Aquarium and electrical safety

[Paul B]

GFI breakers fail when they are used as switches. All breakers fail when used as switches like if people don't know where a light switch is, so they turn off the breaker. They are not built for that and are only supposed to be turned off or on for maintenance while working on the circuit.

I have installed hundreds of GFI breakers and receptacles and can count on one hand how many times they mal functioned. Unless the receptacles were outside in the rain, then they don't last long.

Leviton sent me to school for them when they were invented.

 

[KJoFan]

Just to wrap this saga up, the solution in the end was to switch out the outlet for a GFCI outlet and leave the breaker as just a regular breaker.

Which I had asked for/about last time they were here and they said no, it had to be an AFCI breaker. I guess they changed their minds.

 

[Utwo229]

Just to be precise:

A thermo-magnetic breaker (your panel breaker) may "weaken" after numerous thermal (overload) trips, but the threshold is fairly high, as in many dozens or hundreds of thermal overload trips. This has no effect on magnetic short circuit (think of a solenoid) trips, only thermal overload trips.


GFCI/AFCI receptacles or breakers do not "weaken" or have a lower trip threshold after multiple activations. The trip mechanism is solid-state logic and acts on a magnetic solenoid that trips the breaker receptacle. In the case of the breaker, there is no wear to the thermal mechanism.

Small correction. GFCI breakers and receptacles use a MOV to detect the trip point. The MOV is a sacraficial component and does weaken every time it trips. In time they have to be replaced. In places like Florida where we get a lot of lightening, we see frequent GFCI failures from surges and spikes.

And i am an electrician.

 

[Freenow54]

I assumed he was talking about a straight up breaker no ?. Also I found how a surge protector works , and how they fail to be interesting as well. I believe it uses MOV as well no? It was described as being very close to being like a capacitor

 

[Utwo229]

I assumed he was talking about a straight up breaker no ?. Also I found how a surge protector works , and how they fail to be interesting as well. I believe it uses MOV as well no? It was described as being very close to being like a capacitor

Yes MOV in surge. He was talking about trips or using the breaker to switch the circuit. That will weaken the breaker. Breakers are listed for a finite number of on/off mechanical switches in it’s lifetime.

 

[Freenow54]

As to lightning there is no surge protector that will resist that potential the way I understand it . The ones most common are only rated for 4-600 V . Why don't people in Florida go old School and install lightning rods ? Would be a good business for you . Sounds funny but what the Heck

 

[BeanAnimal]

Small correction. GFCI breakers and receptacles use a MOV to detect the trip point. The MOV is a sacraficial component and does weaken every time it trips. In time they have to be replaced. In places like Florida where we get a lot of lightening, we see frequent GFCI failures from surges and spikes.

And i am an electrician.

I am sorry, but that is not even remotely correct.

MOVs are "Metal Oxide Varistors" they are surge clamping devices and have absolutely nothing to do with the function of a circuit breaker or a GFCI.

The circuit breaker in a residential panel is a thermo-magnetic device. There are two trip mechanisms.
The first is a solenoid. It is set to physically push on the trip mechanism at very high overcurrent levels that are usually many times higher than the breaker's nominal rating. This is the "instant" trip that prevents a massive short from melting the branch circuit wiring. This can be found on the time current curve for the breaker as the vertical line near the 0 second mark.

The second is a bi-metal strip that distorts under thermal load and forces the trip mechanism to activate at a preset current level near the the breaker’s nominal rating. This is the meat of the sloped portion of time current trip curve. This is the part that may weaken over time and alter the breaker’s behavior.

A GFCI uses a differential current transformer and a solid state comparator (a chip) to measure the delta in current between what flows in on the hot leg and out on the neutral. If it detects an imbalance of more than ~5mA it uses the circuit’s power to energize a solenoid against the trip mechanism.

MOVs are used in surge protection. They are normally very high resistance devices connected between conductors of a circuit. Repeated surges lower the clamping voltage and they eventually fail. Yes, large surges or lightning strikes can destroy them as "sacrificial" protectors. In high quality surge protectors, we parallel MOVs with avalanche diodes. They offer some protection to the MOVs by clamping fast transient surges before the MOVs have to handle them.

There may be some GFCI receptacles or various types of breakers with "surge protection" built in, and that surge protection may be MOVs and/or avalanche diodes, but this is not common and has NOTHING to do with the actual function of the breaker or the GFCI. It is there to offer surge protection for the circuit.

 

[BeanAnimal]

I assumed he was talking about a straight up breaker no ?. Also I found how a surge protector works , and how they fail to be interesting as well. I believe it uses MOV as well no? It was described as being very close to being like a capacitor

Not really like a cap at all.

They are high resistance in normal state. When they are presented with a voltage beyond their "clamping voltage" they become low impedance and route the current to ground/neutral (depending on where placed).

Yes MOV in surge. He was talking about trips or using the breaker to switch the circuit. That will weaken the breaker. Breakers are listed for a finite number of on/off mechanical switches in it’s lifetime.

I don't think you are following this conversation well.

There is a difference between:

Magnetic trips (solenoid slams into disconnecter bar)
Thermal trips (bimetal strip presses against disconnecter bar)
Manual actuation (user throws handle, disengaging cammed spring latch)

A typical household breaker is rated for THOUSANDS of mechanical cycles. The primary failure mode is latch wear, not degradation of the bimetal strip or wear on the solenoid.

