UL certification - 30V vs 48V

[hltc]

Not sure if this is the right forum, so let me know if there is a better one. For low voltage systems, typically 48VDC and under, the UL certification is much different than 120VAC of course. But the question I have, I was told in a conversation the other day that its easier to have a system pass UL where 30V is being distributed over a cable, rather than 48V. He said..somewhat to quote "30V UL intrinsic is much easier to pass than doing it at 48V". Now I think of intrinsic as being in a Class/Division where sparks must be suppressed for reduction of energy that could cause an explosion. This thing is a consumer type application so it didn't make any sense to me. Looking for comments.

Thanks

 

[dpc]

There is a UL forum here - normally cross-posting is discouraged, but if you don't get any responses, you could red-flag your own post and ask that it be moved.

 

[itsmoked]

Your friend is correct. Voltage is everything in 'intrinsic land'. But I agree that has nothing to do with your consumer device.

I believe 42V is a cut off voltage where electrocution becomes more likely so 48V may be tougher than 30V in that regard. I could be wrong on this too.

What kind of device are you trying to UL? Maybe we can provide more guidance.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hltc]

The device is..well...best described as a remote audio amplifier. Box 1 takes in audio, box 2 has an amp in it. So going up CAT5 is the analog audio,data and power (2 pairs for power). So running 48V means less current being pushed. The installed environment is commercial, light industrial and possibly consumer. I'll explore the CAT5 and power amount under a different thread.

 

[itsmoked]

OK good description. Thanks. If the normal design has all the stuff enclosed (finger safe) then I would see little difference in the UL testing between 30 and 48.

Have you ever herded a product through UL?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hltc]

I have, but it was all higher voltage AC, not lower level DC levels. I was just a little confused when the contract engineer was talking intrinsic UL cert....this product never would never see an environment such as that. I actually thought the cut off for HV was 52V not 42V, so 48V actually sits just below that. Could be wrong as well. Thanks for responding to this thread, I just wanted to be sure I was not thinking that something else was going on before I questioned the contractor.

 

[itsmoked]

Contractor? UL testing lab?

A lot of times the easiest and fastest route is to use a testing house - not UL directly. It can cost a little more but save you months! They can often quickly answer questions like this for you. I'd call up a testing company and enquire about their services and then your specific voltage question.

Be interested to hear the result too.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hltc]

"Contractor" refers to a guy that is doing this part of the design for us. I agree, there is a local testing house we use for FCC and CE. For "UL" I actually prefer TUV, since its all NRTL certs now. But it might actually turn out we won't even certify this product. Some organizations actually won't purchase if its not UL, but have to see how that works out. At minimum, we would do CE since that can be done locally. NRTL cert really says...its been designed in such a way the normal consumer won't get hurt using it, and should refrain from burning up as well. Designed correctly, it would pass all of that.

I will ask about the voltage tho, just as a matter of curiosity.

 

[busbar]

This is only my gut-level opinion, but I think the maximum 30VACrms—42.4VDC/ACpeak was revised [maybe a half-dozen editions ago] in the National Electrical Code to 30VACrms—42.4VACpeak—60VDC; at the behest of the telecommunications industry via IEEE.

Telecomms have routinely used variously sized nominal-“48VDC” battery sets—where [don’t quote me on this] battery-charger “float” voltage may be 53VDC and “equalize” voltage may be 56VDC…with their [internally] acceptable track record.

 

[itsmoked]

Makes a perverse kind of sense busbar. Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[mcgyvr]

60vdc and under is considered SELV (safety extra low voltage) now by UL's standards.

We use ETL (Intertek) they seem much better at interpreting UL's specs than UL people do. It can cut months off your actual testing time. With UL we end up spending time/money just to prove to them that they are applying their standards incorrectly. Its a joke. Last time (before me switched to ETL) for comparison we sent the same product through 2 different UL offices and both came back with completely different areas that we "supposedly" didn't follow the specs. None of them were correct.