{"id":2221,"date":"2025-11-28T02:25:48","date_gmt":"2025-11-28T02:25:48","guid":{"rendered":"https:\/\/cnkuangya.com\/?p=2221"},"modified":"2026-04-24T16:00:44","modified_gmt":"2026-04-24T08:00:44","slug":"can-i-replace-my-20a-breaker-with-a-25a-over-rate-or-below-rate","status":"publish","type":"post","link":"https:\/\/cnkuangya.com\/ja\/blog\/can-i-replace-my-20a-breaker-with-a-25a-over-rate-or-below-rate\/","title":{"rendered":"20A\u306e\u30d6\u30ec\u30fc\u30ab\u30fc\u309225A\u306b\u4ea4\u63db\u3067\u304d\u307e\u3059\u304b\uff1f| \u30d6\u30ec\u30fc\u30ab\u30fc\u309225A\u306b\u4ea4\u63db\u3067\u304d\u307e\u3059\u304b\uff1f"},"content":{"rendered":"

Can I Replace My 20A Breaker with a 25A? (A KUANGYA Engineer’s Urgent ‘NO’)<\/h2>\n\n\n\n

\u3088\u304f\u3042\u308b\u8a71\u3060\u3002\u3042\u306a\u305f\u306f\u30ac\u30ec\u30fc\u30b8\u306e\u4f5c\u696d\u5834\u3067\u3001\u4f55\u9031\u9593\u3082\u524d\u304b\u3089\u8a08\u753b\u3057\u3066\u3044\u305f\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306b\u3088\u3046\u3084\u304f\u53d6\u308a\u304b\u304b\u308d\u3046\u3068\u3057\u3066\u3044\u308b\u3002\u65b0\u3057\u3044\u3001\u3088\u308a\u5f37\u529b\u306a\u30c6\u30fc\u30d6\u30eb\u30bd\u30fc\u3092\u8d77\u52d5\u3055\u305b\u3001\u3044\u304f\u3064\u304b\u306e\u30ab\u30c3\u30c8\u3092\u884c\u3063\u305f\u3001\u305d\u3057\u3066......\u6697\u95c7\u3002\u96fb\u6c17\u304c\u6d88\u3048\u3001\u30ce\u30b3\u30ae\u30ea\u304c\u30d4\u30bf\u30ea\u3068\u6b62\u307e\u308b\u3002\u96fb\u6c17\u30d1\u30cd\u30eb\u307e\u3067\u6b69\u3044\u3066\u884c\u304d\u3001\u30c8\u30ea\u30c3\u30d7\u3057\u305f20A\u306e\u30d6\u30ec\u30fc\u30ab\u30fc\u3092\u843d\u3068\u3057\u3066\u3001\u3082\u3046\u4e00\u5ea6\u3084\u3063\u3066\u307f\u308b\u3002\u6570\u5206\u5f8c\u3001\u307e\u305f\u540c\u3058\u3053\u3068\u304c\u8d77\u3053\u3063\u305f\u3002.<\/p>\n\n\n\n

A wave of frustration hits. A quick search online suggests a “simple” solution: “Just swap the 20A breaker for a 25A one. It will let more power through.” It seems logical, almost too easy.<\/p>\n\n\n\n

\u306e\u30b7\u30cb\u30a2\u30fb\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u30fb\u30a8\u30f3\u30b8\u30cb\u30a2\u3068\u3057\u3066 \u30af\u30a2\u30f3\u30cb\u30e3<\/a> \u96fb\u6c17\u30b7\u30b9\u30c6\u30e0\u306e\u8a2d\u8a08\u3068\u30c8\u30e9\u30d6\u30eb\u30b7\u30e5\u30fc\u30c6\u30a3\u30f3\u30b0\u306b15\u5e74\u4ee5\u4e0a\u643a\u308f\u3063\u3066\u304d\u305f\u79c1\u306b\u3068\u3063\u3066\u3001\u3053\u306e\u63d0\u6848\u306b\u5bfe\u3059\u308b\u56de\u7b54\u306f\u3001\u5373\u5ea7\u306b\u3001\u660e\u78ba\u306b\u3001\u305d\u3057\u3066\u7dca\u6025\u306e\u3082\u306e\u3067\u3042\u308b\u3002 \u3044\u3044\u3048\u3002.<\/strong><\/p>\n\n\n\n

