2. tech-talk
  3. 137640-1640

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
williewonka OP
3,075 posts
 
Thanks guys - the surge protector that is installed has an LED idicating it is operational. If there is an issue the LED goes out. There is no way to turn it off..

I'm pretty sure there is an issue with the neutral or ground conenctions, so I will take a look at them first.

I have had a similar hum with a consumer DVD player and my NAIM amp - it seems that NAIM has a particular design approach that seems to highlight grounding issues.

I've since installed a ground between the neutral side of the inputs and the ground of the mains supply - this made the amp completely silent (i.e. quieter than before the SP was installed) - BONUS :-)

I'll still check the neutral/ground, but I will then assess the need for the new grounding scheme.

One thing I did notice after the SP install - my home network/TV Streaming became much more reliable.

Many Thanks for all the input
jea48
4,451 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.
.
erik_squires
16,138 posts
 
@jea48 is absolutely right! 

You may have exactly one bonding point between neutral and ground. However, you may (and may have to!) have multiple ground rods which are connected to each other. That does not allow you to connect neutrals willy nilly to your ground rod "farm" though. You may still only have one bonding point. 
williewonka OP
3,075 posts
 
Again, thanks for the input.

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 

Anyhow - that has since been removed

Turns out - all that was required is a slight "repositioning"  to a couple of the wires in the breaker panel.
-  the electrician had repositioned a couple of breakers and those live wires ran paralell to (and was touching)  the neutral wire of the cable run for my dedicated audio outlet
- He just moved the wires to put a little more space between them 
- the hum disapeared.

Regards - Steve
jea48
4,451 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.

.

More to discover