{"id":3735,"date":"2026-08-17T18:47:27","date_gmt":"2026-08-17T18:47:27","guid":{"rendered":"https:\/\/huyuglobal.com\/?p=3735"},"modified":"2026-08-17T18:47:29","modified_gmt":"2026-08-17T18:47:29","slug":"minimum-circuit-ampacity","status":"publish","type":"post","link":"https:\/\/huyuglobal.com\/fr\/blog\/minimum-circuit-ampacity\/","title":{"rendered":"Ampacit\u00e9 minimale du circuit (MCA) : Choisissez la bonne taille de fil"},"content":{"rendered":"<p>If you have just purchased a new air conditioning unit, an electric vehicle charger or a commercial oven, your technician might ask for the minimum circuit ampacity available from the nameplate. At that moment, you might find yourself looking at a number that seems meaningless to you. If you make a mistake, you can either end up using a wire that can be undersized (and thus \u2013 can overheat, cause nuisance tripping and maybe a fire), or you can spend too much money on wiring it with the oversized wire.<\/p>\n<p>In this guide, you will learn what minimum circuit ampacity stands for, how it\u2019s calculated, what&#8217;s the difference between minimum circuit ampacity and breaker sizing and how to get this minimum circuit ampacity turned into the right wire size \u2014 abiding by NEC regulations in the process.<\/p>\n<blockquote><p>In simple words, MCA or Minimum Circuit Ampacity is the minimum capacity of a wire necessary to properly run a device. To calculate it, use the NEC&#8217;s 125% rule, which implies multiplying the largest continuous load, that is, the largest motor full-load current, by 1.25, together with all other loads. After that, the smallest wire that meets or exceeds this requirement as per NEC Table 310.16 is to be chosen.<\/p><\/blockquote>\n<h2>What Is Minimum Circuit Ampacity?<\/h2>\n<p>The Minimum Circuit Ampacity is the smallest calculated value expressed in amperes that shows the minimum ampacity of a circuit conductor needed to supply a load without overheating. MCA does not present the amount of current that the equipment would really consume in normal use. Instead, it is a minimum requirement that was derived from the code in order to make sure that there is a margin of safety for continuous operation of the circuit and for starting surge current.<\/p>\n<p>In practice, you will find the MCA on the nameplates of HVAC systems, heat pumps, commercial refrigeration units, water heaters, chargers for electric vehicles, and the majority of devices that involve motors and heating elements. Manufacturers have to include it in order to comply with the code that states that it is compulsory to account the proper wire size with the adequate margin. Moreover, only a producer is aware of the worst-case combinations of how loads operate.<\/p>\n<p>The most important point is that you have to comply with the required MCA of the conductor. For example, if the nameplate indicates the MCA value as 26.4 A, then the wire must have been rated at not less than this level (i.e., comply with this level after being adjusted according to the derating factors).<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-3737\" src=\"https:\/\/huyuglobal.com\/wp-content\/uploads\/2026\/08\/MCA-vs-FLA-vs-RLA-vs-MOCP.webp\" alt=\"MCA vs FLA vs RLA vs MOCP\" width=\"1448\" height=\"1086\" \/><\/p>\n<h2>MCA vs FLA vs RLA vs MOCP: The Terminology Table<\/h2>\n<p>Half the confusion around MCA comes from the alphabet soup next to it on the nameplate. Here is what each term actually means:<\/p>\n<table>\n<thead>\n<tr>\n<th>Term<\/th>\n<th>Stands For<\/th>\n<th>What It Means<\/th>\n<th>Used For<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>MCA<\/strong><\/td>\n<td>Minimum