UL Class 2 Circuits

theColonel26

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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?
 
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.
 
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
 
My recollection from talking to our UL inspector was that fusing down to <100W was sufficient.
 
:geek: 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:
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... ?
 
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:
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 :oops:



:beer:Where is the fun in that?
 
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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