Thread: Tripless circuit breaker?

I am not familiar with devices such as this and I would like to "phone a friend". Any input would be appreciated. Well....any helpful, kind, well-mannered, friendly input would be appreciated.

This cabinet/panel is just to the right of the main service entrance and panel. It is supplied by a 100 amp breaker. The breaker at the top of photo is the AC disconnect. The mystery device is at the bottom of the cabinet (sorry about the photo centering). The mystery device supplies the storage/building shop.

Thanks!

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That is just a tap (have a mental blank on its name??), the tap and the feeders from the tap need to be rated the same as the service entrance conductors (unless the feeders - tap conductors - meet one of the tap rules).

I agree that it looks like a tap without overcurrent protection.

Subfeed lugs

Thanks everyone. The devices were marked Square D and I wasn't concerned, just interested.

Originally Posted by JB Thompson

Thanks everyone. The devices were marked Square D and I wasn't concerned, just interested.

That is a Challenger* or a Bryant/Westinghoue/C-H BR loadcenter, from what I understand there is not any SQ D breakers / accessories listed / classified for other makes of panels.

* In later years the BR line loadcenters & Challenger looked the same as they were both Westinghouse subsiduaries.

My bad. It is a Cutler Hammer box (I zoomed in on another photo to look) with CH devices.

I am assuming that the 100 amp breaker is the main being reverse feed did it have the screw intalled as a hold down?

'Subfeed tap' ... got it ... thank you Rollie.
Bruce,

Remember, the feeders need to be sized appropriately for the main disconnect size as there is no other overcurrent protection.

Originally Posted by paul hardy

I am assuming that the 100 amp breaker is the main being reverse feed did it have the screw intalled as a hold down?

Yes the screw was installed.

Originally Posted by Jerry Peck

'Subfeed tap' ... got it ... thank you Rollie.
Bruce,

Remember, the feeders need to be sized appropriately for the main disconnect size as there is no other overcurrent protection.

So the feeders coming from the "subfeed taps" should be sized for the 100 amp breaker? Or are you saying they should be sized appropriately for the subfeed tap? In which case, what would that size be?

Originally Posted by JB Thompson

So the feeders coming from the "subfeed taps" should be sized for the 100 amp breaker? Or are you saying they should be sized appropriately for the subfeed tap? In which case, what would that size be?

Let's say you have a 100 amp breaker as the main disconnect, and that the 100 amp breaker is protecting the bus bars in that service equipment (which it is), and that the sub feed tap is connected off the bus bars with no overcurrent protection (which it is and has no overcurrent protection), and that the feeders going from the subfeed tap terminals are only 60 amp rated - the only overcurrent protection provided for those 60 amp feeders is that 100 amp main breaker. This means you *could* draw 100 amps through the 60 amp rated conductors before the 100 amp main tripped.

Now let's presume that the subfeed tap has 125 amp rated conductors going from the subfeed tap terminals, which are also protected only by the 100 amp main breaker ... is there any need to have conductors which have a 'higher' rating than that 100 amp main? If you try to pull more than 100 amps through those feeder conductors the main should trip, and will probably trip well before you get close to 100 amps through those feeders as there are also other circuits drawing current through the main breaker.

That means that you could feed a 150 amp panel with 150 amp rated feeders from that subfeed tap, but the most you will ever get through those feeders will be 100 amps before the main breaker trips (presuming that all other circuits in that panel drawing -0- amps). So why spend the extra money? Would it be wrong? No.

Could it have been planned? Yes. Because they may have intended to, or still may intend to, replace that 100 amp panel and its main and install a 200 amp service, and the subfeed tap feeders are already sized for that future expansion.

The sub feed tap conductors look to be undersized (if the panel has 100A at the main). JB is this what you reported or am I missing something?

You reported the white colored load carrying conductor as well, correct JB?