As to lightning there is no surge protector that will resist that potential the way I understand it . The ones most common are only rated for 4-600 V . Why don't people in Florida go old School and install lightning rods ? Would be a good business for you . Sounds funny but what the Heck

MOVs are odd devices. We understand how they work under normal surges, but at extreme, fast impulses like lightning, their behavior is not predictable, regardless of voltage rating. Sometimes they successfully clamp the surge, sometimes they are bypassed or fail. Similarly, lightning rods and ground systems are not always predictable with strikes. You may see burn marks along the grounding path in one case, and in another the burn marks leave the low resistance path and follow brick grout lines, or tree roots, etc. Lightening strikes are highly unpredictable.

 

[Freenow54]

Point Taken . I was regurgitating things I have read . I don't claim to be an expert at knowing thoroughly anything . Especially Electricity . That is why I throw these things out there . To have a response from you or others to support or not someone's statement . Or elaborate . So I absolutely am not offended as you should know by now about being corrected , and appreciate any and all criticism. Also you should know by now when I come back it is not me arguing just looking for a longer and clearer explanation to penetrate my brain as most people that have a high level of understanding on a subject sometimes assume a certain level of understanding of the person they are talking to . A line I heard in a movie explains it perfectly . A guy says " Explain it to me like I am a two year old "

 

[Paul B]

Remember, the old, glass plug fuses were much safer than circuit breakers. I am old enough to remember way before we had circuit breakers. As an "A"- Rated construction electrician for almost 50 years, I have installed and replaced thousands of breakers, and I've seen dozens fail. Glass plug fuses can't fail.

To find circuits in the field, we used to just short out the outlet with a piece of wire, then look for the tripped breaker. Now we have tools that show us the breaker, but even if we use the tool, we still short out the wires before we work on them for safety.

(We normally worked on circuits live, but because of insurance and so many people dying, we are not allowed to do that anymore. But I normally do if I am working in my house. )

Many of those circuits we shorted, never tripped the breaker, and we could have arc-welded with some of them.
They are a mechanical piece of equipment and prone to failure, and we don't know if it is good after it was installed unless we test each one with equipment most electricians don't carry around.

Of course we had to put in a breaker panel after they invented GFIs.

 

[W31Olds]

Paul, glass fuses are safe when people use them properly. The design is unsafe because it is easily bypassed.

 

[tripdad]

Paul, glass fuses are safe when people use them properly. The design is unsafe because it is easily bypassed.

And this is why we have a label on hair dryer cords telling people not to use them in the bath tub.....because people can't be trusted with thier own safety.

 

[Paul B]

The design is unsafe because it is easily bypassed.

Yes, I have seen many pennies stuck in those fuse holders. I went crazy while working in a very old building. I removed all the glass fuses and still couldn't kill the circuit. A penny from the 40s was stuck in the back of the fuse holder, and it was so corroded that I couldn't see it.

And this is why we have a label on hair dryer cords telling people not to use them in the bath tub.....because people can't be trusted with thier own safety.

I can't help it if you can't fix stupid. Thats also why they still have directions on bottles of shampoo. Not that I know what shampoo is for.

 

[Freenow54]

they have breakers because of idiots that put pennies behind glass fuses which is why most rules are made

 

[BeanAnimal]

Remember, the old, glass plug fuses were much safer than circuit breakers.

What was the ampacity rating of the penny or tinfoil under them?

Friends 400A service at his large college bar had mains bus fuses. We would blow at least two per Friday night when he pushed the audio system too far…

There was a box of them beside the panel, a pair of safety glasses, a leather glove and extra large channel locks. We swapped em hot under load. Kind of silly looking back.

 

[jonelder68]

What was the ampacity rating of the penny or tinfoil under them?

Friends 400A service at his large college bar had mains bus fuses. We would blow at least two per Friday night when he pushed the audio system too far…

There was a box of them beside the panel, a pair of safety glasses, a leather glove and extra large channel locks. We swapped em hot under load. Kind of silly looking back.

Bean you have to stay legit here….keep that quite

 

[Paul B]

What was the ampacity rating of the penny or tinfoil under them?

It depended on the year of the penny.

 

[Euphylliaphyle]

Then:

It depended on the year of the penny.

Now: What's a penny?

 

[Freenow54]

Alcohol is a wonderful thing .

 

[Paul B]

I rewired the Chrysler Building service in Manhattan and those old, big buildings have what we call, Frankenstein Switches".

Each fuse, which may be 1,200 amps or more, is about 2 or 3' long. The switch, which has blades on it about 3' long, has to be opened with a 2X4 about 8' long. Two guys would put the 2X4 behind the switch handle and try to pry the thing open. When you did, a very large spark would jump about a foot from the wall. Remember, those buildings use 3 phase 480 volts and that building is about 100 floors so they carry a lot of power.. Of course, that wasn't the only switch for the building. That was only for a few floors.

We changed many of them to GFI circuit breakers which were almost the size of a Volkswagen bug. To install them, a crane was built on top of the panels, which were the size of a school bus. The crane moved over the breaker, and you connected it to the cable and cranked it out and down.

Then a guy would crawl into the empty breaker cell, while still live, and clean the terminals.

I also changed many of the breakers in the Empire State Building and installed some in the World Trade Center when we were building it.

They were these types of knife switches but weighed a couple of hundred pounds.