Branch Circuit Testing

Branch Circuit Testing
Basics of Branch Circuit Testing

Why test branch circuits Causes of branch circuit failures Emerging Technologies General Tests methods Type of Testers. Basics of Branch Circuit Testing

Why Test Branch Circuits?
Safety Issues Electrocution Equipment failure Fire caused by Electrical circuits Branch Circuits with or without AFCI protection The primary reason for testing branch circuits is safety. Problems with branch circuit wiring can result in fire, electrocution and equipment failure Basics of Branch Circuit Testing

Basics of Branch Circuit Testing
Electrical Shock Every week someone is killed by Electrocution through installed home wiring. 490 people lost their life from Electrocution in 1997* from: Consumer products – 24% Large appliances - 16% Installed home wiring - 12% Although the death rate by accidental electrocutions have decreased from 760 in 1987 to 490 in 1997 (36% reduction) we must always stay vigilant in our efforts to protect ourselves, and our customers. These deaths were a result of consumer products, large appliances and installed home wiring. The there top killers are #1 consumer product, and small appliances like TV, radios, stereos, at 24% #2 Large appliances like air conditioning, pumps, freezers, at 16% #3 Installed home wiring, at 12% This means the an estimated 58 people loose their life from installed home wiring or about one person a week someone died form electrocution. US Consumer Product Safety Commission Memorandum on 1997 Electrocutions *NFPA and US Consumer Product Safety Commission 1997 data Basics of Branch Circuit Testing

Causes of Electrical Shock
Defective protection devices like TVSS, and GFCI There have been several changes to UL943 Requirement for GFCI’s due to studies over several years of older units not operating properly. Effective January 2003 Defective wiring, Neutral to Ground bonds. Poor Ground conductor circuit Poor Earth Ground Electric shock is usually a result of a defective protection device, such as a transient voltage surge suppressor or a ground fault circuit interrupter, a poor grounding circuit, or a poor earth ground. Basics of Branch Circuit Testing

Equipment Failures Failures result in: Erratic operation Lost productivity Lost/corrupt data Damaged equipment Poor power efficiency Many equipment failures are caused by problems within the electrical system. These failures result in inefficient or erratic equipment operation, and damaged equipment Basics of Branch Circuit Testing

Fires NFPA and US Consumer Product Safety Commission 1997 data showed 406,000 residential structural fires Residential fires accounted for 74% of all structure fires 3,390 civilian deaths and 17,775 injuries Residential fires resulted in 97% of all deaths and 87% of injuries 9% of all structural fires and 7% of deaths were a result of failures within the electrical distribution system Based on NFPA and the US Consumer Product Safety Commission data there was an estimated 406,000 residential structure fires in 1997, resulting in an estimated 3,390 civilian deaths, and 17,775 injuries. Approximately 9% of the structural fires and 7% of deaths were determined to be the result of the electrical distribution system. By far, residential fires were the largest problem, accounting for about 97% of the structure fires, and 87% of the deaths. NFPA (National Fire Protection Agency) Fact Sheet on Fire in the US and Canada Consumer Product Safety Commission 1997 Residential Fire Loss Estimated Basics of Branch Circuit Testing

Estimated Fire losses Electrical Distribution Fires Injuries Deaths Installed Wiring 14,600 420 110 Cord, Plug 6,300 320 90 Switch, Outlet 4,900 160 10 Lamp, light Fix. 9,900 350 30 Other 4,600 Total 40,300 1360 250 Installed wiring was by far the largest cause of electrical distribution fires, resulting 14,600 fires, 420 injuries and 110 deaths in 1997. Other causes include cords and plugs, defective devices, switches, and receptacles, and light fixtures. Data from consumer product safety commission 1997 report Estimated Fire losses in residential Structures selected equipment, 1997 *NFPA and US Consumer Product Safety Commission 1997 data Basics of Branch Circuit Testing

Estimated Fire losses According to a recent report by the National Association of State Fire Marshals, during the period from , there was an average of over 70,000 total electrical fires, which were responsible for over 500 deaths Of these 70,000 electrical fires, 60,000 were caused by arcing, not from an overloaded or short circuit Information taking from: The Truth About AFCIs (Part 1) A recent report by the National Association of State Fire Marshals states: According to the National Fire Protection Association and the National Fire Incident Reporting Sys- tem data, during the five-year period from , there were an average of 73,500 total electrical fires annually, which were responsible for 591 Deaths, 2,247 injuries, and property damage totaling $1,047,900,000. The electrical problems that lead to these fires went undetected by conventional circuit breakers. Of these 73,500 electrical fires, 60,900 or 82% were caused by arcing and not by overloads or short circuits "AFCI Inquiry and Report" by the Consumer Product Safety Task Force of the National Association of State Fire Marshals, August 1, 2002. "AFCI Inquiry and Report" by the Consumer Product Safety Task Force of the National Association of State Fire Marshals, August 1, 2002. Basics of Branch Circuit Testing

