Eric said:
erik_squires
2,549 posts 09-01-2017 10:26pm
You don’t by any chance have multiple ground rods placed far apart?
Eric,
Per NEC the bare minimum distance ground rods can be earth driven apart from one another is 6ft. Further apart than 6ft is even better. General rule of thumb is you want the ground rods at least (2X) the length of the rod/electrode from one another.
ALL ground rods must be connected together and connect with one wire to one point, that being the electrical service entrance neutral conductor. NEC defines this as being one grounding electrode. The service entrance neutral conductor shall also be bonded, connected, to the metal enclosure of the electrical service equipment. (At one point only. The neutral conductor shall not be connected to ground at any point there after.)
What you don’t want, and maybe that was the intent of your post, is to have more than one earthed electrode, (as defined by NEC as I stated above), that is not connected directly to the electrical grounding system. An example of an indirectly earth ground connection would be the earth grounding connection of the grounding block for the coax shield of a CATV company’s coax cable. Or a Dish Satellite system. NEC code requires the grounding block shall be bonded, connected, the main grounding system of the electrical service. If the distance is greater than specified, there in the length of the ground wire used, A ground rod must be driven in the earth and a minimum #6 copper wire connect the ground rod to the main electrical service grounding electrode system. The main reason is for lightning protection.
Here is usually the case though. The electrical service maybe on one side of the house and the SAT Dish or CATV provider incoming coax cable and grounding block on another side of the house. Per NEC code the installer is supposed to drive a ground rod. A ground wire is installed from grounding block the the rod. THEN the installer is required, by code, to connect the ground rod to the main grounding electrode system of the electrical service by a minimum size #6 copper ground wire. How many installers install the minimum #6 copper ground wire?
So now two separate earth electrodes exist that will have a difference of potential, voltage, between them.
The coax cable, cable shield, will connects to the grounding block, and the other end connects to a piece of equipment like a SAT or CATV receiver box, and or modem. In some configuration a wire interconnect/s and or video cable will connect from the receiver box to audio and or audio/video equipment that uses a 3 wire cord and plug plugged into a grounding type wall outlet. A ground loop circuit is established. Complete with ground loop hum. Maybe some buzzing to boot too.
.
gearheadmac said:
"When it rained really hard the other night it was noticeably worse."
In my previous post I gave an example what may have been the reason why.
Another might be, (Eric, your post got me thinking about this one.)
More moisture content increasing ground rod to earth conductivity.
As a rule that would not cause the buzz/hum sound the OP is hearing through his speakers to worsen.... JMHO....
But what if there is corrosion in the one or more of the connections in the service neutral conductor somewhere from the utility power transformer through the outside meter socket? (I would rule out the connection in the main 200 amp electrical service panel because the OP said the electrician checked all connections for tightness, and I assume corrosion.)
Any arcing in a feeder conductor connection that feeds an electrical panel could cause an electrical noise buzz in audio equipment that is fed from that feeder by way of the electrical panel, imo. Like RF it would be transferred through the electrical wiring of the house. Again JMHO....
( I should note here, only the imbalanced 120V loads of L1, leg, to neutral, and L2, leg, to neutral, return on the service neutral conductor back to the source, the utility transformer. Depending on how well the 120V loads are balanced across L1 and L2 as a rule the service neutral conductor will not carry all that much current back to the source.)
Current will take any path provided to get back to the source if a path is provided. It prefers the path of least resistance, but it will take any path provided.
If there possibly is corrosion or even if a connection is not tight somewhere in the service neutral conductor, the grounding electrode, (ground rods), for the electrical service could carry some neutral current through the less resistive soil, due to the rain, back to the source, the utility power transformer. But I don’t think that would amplify the OP buzzing sound problem he is hearing through the speakers of multiple audio systems in his home. If anything it probably should have lessened the buzzing sound. (Parallel path provided.)
(Note: Usually the transformer neutral, at the utility transformer, is bonded, connected, to earth to an earth driven ground rod inside the wire connection compartment of the transformer.Transformer steel enclosure is also bonded to the ground rod.
Cut to the chase..... I would look to see if a ground rod was driven for the grounding block of the CATV system coax cable shield. If so I would further check to see if its’ installation meets bare minimum NEC code standards/requirements.
If improperly installed that might/could account for why the OP found the night it rained really hard the buzzing sound was worse. (Better ground rod to soil conductivity. Also less soil resistivity due to more soil moisture content.) The shield of the CATV coax cable could have been/was carrying neutral current. Not only the shield but the branch circuit equipment grounding conductor that was part of the coax cable shield ground loop circuit. JMHO of course...... It would be interesting to know, what if, the OP had disconnected the CATV coax cable at the point ahead of the coax signal splitter that feeds the internet Modem and coax cable/s to CATV receivers elsewhere in the house the night of the heavy rain. Though I did suggest in my earlier post to totally disconnect the CATV coax cable from any thing it is connected to.
(Though even the next day the buzz/noise should have still been worse than before the heavy rain. That kind of makes me go back to my previous post.)
~ ~ ~ ~
At this point all conjecture. The more info the OP can provide the better.
@ gearheadmac ,
Is the main service disconnect breaker inside the 200 amp electrical panel inside the house or outside the house near the electric meter? Or possibly inside a common metal enclosure with the electric meter?
Jim