This isn’t a matter of gatekeeping or being overly cautious. It’s a matter of fundamental electrical safety that stands between a functioning workshop and a potential tragedy. That tripping breaker isn’t the problem; it’s a critical warning sign. It\u2019s doing its job perfectly. “Upgrading” it without understanding the system it protects is like taking the battery out of a smoke detector because the alarm is annoying.<\/p>\n\n\n\n

\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001\u56de\u8def\u4fdd\u8b77\u306e\u80cc\u5f8c\u306b\u3042\u308b\u5de5\u5b66\u7684\u306a\u539f\u7406\u3092\u8aac\u660e\u3057\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30df\u30b9\u30de\u30c3\u30c1\u304c\u3082\u305f\u3089\u3059\u81f4\u547d\u7684\u306a\u30ea\u30b9\u30af\u3092\u63a2\u308a\u3001\u4ee5\u4e0b\u306e\u3053\u3068\u3092\u6c7a\u5b9a\u3059\u308b\u305f\u3081\u306e\u5c02\u9580\u7684\u306a\u65b9\u6cd5\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u8aac\u660e\u3057\u307e\u3059\u3002 \u6b63\u3057\u3044\u30a2\u30f3\u30da\u30a2\u306e\u9078\u3073\u65b9<\/strong> \u3042\u306a\u305f\u306e\u30cb\u30fc\u30ba\u306b\u5408\u3063\u305f\u5b9a\u683c\u30d6\u30ec\u30fc\u30ab\u30fc\u306b\u89e6\u308c\u308b\u524d\u306b\u3001\u3053\u308c\u3092\u8aad\u3093\u3067\u304f\u3060\u3055\u3044\u3002.<\/p>\n\n\n\n

\u7b2c1\u90e8\uff1a\u30b5\u30fc\u30ad\u30c3\u30c8\u306e\u89e3\u5256-\u4fe1\u983c\u306e\u4e0a\u306b\u6210\u308a\u7acb\u3064\u30b7\u30b9\u30c6\u30e0<\/h3>\n\n\n\n

\u30d6\u30ec\u30fc\u30ab\u30fc\u3092\u4ea4\u63db\u3059\u308b\u3053\u3068\u304c\u306a\u305c\u5371\u967a\u306a\u306e\u304b\u3092\u7406\u89e3\u3059\u308b\u306b\u306f\u3001\u307e\u305a\u96fb\u6c17\u90e8\u54c1\u3092\u500b\u3005\u306e\u90e8\u54c1\u3068\u3057\u3066\u8003\u3048\u308b\u306e\u3092\u3084\u3081\u3066\u3001\u30d0\u30e9\u30f3\u30b9\u306e\u53d6\u308c\u305f\u30b7\u30b9\u30c6\u30e0\u3068\u3057\u3066\u3068\u3089\u3048\u308b\u5fc5\u8981\u304c\u3042\u308b\u3002\u5bb6\u5ead\u5185\u306e\u3059\u3079\u3066\u306e\u56de\u8def\u306f\u3001\u4e09\u4f4d\u4e00\u4f53\u3068\u306a\u3063\u305f\u90e8\u54c1\u3067\u69cb\u6210\u3055\u308c\u3066\u3044\u307e\u3059\uff1a<\/p>\n\n\n\n

