A fuse/breaker
6awg would be best to ensure no voltage drop
This guy pulls wire.
Depends, you using Romex or then/thwn? NEC limits 12 awg to 20 amps, but the exception is made when feeding motor load, then you may use the listed ampacity of the wire. We also must factor the distance of the run as well.
20A/12g is fine for this application it gives min/max 20A is right in the middle on a normal length run. if you use max , 25A use #10 You can never go wrong jumping a longer run up a gauge.
12 fine
I would run 10ga wire for 2 reasons. If it's a long run back to breaker then for voltage loss. If it's short then the material cost isn't a whole lot more (far less than labor); in the event a larger unit was installed and needed more than 20A, you have 30A available easily. Then with 10ga wire installed, you can choose to use a 20A or 25A breaker, and no local fuse, or a 30A and use a local fuse at the local disconnect. 20A breaker and 12ga wire would work though, as the cheapest solution.
12Awg is absolutely acceptable. The 80% rule is not for specific use single equipment. A lot of people get this mixed up. As long as the unit etc. is under 20A load then you can use 12Awg There are other rules (125%) for AC equipment and motors, but that’s a different story and would allow you to install a 25A breaker if needed
The 80% rule has nothing to do with what kind of load is on it? It has to do with nuisance tripping as a breaker may trip at 85% of its rated load on continuous current. I have a 50A that trips at 43A running a kiln after about 45min.
The 80% rule is for multi outlet branch circuits, Not Feeders…the only 214 rules that need to be followed are the 125% with NO correction factors OR 100% full nameplate INCLUDING correction factors (heat, VD etc) I used to get tripped up on this in the past but still utilized it correctly most of the time, while also oversizing a couple feeders as well along the way. In your situation, if the 50A breaker is tripping at 43A after 45min then you likely have a worn out breaker or an issue with the equipment. A 50A breaker shouldn’t trip at 43A after a year of use lol
The 80% rating on breakers isnt an NEC thing. It's a manufacturers thing. Standard breakers are 80% rated for 3hrs of continuous load. You can specifically buy 100% rated breakers in larger frame sizes. https://www.se.com/us/en/faqs/FA109750/
I see now it is an NEC thing. Continuous loads (like lighting) require a 1.25 multiplier. This is same as the 80% defined by manufacturer. They don't both apply, they are the same.
The 80% rule is NEC for branch circuits, having multiple outlets and or lighting. That’s where and how we use the 180 VA per outlet calculation to get 16 A on a 20 amp max circuit and 12 A on a 15A… but if it’s for a specific device or equipment, it’s technically a feeder which the 80% rule doesn’t apply, you would go to either 125% without having to do any correction factors for VD, Temp, etc. or you can do 100% of the full load after calculating VD, temp, etc.
215.2A1 covers feeder, however, its just the conductor, not the OCPD. 210.19A1 for branch, same rules, except there's an exception for 100% rated OCPDs don't require 125%. I don't understand the 2nd Exception. Manufacturing standard is OCPD rating +-20%. That's what originates this requirement of 215.2A1 and 210.19A1, the +20% side of the breaker. But there's still a nuisance side of the -20%. NEC isn't going to concern itself with that, as it's not a casualty risk.
Correct, the nameplate will dictate the OCPD but then you’ll have to go back to verify if you’re allowed to use that OCPD on the current wire size. Which in some instances will allow 12awg on a 30A breaker for some specific AC equipment
Your label says 17 amps, so definitely 12 gauge wire with a 20 amp circuit breaker. Hope this is helpful
"water of proof"
Depending on how far the unit is from the breaker you may need to account for voltage drop, although it's unlikely this will affect the wire size for the given load. Also make sure you use a HACR type breaker or mfg equivalent
[How to size an AC circuit Mike Holt](https://m.youtube.com/watch?v=WugJ8-70Sqs) Its 12gauge wire on a 25amp breaker Article 440.4(B)
12 ga my dude
Hmmmm I thought 20 amp breaker is at 80% rating, so 16 amp constant? Unless you get a 20 amp continuous rated breaker, but why not just run a #10 and put in a 25 amp breaker and not worry. Breaker protects the wire installed is what I was taught, but I am in Canada and may differ from the States
Max amps are 17. 12awg is good for 20a but at 80%, that’s 16a. So 10awg, and stranded due to it being a motor. 12awg would work, but do it right.
Unpopular opinion… 14 wire and a 25a breaker can be acceptable here.
If we're talking Romex. 10 wire. Don't put 12 on a 25 amp breaker.
10 is worth the safety factor.
No problem using 10.
I'd bet it would hold its entire life on a 20A and you could legally use #14 if it was fairly close. That being said I'd use #12 on a 25A.
