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Household Surge Protectors - Good or Bad?

A few weeks ago I had a surge protector installed in my breaker panel.

It was a new variey I had not seen before, in that it took the place of two standard sizede breakers and connected to both phases of the breaker panel supply

Since then we’ve had had a couple of power outtages and all the household devices kept running upon power restoraton - so far so good :-)

This past week I had reason to disconnect power and speaker cables to loan to a friend for audition.

Afterwards I reconnected the power cables to the amp and powered up.

NOTE: the system is on a dedicated line - it’s breaker was not touched by the install

Immediately I noticed a hum from the amp, where previously there had been none - even at full volume with the phono stage selected.

After lots of analysis and testing, I remembered the installation of the Surge protector.

I measured the impedance between the ground and the neutral and found around 5 ohms of resistance.

To temporarily get over the hum I have connected the neutral side of the inputs to a common earth tap on the power distribution box - it has worked like a charm - i.e. until I can get the electrician back here to fix the real issue.

So my question:
- Is this just sloppy work? - I’m assuming that the neutral of the dedicated line was disconnected and not reconnected correctly, OR
- do ALL housewide surge protectors such as the one I have had instlaled always present with this problem?

Thanks for any feedback

williewonka

Showing 3 responses by jea48

jea48
2,944 posts
 
@williewonka,

If you turn off the 2 pole breaker in the electrical panel the SPD (Surge Protection Device) is connected to, the SPD will be disconnected, isolated, from the electrical panel.

If you still have the hum then you can’t blame it on the SPD.

Since then we’ve had had a couple of power outtages and all the household devices kept running upon power restoraton - so far so good :-)

This past week I had reason to disconnect power and speaker cables to loan to a friend for audition.

Afterwards I reconnected the power cables to the amp and powered up.
Did the audio system sound fine up to the point when you disconnected it? What changed when you hooked it back up?
jea48
2,944 posts
 
I've since installed a ground between the neutral side of the inputs and the ground of the mains supply -
Not a good idea. Also against NEC electrical safety code. The neutral can only be bonded, connected, to earth ground at one point, the main electrical service equipment. What you have done by connecting the neutral to ground again at the branch circuit wiring is to create a parallel path for load neutral current to return to the electrical panel on the equipment grounding conductor.
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jea48
2,944 posts
 
williewonka OP
1,719 posts                                                                     08-20-2018 8:26am


I think I did not explain myself properly...
- I did not make any changes the bonding points of the neutral and ground in the breaker panel.
- I simply took a wire from the "neutral side" of the inputs on the amp and grounded it to the ground point on the power bar in my audio rack
Yes, I did understand you.
You connected the neutral conductor to the equipment ground/equipment grounding conductor at the power bar at the audio rack.

The neutral conductor is a current carrying conductor. In the case of a two wire circuit the neutral conductor (The Grounded Conductor) will carry the same amount of current as the HOT (The Ungrounded Conductor). If there is a 5 amp connected load on the Hot conductor there will be 5 amps on the neutral conductor.

When you connected the neutral conductor to the equipment ground you provided a parallel path for the current to return to the source, the electrical panel. You made the equipment ground/equipment grounding conductor a current carrying conductor. That can dangerous...... If the equipment grounding conductor is of the same wire gauge and made from the same metal then it will theoretically carry half the current in the circuit as the neutral conductor did before you connected the neutral to it. So if using 5 amps as an example, when you connected the neutral conductor to the equipment ground/equipment grounding conductor there was 2 1/2 amps on each of the two conductors.

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