    \n
  1. \u8ca0\u8377\u3060\uff1a<\/strong> \u3053\u308c\u306f\u96fb\u529b\u3092\u6d88\u8cbb\u3059\u308b\u6a5f\u5668\u3067\u3042\u308b\u3002\u30c6\u30fc\u30d6\u30eb\u30bd\u30fc\u3001\u96fb\u6c17\u81ea\u52d5\u8eca\u306e\u5145\u96fb\u5668\u3001\u96fb\u5b50\u30ec\u30f3\u30b8\u3001\u30c6\u30ec\u30d3\u306a\u3069\u3067\u3059\u3002\u8ca0\u8377\u306f\u3001\u56de\u8def\u304b\u3089\u3069\u308c\u3060\u3051\u306e\u96fb\u6d41\uff08\u30a2\u30f3\u30da\u30a2\u5358\u4f4d\u3067\u6e2c\u5b9a\uff09\u3092\u5f15\u304d\u51fa\u3059\u5fc5\u8981\u304c\u3042\u308b\u304b\u3092\u6c7a\u5b9a\u3059\u308b\u3082\u306e\u3067\u3042\u308b\u3002.<\/li>\n\n\n\n
  2. \u5c0e\u4f53\uff08\u30ef\u30a4\u30e4\u30fc\uff09\uff1a<\/strong> \u3053\u308c\u304c\u96fb\u6c17\u306e\u901a\u308a\u9053\u3067\u3059\u3002\u58c1\u306e\u5185\u5074\u306b\u96a0\u308c\u3066\u3044\u308b\u3053\u308c\u3089\u306e\u96fb\u7dda\u306b\u306f\u7279\u5b9a\u306e\u592a\u3055\uff08\u30b2\u30fc\u30b8\uff09\u304c\u3042\u308a\u3001\u904e\u71b1\u3059\u308b\u3053\u3068\u306a\u304f\u5b89\u5168\u306b\u96fb\u6d41\u3092\u6d41\u3059\u3053\u3068\u304c\u3067\u304d\u308b\u91cf\u304c\u6c7a\u3081\u3089\u308c\u3066\u3044\u307e\u3059\u3002.<\/li>\n\n\n\n
  3. \u904e\u96fb\u6d41\u4fdd\u8b77\u88c5\u7f6e\uff08\u30d6\u30ec\u30fc\u30ab\u30fc\u307e\u305f\u306f\u30d2\u30e5\u30fc\u30ba\uff09\uff1a<\/strong> \u3053\u308c\u304c\u30bb\u30fc\u30d5\u30c6\u30a3\u30fc\u30ac\u30fc\u30c9\u3060\u3002\u305d\u306e\u552f\u4e00\u306e\u4ed5\u4e8b\u306f \u30b3\u30f3\u30c0\u30af\u30bf\u30fc<\/strong>. .\u96fb\u7dda\u3092\u6d41\u308c\u308b\u96fb\u6d41\u3092\u5e38\u6642\u76e3\u8996\u3057\u3066\u3044\u308b\u3002\u305d\u306e\u96fb\u6d41\u304c\u77ed\u6642\u9593\u3067\u3082\u5b89\u5168\u30ec\u30d9\u30eb\u3092\u8d85\u3048\u308b\u3068\u3001\u30d6\u30ec\u30fc\u30ab\u30fc\u304c\u843d\u3061\u3066\u96fb\u6e90\u304c\u906e\u65ad\u3055\u308c\u3001\u96fb\u7dda\u304c\u5371\u967a\u306a\u904e\u71b1\u72b6\u614b\u306b\u306a\u308b\u306e\u3092\u9632\u3050\u3002.<\/li>\n<\/ol>\n\n\n\n

    \u914d\u7ba1\u30b7\u30b9\u30c6\u30e0\u306e\u3088\u3046\u306a\u3082\u306e\u3060\u3068\u8003\u3048\u3066\u307b\u3057\u3044\u3002\u8ca0\u8377\u306f\u86c7\u53e3\u3001\u30ef\u30a4\u30e4\u30fc\u306f\u305d\u308c\u306b\u63a5\u7d9a\u3055\u308c\u305f\u30d1\u30a4\u30d7\u3001\u30d6\u30ec\u30fc\u30ab\u30fc\u306f\u305d\u306e\u30d1\u30a4\u30d7\u306b\u3042\u308b\u5727\u529b\u5b89\u5168\u5f01\u3067\u3059\u300260PSI\u306e\u6c34\u5727\u306b\u5bfe\u5fdc\u3059\u308b\u5b9a\u683c\u306e\u30d1\u30a4\u30d7\u304c\u3042\u308c\u3070\u300155PSI\u3067\u958b\u653e\u3059\u308b\u5b89\u5168\u5f01\u3092\u53d6\u308a\u4ed8\u3051\u308b\u3002\u30b5\u30fc\u30b8\u304c\u767a\u751f\u3057\u305f\u5834\u5408\u3001\u30d0\u30eb\u30d6\u304c\u958b\u304d\u3001\u30d1\u30a4\u30d7\u306e\u7834\u88c2\u3092\u9632\u3050\u3002.<\/p>\n\n\n\n

    Now, imagine replacing that 55 PSI valve with a 100 PSI one because the faucet you want to use requires more pressure than the old valve would allow. The valve won’t trip anymore, but the pipe is now subjected to pressure it was never designed for. It\u2019s a ticking time bomb. Swapping a 20A breaker for a 25A one does the exact same thing to the wires hidden in your walls.<\/p>\n\n\n\n

