Instrument Panel OCPD

[Designer69]

I have an instrument panel, no control of motors or anything, just a bunch of controllers in it for connecting field sensors (vibration/RTDs) and transmitting signals for trending.

Are there any special requirements for the OCPD for these? Does UL508 or anything apply or just put it on panelboard ckt and call it a day?



Thank You

 

[Jraef]

I have an instrument panel, no control of motors or anything, just a bunch of controllers in it for connecting field sensors (vibration/RTDs) and transmitting signals for trending.

Are there any special requirements for the OCPD for these? Does UL508 or anything apply or just put it on panelboard ckt and call it a day?



Thank You

We can't really answer that for you, it's more of a local code issue. States that do require NRTL (such as UL) listing will not really care what the panel is controlling or sensing. But if all of the components are low voltage fed from Class 2 power supplies, they may not care, i.e. fire alarm or building management panels. So without knowing what's in there and where you are, it's impossible to answer specifically.

 

[Designer69]

We can't really answer that for you, it's more of a local code issue. States that do require NRTL (such as UL) listing will not really care what the panel is controlling or sensing. But if all of the components are low voltage fed from Class 2 power supplies, they may not care, i.e. fire alarm or building management panels. So without knowing what's in there and where you are, it's impossible to answer specifically.

thanks. Yes all class 2 power supplies (24VDC), not required to be UL listed or AHJ approved. Just wondering if I need a miniature breaker or fuse inside the panel. Maybe this is a better question for the vendor of the sensor controllers?

Edit: Looking at some similar setups, a lot of these appear to have a mini ckt. breaker ahead of the class 2 pwr. supply. Would make sense in case you want to work inside the panel and have a quick shutoff as well

 

[Designer69]

another question is the max power supply allowed for a class 2 ckt is 100VA. Can I have two 100VA power supplies in the same panel if I need more than 100VA of class 2 power (split in 2 ckts)

 

[Jraef]

another question is the max power supply allowed for a class 2 ckt is 100VA. Can I have two 100VA power supplies in the same panel if I need more than 100VA of class 2 power (split in 2 ckts)

Yes. In fact AB (and probably others) has an 8A 24VDC power supply for DeviceNet networks that can be split into two 4A Class 2 power supplies coming from the same device. The requirement is that the CIRCUIT not have more than 100VA capacity. You can also buy “circuit protector/splitters” that go down stream of larger power supplies and provide up to 4 separate Class 2 circuits, each with their own 4A electronic protection circuit. They are required to have fuses as well because of UL, but the fuses never blow because the ELCB is faster. Most of the major power supply mfrs offer those now.

 

[Designer69]

Yes. In fact AB (and probably others) has an 8A 24VDC power supply for DeviceNet networks that can be split into two 4A Class 2 power supplies coming from the same device. The requirement is that the CIRCUIT not have more than 100VA capacity. You can also buy “circuit protector/splitters” that go down stream of larger power supplies and provide up to 4 separate Class 2 circuits, each with their own 4A electronic protection circuit. They are required to have fuses as well because of UL, but the fuses never blow because the ELCB is faster. Most of the major power supply mfrs offer those now.

thanks Jraef. There are fuse requirements in UL508 for Class 2 panels? I thought these were non-UL listed/ non-AHJ approved.

I was just going to come off one 20A lighting branch ckt to the panel and split via 2 mini cb's to 2 different 100VA 24VDC power supplies, then from there directly to the monitoring controllers.


Thanks again

 

[iceworm]

I have an instrument panel, no control of motors or anything, just a bunch of controllers in it for connecting field sensors (vibration/RTDs) and transmitting signals for trending.

Are there any special requirements for the OCPD for these? Does UL508 or anything apply or just put it on panelboard ckt and call it a day? ...

Consider looking at NEC 409
I have only built a few of these. The AHJ wanted to see compliance with art 409, including all the marking required in 409.110.

And, since there was a 120V control power circuit, they wanted to see compliance with 409.110.4. I used UL508A supplement SB.

Ended up putting in fuses to meet the SCC requirement. As I recall, the little AB CBs (1492?, 1489?) would have also worked.