arc breakers tripping

9 years ago

We have arc fault breakers and one of them keeps tripping, but we are unable to figure out cause. Sometimes it will do it and then go a week without tripping. Doesn't coincide to something we are plugging in or certain lights on. It is always the same breaker except occasionally at the same time the breaker for the dryer will also trip, but again this does not always happen and they are on completely separate breakers. When we had the house inspected before we bought it he said there was no main ground for the breaker box which we have not taken care of yet. Also there is no main shut off for the circuit box. Inspector said that there were multiple breakers that if turned off in combination would turn off the power completely. Any ideas on why nuisance tripping is happening and ways to fix ourselves vs calling electrician.

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Comments (3)

toxcrusadr
9 years ago
Sounds like a very complicated setup with some problems (i.e. not up to code). As an amateur I'd definitely recommend an electrician here. This may just be old installation, but from the sound of it, DIY may be how it got this way in the first place.

I don't know anything about arc fault breakers so I'm no help on your original question. But the box sounds like a mess. :-]
jemdandy
9 years ago
GFCI (ground fault circuit interrupters) work by sensing the difference between the outgoing current and return current. A typical fault limit is 5 miliamp difference. I am assuming that you have GFCI also known as GFI. Also, the return current should pass through the same hole in the breaker box as the outgoing current. Trouble may develop if the return path is somewhere else. In fact, anywhere one lead passes through a hole in metal, its partner lead should also pass through the same hole.

My first suspicion is your dryer. If it is a gas dryer, then a likely source for a sneak ground path is the motor or one of the controls. Relay coils can leak. If the motor is a capacitor start type, the start winding and its capacitor is suspect. If the dryer is by electric heaters, there is ample opportunity for heating elements to leak to the frame of the machine.

As a first check, measure the voltage between the appliance frame and a solid ground such as a metal water pipe. Clip on the meter and turn on the appliance while watching the meter. (An analog meter works better than a digital for this test since the voltage jolt may be too short for the digital to respond whereas the needle on an analog will jump or twitch enough for one to see it. However, if short is present and persists for more than a second, a digital meter will also have a response.) There should be no voltage. If you see a voltage, note its value. If it is line voltage, you have a very dangerous situation. Electrocution may result if a user touches a metal part of the machine and a ground such as a water faucet at the same time.

If you are not comfortable with using a volt-ohm meter, then get an electrician or technican who can trouble shoot your setup. The GFI is telling you that something is wrong. Of course, a GFI contains electronics and could fail, but GFIs from major manufactures have a good reliability record. Most manufacturers recommend that a GFI or ordinary circuit breaker should be replaced if it has opened a short.
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The gfci function is actually pretty easy to create. Both conductors are passed through a single toroid pickup coil. If the currents are equal the toroid has no induced voltage (the magnetic fields cancel) and nothing happens. If the fields do NOT cancel a triac is used to open the circuit. The sensitivity is as simple as how many turns on the toroid the sense winding has. More turns, more sensitive (less current imbalance). AFCI devices look for the high frequency noise generated by an arc. It will be at a multiple of 60 Hz, so filtering is not that hard. You need to consider that an arc generates electrical noise form the frequency of the voltage to light (the arc itself). The noise twice a cycle as the arc starts and stops with the 60 Hz voltage. Sense the noise, turn off the circuit. AFCI devices are not required to be as sensitive to current imbalances GFCI devices. Arcs do not trip a CB since the current does not exceed the CB rating. An arc from a break in the hot line is going to the hot line. TThe load on the circuit limits the currents, but the arc produces very high temperatures. A fault is when the hot shorts to the neutral (or ground) and the current exceeds the CB rating. Breakers for residential use are thermal-magnetic. The thermal is from heating of a section of conductor in the CB. This allows brief overloads to pass without tripping the CB (like 'slo-blo fuses). A motor starting or heating elemt turning on are allowed to operate since the current falls quickly and fails to trip the thermal overload. The magnetic occurs for 200%+ current and results in a very fast operation. The higher the current the more magnetic force is generated and the faster the breaker opens. At very high overloads the breaker opens in just a few milliseconds. People are not very good conductors. You are very unlikely to ever pull enough current through your body to trip the breaker.
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The arc-fault breaker will trip if the ground and neutral are shorted together. This could be caused by a drywall screw easily enough. It would also have been very easy for the electrician to check out and should have been part of the troubleshooting done before changing out the AFCI. The old wiring wouldn't be a problem just because it's old. It would have to have a problem to trip the AFCI. All the arc-fault breakers I've seen have a GFCI function built in. But, unless listed as a dual rated device the GFCI part trips at a higher level than a standard GFCI breaker or receptacle. The same things that trip a normal GFCI will trip an AFCI - except the 5 MA trip level. UNK
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mike_kaiser_gw
9 years ago
I would suggest reposting your message in the Electrical Wiring section.

arc breakers tripping

Comments (3)

toxcrusadr

jemdandy

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