Causes of Electrical Fires
Series Arcing Faults: can be Defined as a partial or total conductor or path in series with the load that alternates between infinite resistance to high resistance or normal. Since the arc condition is in series with the load, the arc current cannot exceed the loads current. Series arcs may contribute to insulation degradation that might lead to parallel arc conditions. Example would be a break in the conductor which has carbonized or has intermittent contact. Arc-fault Circuit Interrupters--A Critical NEC 2005 Issue Series Arcing Fault 4 A series fault at which arcing occurs. [A series (continuity) fault 4 is a partial or total local failure in the intended continuity of a conductor characterized by either infinite resistance (a completely severed conductor) or by resistance that alternates between infinite resistance and high or normal resistance such as intermittent connection at a loose wiring terminal or splice. Note: A series fault may contribute to an insulation fault.] With respect to series arcing faults, we note that, since the fault is only in one of the circuit conductors, the load determines the amount of current that is conducted. These low current arcs have low power dissipation and small diameter. Consequently, the spatial region for ignition is small. 4 Technology for Detecting and Monitoring Conditions that Could Cause Electrical Wiring System Fires. UL Report for CPSC, contract #CPSC-C , September 1995. Arc-fault Circuit Interrupters--A Critical NEC 2005 Issue / High Resistance Series Fault 4 Brendan Foley, Joseph Engel, and Clive Kimblin. Basics of Branch Circuit Testing

Parallel Arcing Faults, occur as a short circuit or a ground fault. A short circuit arc decreases the dielectric strength of insulation separating the conductors, allowing a high-impedance, low-current arc fault to develop, that carbonizes the conductor's insulation, further decreasing the dielectric of the insulation separating the conductors. The result is increased current, exponentially increased thermal energy, and the likelihood of a fire. The current flow in a short circuit, parallel arc fault is limited by the system impedance and the impedance of the arc fault itself. Not necessarily the breakers rating. The Basics of Arc-Fault Protection by Mike Holt, Mike Holt Enterprises, Inc. | Apr 01 '02 EC&M Although new to the NEC, AFCIs are important for protecting against arc faults. Unsafe arc faults can occur as series or parallel arcs. A series arc can occur when the conductor in series with the load breaks. The series configuration means the arc current cannot be greater than the load current the conductor serves. Typically, series arcs don't develop sufficient thermal energy to create a fire. More dangerous is the parallel arc fault, which can occur as a short circuit or a ground fault. A short circuit arc decreases the dielectric strength of insulation separating the conductors, allowing a high-impedance, low-current arc fault to develop that carbonizes the conductor's insulation, further decreasing the dielectric of the insulation separating the conductors. The result is increased current, exponentially increased thermal energy, and the likelihood of a fire. The current flow in a short circuit, parallel arc fault is limited by the system impedance and the impedance of the arc fault itself. The Basics of Arc-Fault Protection by Mike Holt, Mike Holt Enterprises, Inc. | Apr 01 '02 EC&M Basics of Branch Circuit Testing

High Resistance Fault: is a series fault characterized by the presence of abnormally high resistance, compared to a normal wire, wire termination, or wire splice, resulting in a reduction of capacity and heat dissipation at the fault. These high resistance series faults result from a build-up of copper or aluminum oxide that creates a high resistance, "glowing contact.“ This high-resistance point can become extremely hot with temperatures exceeding 600° F causing insulation failure, that can result in a damaging high-power parallel arcing fault or ground fault. Glowing contacts can develop at virtually any electrical connection conducting current. The current in the high resistance fault, like the series arcing fault, is limited to the current being drawn by the load—until the insulation degrades to the point where this type of fault becomes a parallel arcing fault or causes leakage current to ground. Arc-fault Circuit Interrupters--A Critical NEC 2005 Issue High Resistance Series Fault 4 A series fault characterized by the presence of abnormally high resistance (high resistance in comparison to the normal resistance of the normal conductor but not high comparison to the infinite resistance of a completely severed conductor) in a wire, at a wire termination, or wire splice, resulting in a reduction of ampacity and an excess of heat dissipation at the fault. Examples are a partially severed stranded conductor with only a small percentage of the strands intact and a corroded wire terminal or splice. In our experience, these high resistance series faults result from a build-up of copper or aluminum oxide that creates a high resistance "glowing contact."6 This high-resistance point can become extremely hot with temperatures exceeding 600° F causing insulation failure that can result in a damaging high-power parallel arcing fault or ground fault. Glowing contacts can develop at virtually any electrical connection conducting current. The current in the high resistance fault, like the series arcing fault, is limited to the current being drawn by the load—until the insulation degrades to the point where this type of fault becomes a parallel arcing fault or causes leakage current to ground. 4 Technology for Detecting and Monitoring Conditions that Could Cause Electrical Wiring System Fires. UL Report for CPSC, contract #CPSC-C , September 1995. Arc-fault Circuit Interrupters--A Critical NEC 2005 Issue / High Resistance Series Fault 4 Brendan Foley, Joseph Engel, and Clive Kimblin. Basics of Branch Circuit Testing

