breakers safe or not ?

[statictree83]

Are breakers the only fail safe. Do they work all the time. What if I draw more then 50 amps in my garage and the breaker don't trip. I have a 200 amp service in house and a 100 amp box in garage but its only 3cord 6 aluminum wire powered of the house main through a 50amp breaker. I'm hooking up a 5000watt heater in the garage it draws 21 amps using a 220v 30 amp breaker for it. Garage only has 3 other breakers all 20amp. One outlets one lights four bulbs that's it and one for the sensor light that way its on a switch. I only run small power tools and only one at a time plus a radio and my 18v charger

 

[rockwithjason]

for residential they are the most used protective device. most breakers last for decades reliably. fuses can also be used. if you draw more than the rating of the breaker then the breaker enters it's inverse time curve and will eventually trip. the higher the current the faster the trip will come. wire is selected to allow for overcurrents without damaging the wire under normal conditions. does that answer your question?

 

[Slednut]

I had a Zinsco panel and for 25 years had never tripped a breaker. Put a new panel in and have tripped breakers multiple times. Pretty sure the Zinsco was a fire waiting to happen.

 

[ddawg16]

You should have 3 layers of protection.

Your 50A breaker. Most of them are both thermal and magnetic.

Your main breaker is 200A.

And then there should be a pretty large fuse at the pole.

If your 50A breaker fails and does not open....your wire is beefy enough to carry enough current to trip the 200....maybe.

As for your #6 AL wire....unless it's 75 deg or higher....your too small for a 50A breaker.

 

[statictree83]

What do you mean 75 degree f. Temp talk. I'm thinking I have enough power to run it but I rather be safe and do this right. One says my wore is enough to carry an all load enough to trip the 200 main and one says its not enough to trip a 50 amp

 

[volleyball]

It sounds if you are pretty safe. That is assuming you have decent breakers and panels. There are some known sketchy brands still in use.
Use a new breaker for the heater and you should be fine. If you want a belt and suspender solution, you could add a fuse box rated at say 75A between sub panel and feed from house.
I wouldn't. If I was that worried about the breakers, I'd replace them. Which brand/model do you have?

 

[ddawg16]

What do you mean 75 degree f. Temp talk. I'm thinking I have enough power to run it but I rather be safe and do this right. One says my wore is enough to carry an all load enough to trip the 200 main and one says its not enough to trip a 50 amp

The ampacity of wire is based on both size and the temp rating of the insulation. As the current goes up, the wire gets warmer.

In your case, #6 AL has a current rating of 40A if the insulation is good for up to 60 deg C. If the insulation is marked 75 deg, then it's good for 50A

Here is the chart

http://www.usawire-cable.com/pdfs/NEC AMPACITIES.pdf

It's important because if the insulation melts...wires short...and then you really test that ckt breaker

 

[justsam]

At the risk of re-igniting some previous thread "discussions".

If you use the 75 degree column than you must terminate wire ends in like rated terminals, i.e. 75 degree rated breakers. Of course if your wire is not marked 75 degree or better, than you must assume 60 degree.

Even if you elect to reduce to a 40 AMP breaker, you will be fine with your heater add.

 

[Stevie-Ray]

I've had breakers go bad, but generally they constantly trip, if bad. And that *****, because you go through all the other checks first, usually.

 

[ronk5865]

Yea,once the insulation burns off. You can see what else burns b4 that breaker trips.

 

[LS6 Tommy]

Maybe I'm not understanding, but you can't feed a 100A panel from a 50A breaker regardless of wire size…

Tmmy

 

[3rdgen]

Maybe I'm not understanding, but you can't feed a 100A panel from a 50A breaker regardless of wire size…

Tmmy

The rating of the garage panel is 100 amps and your feeding it with 50amps its perfectly fine. Just wont get more then 50 amps out of it. We do it all the time 100 amp panel packages are cheaper then a small sub panel by the time you buy breakers.

