# A/C keeps tripping breaker **URL:** \ **Category:** Factual Questions\ **Created:** [September 5, 2017, 9:44pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594 "2017-09-05T21:44:40Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 5, 2017, 9:44pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/1 "2017-09-05T21:44:40Z")
We have a portable air conditioner that, according to specs, draws 11.2 amps. There is a 20 A arc-fault circuit breaker in our brand new circuit breaker panel for the circuit it’s on. Things on the circuit are two clock radios (always on), a desk lamp (always off), and the overhead light (which is kept off when the a/c is running). It seems to me that the breaker shouldn’t be tripping. But… ISTR a thread about ‘Why aren’t you supposed to use extension cords with air conditioners?’ Since the a/c plug is large, and one clock radio and the desk lamp are on the outlet. I use a 13 A (or is it 15 A?) extension from another outlet, and plug the a/c into that. It gets a warm, but not hot. I’ll also note that the a/c seems not to trip the breaker as often when the fan is on low. Never had this problem when we had a 30 A fuze screwed into the fuze box! 😛 So the questions are: 1. If the a/c draws 11.2 A, why is it tripping a 20 A breaker with only two clock radios (radios off, clocks on) drawing power? 2. Since the extension is warm, it must be resisting. Could the added resistance of the extension be overdrawing the breaker? 3. How many times can a circuit breaker be tripped before it needs to be replaced? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 5, 2017, 9:50pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/2 "2017-09-05T21:50:31Z")
Sometimes breakers are over-sensitive. First step is to switch it with a new/different one to see if it keeps happening. ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [September 5, 2017, 9:54pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/3 "2017-09-05T21:54:05Z")
Does it pop the breaker as soon as the compressor clicks on? Inrush current could be a bit higher. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 5, 2017, 9:59pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/4 "2017-09-05T21:59:52Z")
> [@TriPolar](#): > > Sometimes breakers are over-sensitive. First step is to switch it with a new/different one to see if it keeps happening. It doesn’t _look_ like I can simply pop the breaker out and pop in a new one. It looks like I have to unscrew the door and faceplate (?) of the breaker board to get at the breakers. I haven’t looked that closely, though. (FWIW, it’s a Siemens panel.) > [@snfaulkner](#): > > Does it pop the breaker as soon as the compressor clicks on? Inrush current could be a bit higher. No, it will run for a while before it stops. And it didn’t trip the breaker again yesterday after I reset it. (OOH, the extension was warm. OTOH, we didn’t keep it on very long after that.) That’s why I was wondering about the extension. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 5, 2017, 10:01pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/5 "2017-09-05T22:01:11Z")
I’d wager the one of the motors is tripping the arc fault portion of the arc fault breaker. If it were in my house I’d probably take a reading and see how many amps it’s actually pulling to make sure the breaker or the AC isn’t broken, then swap out the breaker for a regular one. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 5, 2017, 10:02pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/6 "2017-09-05T22:02:28Z")
Arc fault breakers and certain types of electric motors do not play well together. I had a house where an outside outlet was connected to an arc fault protected bedroom circuit (it had a GFCI as well) and when I would plug in an electric lawnmower the breaker would trip every time the motor started. Possible your A/C compressor or fan motor is causing a similar problem: a voltage/current profile that looks like an arc. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 5, 2017, 10:03pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/7 "2017-09-05T22:03:34Z")
> [@Johnny\_L.A](#): > > It doesn’t _look_ like I can simply pop the breaker out and pop in a new one. It looks like I have to unscrew the door and faceplate (?) of the breaker board to get at the breakers. I haven’t looked that closely, though. (FWIW, it’s a Siemens panel.) Yes, you have to take off the face plate. Then they just pop in and out and you take off the hot wire and put it on the new one. It’s very easy to do, you don’t need to come near the bus bars. If you’re nervous just get a flashlight and throw the main breaker to do the switch. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 5, 2017, 10:04pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/8 "2017-09-05T22:04:26Z")