Summary, Series or High Resistance Arc Faults: are the results of defects in the wiring as part of a conductor or connection that is in series with the load Since the arc condition is in series with the load the arc current cannot exceed the Loads current. Glowing contacts in copper or aluminum wiring High resistance in Back-wired devices like receptacles Loose or corroded connections Bad splices Hot plugs, or high resistance contact between outlet to plug. The most common causes of fire were a result of high resistance connections, such as loose or corroded connections, bad splices or improper installation, and defective devices, such as light fixtures, receptacles or switches. In fact, these problems accounted for 75% of the electrical distribution fires. Basics of Branch Circuit Testing

New Technology AFCI breakers were adopted in the NEC defined as a device to provide protection from an ARCing Fault. UL 1699 Defines the requirements for these devices, but the most common and commercially available is the Branch/Feeder or B/F type. In there are discussion that for 2008 a combination AFCI breaker will be adopted. This breaker would sense both Series and Parallel faults. NEC Requirement NEC defines an AFCI as "a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected." The AFCI has two basic functions, which are recognizing arc characteristics and de-energizing the circuit when it recognizes them. There is no protection unless the source of voltage is disconnected from the hazard, once the hazard is detected. The requirement of (B) states, "All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter listed to provide protection of the entire branch circuit Basics of Branch Circuit Testing

New Technology AFCI B/F breakers sense common load current and adds protections from parallel arcing faults and Ground faults UL and EIA determined that protection from a Series arc that included arcing to ground be at least 5 amps They also reported that the lowest short circuit current line-neutral in the US to bewithin 75 amps at a receptacle. The Truth About AFCIs (Part 1) The 5-ampere detection requirement was set for series arcs that include arcing to grounded conductors. The 75-ampere level was taken from a survey conducted by UL for the EIA that reported that the lowest short circuit level available at a receptacle within the United States is 75 amperes. This means that a line-to-neutral fault in a branch circuit will have 75 amperes or more available. Correspondingly, AFCI testing verifies that the AFCI will detect an arc in a circuit with 75 amperes available. Therefore, the 75-ampere detection level will identify and de-energize arcing short circuits that are known fire causes. All currently available AFCIs will detect line-to-ground arcs at 50mA or above Basics of Branch Circuit Testing

New Technology UL 1699 defined six devices, but three major types of AFCI's for branch circuits, Branch/Feeder, Outlet Circuit, and Combination devices. The Branch/Feeder type is the most common and the only device at this time that satisfies the current NEC requirements. What does a Branch/Feeder AFCI do. Over current protection: This is the normal function of a breaker. To trip when the load current has exceed the current rating of the breaker. Hazardous Arcing: An AFCI will trip when it senses a characteristic arcing between line and neutral above 75 amperes. Ground Faults: The standard requirement for an AFCI is to trip on a line to ground fault of 5 amperes or greater. Most AFCI will trip between 30mA to 50mA. Neutral to Ground Faults: If the neutral conductor comes in contact with a grounded circuit the AFCI will trip. AFCI Types There are six devices covered in UL 1699, three of which are defined there as follows: Branch/feeder AFCI — A device intended to be installed at the origin of a branch circuit or feeder, such as at a panelboard. It is intended to provide protection of the branch-circuit wiring, feeder wiring, or both, against unwanted effects of arcing. This device also provides limited protection to branch-circuit extension wiring. It may be a circuit-breaker type device or a device in its own enclosure mounted at or near a panelboard. Outlet circuit AFCI — A device intended to be installed at a branch-circuit outlet, such as at an outlet box. It is intended to provide protection of cord sets and power-supply cords connected to it (when provided with receptacle outlets) against the unwanted effects of arcing. This device may provide feed-through protection of the cord sets and power-supply cords connected to downstream receptacles. Combination AFCI — An AFCI which complies with the requirements for both branch/feeder and outlet circuit AFCIs. It is intended to protect downstream branch-circuit wiring and cord sets and power-supply cords. Definitions of the cord or portable AFCIs or the leakage-current detector-interrupter are not provided here because they are for specialized applications and are not intended for general protection of branch circuits. Basics of Branch Circuit Testing

New Technology Table of ARC Detection and Protection Capability From A Branch Feeder AFCI Arc Condition Branch/Feeder type Line-to-Neutral Yes- 75 A Line-ground Yes- 50 mA Series with ground Yes - 5 A Series without gnd no Table 1 briefly compares the capabilities of the three types plus the outlet branch circuit AFCI. This table, together with the definitions, is intended to help clarify the differences between these three types. So far, only the branch/feeder AFCI has been offered commercially, to the knowledge of the authors. It is the commonly available AFCI in circuit-breaker form. The outlet circuit AFCI is intended for protection of extension and appliance cords. It could also be produced in "feed through" form to protect fixed wiring on its load side. Located at a receptacle outlet, it would not protect the entire branch and would not satisfy the NEC requirement. * Part of Table 1 from The Truth About AFCIs (Part 1) Basics of Branch Circuit Testing

