What is CSST Bonding?
CSST (Corrugated Stainless-Steel Tubing) bonding is a technique in which a conductor is electrically connected to CSST metallic gas piping and then connected to the grounding electrode system to provide a low impedance path to the ground. CSST Bonding is used to reduce the possibility and severity of arcing between conductive systems when energized by a lightning strike on a CSST gas pipe or nearby.
The CSST must be permanently bonded to the grounding electrode system of the electrical service of the home in which the CSST is installed. This arrangement provides an electrically continuous path to stray voltage/current safely to the ground.
Proper bonding of CSST may significantly reduce the risk of fire or damage to the CSST gas pipe caused by a lightning strike.
Why CSST Bonding is Necessary?
When CSST is installed without being properly bonded then there is an increased risk of fire or damage to the gas lines when a lightning strike or power surges happens nearby.
Note that lightning is a highly disruptive force and when it happens nearby, it can travel along the CSST gas pipe. This traveling energy can jump to near metal and dissipated its energy.
Now if the CSST is not being properly bonded, the difference in potential between gas pipe and metal can produce arc which can damage to the CSST gas pipe. When CSST is damaged, it can leak gas and cause fire or an explosion.
The CSST bonding will help to achieve an equipotential state between the CSST gas line and bonded metallic conductor. Therefore, CSST Bonding is necessary to reduce the risk of fire or explosion resulting from damaged gas lines in the event of power surges and lightning strikes. The below figure shows the damaged CSST gas line due to lightning strike.
CSST Bonding Diagram
For proper bonding of CSST, a separate bonding wire is connected to the rigid gas piping before the CSST, or directly to one of the CSST nuts. The below figure shows the CSST bonding diagram.
The below figure shows an example of proper CSST Bonding.
CSST Bonding Code
The CSST bonding, bonding conductor, grounding electrode system, bonding clamp, and grounding conductor must be in accordance with the code. Let’s discuss it one by one.
In accordance with the National Fuel Gas Code, the International Fuel Gas Code, and the Uniform Plumbing Code the direct bonding is provided for CSST gas piping systems for homes and buildings. Bonding of CSST is to be considered an electrification work and it should be installed and inspected by a qualified electrical contractor and electrical inspector.
The bonding conductor must be installed, protected, and connected to the grounding electrode system in accordance with the National Electrical Code, NFPA 70, and Canadian Electrical Code, CSA-C22.1.
The bonding conductor can be a solid or stranded aluminum or copper conductor. The size of the bonding conductor must not be smaller than a 6 AWG (American Wire Gauge) copper wire or the equivalent size of aluminum if the bonding conductor is made of aluminum. The below figure shows an example of a bonding conductor.
The bonding conductor must not be longer than 75 feet (22860 MM) in accordance with the National Fuel Gas Code, the International Fuel Gas Code, and the Uniform Plumbing Code.
The bonding clamp is never attached to the corrugated stainless-steel tubing. It can be attached to any location within the gas piping system.
The location of the bonding clamp on the gas piping system must be selected so that the shortest bonding wire length will improve the effectiveness of the direct-bond. The below figure shows an example of a bonding clamp.
Bonding clamp must be installed based on UL467 and shall make metal-to-metal contact with a rigid pipe component or CSST fitting. The gas pipe surface must be clean, paint and coatings free to allow a proper metal-to-metal connection.
Grounding electrodes must be a metallic conductor and should be connected to the earth. The following materials are typically used as grounding electrodes.
- Structural Steel
All electrodes must be bonded together into one common grounding electrode system. A grounding electrode and grounding system can not be installed separately for the gas piping system. The below figure shows a grounding electrode connection.
Grounding Electrode System
The grounding electrode system comprising of grounding electrodes and a grounding electrode conductor. The installation and inspection of the grounding electrodes and grounding systems must be performed by a qualified electrical contractor and electrical inspector.