 

[malibu101]

The rating of the garage panel is 100 amps and your feeding it with 50amps its perfectly fine. Just wont get more then 50 amps out of it. We do it all the time 100 amp panel packages are cheaper then a small sub panel by the time you buy breakers.

Yep.
I see it often and it passes inspections with no problem.

 

[Norcal]

You should have 3 layers of protection.

Your 50A breaker. Most of them are both thermal and magnetic.

Your main breaker is 200A.

And then there should be a pretty large fuse at the pole.

If your 50A breaker fails and does not open....your wire is beefy enough to carry enough current to trip the 200....maybe.

As for your #6 AL wire....unless it's 75 deg or higher....your too small for a 50A breaker.

There is absolutely no overcurrent protection on the secondary of any PoCo transformer, the cutouts are on the primary side, the wiring on the secondary will have burned off long before those cutout fuses will even think about clearing. This is why anyone not having the faintest idea what they are doing should not screw with any hot SE conductors.

 

[ddawg16]

There is absolutely no overcurrent protection on the secondary of any PoCo transformer, the cutouts are on the primary side, the wiring on the secondary will have burned off long before those cutout fuses will even think about clearing. This is why anyone not having the faintest idea what they are doing should not screw with any hot SE conductors.

Shhhhsssstt.....you weren't supposed to tell him....I as trying to give him some 'comfort'.

Well, actually, the wires from the pole to the house are kind of like fuses....those will burn open.......eventually.....

 

[rlitman]

There is absolutely no overcurrent protection on the secondary of any PoCo transformer, the cutouts are on the primary side, the wiring on the secondary will have burned off long before those cutout fuses will even think about clearing. This is why anyone not having the faintest idea what they are doing should not screw with any hot SE conductors.

Pretty much correct. Though the transformer on my block has a circuit breaker (not sure if it is on the primary or secondary) as well as a fuse. We have open wire distribution (not triplex), and when a tree branch in the wind caused the phases to make contact it would trip that breaker (in the top of the can). In a few instances resetting the breaker would get the power back. In another instance, the short caused one of the live wires to break.

Still, when a neighbor had something fail in his service entrance, and the wire on his mast down to his meter started a fire (melting his neighbor's vinyl siding), the power was not disconnected until the fire department arrived and turned it off with a hot stick.

Shhhhsssstt.....you weren't supposed to tell him....I as trying to give him some 'comfort'.

Well, actually, the wires from the pole to the house are kind of like fuses....those will burn open.......eventually.....

Yeah, I guess.

I've had breakers go bad, but generally they constantly trip, if bad. And that *****, because you go through all the other checks first, usually.

That depends a lot on who makes the breaker. Generally this is true, but when it comes to Federal Pacific breakers, this is known to be not the case.

If you have quality breakers (Square D, GE, Murray, Westinghouse, Siemens, Eaton, Cutler Hammer etc, off the top of my head), you have nothing to worry about.

 

[kd3pc]

Pretty much correct. ....

That depends a lot on who makes the breaker. Generally this is true, but when it comes to Federal Pacific breakers, this is known to be not the case.

If you have quality breakers (Square D, GE, Murray, Westinghouse, Siemens, Eaton, Cutler Hammer etc, off the top of my head), you have nothing to worry about.

I have had some Square D, QO stuff on the construction site (temporary) that we could use the load side of the breaker to weld with. It was inspected every 3 months byt the local AHJ.

I actually have replaced two hot tub sub panels with 50 AMP QO GFCI breakers that would not trip on test, just in the past three months.

For the most part breakers are good....once a month or when you have a really heavy load, just run your fingers along the channel between the breakers, of course with the cover on! but with the door on. You can often "feel" a large heat zone on ?? breakers.

Similarly, cycling the breaker once a year or so will keep the action moving and contacts make/break. If you have GFCI/AFCI then use the test, they should quickly trip.