Testing of the Branch Circuit
General Testers cannot identify High Resistance or Series faults nor can they identify a Neutral to ground bond Glowing contacts in copper or aluminum wiring High resistance in Back-wired devices like receptacle Loose or corroded connections Bad splices Hot plugs, or high resistance contact between outlet to plug. A high resistance connection, can result in hot spots or Glowing connections which can breakdown in insulation and poor efficiency of the electrical system Circuit testers are excellent for quick checks and general function branch testing, but are not suited as an analysis tool. The object in any electrical distribution system is to minimize impedance (resistance) to energy. High resistance results in higher energy usage or heat. A simple Static non-load test preformed with a circuit tester or digital voltage meter cannot identify hidden defects in the circuit which can cause high resistance. Problems and hazards arise when current flows through these high impedance defects which results in hot spots, leading to fires, breakdown in insulation, and poor efficiency of the electrical system, which can contribute to erratic equipment operation. Basics of Branch Circuit Testing

Nor can a General Tester identify a “False” or “bootleg” ground Defined as an accidental short or improper bonding of ground to neutral conductors Shows up as normally wired condition with general receptacle testers Sensed by the new AFCI breakers, Conditions will trip an AFCI at turn on. At times may be very difficult to locate. False ground conditions are shorts between ground and neutral. This condition will not show up on a standard receptacle tester. Only the SureTest can identify a false ground condition. If this condition exists, the SureTest will immediately display a FG on the LED display so it can be checked out prior to testing the circuit. Basics of Branch Circuit Testing

Before the adoption of the AFCI Circuit breaker, Many of the same wiring faults existed and still exist today in standard branch circuits, BUT DO WE TEST FOR THEM ON NON-AFCI CIRCUITS? AFCI’s have helped minimize wiring or load defects in the branch circuits with which they are associated, but it doesn’t address all circuits. Series faults are not covered by the present AFCI technology. Is there a way to Identify many of the problems found in branch circuits today? Circuit testers are excellent for quick checks and general function branch testing, but are not suited as an analysis tool. The object in any electrical distribution system is to minimize impedance (resistance) to energy. High resistance results in higher energy usage or heat. A simple Static non-load test preformed with a circuit tester or digital voltage meter cannot identify hidden defects in the circuit which can cause high resistance. Problems and hazards arise when current flows through these high impedance defects which results in hot spots, leading to fires, breakdown in insulation, and poor efficiency of the electrical system, which can contribute to erratic equipment operation. Basics of Branch Circuit Testing

Using Voltage Drop NEC code Articles {210-19(a) FPN No. 4} {215-2(d) FPN No. 2} - “Branch circuit conductors should be sized so as not to exceed a maximum voltage drop of 3% at the farthest outlet , and that the combined voltage drop for both a branch and feeder should not exceed 5%” By measuring the voltage drop at the furthest receptacle from the panel you can check the integrity of the circuit. A low voltage drop indicates a low impedance electrical system which lowers the risk of hidden hazards and improves power efficiency and equipment operation. The NEC contains several fine print notes which if taking into consideration can help minimize resistances and lower risk of hidden hazards. It will also improve power efficiency and operation. NEC code Articles {210-19(a) FPN No. 4} {215-2(d) FPN No. 2}, state in that – Branch circuits conductors be sized so as not to exceed a maximum voltage drop of 3% at the farthest outlet , and that the combined voltage drop for both a branch and feeder should not exceed 5%. [fn 1] 1. Branch Circuits – This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [210-19(a) FPN No. 4], (1) [fn 1] 2. Feeders – Feeder conductors be sized so as not to exceed a maximum This FPN recommends that feeder conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [215-2(d) FPN No. 2], (1) National Electrical Code and NEC are resisted trademarks of the National Fire Protection Agency (1) Source Measure the voltage drop at the furthest receptacle from the panel Low voltage drop indicates a low impedance system Lowers the risk of hidden hazards Improves power efficiency and operation Basics of Branch Circuit Testing

Testing under a load and calculating voltage drop can identify common wiring problems Undersized wiring for load or length of run NEC (a) FPN no.4 states that conductors be sized to provide reasonable efficiency of equipment operation High resistance connections Loose or corroded connections Poor splices Defective devices Voltage drop can detect an estimated 90% of defects on a branch circuit To identify these problems, the circuit must be tested using a known load. Testing under load and measuring the voltage drop will identify wiring problems, such as undersized wire or high resistance connections, caused by loose or corroded connection, poor splices or bad devices. In fact almost 90% of hidden defects on a branch circuit can be identified by measuring the integrity of a branch circuit with the voltage drop test. Basics of Branch Circuit Testing

