ECN Forum Forums General Topics of the Trade General Discussion Area IWire...or any other commercial guys.....(especially retail....)

Larry separate neutrals, even if possible will not 'fix' this problem. The harmonics remain even on a two wire circuit, all that changes is the point where the harmonic current starts multiplying on a single neutral..with two wire circuit you have just moved the point to the panels feeder neutral which will still be supplying the equipment.

Also harmonics are becoming less of an issue, the European standards have forced the manufactures into dealing with the harmonics at each device.

If it anything like what I saw you have dozens of pieces of equipment interconnected via a switching device and spread out over a large area so much of the equipment ends up on different circuits.

Bob, I've seen this once before, and it ended up being the multiplexer, and cabling.

But the "working when pluged into a 2 prong", throughs my thought off.

Now it don't make sense, if it happens all over the country.

it's about 60 tv's spread out over around 2000 sq ft. different circuits. but they all interconnect into a central computer (so that the programming can be uploaded and changed remotely)

"turned everything on"

Have you tried bringing things on a few at a time and see if you can develop a pattern to the failure?
Different circuits, different types of equipment etc. Think about where the TV signal is coming from and where the TVs are being powered. You might be able to recreate the failure with 2 appliances and that makes it easier to get your head around. When I worked on power quality problems the real fix usually ended up being a regular article 250 issue, like a bad grounding connection somewhere. Usually they had tried lots of exotic things first.

Are the shields to the signal cable properly grounded at one end?

"Bob, I've seen this once before, and it ended up being the multiplexer, and cabling."

You will find the cabling and cable distribution is the problem, the bars are telling you this, their cable distribution has a problem, not your installation, in sayreville, we had a location with the same problem your describing, it turned out to be a faulted cable distribution amp, on a pole 1000 ft down the street.

That was my thinking Les, but what is with the "working with a 2 prong"

I'm lost on that.

i'm leaning towards their equipment or connection.

we turned everything off and on one circuit at a time, didn't make a difference.

they aren't using a cable signal from outside. They all run off a computer (for lack of a better term) that runs pre-programmed commercials for them on all the tv's.

there definately is a problem related to the difference between the neutral and the ground (1.0V) when they plug all the tv's in with 2 prong adapters, the problem disappears.

But it's a problem in the entire store.

I honestly don't know why the problem occurs when then use the ground prong.

I also, don't think that the voltage between the neutral and ground should be a problem.

In the past few years we've done setups like this for thousands of TV's, and have never had this problem.

However, this is the first time for this store and the first time with their equipment.