Enclosure for DIN rail PSU required?


Thread Starter

Damon Seeley

We are a small firm that produces interactive experiences for public and commercial places.

We are using bus couplers and photoelectric sensors in a new installation and all hardware will be protected behind a large wall of laminated glass. The glass is heavy and requires two glaziers to move. The sensing drives interactive lighting which is also housed behind the glass.

In this application do we need to put all DIN rail hardware including 60W PSUs inside an enclosure for human safety, or can we mount the rail directly to substrate? It seems unnecessary to me given that access is restricted to workers who can move the glass. I ask because the enclosure is disrupting the lighting effect in our design and eliminating it would help.

We are getting vague answers from the local electrical sub on this so I am interested in the forum's experience with these issues.


bob peterson

I suspect that some kind of guarding is necessary. Perhaps you could make something out of transparent polycarbonate.

> I suspect that some kind of guarding is necessary. Perhaps you could make
> something out of transparent polycarbonate.

There are SMPS models with built in enclosure. You can use them!

James Ingraham

I would be reasonably comfortable with the power supply mounted in the open. I have, for example, a power supply on a benchtop in our panel shop for testing. We also have exposed terminal blocks on certain equipment that is behind safety fencing. But I have a few caveats and a few suggestions.

Caveat 1: What is the incoming power feed? If it's 360VAC or higher I might be a little worried. If it's plain old 110VAC 60Hz / 220VAC 50 Hz then I'm more comfortable. Not that you can't be killed by this, which leads to...

Caveat 2: Make sure this power supply is finger safe, and that the leads are connected in such a way that there isn't bare copper sticking out past the finger guards.

Caveat 3: There may be some local regulation I'm not aware of. (e.g. in Raleigh, NC, all control panels have to be UL.) I'm not claiming to be an expert on all instances.

Those are the caveats. Here are some suggestions:

Suggestion 1: Don't use DIN-rail mount power supplies. Use a "wall wart" style or laptop-style. Here's a $9 wall wart from Jameco
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_102285_-1 (quite small)

and a bigger laptop style http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2099286_-1

9.2A seems to be the biggest Jameco's got, but $109.95 isn't bad. This style can even be bought in medical grade, at which point NOBODY could complain about it.

Suggestion 2: Use an IP65/67 rated power supply. This will be MUCH more expensive. This 5A from ASI is about $400.

Turck also makes a similar unit, but apparently maxes out at 4A.

Suggestion 3: As someone else pointed out, you don't need a big metal box. Plastic or plexiglass may work. You could also try different paint on the boxes; a flat gray or black, perhaps.

Hope that helps. Good luck!

-James Ingraham
Sage Automation, Inc.