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Install Grounding when you Trench. Nov 23rd 2019, 13:02 1 663 on 23/11/19

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Topic Author Posted On
Tying into power cord N0CHS on 23/11/19
Using conductors which can carry 125% of the power supply's rated continuous output, connect it's single output to some sort of multi port power outlet. If that first cord or wire set is more than a foot long it should be fused in line for it's listed ampacity. The multi port power distribution device does not have to be anything fancy. I strongly recommend that you do not spend money on elaborate assemblies which have all sorts of fancy features or built in fusing. No mater how careful you are you will eventually connect a wire to a connection point which is fused above the wires ampacity. If instead you install fuses in line in all your wire sets and cords the wire will have the proper protection no matter what it is plugged into.

If you are using listed wires or cord you do not have to use the derated value which the National Electrical Code calls out for some conductors. You can use the value from the ampacity tables which give the maximum continuous current for that wire with the insulation used. Select a fuse for the inline fuse holder which matches the table value for the ampacity of the conductor.

If you are using Powerpole connectors there are connecting blocks of those connectors which have up to 12 ports on them. These cost far less than assemblies which have built in fuse holders, meters, alarms, and other features of dubious value.

If you prefer binding posts for your wire terminations than fit each wire set or cord with crimp on fork terminals sized to fit the binding posts you are using. Any project or electrical box with space to fit the needed number of binding posts will make a fine mounting place for the multiple terminals. By adding a brass or copper washer between each crimp on terminal you can fit several on a single binding post.

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Tom Horne W3TDH
Grounding and bonding KG5WKO on 23/11/19
Quote by W1VT
NEC requires that all grounds be bonded together. Otherwise, a lighting strike may cause a lot of damage jumping from conductor to conductor as it travels to the "best" ground rod.

I wouldn't expect tuning issues. But, you can have common mode issues from connecting ground rods together. Common mode chokes are used on coax cables to get rid of this noise.

Zak W1VT
ARRL Senior Lab Engineer

Zak W1VT

I'm not an engineer but I've installed communications shelters in a lot of different places both domestic and international. Any place I have worked there was one certainty. No Grounding Electrode of any kind would be left not bonded to every other Grounding Electrode on any site. Your first sentence says what we always did in the field. Your second sentence throws me completely off my soundings; as in out of my depth. How does connecting Ground Rods or any other Grounding Electrode into a single Grounding Electrode System cause common mode issues? What common mode issues are you referring to? I'm Lost!

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Tom Horne W3TDH
Install Grounding when you Trench. W3TDH on 23/11/19
Any trench you dig, such as for running coaxial cable antenna feed lines or conduit that will contain them, that begins at the building were your Shack is located can be an opportunity to markedly improve your Shack's Grounding System.

20+ feet of any trench can be a good location to install a Grounding Electrode Array. Dig the first 20 to 30 feet of the trench to a depth of 30 inches or more. Drive in a ground rod through the bottom of the trench at least the rod's own length away from any underground structure such as a basement wall. In order to be maximally effective the rod needs to have a shell of earth around it that has a radius of the length of the rod. Drive the second rod the combined length of both rods further out along the trench. Join the 2 rods to each other and the termination point using #2 American Wire Gage (AWG) or larger bare copper wire as the Grounding Electrode Conductor (GEC). Connect the GEC to the driven rods using testing laboratory listed Ground Rod Clamps.

For even greater effectiveness use 2 inch wide or wider copper strap as the GEC. That can be made from a roll of copper roof flashing cut to the desired width. The pieces can be joined using pieces of copper plate held together over the joint and connected through the strap to each other using stainless steel hardware. Connect the copper strapping to the rods using copper plates which you have formed around the rod by clamping both in a vice. Such splicing and rod connection kits can also be purchased from amateur radio equipment dealers.

Remove any copper oxide from any surface that will be part of a connection between the parts of the Grounding Electrode System (GES) and cover the joining surfaces with copper antioxidant paste. This can be done with "Emery Cloth" abrasive tape or with a wire brush.

To avoid your new Grounding Electrode System becoming a problem instead of a solution make sure that it is bonded to the existing electrical service Grounding Electrode System. By bonding the 2 systems together you avoid any marked difference in potential between them and thus avoid any destructive current flow between the 2 separate systems through your radio equipment and accessories. Missing this step could leave you hating me and life in general. Since, like most people I'd rather be liked than hated I ask that you not skip this important step.

If you have to dig a trench anyway why miss the opportunity that the excavation offers to install a highly effective Grounding Electrode Array for your Shack.

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Tom Horne W3TDH

depth in ground of feedline pvc conduit alpease on 23/11/19
The standard depth of burial to the top of buried conduit based on the National Electrical Code's section 300.5, Underground Installations, is 18 inches at 600 volts or less. Any less depth of burial would expose the conduit to physical damage from ordinary yard care and gardening activities.

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Tom Horne W3TDH

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