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Old May 13th, 2022, 07:04 PM   #1
theColonel26
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UL Class 2 Circuits

Ok am finding UL 508a section 44 rather vague....

Does the Power supply that supplies a Class 2 Circuit have to be Listed for UL Class 2?

If No

Does the Power Supply have to be limited to 100W output?

Or

If I use fast blow fuses to limit circuits to less than 100W. Are those circuits Class 2 then?
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Old May 14th, 2022, 10:05 AM   #2
ndzied1
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If the panel will be inspected for listing make your life simple. Use a class 2 power supply.

There are several available.

The class 2 rated power supplies have circuits that guarantee power limiting above what regular power supplies have.
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Old May 14th, 2022, 02:37 PM   #3
theColonel26
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Well I would need a like 3 separate Class 2 power supplies instead of 1 240W power supply.....
Do most people just use more than one power supply if then need more than 100W?


That also takes up a lot of room
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Old May 14th, 2022, 03:13 PM   #4
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I've been using Class 2 Electronic Circuit Breakers for a number of years now. RTFM...
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Old May 14th, 2022, 03:40 PM   #5
theColonel26
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So it seems no one actually knows the answer to my questions.... As no one has directly answered them.
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Old May 14th, 2022, 10:14 PM   #6
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My recollection from talking to our UL inspector was that fusing down to <100W was sufficient.
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Old May 16th, 2022, 02:10 PM   #7
theColonel26
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Quote:
Originally Posted by rupej View Post
My recollection from talking to our UL inspector was that fusing down to <100W was sufficient.
thank you
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Old May 16th, 2022, 04:30 PM   #8
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Quote:
Originally Posted by theColonel26 View Post
thank you
And the above is wrong. Class 2 is limited to 100 ma. Either a class 2 power supply, or class 2 converter. Something like a 1692 ELP.

Fusing doesn’t cut it per UL.

And yes, I often have a class 2 power supply in addition to say a 240W power supply.

Cheers!

Last edited by atc222; May 16th, 2022 at 04:32 PM.
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Old May 16th, 2022, 09:58 PM   #9
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Quote:
Originally Posted by atc222 View Post
And the above is wrong. Class 2 is limited to 100 ma. Either a class 2 power supply, or class 2 converter. Something like a 1692 ELP.

Fusing doesn’t cut it per UL.

And yes, I often have a class 2 power supply in addition to say a 240W power supply.

Cheers!
100 milli Amps... ?
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Old May 16th, 2022, 10:10 PM   #10
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Sorry, 100VA (aka watts.) 3.8A, 24Vdc is typical.

Apologies for not answering your initial question. Yes, it needs to be listed as a UL class 2 power supply.

Remind me not to post after drinking….

Last edited by atc222; May 16th, 2022 at 10:13 PM.
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Old May 16th, 2022, 10:16 PM   #11
theColonel26
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Quote:
Originally Posted by atc222 View Post
Sorry, 100VA (aka watts.) 3.8A, 24Vdc is typical.

Apologies for not answering your initial question. Yes, it needs to be listed as a UL class 2 power supply.

Remind me not to post after drinking….
ok that is what I figured you meant just wanted to check



Where is the fun in that?
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Old May 16th, 2022, 10:24 PM   #12
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Lol! Cheers!
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Old Yesterday, 01:26 PM   #13
Rson
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Quote:
Originally Posted by theColonel26 View Post
Well I would need a like 3 separate Class 2 power supplies instead of 1 240W power supply.....
Do most people just use more than one power supply if then need more than 100W?
That also takes up a lot of room
Use a 240W power supply. Then use a class 2 electronic circuit breaker such as the Allen Bradley 1692 series or Siemens Selectivity modules. Depending on the module, you can usually get 4 class 2 circuits from one.

There are other companies that make them as well - and I believe Automation Direct may have a new electronic circuit breaker - not sure what it is though.
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Old Yesterday, 01:55 PM   #14
titanspark76
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I also would just use the 240watt power supply along with a Class 2 distributor. I linked a few different ones I've used. Maybe you'll get lucky and one of them will actually be in stock somewhere

Puls
https://products.pulspower.com/us/pisa11-class2.html

Murr
https://shop.murrelektronik.com/en/E...rPage=10&pos=1

Omron
https://www.ia.omron.com/products/fa...ification.html
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Old Yesterday, 02:44 PM   #15
atc222
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Now that I'm back in the office.

Puls CD5.241-L1. Is what we typically use DC/DC Converter 3.8A Class 2.
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