Lets do a little Experiment to test this out. I have a circuit with a receptacle at the end of 60 feet of wire With no-load is the voltage the same on DMM A and DMM B? Note reading With a load attached to the circuit is the Voltage the same on DMM A and DMM B ? Calculate Voltage drop DETERMINING CIRCUIT VOLTAGE DROP Load/No-Load Method– Single-Phase Only First remove all loads from the circuit and measure the No-load voltage at the last branch device. Second return all loads back to the circuit. If we we have a 15 or 20 amp breaker the max load is recommended to not exceed 80 % of rating. As an example we have a 15 amp services and a maximum expected load to be around 12 amps. We can use a hair dryer as a load. Measure the load voltage. Now subtract the the No-load voltage from the Load Voltage to get your voltage drop. Then divide the voltage drop by the no load voltage and multiplied by 100. This is your percentage of voltage drop. Voltage Drop = V (no-load) – V (load) % Voltage Drop = Voltage Drop/ V (no-load) Basics of Branch Circuit Testing

We all remember the Old Way A hair-dryer or drill worked well as a load for this test We Measured the line voltage with no-load and then with load and recorded the reading If a circuit was already under a load the additional amp load would trip the breaker An easy experiment can be conducted to demonstrate line lose. You will need 6 to 8, 12 ft or longer extension cords, two digital multimeters, and a hair-dryer The connections between the extension cords represent the devices or a number of contacts. Connect the extension cords together to make up a straight cord. Place one digital multimeter at the first cord and one at the last. Measure the voltage at both ends without and with a load from the hair dryer. Note: The difference between the readings on each meter. You will see a difference on the meters between when you apply the load. Use the voltage drop calculation to determine the voltage drop and percentage of voltage drop. Basics of Branch Circuit Testing

Using Modern Technology A Device like the IDEAL SureTest circuit analyzer places a load on the line and Calculates the 12, 15, and 20 ampere voltage drop. One method to Identifying High resistance circuit faults Patented technology pulses the load on the line without tripping circuit breakers or interrupting existing equipment Voltage drop can also be measured with a SureTest Circuit Analyzer. The SureTest places a full 15 amp load on the line and calculates the voltage drop. It has a patented technology to place a load on the line and without tripping the circuit breaker, or interrupting any equipment on the circuit. Basics of Branch Circuit Testing

Calculating Voltage Drop VD = I x R I = Current = 16 Amperes R = Resistance of conductors = .4 Ohms 2 Ohms/1000 feet for 12 gauge (Chapter 9, Table 8) 2 Conductors of 100 ft = 200 Feet (2/1000) x 200 = 0.4 Ohms VD = 16 A x 0.4 = 6.4 Volts VD% = 6.4/120 = or 5.3 Answer: (b) 6.4 volts Voltage Drop = I x R “I” is equal to 16 amperes “R” is equal to 0.4 ohms (Chapter 9, Table 9: (2 ohm/1,000 feet) x 200 feet Voltage Drop = 16 amperes x 0.4 ohms Voltage Drop = 6.4 volts, (6.4 volts/120 volts = 5.3% volts drop) Operating Voltage = 120 volts – 6.4 volts Operating Voltage = volts Author’s Comment: The 5.3% voltage drop for the above branch circuit exceeds the NEC’s recommendations of 3%, but it does not violate the NEC unless the 16 ampere load is rated less than volts [110-3(b)]. (1) Source Basics of Branch Circuit Testing

Using this method not only helps us determine the integrity of the circuit, it also gives additional information, not just the resistance of the conductors, but of the entire circuit. Ohm’s Law Method – Single-Phase Only Voltage drop of the circuit conductors can be determined by multiplying the current of the circuit by the total resistance of the circuit conductors: VD = I x R. “I” is equal to the load in amperes and ”R” is equal to the resistance of the conductor as listed in Chapter 9, Table 8 for direct current circuit, or in Chapter 9, Table 9 for alternating current circuits. The Ohm’s law method cannot be used for three-phase circuits. Basics of Branch Circuit Testing

Finding the Cause of High Impedance Measure the voltage drop at the furthest receptacle from the panel and record the reading Repeat this at each receptacle until you find a significant decrease in voltage drop from one receptacle to the next At that point check the circuit and wiring leading to the last receptacle. Check voltage drop on remaining receptacles If voltage drop is acceptable in remaining receptacles, then the problem is probably localized at the receptacle connection If voltage drop is unacceptable, then the problem exists within the hot or neutral conductors Move to the next furthest receptacle, record the voltage drop and compare it to the previous receptacle. Repeat this process until you find a significant decrease in the voltage drop from one receptacle to another. Once you find it, check the remaining receptacles. If the voltage drop is acceptable in the remaining receptacles, than the problem is probably localized at or between the receptacles where the change occurred. If not, than the problem exists within the hot or neutral conductors. Basics of Branch Circuit Testing