Circuit Ampacity<\/td>\n<td>Smallest conductor ampacity allowed<\/td>\n<td>Sizing the wire<\/td>\n<\/tr>\n<tr>\n<td><strong>FLA \/ FLC<\/strong><\/td>\n<td>Full-Load Amps \/ Current<\/td>\n<td>Current a motor draws at full rated load<\/td>\n<td>Motor calculations<\/td>\n<\/tr>\n<tr>\n<td><strong>RLA<\/strong><\/td>\n<td>Rated Load Amps<\/td>\n<td>Compressor current at rated conditions<\/td>\n<td>HVAC calculations<\/td>\n<\/tr>\n<tr>\n<td><strong>LRA<\/strong><\/td>\n<td>Locked-Rotor Amps<\/td>\n<td>Inrush current at startup (5-8\u00d7 RLA)<\/td>\n<td>Explains why MOCP is larger<\/td>\n<\/tr>\n<tr>\n<td><strong>MOCP \/ MOP<\/strong><\/td>\n<td>Maximum Overcurrent Protection<\/td>\n<td>Largest breaker or fuse allowed<\/td>\n<td>Sizing the breaker<\/td>\n<\/tr>\n<tr>\n<td><strong>OCPD<\/strong><\/td>\n<td>Overcurrent Protection Device<\/td>\n<td>The breaker or fuse itself<\/td>\n<td>General term<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The main component of mental modeling is taking into account two different parameters involved in this calculation \u2014 MCA and MOCP, which are not the same figures \u2014 the former is typically less than the latter because the breaker has to withstand the surge in current when the equipment is started while the wire takes care of an ongoing current flow plus its factors set by codes.<\/p>\n<h2>The 125% Rule Explained<\/h2>\n<p>The rule of 125% lies at the foundation of every calculation for MCA. It can be found in various sections of NEC and, in each of them, the goal is to provide a specified margin of safety in case of either loads, which work continuously, or loads that are turned on with the inrush current.<\/p>\n<ul>\n<li>NEC 210.19(A)(1) \u2014 branch circuits: wires must have the ampacity of minimum 125% of the continuous load, and 100% of the non-continuous load. A load is referred to [as] a \u201ccontinuous load\u201d if the load in question operates at full value for 3 hours or more (NEC 100 definition).<\/li>\n<li>NEC 215.2 \u2014 feeders: the same 125% requirement is also applicable to feeders.<\/li>\n<li>NEC 430.22 \u2014 one motor: wires must be calculated based on 125% of the motor\u2019s FLA.<\/li>\n<li>NEC 440.22 \/ manufacturer practice \u2014 HVAC: MCA = 125% of the RLA for the largest motor.<\/li>\n<\/ul>\n<p>Why 125%? There are two reasons for it. First of all, no continuous heat: when a wire carries its rated current for a long period of time it heats up to its peak temperature. The extra 25% means that insulation remains cool. Secondly, when starting any motor operating in a regular mode draws many times more than during the actual operation of the motor.<\/p>\n<h2>How to Calculate MCA (With Worked Examples)<\/h2>\n<p>For individual motors (following NEC 430.22 code),<\/p>\n<p>MCA = motor FLA \u00d7 1.25<\/p>\n<p>For example, if there\u2019s a 3 HP, 230V single-phase motor with FLA of 17 A then,<br \/>\nMCA = 17 \u00d7 1.25 = 21.25 A. Now, according to NEC table 310.16 (75 \u00b0C column), it can be inferred that the small wire that can handle this value of 21.25 A is 12 AWG, which is rated for 25 A of current carrying ability.<\/p>\n<p>For the multiple load system (NEC 430.24),<\/p>\n<p>MCA = (highest motor FLA \u00d7 1.25) + all other motor SLAs<\/p>\n<table>\n<thead>\n<tr>\n<th>Load<\/th>\n<th>FLA (Amps)<\/th>\n<th>Multiplier<\/th>\n<th>Contribution<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Largest motor (10 HP, 460V)<\/td>\n<td>14.0<\/td>\n<td>\u00d71.25<\/td>\n<td>17.5 A<\/td>\n<\/tr>\n<tr>\n<td>Second motor (5 HP)<\/td>\n<td>7.6<\/td>\n<td>\u00d71.00<\/td>\n<td>7.6 A<\/td>\n<\/tr>\n<tr>\n<td>Third motor (2 HP)<\/td>\n<td>3.4<\/td>\n<td>\u00d71.00<\/td>\n<td>3.4 A<\/td>\n<\/tr>\n<tr>\n<td colspan=\"3\"><strong>Total MCA<\/strong><\/td>\n<td><strong>28.5 A<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>For 28.5A, NEC 310.16 (75\u00b0C) says 10 AWG copper (35A) is the smallest adequate size \u2014 12 AWG (25A) would be too small.