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Blog posts tagged with 'westinghouse breakers'

What Do Westinghouse Housing Codes Mean?

On some Westinghouse air breakers, a special code is stamped on the nameplates which causes some confusion when replacing and maintaining the breakers in the field. It is called the “Housing Code” and is designated with a single letter. Ironically, the housing code was originally intended to avoid the very confusion that it is causing today. So, what is a housing code—and more importantly, what do we use it for today?

Breaking Down Westinghouse Air Breaker Housing Codes

In the 1960s and early ‘70s, a housing code was the factories designation to indicate interchangeability between circuit breakers within the lineup of switchgear as it was produced from the factory. Let’s look at an example. If you have a double-ended lineup of Westinghouse type DB air breakers and it’s designed with 3,000 amp electrically operated DB 75 mains, A DB 75 tie with 2,500 amp trips, and 12 1,600 amp, DB 50 feeders and the feeder breakers have trip units rated 1,600 amp, 1,200 amp and 800 amp, you might have the following designations.

The DB 75 mains all have the same control wiring and trip units and are both mechanically and electrically interchangeable, so they would logically both have a housing code of “A” stamped on them, as would any spare breakers on hand. The DB 75 tie is unique to the lineup because of the smaller trip unit, so it would have a housing code of “B,” as would a spare breaker if it was built at the time of the purchase. The 1,600 amp frame feeders are all mechanically interchangeable but have three different-sized trip units so they are not electrically interchangeable, the 1,600 amp breakers would all have the same housing code of “C,” the 1,200 amp breakers would be “D,” and the breakers with 800 amp trip units would all be “ E.”

This system ensured that operators had an easy way to identify interchangeability when the switchgear was new. However, housing code designations effectively became obsolete over the years with modern solid state trip units. These new solid state trip systems are more effective and accurate and much more adjustable than the original series overcurrent trips supplied by the OEM. They allow breakers that are mechanically interchangeable to also be adjusted to be electrically interchangeable with other breakers in the same line up. These trip units can and must be adjusted by qualified technicians to ensure that each breaker is set to protect each load safely and effectively.

This housing code continues for breakers in the medium voltage class as well but is less complicated. For example, if there is a lineup with 2,000 amp mains and 1,200 amp feeder breakers, the 2000s would all be designated “A” and the 1200s all designate “B” because they are all mechanically and electrically interchangeable. The overcurrent trip function is controlled by current transformers and panel mount relays and are separate from the draw out elements.


NPE: Experts in Used and Remanufactured Air and Vacuum Circuit Breakers

Whether you need help identifying circuit breakers or finding the right switchgear parts for your facility, NPE can help. Our extensive inventory of parts and expertise has made us to-go source for solutions for switchgear and circuit breaker needs. Go to our NPE on the Go mobile site or contact us today to talk about your needs and how NPE can help.

Westinghouse DA Circuit Breaker Line

George Westinghouse was one of the primary innovators of the Industrial Revolution and of the electrical power distribution and control industry that developed along with it. His company continued to spearhead innovations created by inventors such as Edison, Tesla and others which included polyphaser motors and the first resettable circuit breakers made with interchangeable parts. This product line is commonly known in the industry as Westinghouse slatebacks or the DA series of breakers. They both used thermal and inverse time overcurrent trip devices that sensed an overload condition and safely tripped to open the circuit to prevent damage to infrastructure, equipment as well as injury to personnel. Once the circuit was safely de-energized, technicians could locate and clear the cause of the fault and re-energize the circuit with minimal efforts.

Westinghouse Slatebacks or the DA Series of Breakers

This product line consisted of a robust current path mounted on a heavy slateback board and integrated into both live front and later dead front (enclosed) switchgear sections. Although this product line was advertised to have interchangeable units and parts, there was a wide variety of products to choose from and variables could only be identified by technicians familiar with the equipment, including changes caused by products marketed by a budding OEM of the time. In order to weed through these issues I will begin with the basics and fine tune the details as we go. Of course, if you need one of these quickly and don’t want to get bogged down in the weeds, just contact one of our experts at 800-647-0815 or use NPE’s “On the Go” tool - M.NPEINC.COM.

The basic product line came in 5 different designations, defined by how many amps each could be relied on to interrupt safely, based on standards in place at the time. These are DK 15, DK 25, DA 50, DA 75 and DA 100. Each of these breakers could be provided in either a drawout or bolt-in frame. These breakers were built to last and it’s not unusual to see them still in service today with upgraded electronic trip units. The bolt-in breakers are the toughest to identify and replace because they have often been incorporated into large control panels with various other controls. Things like size and placement of the bus, vertical or horizontal bus alignment and number of phases along with field discharge legs are a few of the criteria which must be identified and are best done with photographs and sketches along with the technical details.

The drawout breakers, while they still needed to be carefully examined, are much easier to identify and replace. The vast majority of them (say 98%) worked with a standard design that George Westinghouse was proud to put his trademark on. More on the other 2% later… 

Westinghouse Drawout “DA” Style Slateback Breaker Types and Sizes:







DK 15


225 amps


Finger cluster style does not affect interchangeability as long as they are for round bus**.

