UL listing required for low voltage gear?

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tallgirl

tallgirl

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Location
Glendale, WI
Occupation
Controls Systems firmware engineer
Greets,

I have a client (they're an electrical contractor ...) who needs to provide a 0 to 10 volt DC signal that is proportional to current being produced by an AC inverter (SMA SB5000U for anyone who cares) and I pointed them at a Veris Industries H923 (if you aren't bored yet ...)

Anyway, their client is providing the Analog-to-Digital conversion, but I've been spec'ing parts that operate on 12 volt DC. It's my understanding that anything operating at that low of a voltage and current (something around 50ma) doesn't require UL listing.

Someone want to set me straight?
 
Is it going into a UL listed control panel or other UL listed gear? If so, yes it will need to be listed. If you have no UL listed options and it does need to go in a listed panel assembly, then you can still use it, but the panel builder would have to follow strict UL guidelines for installing it. Those usually make it not worth doing if there is a UL listed alternative.

If not in a listed panel, i.e. its in a little box all by itself and not fed with anything that did not come from a "Class 2 transformer" (i.e. output under 50V and 100VA max.), then it would likely fall under a "limited energy" classification, like an alarm system or HVAC controller.
 
I guess I'll say it depends on what you call your “device”. See UL 758 for your below 30 volts statement.

This link is a very good cross reference to what’s required per what your doing, it sounds like it’s secret or classified since your didn’t name it. For whatever reason I believe you can get a good start from this Link.

It also cross-references CSA standards!

UL
 
I guess I'll say it depends on what you call your ?device?. See UL 758 for your below 30 volts statement.
Click to expand...

Thanks!

This link is a very good cross reference to what?s required per what your doing, it sounds like it?s secret or classified since your didn?t name it. For whatever reason I believe you can get a good start from this Link.
Click to expand...

I wasn't mentioning because I thought advertising was forbidden. I make solar power system monitoring and management gear these days. Wanna monitor a 50KW solar power plant? Drop me a dime ;)

The gear in question is typically opto-isolated from whatever other equipment there is and is all as low on the volts and amps as I can get away with. 12 volts @ 0.7 amps is a lot. I'm shooting for 5 volts @ 0.5 amps next.

And I stopped doing crypto / red-black stuff years ago. Still paranoid, just not as paranoid as I used to be.
 
101210-0931 EST

tallgril:

Can you restate your question?

I am confused. Is your question ---

Do the
1. The signal leads, 0 to 10 V probably current limited to maybe 10 to 20 MA, or a similar low energy signal, from a UL listed isolating current transducer, and probably of some substantial length; and
2. the device to which these leads connect have to be UL listed, for example an A/D converter connected directly to a computer.

There are many other possibilities for what a device includes.

OR

Maybe your question is if you attach an A/D converter almost directly to the current transducer and have to pipe DC power to the A/D, and receive digital data from the A/D, then does this A/D and/or its wiring method require UL listing?

Other questions.
Do you need RMS measurement of the current?
Do you need to measure voltage?
Do you need to measure power?
What accuracies are required?
What data sample rate is required?
What resolution?
What temperature range?
What other information needs to be collected? Like temp and wind speed.
How far does the information have to be transferred?
What is the noise environment?

.
 
Gar,

Does the A/D conversion device, which is typically powered with something on the order of 12 volts at 100 milliamps or less, require UL listing?

That's the question.

Sorry -- slammed for time. Trying to build a new web server that I need to take to a new ISP for hosting.
 
101210-1203 EST

If the power supply is a Class 2, then what are the restrictions on what, where, and how circuitry and devices can be connected to that supply? This would seem to be the basic question in which tallgril is interested.

.
 
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