<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-3738\" src=\"https:\/\/huyuglobal.com\/wp-content\/uploads\/2026\/08\/How-to-Calculate-MCA.webp\" alt=\"How to Calculate MCA\" width=\"1448\" height=\"1086\" \/><\/p>\n<p>In the case of an HVAC unit with a compressor and fan motor, the ideal RLA values would be the following:MCA = (Largest Motor RLA \u00d7 1.25) + Other Motors FLAs + Other Loads.<\/p>\n<p>For example, if the compressor has RLA of 18.2 Amps and the condenser fan has FLA of 1.5 Amps, then we have the following:MCA = (18.2 \u00d7 1.25) + 1.5 = 24.25 Amps.<\/p>\n<p>Please keep in mind that this value is rounded by the manufacturer to a more standard 22-24 Amps, on the nameplate of the HVAC unit.<\/p>\n<h2>MCA vs Maximum Overcurrent Protection (MOCP)<\/h2>\n<p>This is where DIYers often go wrong: they think that the breaker needs to match the MCA. It doesn\u2019t. The breaker is rated according to the MOCP, which is different from the number on the nameplate.<\/p>\n<table>\n<thead>\n<tr>\n<th>Factor<\/th>\n<th>MCA (Wire)<\/th>\n<th>MOCP (Breaker)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>What it sizes<\/td>\n<td>Conductor (wire)<\/td>\n<td>Overcurrent device (breaker\/fuse)<\/td>\n<\/tr>\n<tr>\n<td>Typical relationship<\/td>\n<td>Smaller number<\/td>\n<td>Larger number (must allow inrush)<\/td>\n<\/tr>\n<tr>\n<td>Protects against<\/td>\n<td>Overheating of insulation<\/td>\n<td>Short circuit and ground fault<\/td>\n<\/tr>\n<tr>\n<td>Rule<\/td>\n<td>Wire ampacity \u2265 MCA<\/td>\n<td>Breaker size \u2264 MOCP (per NEC 240.6 standard sizes)<\/td>\n<\/tr>\n<tr>\n<td>Example unit<\/td>\n<td>MCA 26.4A<\/td>\n<td>MOCP 45A<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>In this instance, copper wire with an AWG of 10 (30-35A in ampacity) is used to supply power to the unit and is safeguarded against surges by a 45A breaker. Is that allowed \u2014 having a breaker that has a higher rating than the wire? It is permissible under NEC 440.22(a) because the compressor has its own protective mechanisms. Therefore, in this case, only the protection against surges is required from the breaker. This applies to both motor and HVAC systems, with the exception of regular wiring systems, where a circuit breaker has to have a rating lower than that of the wires.<\/p>\n<h2>How to Choose the Right AWG Wire Size<\/h2>\n<p>When you have MCA, selecting the wire is simply referring to NEC Table 310.16. Refer to the 75\u00b0C column when using THHN\/THWN-2 copper (which is the standard wire for conduits), or if using NM-B (Romex) or wiring older installations, refer to the 60\u00b0C column.<\/p>\n<table>\n<thead>\n<tr>\n<th>Copper Wire Size (AWG)<\/th>\n<th>Ampacity @ 60\u00b0C<\/th>\n<th>Ampacity @ 75\u00b0C<\/th>\n<th>Covers MCA Up To<\/th>\n<th>Typical Breaker<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>14 AWG<\/td>\n<td>15 A<\/td>\n<td>20 A<\/td>\n<td>15-20 A<\/td>\n<td>15 A<\/td>\n<\/tr>\n<tr>\n<td>12 AWG<\/td>\n<td>20 A<\/td>\n<td>25 A<\/td>\n<td>20-25 A<\/td>\n<td>20 A<\/td>\n<\/tr>\n<tr>\n<td>10 AWG<\/td>\n<td>30 A<\/td>\n<td>35 A<\/td>\n<td>30-35 A<\/td>\n<td>30 A<\/td>\n<\/tr>\n<tr>\n<td>8 AWG<\/td>\n<td>40 A<\/td>\n<td>50 A<\/td>\n<td>40-50 A<\/td>\n<td>40 A<\/td>\n<\/tr>\n<tr>\n<td>6 AWG<\/td>\n<td>55 