Class 2 Power Supply

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hshrainey

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Memphis, TN
Hello,

we are using different types of sensors in our machine.
encoders, light barriers etc.
Now we want use the machine in the USA.

We are now looking for UL-Listed/recognized parts.
Does the NEC permit the use of non listed/recognized sensors (24V), that are supplied from a class 2 supply.

The NEC describes in 725,2 Definitions:

"Due to its power limitations, a Class 2 circuit
considers safety from a fire initiation standpoint and provides
acceptable protection from electric shock."

Can we generally say, that components in class 2 circuit are not investigated?
 
hshrainey said:
Hello,

we are using different types of sensors in our machine.
encoders, light barriers etc.
Now we want use the machine in the USA.

We are now looking for UL-Listed/recognized parts.
Does the NEC permit the use of non listed/recognized sensors (24V), that are supplied from a class 2 supply.

The NEC describes in 725,2 Definitions:

"Due to its power limitations, a Class 2 circuit
considers safety from a fire initiation standpoint and provides
acceptable protection from electric shock."

Can we generally say, that components in class 2 circuit are not investigated?
Click to expand...

IMO, a sensor such as a prox switch is not generally required to be listed by anything in the NEC.

I also don't see anything that is required to be listed by the NEC would have that requirement changed just because it was part of a class 2 circuit.

I am also of the opinion that for the most part components of an industrial machine are not in general covered under the NEC requirements.
 
Last edited:
don_resqcapt19 said:
While the NEC may not require the use of a listed sensor, OSHA might if the equipment is used in a workplace.
Click to expand...

The OP did not ask about anything other than the NEC.

In any case, my argument would be the end user did not buy a prox switch. he bought a machine. The OSHA letter cited does not require the machine components to be listed.

The URL you referenced also points out just what kinds of things are required to be listed.

https://www.osha.gov/dts/otpca/nrtl/prodcatg.html

Industrial machines are not in the list of things required to be listed.
 
hshrainey said:
Thank you gentleman for the answers and I am forwarding this information to my friends in Germany. Thank you again
Click to expand...

I would point out that the OSHA letter cited might well require the control panel itself to be listed, and there are a fair number of localities in the US that specifically require control panels be listed.

It is not real difficult to get a control panel UL listed. These days mostly you can use the same components and just wire it a little different, mostly wire color coding and wire insulation types. Some other relatively minor issues that would need to be taken care of as well.
 
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