43V shock on satellite install

[duskglow]

Hi, I have a problem, and I was hoping someone here could shed some light on it.

I have been doing the infrastructure work for a client of mine, who lives in a (brand new) very large house. He has a lot of TV ports, fed off a Direct TV dish. When the installers came by, they provided an 8 port Zinwell multiswitch, which has been working well.

I was tasked with installing a second Zinwell switch, and cascading it to the first. I went up to the equipment room, removed one of the cables (the one going out to the second tuner of a tivo box), and immediately got a shock. All I did was touch the outside housing of the cable, under no circumstances did I touch the inside conductor. It was not a serious shock, but I did feel it. It felt like an AC pulse with a few higher voltage spikes spaced about 1 to 2 seconds apart. I turned off both switches (pulling the power cord), and the voltage was still present.

It appeared to be only this cable that was live, although I didn't test the others. I screwed it in to the other multiswitch, and after the cascading was done, no longer got a shock.

I came back wearing some vinyl gloves (which work pretty well for things like this) and took a voltmeter to the system, touched one end to the case of the switch (with all conductors installed), and got a reading of 3mv... basically 0V. I took off the offending cable, it also showed 0V. *then* I took off the offending cable, and another feed cable, and put a multimeter between the outer housings of the two cables. I got a 43V reading. This was probably what was shocking me.

Essentially, it appears that somewhere 43V are being injected into the system in the outer housing, and is being grounded out through one or more of the other cables.

My question is this: Is this voltage being in the system normal, abnormal, or hazardous? If it is normal, why is it present, and if it is not, where could it be coming from? And a related question is: Should the Direct TV installers have grounded the case of the multiswitch? There is a readily available copper pipe to clamp to.

Thanks in advance for your help.

 

[rkrenicki]

A lifted neutral or miswired outlet (reversed hot and neutral) at the device at the other end of that wire.

I find this problem alot with cable tv stuff and occasionaly with a computer.

I try to ground every device I can.. in my current house I have all of my diplexers and splitters grounded to the building ground (since its right next to the service box for the house)

While that wont rectify the problem, it will help protect your other equipment.

 

[duskglow]

I purchased one of those polarity testers, and I'll let you know what I find.

 

[Floyd]

Check the equipment at the other end of the cable with the voltage on it and find where the voltage is coming from. It wouldn't hurt to get an outlet tester and go around the house to make sure all the outlets are wired properly.
It is possible that a TV is bleeding some voltage onto the system.

 

[Jared Twomey]

also, just another bit of information that might be helpful to you... the satellite receiver itself is putting out between 13 and 18 volts at all times, (depending on what transponders it is looking for). 42 seems really really high,
i had a system one time do basically the same thing... a directv that when i removed the cables on the switch, it shocked me hard... the problem ended up being a bad ground on a trailer. When i pulled the cable i guess i became the "least path of resistance".
I isolated the problem by hooking up the receiver off of a power inverter ran off of my truck.
i would check all your grounding points.

 

[Ilya]

Incidentally, a typical phone line has 48 Volts (on-hook). Another potential source of voltage in your wiring.

 

[Jimbo]

Incidentally, a typical phone line has 48 Volts (on-hook). Another potential source of voltage in your wiring.

I don't think this is his problem, the telephone system puts out 48v DC, from batteries in the Central Office, this is used for Talk voltage, one side of your line coming to the house.

I touch this voltage all day long, never even feel it.

Ringer voltage is different , that can be felt, if your touching both sides while someone is ringing your phone, that will range between 80 and 120 V AC


Jimbo

 

[Dishpointer]

Was this a D* system? I use to get shocked all of the time when I had D*. Hasn't happened with E* equipment.

 

[duskglow]

Quick update.

I tested the outlets they were all fine. My client asked the electrician about it, he said that a current of 40V or so was normal and he won't fix it, and recommended just using latex gloves like I did.

I don't understand his reasoning but I don't feel like fighting with it.

I give up.

Thanks for all your help.

 

[Change]

My guess would be a difference between earth ground and utility ground...at our ham shack we had to put in a decoupling transformer, as there was some hideously large voltage potential between our earth ground and the power company's ground. (One would expect ground to be ground, but that appears to not always the case)

If the coax is grounded to a grounding rod outside somewhere, you can check the voltage between that and the ground in a power outlet.

 

[sksatellite]

What about if you get shock from just doing the dish, I means nothing get connect yet. ONe experienced was, putting the dish attached to the wall stone, I am sure the lag screws will not pass through the stone, when you touch the dish you get shock. And touch the gutter sometime feeling shock too.

 

[dishcomm]

Quick update.
I tested the outlets they were all fine. My client asked the electrician about it, he said that a current of 40V or so was normal and he won't fix it, and recommended just using latex gloves like I did.
I don't understand his reasoning but I don't feel like fighting with it.
I give up.
Thanks for all your help.

That is not normal..the electrician probably did not want to deal with the problem....ihave experienced this a couple of times..Getting shocked..once it was voltage going across the house ground. that I think was due to redneck engineerring..Told trhe guy that his system wasn't geting grounded at all...
NAother time I was catching voltage of the tv....
the theory that an outlet is miswired is the most logical.