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LV lighting not all that Low Voltage afterall? #51904 05/15/05 02:54 PM
Joined: Sep 2001
Posts: 806
N
NJwirenut Offline OP
Member
Just got a callback on a LV landscape lighting install I did a week or so ago. Customer stated that all the lights along one side of the walkway were out. Sure enough, they were. A quick check of the connections at the transformer showed nothing wrong, but there was no voltage at the beginning of one string of lights. An open in the wire somewhere....

The wiring passed behind some shrubbery, where I found the problem--a stray cat had dug up the cable, and chewed through one of the conductors, using up the rest of its 9 lives in the process! After removing the dead cat and resplicing the cable, all was working again.

Has anyone seen anything like this before? I wouldn't have thought that 12VAC would be enough to kill a cat. No idea what made it dig the cable up in the first place, maybe the recently disturbed ground got the better of its curiosity? Just glad it was a stray, and not the customer's pet!

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Re: LV lighting not all that Low Voltage afterall? #51905 05/15/05 03:32 PM
Joined: Feb 2004
Posts: 133
E
Electric Ian Offline
Member
Not sure if this is true or not but I have heard that animals have a lower body impedance than humans.

Re: LV lighting not all that Low Voltage afterall? #51906 05/15/05 03:45 PM
Joined: Jul 2004
Posts: 145
C
chipmunk Offline
Member
Maybe by chewing open the conductor it put its head in series with the circuit? I know with humans 18mA is supposed to be the "can't let go" current for the average human.

I would imagine a cat's critical current is proportionally lower. Compared to the resistance of the cat, the lamps would have minimal resistance, so the cat probably saw the full 12 volts across its mouth, (quite a low resistance area and close to the brain).

I guess its jaw clamped tight on the severed ends and ... ouch, poor cat [Linked Image]

Re: LV lighting not all that Low Voltage afterall? #51907 05/15/05 05:01 PM
Joined: Mar 2005
Posts: 1,803
Alan Belson Offline
Member
Cats (and dogs), as any owner will testify, have certain senses heightened beyond the imagination of us mere mortals. It may have sensed the voltage, or heat, or the plastic smelled in some way, before biting it. Cats have a very high pain threshold, (feel little pain), and one of their instincts is to bite harder if a victim put up a fight, and someone posted a piece recently about a guy who died after putting 12v wires in his mouth....
Alan


Wood work but can't!
Re: LV lighting not all that Low Voltage afterall? #51908 05/16/05 04:40 PM
Joined: Feb 2002
Posts: 114
E
electech Offline
Member
Twelve volts would hurt in the mouth - maybe the wire was stuck in the cats mouth and it died of a heart attack? My second guess would be the transformer might have a high leakage current due to a defect or damage. Short of using a leakage current tester, you could test for this by measuring the current from the low voltage circuit to ground through 2000 ohms. There should be less than one milliamp (safety standards might allow more, but I've never seen anything over 1 mA in a good transformer). Just a guess.

Re: LV lighting not all that Low Voltage afterall? #51909 05/16/05 06:26 PM
Joined: Jul 2002
Posts: 17
Q
qopanel Offline
Member
Wow what a great IDEA!!!! "Hunny, I'm going to be putting in some of those lights you like so much next to the garden. Oh BTW, I also planted some catnip along the sides...you can let the cats out to feed whenever you like".

Re: LV lighting not all that Low Voltage afterall? #51910 05/16/05 08:04 PM
Joined: Sep 2001
Posts: 806
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NJwirenut Offline OP
Member
I thought there might have been leakage in the transformer, as well. I checked for voltage from secondary to earth ground, and looked for primary/secondary leakage with a megger, none found. The unit is also plugged into a GFCI receptacle.


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