Re: Crowbar circuit?

Suggest you make sure it never happens again. If it _can_ happen it's almost surely unsafe and in violation of electrical code.

IIRC, CSA wants low voltage lines in the vicinity of mains wiring to have insulation rated for the mains voltage (eg. 300V) or to be sleeved with something that brings it up to that rating (eg. fiberglass sleeving).

True. However, occasionally I am asked to make sure my circuit survives if the installer accidentally connects the black and the white 12AWG wires where it said RS485 :-)

Just leave it alone. Sounds like a perfect setup for a Darwin Award: Chlorinating the Gene Pool !-) ...Jim Thompson

If a single fault resulted in damage, then the 12V circuit was not isolated.

It sounds like an iffy installation that would benefit from proper insulation , isolation, and a gfi. These won't protect your bulbs, but might reduce the hazardous nature of the site.

RL

I'd have to wonder at the economics. Does the marginal cost of one of these boards justify the extra expense of protecting them against ham-fisted installers? The worst solution, to my mind, would be one where the installer doesn't have to admit their error, and thus can't be fired promptly for incompetence.

Sylvia.

On the ones I did? Oh yeah!

It's mostly warranty claims that you can't turn down because So-and-so Corporation is a key customer, et cetera. "No, we haven't dunnit, done nuthin' wrong, honestly, it suddenly exploded all by itself ..."

Ah, yes. That puts a different slant on it. Best make it idiot-proof then, which I gather is what you're trying to do.

Sylvia.

Er, I mean were trying to do, since you're not the OP.

Sylvia.

Yeah, it seems sad that the bulk of customers (the competent ones) must carry the cost of extra parts etc. for the few that will screw up, but they have to one way or the other (parts or "warranty" repairs).

No. Repair or redesign the equipment so that the 120V doesn't short to the 12V any more.

Good Luck! Rich

If the installer is union, it's probably illegal to fire him (or her) for incompetence, thanks to the Liberal/Union cabal. >:-[

Cheers! Rich

agreed.

And if you have problems with installers running power into signal terminals like for rs485, use different connectors or terminal blocks for the low voltage stuff.

If you can't fit 12 guage power cables in the terminal block for serial communiations, mixing them up isn't a problem anymore.

When recently redoing some video routing I found that isolated (separate chambers for LV and HV) outlet boxes are now required. Quite nice... available at Lowe's, etc. ...Jim Thompson

"now required"? Wasn't it even stiffer before, where one had to maintain

No. They sold wiring duct with metal separators for phone and power at least 25 years ago.

I know. You can also use conduit. What I meant was the outlets. This house was built quite meticulously and there is always exactly 6" separation. Believe it or not but they partially put structured wiring into it. In 1970 ...

Believe it or not, I was doing that work in 1970. Phone, intercom, background music, two way radio, fire & burglar alarm and special control wiring. I was also teaching new techs how to do it.

No, I remember designing a bunch of stuff for the video system at UCSB that basically had a 12"x12"'3" wall box divided by a metal barrier back in '92...

Charlie

In the 90's you could get those divider boxes but in the 70's telephone jacks were those round recess thingies. That had to maintain a 6" distance. Not sure why but I've read that placing them close together is one of the more common mistakes by DYIers and a core reason for flunking the inspection.