A<\/td>\n<td>65 A<\/td>\n<td>55-65 A<\/td>\n<td>60 A<\/td>\n<\/tr>\n<tr>\n<td>4 AWG<\/td>\n<td>70 A<\/td>\n<td>85 A<\/td>\n<td>70-85 A<\/td>\n<td>80 A<\/td>\n<\/tr>\n<tr>\n<td>2 AWG<\/td>\n<td>95 A<\/td>\n<td>115 A<\/td>\n<td>95-115 A<\/td>\n<td>100 A<\/td>\n<\/tr>\n<tr>\n<td>1\/0 AWG<\/td>\n<td>125 A<\/td>\n<td>150 A<\/td>\n<td>125-150 A<\/td>\n<td>150 A<\/td>\n<\/tr>\n<tr>\n<td>2\/0 AWG<\/td>\n<td>145 A<\/td>\n<td>175 A<\/td>\n<td>145-175 A<\/td>\n<td>175 A<\/td>\n<\/tr>\n<tr>\n<td>3\/0 AWG<\/td>\n<td>165 A<\/td>\n<td>200 A<\/td>\n<td>165-200 A<\/td>\n<td>200 A<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Choose the smallest wire whose ampacity is at least equal to the rated ampacity (after derating, which is explained below). For a rated ampacity of 24.25A, the smallest wire that may be used is 12 AWG (25A). However, many installers go to a bigger wire, such as 10 AWG, to accommodate long runs and\/or future needs.<\/p>\n<h2>200-Amp Service: Can You Use 1\/0 Wire?<\/h2>\n<p>This question is often asked with regards to residential service upgrades, and the answer is that, with regards to 200A full service, it is a quaint but false no. Keeping in mind the 75\u00b0C, the 1\/0 copper would have a maximum rating of 150A, and won\u2019t be capable of handling a 200A service load according to the law. If there is a need to achieve 200A residential service, it requires using one of the following types of copper or aluminum wires:<\/p>\n<ul>\n<li>2\/0 copper which can handle 175A with the temperature of 75\u00b0C. This wire is allowed for 200A in some areas (with Special Commercial Code A).<\/li>\n<li>3\/0 copper which will successfully handle a load of 200A at 75\u00b0C.<\/li>\n<li>4\/0 aluminum wire capable of feeding 180A at 75\u00b0C often used in service entrance lines requiring wiring of 200A.<\/li>\n<\/ul>\n<p>Another variant is to use 1\/0 copper wire, which is suitable for use only in case of 150A service lines, and charging 150A sub-panel only. Avoid using 1\/0 wire with a 200A service line at all costs since it heats too much when processed for a long time. In addition, make sure to verify with local wiring code and inspector since there are many ambiguities in the NEC 310.12 Service Entrance.<\/p>\n<h2>The 80% Rule for Circuit Breakers<\/h2>\n<p>NEC 210.20(A) and 215.3 rules say that a circuit breaker should not be loaded for more than 80% of its rating. For example:<\/p>\n<ul>\n<li>A 15A breaker should handle a continuous load of only 12A.<\/li>\n<li>A 20A breaker should handle a continuous load of only 16A.<\/li>\n<li>A 30A breaker should carry a continuous load of only 24A.<\/li>\n<li>A 100A breaker should bear a full-load of only 80A.<\/li>\n<\/ul>\n<p>Provide comparisons between all the above examples. The principle behind the regulation is the same in both cases: 80% and 125% factor are identical in their essence claiming that maximum load should not be higher than the rated capacity of the device and can be expressed in a particular order (1\/1.25=0.8). For instance, if the device is used with a continuous load of 16A, the conductor should withstand 16*1.25=20A; thus, the particular breaker needs to be rated for a 20A load, and in fact, is rated at only 20A. When you need to match protection devices to a new circuit, a certified miniature circuit breaker range rated for the job \u2014 like the <a href=\"https:\/\/huyuglobal.com\/product\/hum18-63n-mcb-1p-to-4p-63a-type-b-c-d\/\" rel=\"nofollow\">HUYU HUM18 MCB series<\/a> covering 1P to 4P and B\/C\/D curves \u2014 makes the wire-to-breaker match straightforward for panel builders and contractors.