Industrial Machine - Rated Enclosure Required?

[drumburg]

Hello Gang,

I have a question about when an industrial machine requires a rated enclosure. We are looking to use an outside vendor for a piece of equipment that isn't UL listed but might be the only cat in town that can complete our task. Their machine doesn't have a rated enclosure. They are folding steel into a box and placing their components inside as protection. We are having some discussion internally about if this is still NFPA 79 compliant or not and was hoping someone here could help shed some light on the topic. I have searched through the NFPA 79 book for enclosure requirements and can find places that reference the type of enclosures needed if you use but not if a rated enclosure is required at all. I have even found an exception that states:

NFPA 79 - 2015

6.2.3 Direct Contact from Outside an Enclosure. Equipment
enclosures and enclosure openings shall meet the requirements
of ANSI/UL 508, UL 508A, ANSI/UL 50, or NEMA 250.
(See Figure 6.2.3.)

Exception: In the absence of a rated enclosure, the determination of
the suitability of an enclosure as protection from electrical shock shall
be determined by using a test finger as described in Figure 6.2.3. The
test finger shall be applied, with only minimal force, in every opening
in the enclosure after removal of all parts of the enclosure that are
capable of being removed without the use of a tool. The test finger shall
not encounter live parts in any direction.

 

[petersonra]

Do you mean "listed" as opposed to rated?

NFPA79 is a consensus standard but not one anyone is compelled to design to, although some people will argue that OSHA requires it, but OSHA requirements only apply to employers for the most part, not manufacturers of equipment.

As long as you can't stick a pencil into any openings it is roughly a type 1 enclosure.

Suppose as part of your electrical safety program you decide industrial machines must comply with NFPA79.

In the 2015 edition, requirements for enclosures are found in chapter 11. here are some relevant requirements as to what type of enclosure is required. Type being UL (formerly NEMA) type).

11.3 Degrees of Protection.
11.3.1* The protection of control equipment against ingress
of solid foreign objects and of liquids shall be adequate, taking
into account the external influences under which the machine
is intended to operate (i.e., the location and the physical
environmental conditions, including dust, coolants, and
swarf).
11.3.2 Enclosures of control equipment shall provide the degree
of protection required for the environment. A minimum
degree of protection of at least Type 1 is required.
Exception: Where removable collectors on collector wire or collector bar
systems are used and Type 1 enclosures are not practicable, suitable
protection shall be provided (e.g., elevation, guarding).

So it would appear that the type of enclosure you describe is quite adequate for at least some cases.

NFPA79 does require many components to be listed but I don't think enclosures are one of those components.

ETA: Very few industrial machines are "listed". The control panels can be (via UL508a), but the machines themselves are not.

 

[drumburg]

We have adopted the use of NFPA 79 for our equipment. On most topics it is pretty clear but there a few where some discussion is required.

Is there any kind of "line" for when an industrial machine is required to have a NEMA "rated" or UL "listed" enclosure; when a folded steel case doesn't work anymore?

 

[petersonra]

We have adopted the use of NFPA 79 for our equipment. On most topics it is pretty clear but there a few where some discussion is required.

Is there any kind of "line" for when an industrial machine is required to have a NEMA "rated" or UL "listed" enclosure; when a folded steel case doesn't work anymore?

AFAIK, there is nothing in NFPA79 that requires enclosures to ever be listed or rated, only to be adequate for the conditions of service.

It is an engineering decision. Like many such design decisions it is not always something you can quantify.

I see nothing wrong with a steel case. I don't know why you keep saying folded like that is somehow bad. Most steel enclosures are made by bending at least some of the edges. That reduces the cost by reducing the amount of welding required. It actually makes for a more precise enclosure overall as bending is more precise than trying to weld the edges of two pieces of sheet metal together. Reduces the need to grind and fill as well so the paint job is better.

If you don't like the enclosure it comes with maybe you can get whomever is specing the machine to ask for some other kind of enclosure. Most likely it will be a huge adder though as it will have to be a specially engineered and with engineering costs what they are it may well end up being well into 5 figures to get a different box.