Finding the Cause of High Impedance If all devices have high voltage drop then the high impedance is caused by: Undersized wire for length of run Splice between the panel and the first device Poor connections or corroded contacts at panel, breaker, neutral bus, etc. If the voltage drop is unacceptable on all devices, then the problem may be undersized wire for the load, or length of run, a bad splice between the panel and the first device, or a problem at the panel itself, such as a poor connection or corroded contact. Basics of Branch Circuit Testing

Finding the Cause of High Impedance In this example there is a poor connection between Device 2 and 3. This poor connection didn’t show up with just a DMM reading, but under a load test the voltage drop on device 2 was 8% while device 3 and 4 was 12% This identifies that we have either a poor connection or defective device between device 2 and 3. It turns out to be poor connection in on the device between 2 and 3. Note The electrician who wired this used 14 gauge wire and push in contactors. The distance from the panel to the last receptacle was 85 feet. The average current draw to this branch circuit is 12 amps on a 20 amp breaker. Using Ohms law method what would be an expected voltage drop on the last device. In this example there is a poor connection between Device 2 and 3 which did not show up with a DMM reading. Under a load test the voltage drop on device 3 and 4 was 12%. The voltage drop at device 2 decreased to 8%. Basics of Branch Circuit Testing

SureTest also shows correct wiring including Identifying Neutral to ground contact faults to within 15’ of the fault and 15’ from the panel. Conductor impedance of Hot, Neutral and ground N-G Voltage GFCI With time to trip ARCI Fault testing Voltage drop can also be measured with a SureTest Circuit Analyzer. The SureTest places a full 15 amp load on the line and calculates the voltage drop. It has a patented technology to place a load on the line and without tripping the circuit breaker, or interrupting any equipment on the circuit. Basics of Branch Circuit Testing

Finding Hot Spots Most poor panel connections show up as hot spots in the panel Test quickly with an infrared temperature meter Voltage drop across contact point, such as a breaker should not exceed 10mV to 100mV. This is also true for switch contacts. Check contact points and breaker Most poor panel connections show up as hot spots on the panel. These can be checked quickly with an infrared temperature meter. Check voltage drop across breaker. The voltage drop should not exceed between 10mV and 100mV. If greater than 100mV check contact points and breaker. Basics of Branch Circuit Testing

Importance of the Ground wire Three major reasons for ground To provide Zero reference for the electrical service Provide a low resistance path to protect from electrical faults Protect equipment against static electricity and protect against frame potential for the operator’s safety The grounding circuit is responsible for protection Basics of Branch Circuit Testing

Common Faults with the Ground wire High impedance grounds Rule of thumb < 1 Ohm Electronic equipment and data networks require very low impedance IEEE recommends < 0.25 Ohms False Grounds Undersized ground conductor, corroded or loose contacts If circuit conductors are increased in size to accommodate voltage drop the ground should also be sized accordingly (NEC –122(b) The SureTest Patient Technology can test the Impedance The ground wire and also Identify false or N-G faults Basics of Branch Circuit Testing

Installation of Safety Devices
Ground Fault Circuit Interrupters NEC requires installation of GFCI in bathroom, kitchens and outside. Purpose is to protect individuals by detecting ground faults. Defective or improperly installed GFCI can lead to shock. NEC section see Pass & Seymour’s booklet “Overview of 1999 NEC Changes” The purpose of a ground fault circuit interrupter (GFCI) is to protect personnel by detecting potentially dangerous ground fault and quickly disconnecting power from the circuit. Improperly installed (example would be the last receptacle of a branch circuit) or defective GFCI will not protect an individual from electrical shock. Any current over 8mA is considered potentially dangerous. A GFCI compares the current in the hot conductor to the current in the neutral conductor. If the current in the neutral becomes less than that of the hot, a ground fault exist and the device should trip. It is important that the GFCI trip on fault current as low as 4mA to 6mA to adequately protect against shock. Point of reference: Underwriters Lab. SureTest family have GFCI testing, some provide in the test Current and time to trip information Basics of Branch Circuit Testing

Ground Electrode NEC Code requires a single ground electrode to have 25 Ohms or less resistance, and if not, be augmented by one additional rod spaced at least 6’ apart of any type specified in section or This measurement can be taken with a three point earth resistance tester or a ground resistance clamp meter We are all for-mil-ur with the NEC code requirement for a single ground electrode to have a resistance of 25 ohms or less, and if the resistance is not >25 ohms to drive a second electrode at less 6 feet from the first. Depending on where you live in this country, that may not be enough. How would we know when so few actually measure ground resistance of an electrode. Basics of Branch Circuit Testing