<\/p>\n<h2>Temperature &amp; Conduit-Fill Derating<\/h2>\n<p>The ampacity table base its assumption on 30 degrees Celsius (86 degrees Fahrenheit) ambient temperature, with no conduction of more than 3 wires through a conduit. When the temperature deviates, you have to derate (lower) the ampacity of the wire before comparing it with the MCA.<\/p>\n<ul>\n<li>High ambient temperature: According to Table 310.15(B)(1) of NEC, correction factors can be used. For example, the current-carrying capacity of a conductor rated for 75\u00b0C becomes 22A because at an ambient temperature of 40\u00b0C it is multiplied by 0.88.<\/li>\n<li>Conduit fill: In most cases, the Table 310.15(C)(1) of NEC indicates different correction factors according to the number of wires through the conduit. Thus, for 4-6 conductors, the correction factor is 0.80; for 7-9 conductors, it is 0.70; and for 10-20 it is equal to 0.50. Thus, the bigger number of wires leads to a more considerable heat amount trapped in the conduit.<\/li>\n<li>Norm: after the derating condition, the new ampacity must be no less than the MCA.<\/li>\n<\/ul>\n<h2>Voltage Drop on Long Runs<\/h2>\n<p>In most U.S. locations, voltage drop isn&#8217;t a code requirement (excluding a few applications) but is still useful and smart: the branch circuit voltage drop must be 3% and the voltage drop for the whole feeder + branch must equal 5%. A good guideline is when the distance is more than 50 to 100 feet, you have to go one size higher. So for a 120-volt circuit run more than 150 feet, you need to use a bigger wire size even if the MCA table says that you can use 12 AWG (10 AWG will do a better job). Using the wrong sized wire over longer distances results in dim lights, slow motors, and overheating.<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-3739\" src=\"https:\/\/huyuglobal.com\/wp-content\/uploads\/2026\/08\/Common-MCA-Wire-Sizing-Mistakes.webp\" alt=\"Common MCA &amp; Wire-Sizing Mistakes\" width=\"1448\" height=\"1086\" \/><\/p>\n<h2>Common MCA &amp; Wire-Sizing Mistakes<\/h2>\n<table>\n<thead>\n<tr>\n<th>Mistake<\/th>\n<th>Why It&#8217;s Wrong<\/th>\n<th>Correct Approach<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Using FLA instead of MCA<\/td>\n<td>FLA is actual running current; MCA already includes the 25% margin<\/td>\n<td>Size wire from nameplate MCA, not FLA<\/td>\n<\/tr>\n<tr>\n<td>Sizing the breaker from MCA<\/td>\n<td>Breaker must allow startup inrush \u2014 MCA-based breaker trips constantly<\/td>\n<td>Use MOCP for the breaker<\/td>\n<\/tr>\n<tr>\n<td>Ignoring derating factors<\/td>\n<td>Hot location or packed conduit reduces real ampacity<\/td>\n<td>Apply Table 310.15(B)(1) and (C)(1) corrections<\/td>\n<\/tr>\n<tr>\n<td>Assuming bigger breaker = better<\/td>\n<td>Breaker must protect the wire, not just the load<\/td>\n<td>Breaker \u2264 MOCP and \u2264 wire rating (non-motor circuits)<\/td>\n<\/tr>\n<tr>\n<td>Forgetting voltage drop<\/td>\n<td>Long runs lose voltage and generate heat<\/td>\n<td>Upsize one gauge beyond 50-100 ft<\/td>\n<\/tr>\n<tr>\n<td>Mixing 60\u00b0C and 75\u00b0C columns<\/td>\n<td>NM-B is limited to 60\u00b0C; THHN can use 75\u00b0C<\/td>\n<td>Use the column matching your insulation type<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Typical MCA Values for Common Equipment<\/h2>\n<table>\n<thead>\n<tr>\n<th>Equipment<\/th>\n<th>Typical MCA<\/th>\n<th>Wire Size (75\u00b0C copper)<\/th>\n<th>MOCP \/ Breaker<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>3 HP 230V motor<\/td>\n<td>~21.3 A<\/td>\n<td>12 AWG<\/td>\n<td>30 A<\/td>\n<\/tr>\n<tr>\n<td>5 HP 230V motor<\/td>\n<td>~26.3 A<\/td>\n<td>10 AWG<\/td>\n<td>40 