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I have a little utility room with bare cement walls. So I want to install a little surface switch. As far as i understand normally switches are installed on a hot wire, but this switch has no grounding, so i wonder if it's better to install it on a neutral wire?

The switch looks like this: enter image description here

EDIT: here is a picture of it when it's open. As you can see there is a metal plate that i would think should be grounded. But it is covered under normal circumstances: enter image description here

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I don't understand why it has no grounding.. it sounds like it hasn't been installed yet? Why can you not ground it? – gregmac Apr 1 '11 at 22:45
there is no way to ground it. It's all plastic on the outside, there is a little metal panel inside, but there are not enough openings to put a ground wire inside – Vitalik Apr 2 '11 at 0:05

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Install the switch on the hot wire for several reasons. While installing on the neutral wire would likely work, realize that in 110v installations, the neutral and the ground are effectively the same wire (the neutral line connects to the ground within the breaker panel so you only get one phase of the 220v or 110v). So switching off the neutral is akin to switching off a ground wire. It also means that anyone replacing a bulb with the light switch turned off is risking frying themselves if they contact the hot contact and any ground. And finally, any electrician working behind you will be confused at best or mis-wire things at worst.

As for the switch itself not being grounded, that never made much sense to me. The only thing I believe you are grounding are the screws and metal tabs that hold the switch in place.

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It's against code to have the neutral switched, for exactly the safety reason you outlined. All metal boxes that are part of electrical system must be grounded as well (including, eg, metal conduit). If there is a short and the metal is not grounded, when someone touches it they'll be electrocuted. If it's grounded, the breaker/fuse will blow as soon as it shorts. If there's no exposed metal, then things may be different. – gregmac Apr 1 '11 at 22:44
all this is true as long as the hot wire is switched BEFORE it is connected to the light fixture. If the switch is downstream, the same hazards exist as B Mitch described. The center conductor will always be hot. use a grounded switch, tie the neutrals together and be sure to switch the hot between the breaker and fixture. – shirlock homes Apr 1 '11 at 23:03
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side note: any device installed on a bare concrete wall must be in a metal box with the wires in metallic conduit. Thus you do have a grounding path. Seriously Vitalik, if you don't understand what we are saying, please seek some professional help. Don't want to see you get hurt. Glad to help you out, but want to be sure you understand the answers. – shirlock homes Apr 1 '11 at 23:08
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If the main problem is bumping into the box, you may want to look into the shallow boxes that are designed for a 1.5" clearance (2x4 mounted on it's side). I suspect they are mostly used for framing over a concrete wall. – BMitch♦ Apr 2 '11 at 1:29
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what I meant was the center button/bulb contact in the light socket will be hot if switch is down stream. So even though the light is off, the center of the socket is still at 120vac potential and ready to go to ground through any path availuble. – shirlock homes Apr 2 '11 at 7:59
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