Up until now in the previous blog entries we have seen that the amateur station must be installed in accordance to the National Electrical Code. For those of you reading this that are outside the jurisdiction of the NEC and NFPA, I apologize in advance as the subject will be geared towards hams in the USA. That does not mean that you shouldn’t consider the NEC as good, basic guidelines, but you need to be ensure that your station is constructed in compliance of the regulatory body or the local requirements in your area.
Let’s get started.
How do we install a station so that it complies with NEC? We will first start at the ground electrode system, or as most might know it: the ground rods. That’s where most folks begin in this journey and where most folks deviate and create problems.
What is a ground electrode? This is defined in NEC Article 100 as “A conducting object through which a direct connection to the earth is established.”. It is most common to hear folks refer to electrodes as ground rods, or just rods. Advanced or exotic forms of electrodes are beyond the scope of this blog.
What qualifies as a grounding electrode? As per 250.52 (some material removed for brevity please reference NEC for original text prior to performing any system design or work):
250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10ft) or more (including any metal well casing bonded to the pipe) and electrically continuous to the points of connection of the grounding electrode conductor and the bonding conductor(s) or jumper(s), if installed. (Note: There are specific requirements that must be met in order to utilize underground water pipes. Please reference appropriate sections.)
Metal Frame of the Building or Structure. The metal frame of the building or structure that is connected to the earth by one or more of the following methods:
At least one structural metal member that is in direct contact with the earth for 3.0 m (10 ft) or more, with or without concrete encasement.
Hold-down bolts securing the structural steel column that are connected to a concrete-encased electrode that complies with 2S0.52(A)(3) and is located in the support footing or foundation. The hold-down bolts shall be connected to the concrete-encased electrode by welding, exothermic welding, the usual steel tie wires, or other approved means.
Concrete-Encased Electrode. A concrete-encased electrode shall consist of at least 6.0 m (20 ft) of either (1) or (2):
(1) One or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (V2 in.) in diameter, installed in one continuous 6.0 m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effective means to create a 6.0 m (20 ft) or greater length; or
(2) Bare copper conductor not smaller than 4 AWG Metallic components shall be encased by at least 50 mm (2 in.) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or within vertical foundations or structural components or members that are in direct contact with the earth. If multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system. Informational Note: Concrete installed with insulation, vapor barriers, films or similar items separating the concrete from the earth is not considered to be in “direct contact” with the earth.
Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.
Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.
(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of steel, shall have the outer surface galvanized or otherwise metal- coated for corrosion protection.
(b) Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.) in diameter, unless listed.
Other Listed Electrodes. Other listed grounding electrodes shall be permitted.
Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of bare or conductively coated iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Solid, uncoated electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness.
Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems, underground tanks, and underground metal well casings that are not bonded to a metal water pipe.
(B) Not Permitted for Use as Grounding Electrodes. The following systems and materials shall not be used as grounding electrodes:
Metal underground gas piping systems
Wow, that was a lot of information!
So we know what ground electrodes are now. For our purposes, we generally use ground rods, 8′ long by 5/8″ in diameter, copper clad steel. They are not solid copper, as some folks might think. They look like they are, but if you examine each end of the rod you can clearly see it is steel-cored. If rods were solid copper, they would bend as soon as you tried to put them into the earth. Copper itself is very malleable; try using a sledge hammer to drive a 3/4″ copper pipe, it will bend in half.
As for terminology, lets make sure we use the right terms. The ground rods are not stakes, I see them referred to that a lot, and it is very confusing. Let’s use the right terms, so we can sound more like professionals and not like a bunch of blithering idiots. We want to be treated as professionals, so lets act like one, or at least try to. They are called ground electrodes, or just simply put, ground rods.
With all of that said, I think most folks will simply install an 8-foot or longer ground rod at the entry of their station. That’s about the simplest you can do, unless you happen to be lucky enough to have the antenna and control lines entering the station/home/shed/shanty at the same point where the electrical utility is. In that case, the electrode(s) are already installed and all that must be done is to properly bond everything to that point.
For those amateurs that may be in a situation where they have one or many of the other options available, unless it is easily done (i.e. there is a stub of wire from the UFER in the foundation or there is a metal beam available, etc), it is best to still install an additional electrode and bond that back to the other electrodes in the system (code requirement).
One important point to note, is that in no where was it stated that it is approved to use a piece of copper pipe. I see a lot of hams using copper pipes that they are ‘jetting’ into the earth using water. That might work, and seems like a good idea, except it doesn’t meet code requirements. Code states that a pipe can be used provided that it is 3/4” trade size diameter, galvanized steel, 8 feet in length, and is driven.
Exotic electrodes such as “chemical rods”, seem like they are copper pipes with electrolytic salts in them and they are UL-Listed and therefore approved by the NEC to be used as ground electrodes, in all areas of the ground electrode system.
Installation of the electrode(s):
Now that we have the ground electrode(s), we can install them. The first task to do is we must call the utility location service and have the location of the utilities marked. Some areas refer to this as DigLine, OneCall, or some other term. This is to reduce the chances of damage to the underground utilities during the installation of the electrode(s). It is simple to do, and it is the law.
Once the utilities are located, we have determined and ensured the location of the rods will not impact any underground utilities, and it is safe to do so (not during a lightning storm), the next thing is we need to some how get this electrode into the earth. This is the fun part. Sometimes.
This can be done using a sledge hammer, a fence post driver, or my favorite, a power or pneumatic tool. It really doesn’t matter how it is done, but it needs to be done such that it meets code requirements. Those are: if practicable, below permanent moisture level, the rod must not be cut down or shortened, and the head should not be deformed.
It is important to note that any supplemental electrodes (those electrodes above and beyond one, or the first driven electrode in the system, i.e. the utility entry electrode found at homes and other buildings) shall not be less than 6 feet apart from any other electrode of another grounding system (NEC 250.53 (A) 1 through 3). Again, here we have an electrical code requirement.
Something to be noted, is that it is widely understood that you actually want to have these electrodes further apart than 6-feet; something more along the lines of 8 to 15 feet, but ideally 10 to 15 feet. This is not a place for any debate on the subject or to go in-depth as to why, so we will leave it at that. Don’t put electrodes closer than 6 feet. Period.
Rods shall be installed in a vertical manner, straight down into the earth, or if that is not possible due to rocks, installed at a no more than a 45-degree angle. If you hit rock, you’ll need to start again, in a different location. There is a stipulation for installing electrodes horizontally, however that requires additional considerations, beyond the scope of this blog at this time.
Pro tip: Install the ground conductor clamp (the acorn clamp) over the top of the rod and down onto it a few inches and cinch the bolt down. You don’t want to try and do this after the rod has been driven and the head is slightly mashed/deformed (it happens).
Pro tip: The way I always advocate that rods are installed regardless of practicable methods, is that the rod head should be below frost line, or at least 12-18” down in the earth. This also allows you to install inspection wells (use a small 8” circular sprinkler valve box) over the top of the rods so that you can properly inspect the acorn clamp yearly to ensure it has not worked its way loose. This of course becomes irrelevant if you are making your rod-to-wire connections using exothermic welds. If that is the case, simply bury the head of the rod below grade, ideally below the frost line.
Continue to add ground electrodes to your system until you have installed the required amount as per your system design and in accordance with the guidelines set forth by the NEC. This might be one rod at the station entry, or a series of rods in a ring configuration, counterpoise configuration, etc.
In the next blog entry, we will address connecting the rods together.
Until next time, 73 de ke7ii sk sk sk