 

[rlitman]

QO is thermal magnetic. The magnetic trip curve depends on the specific model breaker, but currents of 10x to as much as 20x the actual rating may be required to get it to trip on the "instantaneous" magnetic trip. Yes, it is entirely possible that a 20A breaker might pass 400A without tripping on the magnetic. "Weld"ing currents are surprisingly low BTW. In your jobsite scenario, if there is a short at the end of a long extension cord, the cord may provide enough resistance (as it burns up) to limit the current to below the magnetic trip threshold.

The thermal portion takes time to trip (seconds to hours depending on details).

GFCIs failing. Yeah, it happens. There's a reason they come with a test button.

I use a thermal imager to scan my electrical panels at work. It's not as easy to detect a potential problem as you make it seem, and "feeling" it is not a really diagnostically useful test. All breakers that have current running through them will show elevated temperature.

 

[alfredeneuman]

There is absolutely no overcurrent protection on the secondary of any PoCo transformer, the cutouts are on the primary side, the wiring on the secondary will have burned off long before those cutout fuses will even think about clearing. This is why anyone not having the faintest idea what they are doing should not screw with any hot SE conductors.

A typical aerial service drop for a 100 Amp Service drop has #6 Aluminum wire.

Depending on how solidly it's shorted the transformer on the pole will put out 10,000 Amps (or more) instantaneously before the cutouts have a chance to work.

Norcal has it right, Service Entrance conductors are not things to be messed with by DIYers

 

[wyliesdiesels]

Are breakers the only fail safe. Do they work all the time. What if I draw more then 50 amps in my garage and the breaker don't trip. I have a 200 amp service in house and a 100 amp box in garage but its only 3cord 6 aluminum wire powered of the house main through a 50amp breaker. I'm hooking up a 5000watt heater in the garage it draws 21 amps using a 220v 30 amp breaker for it. Garage only has 3 other breakers all 20amp. One outlets one lights four bulbs that's it and one for the sensor light that way its on a switch. I only run small power tools and only one at a time plus a radio and my 18v charger

What brand of breakers do u have?

I had a Zinsco panel and for 25 years had never tripped a breaker. Put a new panel in and have tripped breakers multiple times. Pretty sure the Zinsco was a fire waiting to happen.

Zinscos are garbage. They dont trip sometimes when theyre suppose to!

You should have 3 layers of protection.

Your 50A breaker. Most of them are both thermal and magnetic.

Your main breaker is 200A.

And then there should be a pretty large fuse at the pole.

If your 50A breaker fails and does not open....your wire is beefy enough to carry enough current to trip the 200....maybe.

As for your #6 AL wire....unless it's 75 deg or higher....your too small for a 50A breaker.

U got that backwards. Line side high voltage fuses/cutouts on typical residential transformers are small compared to breakers in a house.

It sounds if you are pretty safe. That is assuming you have decent breakers and panels. There are some known sketchy brands still in use.
Use a new breaker for the heater and you should be fine. If you want a belt and suspender solution, you could add a fuse box rated at say 75A between sub panel and feed from house.
I wouldn't. If I was that worried about the breakers, I'd replace them. Which brand/model do you have?

What is the point in doing that? That would accomplish nothing seeing as the feeder breaker is 50a....

 

[Speedy Petey]

Maybe I'm not understanding, but you can't feed a 100A panel from a 50A breaker regardless of wire size…

Tmmy

Totally incorrect. Post #12 corrects this.

In these cases the 100A breaker is simply a means of disconnect, which is required for feeders to a detached structure.

 

[volleyball]

What is the point in doing that? That would accomplish nothing seeing as the feeder breaker is 50a....

Apples and oranges. The 75 is to allow the normal operation to leave the fuse intact, even with something that would normally trip the breaker. But breakers and fuses work differently and a 75 a fuse can pop way sooner than a functioning 50a breaker.
So there is a point to do it.

 

[wyliesdiesels]

That depends on the type of fuse used!

 

[volleyball]

Good, you understand my reason for mentioning a fuse.