A<\/td>\n<\/tr>\n<tr>\n<td>10 HP 460V motor<\/td>\n<td>~17.5 A<\/td>\n<td>12 AWG<\/td>\n<td>25-30 A<\/td>\n<\/tr>\n<tr>\n<td>3.5-ton heat pump<\/td>\n<td>~22-26 A<\/td>\n<td>10 AWG<\/td>\n<td>30-45 A<\/td>\n<\/tr>\n<tr>\n<td>5-ton AC unit<\/td>\n<td>~30-35 A<\/td>\n<td>8 AWG<\/td>\n<td>45-60 A<\/td>\n<\/tr>\n<tr>\n<td>Level 2 EV charger (48A)<\/td>\n<td>~60 A<\/td>\n<td>6 AWG<\/td>\n<td>60 A<\/td>\n<\/tr>\n<tr>\n<td>Electric water heater (4500W\/240V)<\/td>\n<td>~23.4 A<\/td>\n<td>10 AWG<\/td>\n<td>30 A<\/td>\n<\/tr>\n<tr>\n<td>200A residential service<\/td>\n<td>N\/A<\/td>\n<td>2\/0-3\/0 copper or 4\/0 aluminum<\/td>\n<td>200 A main<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>These are general figures \u2014 you should regularly refer to the nameplate of your unit. Also, when you are designing or enlarging your distribution installation, ensuring that the protection devices suit the cables is the kind of issue which certified equipment produced by a manufacturer ensuring the whole range addresses: <a href=\"https:\/\/huyuglobal.com\/blog\/how-many-watts-on-a-15-amp-circuit\/\" rel=\"nofollow\">understanding what a 15-amp circuit can actually carry<\/a> is a good starting point, and for replacement decisions our guide on <a href=\"https:\/\/huyuglobal.com\/blog\/how-to-tell-if-a-breaker-is-bad\/\" rel=\"nofollow\">how to tell if a breaker is bad<\/a> covers the inspection side of the story.<\/p>\n<h2>Frequently Asked Questions<\/h2>\n<h3>What is the 125 rule for breakers?<\/h3>\n<p>According to the 125% rule (NEC 210.19, 215.2, 430.22), conductors must be sized at 125% of the continuous load, or 125% of the motor&#8217;s full-load amps. In the case of the breaker, it can be seen that the same philosophy is entailed in the 80% rule, meaning that the breaker can only sustain 80% of its rating over time. Both are used to prevent overheating of the insulation. One example would be the case when the continuous load of 20A requires conductors of 25A rating (12 AWG) and a breaker rated 25A or 30A, while only 20A is used continuously in the circuit.<\/p>\n<h3>Can I use 1\/0 wire for 200 amp service?<\/h3>\n<p>1\/0 copper can carry 150A current at 75\u00b0 C. Thus, 1\/0 copper is not an appropriate option for 200A power. The right options include either 2\/0 copper, good for 175A, or 3\/0 copper of 200A. 4\/0 aluminum can also be considered as it is good for 180A. In the case of a power of less than 150A, 1\/0 copper can be successfully used. Consult a local inspector as NEC 310.12 states that service entrance has its own exceptions.<\/p>\n<h3>Will a 100 amp breaker accept 1\/0 wire?<\/h3>\n<p>In most cases, if the terminal of the breaker is okay for it, then yes\u2014most of the terminals for 100A breakers can take a wire sized up to 2\/0 copper or 4\/0 aluminum. However, a 100A breaker does not need a wire gauge of 1\/0; the only determining thing is the load as it is what tells us what wire size to use in this instance; as an example, when the load is only 70A, then 4 AWG (85A) is the right size. It is important to read the information given on the terminals of the breaker because it is what offers all the necessary information.<\/p>\n<h3>What is the 80% rule for circuit breakers?<\/h3>\n<p>The 80% rule (NEC 210.20(A), 215.3) indicates that a breaker is limited to carrying 80% of its rating for continuous loads. For example, a 15A breaker has a continuous current maximum of 12A, whereas a 20A breaker can carry 16A and a 100A breaker can carry 80A. There is a balance in the safety margin because it mirrors the 125% rule of current rating in conductors. The full breaker rating can be used for non-continuous loads since they do not follow this rule.