> [@Johnny\_L.A](#): > > It doesn’t _look_ like I can simply pop the breaker out and pop in a new one. It looks like I have to unscrew the door and faceplate (?) of the breaker board to get at the breakers. I haven’t looked that closely, though. (FWIW, it’s a Siemens panel.) Yes, you would have to remove the faceplate (usually four screw around the edge), the door stays put, just closed so it doesn’t swing around. However, if you have to ask, I’d suggest you don’t. Once you open that, it’s a whole 'nother can of worms. Now you’ve got a lot of exposed wiring and, even if you shut of the main breaker, there’s still things in there that are live. However, find someone to show you, it’s not hard, but can be a bit panic inducing that first time you open it and all the wires come springing out. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 5, 2017, 10:05pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/9 "2017-09-05T22:05:36Z")
> [@Marvin\_the\_Martian](#): > > Arc fault breakers and certain types of electric motors do not play well together. I had a house where an outside outlet was connected to an arc fault protected bedroom circuit (it had a GFCI as well) and when I would plug in an electric lawnmower the breaker would trip every time the motor started. Possible your A/C compressor or fan motor is causing a similar problem: a voltage/current profile that looks like an arc. That’s not great news, I have to use arc fault breakers for everything. My air compressor, dust collector, and other heavy power tools may become a problem since I want to move them into the new basement in the addition which has flat floors and no support columns. ---
**Author:** ![Crazyhorse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crazyhorse/32/31_2.png) [@Crazyhorse](https://boards.straightdope.com/u/Crazyhorse)\ **Post date:** [September 5, 2017, 10:05pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/10 "2017-09-05T22:05:49Z")
> [@Johnny\_L.A](#): > > It doesn’t _look_ like I can simply pop the breaker out and pop in a new one. It looks like I have to unscrew the door and faceplate (?) of the breaker board to get at the breakers. I haven’t looked that closely, though. (FWIW, it’s a Siemens panel.) > > No, it will run for a while before it stops. And it didn’t trip the breaker again yesterday after I reset it. (OOH, the extension was warm. OTOH, we didn’t keep it on very long after that.) That’s why I was wondering about the extension. Wouldn’t it be possible to unplug the other clock or whatever and plug the AC directly into the outlet to test if it still happens? FWIW I discovered that a portable AC that has had the exhaust hose extended beyond specs (or crimped or otherwise blocked) will cause the breaker to trip. For whatever reason if it can’t exhaust the hot air efficiently enough it pulls a higher electrical load. An expert may know why, but I am 100% certain that is the case with one particular AC, exhaust hose, and breaker box that I am personally familiar with. If that isn’t the case I agree there’s a good chance you have a trigger happy breaker switch and replacing it should be fairly cheap and easy. If you’re in any way not sure of what that entails though, call an electrician. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 5, 2017, 10:19pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/11 "2017-09-05T22:19:07Z")
> [@Crazyhorse](#): > > Wouldn’t it be possible to unplug the other clock or whatever and plug the AC directly into the outlet to test if it still happens? We’re supposed to have one more hot day tomorrow, and that was my planned next experiment. > [@Crazyhorse](#): > > FWIW I discovered that a portable AC that has had the exhaust hose extended beyond specs (or crimped or otherwise blocked) will cause the breaker to trip. For whatever reason if it can’t exhaust the hot air efficiently enough it pulls a higher electrical load. Interesting you should say that. The exhaust hose is extended pretty far. Not such that it is completely extended, but far enough that it heats up the room. There are no kinks in it. > [@Crazyhorse](#): > > If you’re in any way not sure of what that entails though, call an electrician. Sounds easy enough. I never had to replace breakers, growing up. And this house had a fuze box. I guess I’d always just assumed they pop in and out without having to remove anything, in the same way you just open a door to replace a fuze. I need to contact the electrician again. How long has it been since we had the electrical work done? And he still hasn’t gotten PSE to come out and sign off on it. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [September 5, 2017, 10:48pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/12 "2017-09-05T22:48:29Z")
> [@TriPolar](#): > > That’s not great news, I have to use arc fault breakers for everything. My air compressor, dust collector, and other heavy power tools may become a problem since I want to move them into the new basement in the addition which has flat floors and no support columns. Yes, not good news, you will have them tripping over everything. They are good for specific things, not everything. ---
**Author:** ![ThisSpaceForRent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thisspaceforrent/32/345_2.png) [@ThisSpaceForRent](https://boards.straightdope.com/u/ThisSpaceForRent)\ **Post date:** [September 5, 2017, 11:18pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/13 "2017-09-05T23:18:45Z")
My guess is a faulty start capacitor…trying to draw more than the 11.2 amps as specs say it should. ymmv ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [September 6, 2017, 12:40am UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/14 "2017-09-06T00:40:56Z")
