4 Grounding and Bonding Tips Electricians Should Follow
21 Mar 2018
Without proper grounding and bonding, power outages, downtime and costly repairs are just a few of the problems building owners and facility managers may have to endure when lightning strikes. For 9-1-1 call centers, broadcast facilities and data centers, such problems could result in data loss or jeopardize the safety of individuals in emergency situations.
Because Mother Nature is unpredictable, it is important to install precautionary systems that can direct electrical charges harmlessly into the earth before it damages equipment. Grounding and bonding systems are a simple and cost-effective solution. Experience and many case studies have taught us that simply following the National Electrical Code is inadequate for sensitive installations such as those mentioned.
The best time to consult a certified electrician or designer with power quality expertise about installing a grounding and bonding system is before emergencies occur. Retrofit of existing facilities can be more expensive, but is usually very cost-effective. Below are just a few recommendations that should be followed when inspecting and installing grounding or bonding systems:
Prepare the soil: The soil is very important to the effectiveness of a proper grounding system. An area of low resistance offers a better grounding opportunity; soil resistivity is determined by the soil’s composition, contaminants, temperature and moisture. Preferably, rods should be installed in areas where the soil can be kept wet; such as near a retention pond and where the soil resistivity is consistent and undisturbed. In areas where deep frost is a possibility, deep-driven rods should be considered.
Install sufficient ground electrodes to achieve 5 Ohms to earth. The NEC requires a second ground rod or electrode if a single rod does not have a resistance to ground of 25 ohms (unit of electrical resistance) or less. Sensitive installations require a more robust grounding system, usually comprised of multiple electrodes. IEEE recommends 1-5 ohms as usually sufficient.
Ground the electrode system: Bond all present grounding electrodes together, such as metal underground piping, structural building steel, pipe and rod electrodes, plate electrodes and concrete-encased electrodes to create a grounding electrode system. All electrical systems such as power, cable television, satellite television and telephone systems should be bonded to the grounding electrode system, as well.
Install equipment grounding: Branch circuits that do not contain an equipment ground (sometimes found in older residential structures) should be replaced with branch circuits that do.
Sensitive equipment should have its own separate branch circuit all the way back to the service. Isolated ground circuits are frequently recommended.
Executing proper grounding and bonding installation, maintenance and system inspection helps keep the electrical system and individuals safe. For more information about copper wiring or grounding and bonding, visit copper.org. CDA also offers free or low-cost seminars focusing on this topic as well as other applications to electrical groups.