 

[Jraef]

IF the entire control panel needs a UL 508a label, the enclosure will need to be listed under UL 50. Trying to use a bent up sheet metal box that has not been tested/listed in an assembly that needs to be listed is not going to be cheaper than buying a listed box.

 

[petersonra]

IF the entire control panel needs a UL 508a label, the enclosure will need to be listed under UL 50. Trying to use a bent up sheet metal box that has not been tested/listed in an assembly that needs to be listed is not going to be cheaper than buying a listed box.

18.3 An enclosed industrial control panel shall comply with Sections 18 – 27 and the enclosure shall
comply with:
a) The requirements in the Standard for Enclosures for Electrical Equipment, UL 50; or
b) The industrial control panel enclosure requirements in Sections 62 – 64.

62 General
62.1 The requirements in Sections 63 and 64 cover Type 1 enclosures constructed of sheet or cast metal.
62.2 A Type 1 – 13 enclosure constructed of polymeric material enclosure shall be investigated to the
construction requirements in 6.3, Section 7, 8.3, 8.4, 8.5, Section 14, Sections 15, 15A, and 15B,
performance requirements in Sections 30 – 43, and marking requirements in 49.1 – 49.6 applicable to the
enclosure environmental Type(s) in the Standard for Enclosures for Electrical Equipment, UL 50.
62.3 A Type 2 – 13 enclosure constructed of sheet or cast metal shall comply with:

Note the curious omission here of type 1 metallic enclosures.

here is what the component requirement section says.

18.3(b) Enclosures not
previously Listed or
Recognized
– – 1) Construction shall
comply with Sections 62 –
64 as Type 1 enclosure; or
2) Described in Procedure

I think a careful reading will tell you that a metallic enclosure that meets the requirements of a type 1 enclosure does not have to be listed or even be procedure described.

 

[drumburg]

AFAIK, there is nothing in NFPA79 that requires enclosures to ever be listed or rated, only to be adequate for the conditions of service.

It is an engineering decision. Like many such design decisions it is not always something you can quantify.

I see nothing wrong with a steel case. I don't know why you keep saying folded like that is somehow bad. Most steel enclosures are made by bending at least some of the edges. That reduces the cost by reducing the amount of welding required. It actually makes for a more precise enclosure overall as bending is more precise than trying to weld the edges of two pieces of sheet metal together. Reduces the need to grind and fill as well so the paint job is better.

If you don't like the enclosure it comes with maybe you can get whomever is specing the machine to ask for some other kind of enclosure. Most likely it will be a huge adder though as it will have to be a specially engineered and with engineering costs what they are it may well end up being well into 5 figures to get a different box.

I don't think i have been completely clear on the "folded steel enclosure". I don't mean to say that bent steel enclosures are bad, we use them all the time. I mean to say that the electrical components are housed in a folded steel box that is part of the machine, not a purchased and mounted enclosure. For example, the back of the "enclosure" is a side wall of the machine and the manufacture has constructed an electrical enclosure by bending and attaching (spot welded or bolted) other pieces of the same gauge steel. There is no door, just a bolt on steel plate that acts as the cover. This enclosure would probably qualify as a Type 1 if tested but it doesn't have any markings or labels to say as such.

 

[petersonra]

I don't think i have been completely clear on the "folded steel enclosure". I don't mean to say that bent steel enclosures are bad, we use them all the time. I mean to say that the electrical components are housed in a folded steel box that is part of the machine, not a purchased and mounted enclosure. For example, the back of the "enclosure" is a side wall of the machine and the manufacture has constructed an electrical enclosure by bending and attaching (spot welded or bolted) other pieces of the same gauge steel. There is no door, just a bolt on steel plate that acts as the cover. This enclosure would probably qualify as a Type 1 if tested but it doesn't have any markings or labels to say as such.

Read carefully what I wrote before. Neither the national electrical code or UL 508a requires type 1 enclosures that are metallic to be listed. There's also no requirement that there be a hinged door that I can recall. You might make an argument that the cover plate needs some kind of interlock with the disconnecting means depending on what this enclosure is actually used for.