<\/p>\n<h2>References<\/h2>\n<ol>\n<li><a href=\"https:\/\/www.nfpa.org\/codes-and-standards\/nfpa-70-standard-development\" rel=\"nofollow noopener\" target=\"_blank\">NFPA 70 \u2014 National Electrical Code (NEC), Articles 210, 215, 240, 310, 430, 440<\/a><\/li>\n<li><a href=\"https:\/\/www.osha.gov\/laws-regs\/regulations\/standardnumber\/1910\/1910.303\" rel=\"nofollow noopener\" target=\"_blank\">OSHA 1910.303 \u2014 Electrical Systems: General Requirements<\/a><\/li>\n<li><a href=\"https:\/\/www.mikeholt.com\/code_changes.php\" rel=\"nofollow noopener\" target=\"_blank\">Mike Holt \u2014 NEC Code Change Explanations (125% \/ 80% rules)<\/a><\/li>\n<li><a href=\"https:\/\/www.ecmweb.com\/\" rel=\"nofollow noopener\" target=\"_blank\">EC&amp;M Magazine \u2014 Conductor Sizing and MCA\/MOCP Applications<\/a><\/li>\n<li><a href=\"https:\/\/www.energystar.gov\/\" rel=\"nofollow noopener\" target=\"_blank\">ENERGY STAR \u2014 HVAC Installation and Circuit Sizing Guidance<\/a><\/li>\n<li><a href=\"https:\/\/www.nema.org\/\" rel=\"nofollow noopener\" target=\"_blank\">NEMA \u2014 Motor and Electrical Product Standards<\/a><\/li>\n<\/ol>\n<h2>Conclusion<\/h2>\n<p>Minimum circuit ampacity provides the lowest size of wire that can be used for different types of equipment. The number is calculated based on the 125% rule by taking the largest current load or motor load multiplied by 1.25 and adding other loads to get the calculation. The wire size is determined by the MCA but the size of the breaker is determined by a separate number called MOCP. Be aware of applicable features such as the 80% rule for continuous loads, derating for heat as well as conduit fill, and voltage drop on long runs to avoid the problems of underused wires as well as wasted copper. And when a replacement breaker or panel upgrade is part of the job, understanding <a href=\"https:\/\/huyuglobal.com\/blog\/how-much-to-replace-a-circuit-breaker\/\" rel=\"nofollow\">breaker replacement costs<\/a> and the differences between protection devices like <a href=\"https:\/\/huyuglobal.com\/blog\/what-is-mccb-and-mcb\/\" rel=\"nofollow\">MCBs and MCCBs<\/a> helps you plan the whole circuit \u2014 not just the wire.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>If you have just purchased a new air conditioning unit, an electric vehicle charger or a commercial oven, your technician might ask for the minimum circuit ampacity available from the nameplate. At that moment, you might find yourself looking at a number that seems meaningless to you. If you make a mistake, you can either [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3736,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_gspb_post_css":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-3735","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blogs"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/posts\/3735","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/comments?post=3735"}],"version-history":[{"count":2,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/posts\/3735\/revisions"}],"predecessor-version":[{"id":3741,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/posts\/3735\/revisions\/3741"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/media\/3736"}],"wp:attachment":[{"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/media?parent=3735"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/categories?post=3735"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/huyuglobal.com\/fr\/wp-json\/wp\/v2\/tags?post=3735"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}