 

[Norcal]

Apples and oranges. The 75 is to allow the normal operation to leave the fuse intact, even with something that would normally trip the breaker. But breakers and fuses work differently and a 75 a fuse can pop way sooner than a functioning 50a breaker.
So there is a point to do it.

Where are you going to find a 75 ampere breaker? They don't exist as a standard item.

 

[volleyball]

At the 75 amp fuse store. Duh!

 

[Norcal]

At the 75 amp fuse store. Duh!

Right next to the Easter bunny & Santa Claus?

 

[Daniel Dudley]

Are breakers the only fail safe. Do they work all the time. What if I draw more then 50 amps in my garage and the breaker don't trip. I have a 200 amp service in house and a 100 amp box in garage but its only 3cord 6 aluminum wire powered of the house main through a 50amp breaker. I'm hooking up a 5000watt heater in the garage it draws 21 amps using a 220v 30 amp breaker for it. Garage only has 3 other breakers all 20amp. One outlets one lights four bulbs that's it and one for the sensor light that way its on a switch. I only run small power tools and only one at a time plus a radio and my 18v charger

The setup you have is not uncommon. Just from what you describe, you are not going to over drive your circuit running the things you run through it.

Realize that this technology has been around for years, and it works very well. If your breaker is ancient, replace it. Otherwise, don't worry. DO you worry about any other breaker anywhere else failing ? Because worrying about just one breaker out of thousands going bad is a waste of energy.

Also consider that the wire itself is very big, and very tough. I don't see you being able to get it dangerously hot doing the things you will be doing, breaker or not.

 

[Daniel Dudley]

Similarly, cycling the breaker once a year or so will keep the action moving and contacts make/break. If you have GFCI/AFCI then use the test, they should quickly trip.

This is good.

 

[Stevie-Ray]

That depends a lot on who makes the breaker. Generally this is true, but when it comes to Federal Pacific breakers, this is known to be not the case.

If you have quality breakers (Square D, GE, Murray, Westinghouse, Siemens, Eaton, Cutler Hammer etc, off the top of my head), you have nothing to worry about.

Last one I replaced was a Siemens ITE type. I'm making a note of the Federal Pacific breakers as well. Generally, I'm using Square D now.

 

[wyliesdiesels]

FPE panels and breakers are dangerous and a fire waiting to happen!!

 

[dutchgray]

Do you Americans have RCD's (residual current devices)?
Here in the UK we have to have them on most circuits.
Basically they trip if there is 30mA or more between the neutral and earth.

 

[wyliesdiesels]

Yes we do have them. Theyre called GFCIs aka ground fault circuit interrupters. Except ours monitor current between hot and neutral and are required on 120v circuits in kitchens, laundry rooms, garages and on exterior outlets as well as hot tubs(240v and 120v) and jet tubs. Theyre also required on 3 phase services of 1000a or more.

Ours trip if theres more than a 5ma imbalance between hot and neutral.

 

[alfredeneuman]

In addition to the 5ma trip levels for personnel protection, though in much less usage than the 5ma models, there are GFI circuit breakers available set to trip at 30ma for equipment protection.

 

[LS6 Tommy]

The rating of the garage panel is 100 amps and your feeding it with 50amps its perfectly fine. Just wont get more then 50 amps out of it. We do it all the time 100 amp panel packages are cheaper then a small sub panel by the time you buy breakers.

Yep.
I see it often and it passes inspections with no problem.

I was pretty sure what you're stating was OK. I thought he was trying to use the full capacity of the 100A panel...

Tommy

 

[statictree83]

No I'm just trying to have a fire involving electrical wires I'm a new home owner and until a week ago didn't even know what wire gauge met. Amazing the things Google can teach a person should they want to learn it. But I'm still far from being able to say I know for sure about anything yet. I did manage to wire in a few light fixtures and a sensor light from a breaker though.

 

[wyliesdiesels]

U sill havent said what brand of panel u have..... :/

 

[statictree83]

I'll check them all in a little bit and breaker brands to