[nwilcox]

Probably a total idiot question... but I can find nothing online about grounding any Acopian mini-encapsulated power supply. Every other linear power supply I have played with comes with instructions describing where to attach your ground wire on the incoming AC power cord. Usually, it is to the frame (in the case of open frame supplies) or to a dedicated screw terminal (in the case of Acopian's other linears, for example).

Part of me thinks that perhaps one attaches the ground wire to one of the mounting screws on the back plate of these little units. But as I said, I find nothing about this in Acopian's docs on these units.

Anyone have an opinion about this?

[Folsom]

What model?

This one has a ground tap.

https://www.ebay.com/p/?iid=152542154808&&&chn=ps

[nwilcox]

Thanks Folsom. I should have been more specific. The "WB" model numbers are switching regulated and, indeed, those seem to have a ground tap. The ones I am puzzled about have the "EB" model numbers and are linear regulated, and those do not seem to have any explicit ground tap: The one I am looking at is the 5EB150. Here is a link to the instruction sheet for these:

https://www.acopian.com/inc/streamFile.asp?loc=info&id=AcopianMini.pdf

The only mention of "ground" or its cognates is in a reference to "fusing the hot (ungrounded) side of the AC line" (which I will do).

On my model the T/C tap is for placing a trim pot on the DC outputs.

I found this after thinking a little more:

https://electronics.stackexchange.com/questions/193403/is-there-a-reason-why-some-ac-dc-adapters-dont-have-a-grounding-pin

This begs a question, however, which maybe someone can answer: Why is it that an encapsulated linear regulated ps is "isolated" while an encapsulated switching regulated ps is not. Is it because a transformer is the first thing in the circuit path of a linear ps (and so acts like an isolator) while transformers appear rather later in the circuit path of a switching ps?

Again--any wisdom is appreciated. I am very much a freshman when it comes to electronics.

[CurtisIIX]

When you mention "ground" in this context, I assume you are talking about "safety ground" on the mains AC. That is, the green wire on the 3-prong main AC cord.

Your Acopian supply is low power and encapulated, so I am guessing that is passes the 2-prong safety limits for UL. In fact, Acopian says that all models are UL Recognized. I don't know difference between UL Recognized and UL Listed. Perhaps there is a distinction between end-user devices (UL Listed wall-wart) and a supply to be installed into another product.

Per Bill Whitlock, the safety limits for 2-prong UL "listed" equipment are as follows:

• 0.75mA limit for leakage current (power line to chassis)
• Insulation creepage distances must be large
• Thermally protected
• Remain safe in spite of component failure, overload, and mechanical abuse

It appears that you could use a two-prong plug with this supply. With a three-prong plug, I would just connect the safety ground to the chassis of whatever device you are installing this supply into. I don't think you have to connect the safety ground to the supply since it is encapsulated.

I am not an electrical engineer or electrician, just a hobbyist. Your best option would be contact Acopian.

[CurtisIIX]

I think that you edited your post as I was writing mine or I just didn't read the last part  .

I was suggesting that encapsulated implies isolated.  You now point out that this may not be valid in the switching supply - especially since Acopian lists specs for isolation for the switching supply. I don't know why this is the case. Also, there may be other reasons that switching supply does not met the safety limits for 2-prong equipment.

[nwilcox]

Thanks CurtisIIX. All of this discussion is helpful!

[Speedskater]

Most likely the supply has a Class II double insulated safety rating. With a symbol of a square inside a square.
The reason that so many small external supplies are being sold is that they have a Class II safety rating. That way the manufacture of the main product doesn't have to do any expensive safety testing.

The chassis of a Class II product shall not be connected to the Safety Ground.

[srb]

I don't know difference between UL Recognized and UL Listed. Perhaps there is a distinction between end-user devices (UL Listed wall-wart) and a supply to be installed into another product.

Yes, per Hammond Power Solutions

"The UL Listed Mark on a product is the manufacturer’s representation that samples of that complete product have been tested by UL to nationally recognized safety standards and are found to be free from reasonably foreseeable risk of fire, electric shock and related hazards.  UL’s Component Recognition Service covers the testing and evaluation of component products that are incomplete or restricted in performance capabilities.  These components will later be used in complete end products or systems Listed by UL."

[nwilcox]

The chassis of a Class II product shall not be connected to the Safety Ground.

Thank you Speedskater. So I am very clear, is the intended meaning "shall not be" or more "need not be?" If the former, that would be an important consideration for how one mounts such a ps within another case. If the latter, then no worries such as that.

[nwilcox]

I sent Acopian an inquiry about this and, as is usual for them, had a reply first thing this morning. FYI, their reply:

Acopian Model 5EB150 does not have an earth ground terminal.  It does not have any exposed earth ground that would provide a shock hazard.  The only reason the [switching power supplies have] this terminal is that we incorporate some line to ground capacitors to reduce the conducted EMI back onto the AC line.  It is simply to connect these capacitors but is not for safety.

Most customers will connect their earth ground wire to the metal they are mounting the power supply to.

Best Regards,
Todd Reichenbach

[Speedskater]

Thank you Speedskater. So I am very clear, is the intended meaning "shall not be" or more "need not be?" If the former, that would be an important consideration for how one mounts such a ps within another case. If the latter, then no worries such as that.

Must not be.
Connecting a ground wire will defeat the UL listing.