    \n

    \u91cd\u8981\u306a\u53ce\u7a6b<\/strong> \u30b5\u30fc\u30ad\u30c3\u30c8\u30d6\u30ec\u30fc\u30ab\u30fc\u306e\u5b9a\u683c\u96fb\u6d41\u306f\u3001\u3069\u308c\u3060\u3051\u306e\u96fb\u529b\u3092\u5f97\u3089\u308c\u308b\u304b\u3068\u3044\u3046\u3053\u3068\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u3002\u58c1\u306e\u4e2d\u306e\u96fb\u7dda\u306e\u30b5\u30a4\u30ba\u306b\u5408\u308f\u305b\u305f\u5b89\u5168\u5b9a\u683c\u3067\u3059\u3002\u30d6\u30ec\u30fc\u30ab\u30fc\u306f\u3001\u30ef\u30a4\u30e4\u30fc\u304c\u6545\u969c\u3059\u308b\u524d\u306b\u30d6\u30ec\u30fc\u30ab\u30fc\u304c\u6545\u969c\u3059\u308b\u3088\u3046\u306b\u3001\u5e38\u306b\u30c1\u30a7\u30fc\u30f3\u306e\u4e2d\u3067\u6700\u3082\u5f31\u3044\u30ea\u30f3\u30af\u3067\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002.<\/p>\n<\/blockquote>\n\n\n\n

    \u30d1\u30fc\u30c82\uff1a\u81f4\u547d\u7684\u306a\u6545\u969c\u306e\u9023\u9396\uff1a\u30b5\u30a4\u30ba\u8d85\u904e\u304c\u706b\u707d\u306e\u539f\u56e0\u3068\u306a\u308b\u7406\u7531<\/h3>\n\n\n\n

    So, what actually happens when a wire is forced to carry more current than it\u2019s rated for? The result isn’t a small problem; it’s the primary cause of electrical fires. According to the Electrical Safety Foundation International (ESFI), around 51,000 electrical fires occur in U.S. homes each year, causing over $1.3 billion in property damage . Many of these are preventable and start inside the walls.<\/p>\n\n\n\n

    25A\u306e\u30d6\u30ec\u30fc\u30ab\u30fc\u304c\u3042\u308b\u56de\u8def\u306b25A\u306e\u8ca0\u8377\u3092\u304b\u3051\u308b\u304c\u3001\u914d\u7dda\u306f20A\u5b9a\u683c\uff08\u901a\u5e3812\u30b2\u30fc\u30b8\u306e\u30ef\u30a4\u30e4\u30fc\uff09\u3057\u304b\u306a\u3044\u5834\u5408\u3001\u30d6\u30ec\u30fc\u30ab\u30fc\u306f\u6e80\u8db3\u3059\u308b\u3002\u30d6\u30ec\u30fc\u30ab\u30fc\u306f25A\u3092\u898b\u3066\u3001\u305d\u308c\u3092\u51e6\u7406\u3067\u304d\u308b\u3053\u3068\u3092\u77e5\u308a\u307e\u3059\u3002\u3057\u304b\u3057\u3001\u30ef\u30a4\u30e4\u30fc\u306f\u305d\u3046\u306f\u3044\u304b\u306a\u3044\u3002\u30c8\u30fc\u30b9\u30bf\u30fc\u306e\u30a8\u30ec\u30e1\u30f3\u30c8\u306e\u3088\u3046\u306b\u71b1\u3092\u6301\u3061\u59cb\u3081\u308b\u3002\u3053\u308c\u304c\u60b2\u60e8\u306a\u9023\u9396\u3092\u5f15\u304d\u8d77\u3053\u3059\uff1a<\/p>\n\n\n\n

      \n
    1. \u65ad\u71b1\u6750\u306e\u5185\u8a33\uff1a<\/strong> \u9285\u7dda\u306e\u5468\u56f2\u306b\u65bd\u3055\u308c\u305fPVC\u7d76\u7e01\u306b\u306f\u3001\u7279\u5b9a\u306e\u6e29\u5ea6\u5b9a\u683c\u304c\u3042\u308a\u307e\u3059\u3002\u30ef\u30a4\u30e4\u30fc\u304c\u9ad8\u6e29\u306b\u306a\u308b\u306b\u3064\u308c\u3066\u3001\u3053\u306e\u7d76\u7e01\u4f53\u306f\u67d4\u3089\u304b\u304f\u306a\u308a\u3001\u6eb6\u3051\u3001\u3055\u3089\u306b\u306f\u71c3\u3048\u3066\u3057\u307e\u3044\u3001\u751f\u304d\u3066\u3044\u308b\u5c0e\u4f53\u304c\u9732\u51fa\u3059\u308b\u3053\u3068\u3082\u3042\u308a\u307e\u3059\u3002.<\/li>\n\n\n\n
    2. \u30a2\u30fc\u30af\u30d5\u30a9\u30eb\u30c8\uff1a<\/strong> Once the live conductor is exposed, it can make contact with a neutral wire, a ground wire, a metal electrical box, or even a stray screw or nail in the wall. This creates a powerful, high-temperature electrical discharge known as an arc fault. An arc fault is essentially a continuous spark that can reach temperatures hot enough to ignite surrounding wood studs, insulation, and drywall in an instant. This is like “inserting a live toaster element into your wall.” <\/li>\n\n\n\n
    3. \u706b\u4e8b\u3060\uff1a<\/strong> The breaker will not protect against this! Because the current of an arc fault can sometimes be lower than the breaker’s trip rating, the oversized 25A breaker may never trip. It will continue to feed power to the fault, fueling the fire as it grows within your walls, often undetected until it’s far too late.<\/li>\n<\/ol>\n\n\n\n

