UL508A related question

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Rmore

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In our UL508A listed product, we are replacing the 120VAC powered UL listed HMI with a 24VDC powered HMI. Does the new 24VDC powered HMI need to be UL listed?

Similarly, we are adding a 24VDC powered pressure sensor. Does this also need to be UL recognized/listed?
 
Rmore said:
In our UL508A listed product, we are replacing the 120VAC powered UL listed HMI with a 24VDC powered HMI. Does the new 24VDC powered HMI need to be UL listed?
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Probably. If it is mounted thru the door than it almost certainly has to be listed, unless the cutout is fairly small.

Rmore said:
Similarly, we are adding a 24VDC powered pressure sensor. Does this also need to be UL recognized/listed?
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If the pressure sensor is located inside the control panel, the answer is probably that it has to be listed. If it is outside of the control panel, UL508a does not care.

Read carefully what appendix B says. Also 44.2.1.
 
The device mounted in the door must replicate the environmental rating of the enclosure, i.e. Type 1, 12, 3R, 4, 4X etc.. Without that device having it's own UL listing, it has no acceptable environmental rating.
 
Jraef said:
The device mounted in the door must replicate the environmental rating of the enclosure, i.e. Type 1, 12, 3R, 4, 4X etc.. Without that device having it's own UL listing, it has no acceptable environmental rating.
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That makes sense. The HMI we are considering "meets Nema4x (indoor only) when mounted in the following manner..." however, it is not listed.
 
Rmore said:
That makes sense. The HMI we are considering "meets Nema4x (indoor only) when mounted in the following manner..." however, it is not listed.
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If you were to use the provisions of appendix B, you would have to abide by the cutout dimension restrictions found in B2.1.1, exception 1.

However, since you are at 24 VDC, I don't think this appendix applies. You would have to use 44.2.1. It does not seem to require the device not be mounted in the door. BUT I would look very closely at ALL the requirements before I would do this. UL has a bad habit of giving you permission to do something in one section while restricting it in a completely unrelated section.

As far as the enclosure type rating goes, read carefully what section 19 says about closing them. depending on the very confusing way UL508a describes this, you may have to cross off whatever rating the enclosure has beyond type 1 and call it type 1.
 
petersonra said:
If you were to use the provisions of appendix B, you would have to abide by the cutout dimension restrictions found in B2.1.1, exception 1.

However, since you are at 24 VDC, I don't think this appendix applies. You would have to use 44.2.1. It does not seem to require the device not be mounted in the door. BUT I would look very closely at ALL the requirements before I would do this. UL has a bad habit of giving you permission to do something in one section while restricting it in a completely unrelated section.

As far as the enclosure type rating goes, read carefully what section 19 says about closing them. depending on the very confusing way UL508a describes this, you may have to cross off whatever rating the enclosure has beyond type 1 and call it type 1.
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Great advise. Thanks!
 
HMI NEMA rating 4x is irrelevant. It has to be UL type rating to match UL type rating of enclosure. We got burned buy this once by using door mounted temperature controllers. These temperature controllers were NEMA type rated but not UL type. We had to look for replacement.
 
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