UL stands for Underwriters Laboratories, a non-profit safety organization established over 100 years ago. UL is one of the world’s oldest safety certification companies. Through comprehensive procedures and guidelines UL requires their standards are met before certification is granted. Another part of the agreement is traceable labels. Each product listed must have a label affixed to the product traceable to the manufacturer through Underwriters Laboratories.
UL 467 – Standard for safety for grounding and bonding equipment, explains about the requirements for connecting clamps, bonding equipment, wire mesh and earth electrodes. Let us discuss about the specifications, test requirements and testing procedure of earth electrodes as specified by this standard.
- The rod electrode shall not be less than 3m of length. If the rod has to be used in US, the length of rod electrode shall not be less than 2.44m.
- A solid rod electrode of iron or steel shall have a diameter not less than 16mm.
- An uncoated solid rod electrode of SS, copper or suitable non-ferrous metal shall have a diameter not less than 12.7mm. For Mexico, the diameter should be not less than 14.8mm
- A coated solid rod electrode shall have a diameter not less than 12.7mm.
- The stainless-steel coating or a stainless-steel rod shall be formed of an austenitic stainless steel of the 18% chromium, 8% nickel type.
Chemically charged rod electrodes are made of a hollow tube made of copper or equivalent material filled with corrosion resistant chemical substances.
- The hollow tube is made of copper or equivalent material resistant to corrosion
having an internal diameter not less than 49.3mm and wall thickness not less
- The chemical charge within the rod electrode shall be a substance that does not
cause the electrode to corrode at a faster rate.
- A chemical charge of 60% sodium chloride and 40% calcium chloride having a
total weight of less than 5 kg (11 lb) may be used without further evaluation.
A plate electrode shall
a) be not less than 6.4 mm (6mm for Canada) in thickness if of iron or steel, or 1.5 mm if
of nonferrous metal, other than aluminium;
b) have a total surface area of not less than 0.186 m2 (0.4 m2 for Canada);
If the grounding or bonding devices are provided with specific instructions for assembling the connector to the conductor, such instructions shall be followed in the preparation of the test specimen.
The test current shown in below table shall pass through the assemblies specified. After supplying the current for specified duration, continuity of the materials should be checked. A grounding or bonding device should not crack, break, or melt when subjected to the current and time specified by the standard.
The current values of electrode materials other than the ones listed can be derived as
per Annex C of IEEE std 837-2002.
The thickness of a protective coating shall be determined by a reliable electronic or magnetic method, or by an electrochemical method. The measured thickness of any protective coating shall comply with the values specified by the standard.
A 457 mm (18 in) length of the rod with one end cut to a 45° point shall be driven between two steel clamping plates or the jaws of a vise set 1.02 mm (0.04 in) less than the diameter of the rod, so as to shear off sufficient metal to expose the bond between the coating and rod. There shall be no separation of the coating from the steel core when subjected to adherence of coating test
A length of the rod shall be rigidly held in a clamp or vise. A force shall be applied normal to the free end of the rod at a distance from the clamping device equal to 40 times the rod diameter. The application of force shall be such that the rod is permanently bent through a 30° angle. There should not be any cracks on the coating of electrode after bend test.
A cut, stencilled, or threaded surface of a device not intended for burial in earth or embedment in concrete need not be tested.
The marking of a ground rod shall be located within 305 mm (12 in) of the top of the rod and shall include the following:
a) the manufacturer’s name, trade name, or both, or any other distinctive marking
whereby the organization responsible for the product can readily be identified;
b) a distinctive catalog number or an equivalent identification; and
c) the length of the rod.
We can verify the certification of the product using the Online Certifications Directory.The Online Certifications Directory includes the names of companies authorized to use the UL Mark on or in connection with products in compliance with UL’s requirements.
Having UL Listing guarantees that the product fully complies with each and every one of UL’s requirements in the applicable standard. Since UL467 explains about all the requirements of earth electrodes (dimensions, coating thickness, adherence of coating, bending and current carrying capacity), the products tested and certified as per UL 467 will be of very good quality. Because of very stringent testing procedures, UL certification makes the earth electrodes more reliable and provides unbiased accuracy of safety.