12 awg on a 25 amp fuse
Minimum ampacity is 17A. That means you need at least a 20A breaker and 12ga wire. Max breaker is 25A. That means even if you use 10ga you can’t use a 30A breaker. So there’s really only one thing to do here. There’s no point in using 10ga unless you imagine switching to a bigger unit in the future. In either case a 20A breaker is in your future.
440.4(B) *clearly* explains how a 25A breaker on 12 AWG is completely code compliant.
It's also completely unnecessary; this device draws well under 20
The inrush can be up to 76A, so even with an HACR breaker you can push the trip curve and come home to find it's hot as balls inside because you tripped the breaker by not allowing any inrush headroom. Why ask for problems?
I thought mini spot had much lower inrush than traditional condensers?
Typically an inverter drive will have a lower inrush, but the drive manufacturers typically still recommend significantly upsized OCPDs. Power bumps can drain then rapidly recharge caps under a flying restart, for example. Typically less but not always none.
Except for when you have nuisance tripping from inrush.
Your thought process is wrong. Use 12ga wire AND use 25A breaker. Walk away knowing you performed safe and a code compliant installation without spending more of the client's money than was necessary.
This makes sense. Thank you.
If you’re in Canada even #14 would be compliant at 75° C. Real question is how long is the wire run and with which size can you achieve 3% or better voltage drop under load ?
7-8 feet from breaker panel
12 and send it
Though with a shorter distance, the incremental cost to jump up to 10AWG is less as well. I'd put 10AWG on a 25A breaker. That would allow a system change in the future to swap the breaker out to up to a 35A without changing out the feeder.
Sure, the customer is very unlikely to replace a 9k BTU mini split with a 4 ton central unit though.
Canada is so much more permissive. I ran 14/2 on a 15a dp breaker for my 18k ceiling cassette mini split and that’s totally fine. You can also go as high as 25a dp and 4800W on 14/2 for heating circuits. I’m going to do a 4000W (2k main area plus two bedrooms at 1k).
I'm sorry but if you have to ask you might want to have an electrician do the work.
Clearly a lot of electricians here have a hard time reading a nameplate.
What would YOU do?
10
So many wrong answers.🤣 You need a fused disconnect with 25A fuses (could use 20A, but don't) and 12awg wire. You can feed this fused disconnect with 10awg on a 30A breaker.
#12 on 25 amp breaker feeding a fused 25 A disco. All day, every day. Simple stuff here.
If you look up the model and pull the manual it will tell you what size they want
What? The nameplate is literally right there. 🤷🏿♂️
The lowest amperage is 17 witch is a 12 for better power and not a lot of money in wire I would still go with a 10
You can even use 14s on this
10 Breakers should only be continuously loaded to 80 percent of their rated amperage. Thus a 20 amp breaker should only be loaded to 16 amps. This thing is going to draw 17 amps. Thus you need a 25 amp breaker. No. 10 wire is rated to 25 amps. 25 amp breaker, 25 amp wire. Guaranteed good to go.
It would work but that is not what code requires. Please read some of the other comments. The manufacturer did the work for you.
25 amp breaker with 10 gauge wire. You have to factor in continuous load for minimum circuit ampacity, and there can be a spike of in rush current on start up. Maximum fuse already has these factored in. 240.4(D) prohibits 12 gauge wire being protected by a 25 amp breaker
Incorrect, read 440.4(B). 12 AWG on a 25A breaker is absolutely acceptable for an HVAC condenser exceptions. You'll also find in article 440 that the required nameplate already has continuous load calculations factored in at 125% - size wire to minimum ampacity, OCPD to max OCPD.
Wrong on many levels. First, the nameplate takes into consideration a continuous load, add up the compressor motor and fan motor numbers and compare to minimum circuit ampacity. Then go read article 440, 12 on a 25a breaker is a code compliant installation.
The compressor has overload protection. So you can use a 25 amp breaker.
I don’t understand why people over complicate this stuff. Minimum ampacity for wire size. Max fuse for breaker size. It’s not that complicated
10 gauge. To me, it's a no brainer. I'd rather be safe than sorry.
Why not follow code? It's a 12.7A device, why waste money?
Educating yourself would cover being safe.
12ga is 20A, 10ga is 30A. Because your max fuse is 25 I'd go with the 10.
Those amperages are correct for romex. Regardless you can still use a 25a breaker
12awg on a 25a is code compliant
12
What do you have in the truck?
Go with 12ga. 20amp circuit should be enough, sounds like your running a dedicated outlet so nothing else should draw current on this ckt
I'd return it to Amazon and purchase something better.