Integrity of the Branch Circuit
Causes of AFCI Tripping at turn on Over-current. For any current above its current rating it will trip according to its circuit breaker time-current characteristic. Hazardous arcing. For arcing at current levels of about 75 amperes and above, the AFCI will trip. Commercially available AFCIs will actually operate at some level below 75 amperes. The AFCI will operate faster than a fuse or circuit breaker under short-circuit over-current conditions up to about 125 amperes. Arcing ground faults. The standard requires tripping on faults of 5 amperes and greater. Commercial units will actually detect ground faults of 50 milli-amperes and greater. Tripping will be instantaneous, with no intentional delay. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI The circuit-breaker branch/feeder AFCI incorporates functions of both an overcurrent protective device and an arc-detection device. It is designed to trip under the following conditions. Overcurrent. For any current above its current rating it will trip according to its circuit breaker time-current characteristic. Hazardous arcing. For arcing at current levels of about 75 amperes and above, the AFCI will trip. Commercially available AFCIs will actually operate at some level below 75 amperes. The AFCI will operate faster than a fuse or circuit breaker under short-circuit overcurrent conditions up to about 125 amperes. Arcing ground faults. The standard requires tripping on faults of 5 amperes and greater. Commercial units will actually detect ground faults of 50 milliamperes and greater. Tripping will be instantaneous, with no intentional delay. Basics of Branch Circuit Testing

Shared Neutral in residential wiring t Shared Neutrals is a practice where one three wire conductor is used as a homerun for two single-phase circuits. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. Basics of Branch Circuit Testing

Causes of Tripping at breaker turn on or with load Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches the ground wire or grounded metal, the AFCI will trip, if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. Basics of Branch Circuit Testing

Finding the Causes for the Trip If after Energized, an AFCI circuit immediately trips, what steps should be taken? Well , a lot of approaches have been suggested , but an orderly search or approach will help reduce the stress. Remember that AFCI’s have two primary Functions Over-Current sensing Arc Fault condition One of the most common faults is found to be a * Neutral to ground contact fault or false ground. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. * The SureTest Patient Technology can test the Impedance of the ground wire and also Identify false or N-G faults Basics of Branch Circuit Testing

Finding the Causes for the Trip The AFCI will sense an arc that occurs because of Insulation or isolation break-down, which can be tested with an insulation tester Disconnect all loads and verify that unconnected wire ends are insulated. Disconnect the load wire to the AFCI, or GFCI in the circuit. Use the Megger to apply a direct voltage starting with 250 then 500. It is always best to start with a voltage that is 2X the rating of the source and increase if necessary A rule of thumb is, roughly 1 megohms per 1000V, but it is always best to consult with the wire manufacturers for best results. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. Basics of Branch Circuit Testing

Finding the Causes for the Trip If the trip is not Instantaneous, it would indicate an overload trip Energize the circuit and measure the load current over time. A clamp meter should be able to determine this. A DMM with CT that has a fast Peak hold function, may also be useful in Identifying between Over-Current and Arcing. Disconnect load and reinstall to Identify the defective device. Finding the Causes for the Trip The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. Basics of Branch Circuit Testing

Finding the Causes for the Trip If the trip is Instantaneous, it could indicate Ground Faults or earth leakage. Ground faults are small amounts of current that “leak” over to ground caused by deteriorating insulation or moisture. A Low amperage current clamp or clamp meter, with a low range having the ability to measure 5-10 mA accurately, could help. The GFCI or AFIC measure the difference between current out and current in. If there is an imbalance, it will trip. Disconnect load and reinstall to Identify the defective device. The Truth About AFCIs Part 1 Causes of Tripping of the Branch/Circuit AFCI Neutral grounding. If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance. Abnormal environments. Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock. Basics of Branch Circuit Testing

Protect personnel and equipment by: Verify that electrical devices have been wired up correctly Maintain a low impedance electrical system Maintain a good electrical ground In summary branch circuit testing is an important part of wiring any circuit. It verifies that devices have been wired up correctly, helps ensure a low impedance electrical system and good electrical ground, which are all necessary to adequately protect personnel and equipment. Basics of Branch Circuit Testing

Use certified devices and testing equipment Not all Testers are what they seem to be! Branch circuit testing should Verify proper wiring Measure the integrity of the branch circuit Measure the integrity of the ground conductor Measure the integrity of the ground electrode Install and test the operation of safety devices The dangers are very serious, but fortunately the precautions are very straight forward. We can protect ourselves and equipment by using certified devices and testing equipment from reputable manufacturers. Implementing policies on branch circuit testing which include verifying proper wiring, checking the integrity of the branch circuit, measure the integrity of the ground conductor and ground electrode and install safety devices. Basics of Branch Circuit Testing