      \u3053\u306e\u30d5\u30ed\u30fc\u30c1\u30e3\u30fc\u30c8\u306f\u5371\u967a\u306a\u30b7\u30fc\u30b1\u30f3\u30b9\u3092\u793a\u3057\u3066\u3044\u308b\uff1a<\/p>\n\n\n\n

      \"\"<\/p>\n\n\n\n

      <\/p>\n\n\n\n

      This isn\u2019t just a theoretical risk. It violates fundamental safety codes written to prevent exactly this scenario. The National Electrical Code (NEC) Section 240.4 states plainly that “conductors…shall be protected against overcurrent in accordance with their ampacities.” Bypassing this rule by installing an oversized breaker is not a clever workaround; it is creating a serious, code-violating fire hazard.<\/p>\n\n\n\n

      \n

      \u91cd\u8981\u306a\u53ce\u7a6b<\/strong> \u30aa\u30fc\u30d0\u30fc\u30b5\u30a4\u30ba\u306e\u30d6\u30ec\u30fc\u30ab\u30fc\u306f\u3001\u56de\u8def\u306e\u4e3b\u8981\u306a\u5b89\u5168\u6a5f\u80fd\u3092\u7121\u52b9\u306b\u3057\u307e\u3059\u3002\u58c1\u306e\u914d\u7dda\u304c\u904e\u71b1\u3057\u3001\u4fdd\u8b77\u7d76\u7e01\u304c\u6eb6\u3051\u3066\u3001\u96fb\u6c17\u706b\u707d\u306e\u4e3b\u306a\u539f\u56e0\u3067\u3042\u308b\u30a2\u30fc\u30af\u30d5\u30a9\u30eb\u30c8\u304c\u767a\u751f\u3057\u307e\u3059\u3002.<\/p>\n<\/blockquote>\n\n\n\n

      \u30d1\u30fc\u30c83\uff1a\u30d7\u30ed\u306e\u57fa\u6e96\uff1a\u6b63\u3057\u3044\u30a2\u30f3\u30da\u30a2\u5b9a\u683c\u306e\u9078\u3073\u65b9<\/h3>\n\n\n\n

      Now that you understand the danger, let\u2019s focus on the correct engineering approach. The question isn’t “how can I force my circuit to handle more power?” but rather, “what does my load \u672c\u5f53\u306b<\/em> require, and what kind of circuit is needed to provide that power safely?”<\/p>\n\n\n\n

      \u4e3b\u306a\u30c8\u30d4\u30c3\u30af\u306f\u3053\u308c\u3060\uff1a \u8ca0\u8377\u304c20A\u306e\u5834\u5408\u3001\u3069\u306e\u3088\u3046\u306b\u30d6\u30ec\u30fc\u30ab\u30fc\u3092\u9078\u3079\u3070\u3044\u3044\u306e\u304b\uff1f<\/strong> \u305d\u306e\u7b54\u3048\u306f\u3001\u3042\u308b\u91cd\u8981\u306a\u6982\u5ff5\u306b\u304b\u304b\u3063\u3066\u3044\u308b\uff1a \u9023\u7d9a\u8ca0\u8377\u3068\u975e\u9023\u7d9a\u8ca0\u8377\u3002.<\/strong><\/p>\n\n\n\n

      The National Electrical Code (NEC) in Article 100 defines a “continuous load” as any load where the maximum current is expected to continue for 3\u6642\u9593\u4ee5\u4e0a.<\/strong> <\/p>\n\n\n\n