How quickly does the AC trip the breaker? If it’s a reasonably short time, can you try plugging the AC directly into the same outlet? If it keeps running, then you’ve pretty well identified the extension cord as the culprit. Is the cord fully unwound? High-draw motor loads and coiled extension cords can cause all sorts of electrical oddities. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 6, 2017, 12:58am UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/15 "2017-09-06T00:58:30Z")
I glanced at my copy of the 2011 NEC to look at the requirements for AFCI breakers and it made mention of stand alone A/C units being required to have their own AFCI (or maybe it was GFCI) built into the plug. If yours has that, that could also be part of the issue. I will say that I don’t know if this happens for AFCI, but I can say for sure that when GFCIs are daisy chained, they will trip each other. Even if this doesn’t happen with AFCI, your cord and your breaker could be combination AFCI/GFCI and be causing an issue. Also, I don’t know if this is still an issue (GFCIs tripping other GFCIs), just that it used to be. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [September 7, 2017, 12:15am UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/16 "2017-09-07T00:15:33Z")
> [@Johnny\_L.A](#): > > It doesn’t _look_ like I can simply pop the breaker out and pop in a new one. It looks like I have to unscrew the door and faceplate (?) of the breaker board to get at the breakers. I haven’t looked that closely, though. (FWIW, it’s a Siemens panel.) Warning! Make sure you replace it with one of the same amperage. Breakers are all about the same size, so you could easily replace a 15A one with a 20A one, and connect the wire to that. But the wire hasn’t changed, it’s still only 15A size, so it can heat up in the wall and start a fire. Don’t do that. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 7, 2017, 1:29am UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/17 "2017-09-07T01:29:12Z")
It wasn’t hot enough today to run the a/c. I might not get to run it anytime soon. It seems like sometime in September, the climate says, ‘OK, it’s Autumn now,’ and then it cools down until June or July. Now that we have a breaker board, I’m thinking of having an a/c installed in the living room with a dedicated line. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 7, 2017, 1:36am UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/18 "2017-09-07T01:36:52Z")
If you’re just looking to troubleshoot it, you can still run it. Unless it’s so cold in your house that the t-stat won’t let it kick on. Also, if it is getting cold, you can leave the exhaust tube inside so the hot air doesn’t get pushed out. If you do that, instead of cooling off the room, it’ll slightly warm it. It’ll act like a dehumdifier. Speaking of which, be mindful of what it does with the condensation. If it runs a liquid line out with the exhaust, you’d have to have a bucket. If it evaporates it and sends it out as vapor, make sure it’s not running for too long and maybe don’t aim the exhaust directly at anything. But just for troubleshooting, you can run it for a few minutes here and there. Personally, I’d rather get the problem figured out now rather than forgetting about it until the first time it’s 90 out next summer. And if all you want to do is grab an amp or watt reading from it or replace a breaker and see if that fixes anything, you’ll probably only need to run it for a few minutes anyways. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [September 7, 2017, 3:26pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/19 "2017-09-07T15:26:27Z")
Many years ago I had an electrical heat add-on to my oil furnace. It started tripping the main house breaker. As time went on, it tripped it more frequently, so I gave up on it. then later, my main breaker started tripping on its own. The electrician was looking to replace the main breaker - instead, he found that the connection from the power mains was loose enough that he could grab the wire and wiggle in back and forth (with the power off!!!) The copper had deformed over time. So the first thing to look at is that all the connections to the problem breaker are tight - presumably whatever point the wires are screwed down. if you don’t know what you are looking at, get an electrician to have a look. ---
**Author:** ![dougrb](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dougrb](https://boards.straightdope.com/u/dougrb)\ **Post date:** [September 7, 2017, 4:18pm UTC](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594/20 "2017-09-07T16:18:06Z")
> [@Johnny\_L.A](#): > > 1. How many times can a circuit breaker be tripped before it needs to be replaced? I know this is derailing the thread a bit, but fond memories from my college days when I worked at Square D Company. One of my jobs was to subject circuit breakers to direct short circuits of up to 20,000 amps and then test that they still functioned under normal overloads from 135% to 200%. They had 1 hour to trip at 135% and smoke was rolling out of them the entire time. [Next page](https://boards.straightdope.com/t/a-c-keeps-tripping-breaker/795594.md?page=2)