DK 25


600 amps


Finger cluster style does not affect interchangeability as long as they are for round bus**.

DA 50


800, 1200 and 1600 amps


Frame size is not indicated by the nameplate on the front of the breaker. The breaker nameplate indicates the rating of the trip unit as supplied from the factory. Frame size, can be best be identified by the size of the round copper stab that the finger clusters are mounted on 7/8” for 800, 1 ¼” for 1200 and 1 5/8” for 1600 amp. Electrically operated breakers are in no way interchangeable with manually operated breakers. The 800, 1200 and 1600 amp frames are not interchangeable.

DA 75


2000, 2500 and 3000 amps


Finger cluster style does not affect interchangeability as long as they are for round bus**. Frame size is not indicated by the nameplate on the front of the breaker. The nameplate only indicates the rating of the trip unit as supplied by the factory. Frame width varies between two sizes and finger cluster/back stab arrangement can also vary between 6 stab and 12 stab versions on a “standard” three phase breaker. The only reliable way to identify the breaker is with a measurement of the width and to photograph or otherwise visually inspect the back of the breaker.

DA 100


various 4000-12,000 amps


Frame width varies and finger cluster/back stab arrangement can also vary between 6 stab and 12 stab versions on a “standard” three phase breaker. The only reliable way to identify the breaker is with a measurement of the width and to photograph or otherwise visually inspect the back of the breaker. This is a very rare breaker in today’s world. Engineers of the day theorized that anything above a 100,000 amp fault was impossible and used the base DA 100 design with a variety of ever increasing frame sizes. 4000 amp is the most common. Use all of the above guidelines to identify your application.



image of DA-50 manual circuit breakerimage of DA-EO westinghouse circuit breaker




**The Other 2 Percent:


The above guidelines will help you identify the correct replacement for your Westinghouse slateback breaker 98% of the time. However, “back in the day”, Westinghouse also sold its stationary breakers to Allis Chalmers for use in its own OEM version of switchgear. Allis Chalmers would take stationary breakers, with flat stab (and all of the variables associated with them) and add their own finger clusters and drawout hardware. This resulted in a drawout circuit breaker with finger clusters designed to mount on flat bus rather than the standard Westinghouse round stab as noted above. To complicate matters, the Westinghouse factory nameplates remained on the breakers and no outward indication was given that they have been modified by an OEM and not interchange with standard factory breakers.

In conclusion,please keep in mind that equipment of this era was made during a period of time when the idea of standards for interchangeable parts left some room for interpretation. It will take a supplier with experience and an eye for detail to ensure that the your equipment fits and functions the way that George Westinghouse’s company intended, like the professionals at NPE. We’re breaker geeks -this is what we do. Contact us or use NPE’s “On the Go” tool and have it guide you through all of the steps you will need to find the right breaker for your job.

               image of westinghouse DA circuit breakerimage of DA-75 flat stab circuit breaker                                







Are Eaton, Westinghouse, Square D, and Cutler Hammer Breakers Compatible?

The search for old or obsolete circuit breakers isn’t always easy. Many factories and government or commercial facilities operate on electrical equipment that is no longer supported with new parts, which means you need to either find a remanufactured air or vacuum circuit breaker or aftermarket breaker parts that are a match for your equipment.

There are several companies that have manufactured breakers in the past century and beyond, but you typically can’t swap out one competitor’s breaker parts for another’s. However, there are some instances where one brand of breaker is nearly identical. Westinghouse and Eaton are two such examples.

Circuit breaker with Eaton nameplateA Westinghouse low-voltage circuit breaker that is compatible with some Eaton breakers.

Why Does Eaton and Westinghouse Have Compatible Circuit Breakers?

While you may wonder why two different brands would have compatible circuit breakers, the answer is simple: the same company owns the production rights for both Eaton and Westinghouse.

Back in the past, Westinghouse had a low-voltage air circuit breaker line. The company eventually sold the rights to this product line to Square D, another American electrical equipment manufacturer. That line didn’t stop there – Square D then sold the Westinghouse line to Eaton Corporation in 1993. As a result of rights ownership, there are nearly identical breakers with four different nameplates on them:

  • Westinghouse
  • Square D
  • Eaton
  • Cutler-Hammer

These breakers can be compatible with each other despite the different nameplates, as certain models are largely the same aside from some upgraded electronics. That flexibility means that you may have some options when trying to replace your current low-voltage air circuit breakers

   Compatible Square D circuit breaker.Circuit breaker with Cutler Hammer nameplate


Find Compatible Old and Obsolete Eaton and Westinghouse Breakers

While you now know that Eaton breakersWestinghouse breakers, Square D breakers, and Cutler-Hammer breakers are largely compatible, you still need to find the exact models you need for your facility. At NPE, we have amassed and refurbished old electrical equipment, including breakers and aftermarket parts for Eaton, Westinghouse, and more.

Ready to find the right breaker parts for your facility? Submit information about what you need on our NPE on the Go mobile site or contact us today to talk to one of our experts about finding the rights solution for your needs.