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Can Unrelated Electrical Fault Fry the Coax? (1 Viewer)

Allan Jayne

Senior HTF Member
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Nov 1, 1998
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Perhaps someone here could settle an argument between me and an electrician.

Abstract question: A thin wire and a thick wire are connected in parallel, namely at their ends. They are subjected to a brief large current, more than enough to melt the thin wire but not enough to melt the thick wire.

Will the thin wire melt?

The same question in a practical or real live situation:

A coax cable such as for cable TV, goes from the (main) house to a home theater in a separate buiilding. Its shield is grounded at both ends (house and theater) to the home electrical system that also serves the theater. The system is not quite correct in that there is no ground rod at the theater and grounding takes place via the ground wire going back to the house. An AC power short to ground occurs in the theater, namely involving that section of the ground wire. Then the circuit breaker for that circuit trips. We're talking about a household short circuit, not a lightning strike.

Was the coax shield in danger of being fried?

The electrician says yes. Some of the short circut current takes the route of the ground wire, some takes the route of the coax shield back to the house.

I say no; the coax shield upon heating up from a share of the short circuit current coming through, has the resistance over its length increase more than the thicker ground wire and this causes the share of current going through the coax to decrease drastically, most of the short circuit current then taking the path of the ground wire.
 

chuckg

Supporting Actor
Joined
Apr 27, 2004
Messages
921
I say set up an experiment and try it.

Personally, I think as long as the thick wire is much thicker, and there is nothing wrong with the connections for it, that the thinner wire would be safe.

I also think that it's a bad idea to ground both ends of a shield . . . this is what produces ground loops.
 

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