Circuit Breaker No Longer Stopping Current to HPWC

[Rockster]

Our MS was recently in the body shop for some repair to the rear end. Since we weren't going to need the HPWC during this time, I threw the circuit breaker so the HPWC wouldn't be energized. When I threw the breaker, however, the green lights on the HPWC stayed illuminated. Now that we have the MS again, I verified that the HPWC delivers full power, even with the circuit breaker tripped. (I'm certain the breaker worked before because I've used it in the past to kill power to the HPWC.)

I'm going to call an electrician to look things over and in the interim I've switched to my mobile charger and NEMA 14-50 but I'm very curious. Can a breaker fail in such a manner as to continue powering its circuit or is the problem likely somewhere else in the panel?

 

[FlasherZ]

It is extremely rare, but was an occasional problem known in Federal-Pacific (FPE) and Zinsco breakers in particular.

Circuit breakers aren't "tripped" when you turn them off - they "trip" when exposed to enough overcurrent that they shut off the flow automatically.

If you have a volt-meter, one way to check the breaker's operation is to take the front of the panel off, then measure the voltage at the two screw terminals while the breaker is off. If there is 240V found on those terminals while off, it's a bad sign. If there is not 240V, then you have found the wrong breaker.

Can you upload a pic of the panel / breaker in questions?

 

[Rockster]

I just went out to take a picture and discovered that I was tripping the wrong breaker. I was tripping a double (bridged?) breaker pair, each of which is labeled "50," thinking that was the 100-amp circuit. In fact, the HPWC is on a pair, each of which is marked "100."

Clearly I don't get this stuff.

 

[mikeash]

The question then is, what exactly did you turn off, and why didn't you notice that it stopped working? :biggrin:

 

[FlasherZ]

I just went out to take a picture and discovered that I was tripping the wrong breaker. I was tripping a double (bridged?) breaker pair, each of which is labeled "50," thinking that was the 100-amp circuit. In fact, the HPWC is on a pair, each of which is marked "100."

Clearly I don't get this stuff.

No worries... 240V breakers are called "double pole", and the handles are connected together because you're turning off two different "hot" conductors vs. just one with 120V (lights and appliance receptacles), and they have to be switched off at one time. You never add up breaker handle capacities, they're always marked with the current they'll pass on one wire, so 100A is appropriate. Glad you figured it out.

 

[Rockster]

I was flipping the 50-amp pair, thinking that was the 100 amp HPWC circuit. I was actually disabling the NEMA 14-50 circuit that was unused at the time.

One of my New Year's resolutions is to spend an afternoon tracking all the circuits and labeling my poorly labeled, 15-year old breaker panel. I'm going to take a hint from some of the people here and make a nice Excel spreadsheet that I tape to the wall instead of trusting fading marker writing on the inside of the breaker box.

 

[AB4EJ]

I was flipping the 50-amp pair, thinking that was the 100 amp HPWC circuit. I was actually disabling the NEMA 14-50 circuit that was unused at the time.

One of my New Year's resolutions is to spend an afternoon tracking all the circuits and labeling my poorly labeled, 15-year old breaker panel. I'm going to take a hint from some of the people here and make a nice Excel spreadsheet that I tape to the wall instead of trusting fading marker writing on the inside of the breaker box.

An excellent idea. I just moved, and the house we moved to has probably 50 breakers, and not a single one was labeled. So I have to do this procedure with 2 cell phones, flipping breakers until the person by the outlet tells me that it is off. Meanwhile, all the clocks lose their settings, wifi router killed, etc. Pretty tedious. I have a circuit tracer, but it requires the power to be off to use it. Maybe somebody knows of a tracer that can be safely used with power on.

 

[Solarguy]

Here is one that will do the trace with the circuit energized:

http://www.amazon.com/Amprobe-BT-12...qid=1451922355&sr=8-5&keywords=circuit+tracer

Not a bad price and can be done with one person moving the plug sender between outlets.

 

[FlasherZ]

An excellent idea. I just moved, and the house we moved to has probably 50 breakers, and not a single one was labeled. So I have to do this procedure with 2 cell phones, flipping breakers until the person by the outlet tells me that it is off. Meanwhile, all the clocks lose their settings, wifi router killed, etc. Pretty tedious. I have a circuit tracer, but it requires the power to be off to use it. Maybe somebody knows of a tracer that can be safely used with power on.

I am not aware of any that are reliable. For receptacles, I carry a night-light. For lights, I use the switches. For big appliances, I use either front-panel indications (where possible), or a voltmeter (where not indicated, e.g., water heater). Two-way radio and a helper at the panel.

- - - Updated - - -

Here is one that will do the trace with the circuit energized:

http://www.amazon.com/Amprobe-BT-12...qid=1451922355&sr=8-5&keywords=circuit+tracer

Not a bad price and can be done with one person moving the plug sender between outlets.

These mostly work, but can give false indications. The device reduces sensitivity as you pass over the breakers to try and point out the strongest signal from the panel, doing its best to narrow it down for you; you should always double-check by turning the breaker off though.