BOLT ON BREAKERS

[BKELLEY]

My company builds generator set enclosures which we install electrical packages in them such as load centers, panel boards and mini power centers. my question is does any of the codes require bolt on breakers for Emergency and Stand by generators that are for a Hospital, or any medical facility? I have had a few engineers require bolt on breakers I just can't find where it states in any of the codes or standards. ex. NFPA 110, NFPA 99, or NFPA 70.

Could anyone point me in the right direction?

 

[don_resqcapt19]

That is a design issue, and not a code issue.
That being said, I only specify bolt on breakers for commercial and industrial applications.

 

[Jraef]

The NEC is not a design guide, it’s just a set of minimum requirements. Minimums are never a good idea for critical infrastructure like hospitals. If you are relying on a machine to keep you alive, would you want just the minimum necessary equipment providing power to it?

The issue with plug-in branch breakers is that they only exist out of convenience for residential consumers who might want to make their own changes without needing an electrician. They are really bad when it comes to any possible vibration, but that is rare in a residential setting. Commercial, industrial and hospital settings can have a LOT of vibration from large machines (and by the way, generators…) that gets expressed onto the structure and so eventually into the panelboards.

Something else to consider; if a specification calls for a “panelboard”, that will be by definition, bolt-on. If the branch breakers are plug-in, it is called a “load center”. The terms are NOT interchangeable.

 

[BKELLEY]

Thanks for the information.

 

[don_resqcapt19]

The NEC is not a design guide, it’s just a set of minimum requirements. Minimums are never a good idea for critical infrastructure like hospitals. If you are relying on a machine to keep you alive, would you want just the minimum necessary equipment providing power to it?

The issue with plug-in branch breakers is that they only exist out of convenience for residential consumers who might want to make their own changes without needing an electrician. They are really bad when it comes to any possible vibration, but that is rare in a residential setting. Commercial, industrial and hospital settings can have a LOT of vibration from large machines (and by the way, generators…) that gets expressed onto the structure and so eventually into the panelboards.

Something else to consider; if a specification calls for a “panelboard”, that will be by definition, bolt-on. If the branch breakers are plug-in, it is called a “load center”. The terms are NOT interchangeable.

Where do you find that? Panelboards and load centers are listed to the exact same product standard, and the term "load center" does not exist in the product standard, UL 67.

There is no real definition of a load center, and it is only a marketing term for the type of panels typically used in residential applications.

From SquareD:

Issue:
Differences between load centers and panelboards.
Product Line:
QO Load Centers, NQ Panelboards
Environment:
Panelboards
Resolution:
A QO load center is a panelboard. Both QO load centers and NQ panel boards are tested to the same test parameters outlined in UL67. Some of the functional differences may include:
QO load centers are merchandised products. NQ can be factory assembled to custom specifications, as well as mechandised.
QO indoor load center enclosures are 14.25" W x 3.75" D. NQ NEMA 1 panelboard enclosures are is 20"W x 5.75" D, with other widths and depths available.
QO load center enclosures are painted cold rolled steel (NEMA Type 1) or painted galvannealled steel (NEMA Type 3R). NQ panelboard enclosures are unpainted hot zinc dipped galvanized steel (NEMA 1), painted phosphatized steel (NEMA 3R/5/12), or stainless steel or fiberglass (NEMA 4X).
For NEMA 1 enclosures, QO trims show the mounting screws and use a raised door latch with optional lock. NQ trims are monoflat with no exposed screws and a recessed handle lock. Hinged trims that offer a hinged cover over the breaker wiring in addition to the one over the breaker handles are also available for NQ.
NQ accepts both plug-on and bolt-on breakers. QO accepts plug-on only.
NQ panelboards are generally considered to be for commercial, institutional, and industrial applications. The QO load center is primarily targeted for the residential, light commercial, and light industrial marketplaces.

If an engineer wants a bolt-on breaker, that needs to be specifically specified as saying "panelboard" does not get you there.