Certification labs test devices and equipment for failure under extreme conditions to protect consumers With “Free trade and open markets” there has been an surge of counterfeited certifications UL provides information on their web site Certification labs such as UL put products through a series of rigerous tests to determine how the products will hold up in the most extreme conditions. With “Free trade and open markets” there has been an entrance of counterfeited lab certifications such as UL. Find out weather the products are UL certified, or purchase only from reputable manufacturers. Example of a press release Underwriters Laboratories Inc. (UL) is notifying consumers, electrical distributors, electrical contractors and retailers that Ground Fault Circuit Interrupters (GFCI) bearing the company name KIC Corporation do not comply with UL's safety requirements and bear a counterfeit UL Mark on the device packaging. These GFCI's do not interrupt the supply of power during the presence of a ground fault condition and may present a potential safety hazard. Basics of Branch Circuit Testing

Receptacle Testers Check to ensure that devices have been wired up correctly immediately after installation Proper wiring of receptacle Correct voltage level Good continuity on switches Warn against faulty wiring in 3-wire receptacles Test GFCI receptacles for proper operation Receptacle testers warn against faulty wiring in 3-wire receptacles. They plug directly into an outlet, and have three lights to indicate common wiring problems, such as reversed polarity or open grounds. Models are also available that will verify the proper operation of GFCI receptacles. Basics of Branch Circuit Testing

To test a GFCI, an imbalance needs to be placed between hot and neutral The the amount of imbalance and time to trip should be monitored to verify GFCI performance Many receptacle testers will test GFCI receptacles The Ideal will not only test GFCI but will also test the AFCI Breaker A GFCI compares the amount of current in the ungrounded Hot and Neutral conductors. It the current in the Neutral conductor is less than that of the Hot, then a fault current condition exist. Any current over 8mA is considered potentially dangerous. A GFCI compares the current in the hot conductor to the current in the neutral conductor. If the current in the neutral becomes less than that of the hot, a ground fault exist and the device should trip. It is important that the GFCI trip on fault current as low as 4mA to 6mA to adequately protect against shock. Most GFCIs’ should trip within 30 milliseconds with fault currents as low as 4mA to 6mA and should not exceed 8ma. Point of reference: Underwriters Lab. Basics of Branch Circuit Testing

Circuit Identifiers Identify circuit breakers and fuses without service interruption Automatic or adjustable sensitivity levels Visual and audible indication Circuit identifiers, or circuit breaker finders, can be used to determine the branch circuit that devices are on. They do this while the power is on, without any service interruption. The transmitter emits a signal onto the line which is picked up by the receiver at the panel. A thumbwheel on the receiver allows you to adjust the sensitivity. On the first pass, the receiver may pick up more than one breaker. After a few adjustments, the exact breaker can be identified. This process can be done electronically with IDEAL’s automatic circuit breaker finder. On the first pass over the breakers, the unit will calibrates itself to the signal strength of the transmitter. On the second pass, the receiver identifies the breaker or fuse. These units give an audible and visual signal to indicate when the correct breaker has been found. In addition to these features, the circuit identifier and automatic circuit identifier have designed the transmitter into an E-Z Check Plus GFCI receptacle tester. You get all the testing capabilities that come with the receptacle testers along with the transmitter. model has an Analog Receiver has Digital Receiver w/ NCV, High voltage transmitter with GFCI Basics of Branch Circuit Testing

Voltage/Continuity Testers
Test from ranges of 6-600V volts AC or DC Some units vibrate to provide tactile indication of voltage level Audible continuity Voltage/Continuity testers are used to quickly check the voltage level of an outlet or device to make sure it was wired for the appropriate level of voltage. These are often referred to as solenoid testers, because of the solenoid device that creates a vibration. The stronger the level of voltage, the stronger the vibration. After time, the feel of the meter allows the user to determine the level of voltage without looking at the readout of the tester. This is an additional safety feature, as it provides a third method of indicating the presence of voltage if the environment makes it difficult to see the display or hear the audible alarm. Digital testers are also available which quickly test for voltage and continuity. They offer the advantages of digital circuitry, such as better accuracies, quicker response times, and Category III safety ratings. The Vol-Con Elite is unique because it gives the feel of a solenoid tester with its unique vibration mode. Like the solenoid testers, the vibration increases as the level of voltage increases. Basics of Branch Circuit Testing

To test a AFCI you need to generate a number of high current pulses to simulate the effect of an arc condition that may exist in wiring or cords, IDEAL has Two Testers which can simulate an arc They Are the; GFCI/AFCI testers Circuit Analyzer with AFCI and GFCI Basics of Branch Circuit Testing

SureTest Circuit Analyzer
Measures integrity of a branch circuit Voltage drop under an actual 12, 15, 20 Amp load Measures Conductor and ground impedance Wiring and Identifies false grounds GFCI AFCI Some models not shown Measure harmonic distortion 61-164 SureTest Circuit Analyzer While receptacle testers can identify problems at the receptacle, only the SureTest can look beyond the receptacle, and identify problems all the way back to the panel. A patented feature allows the SureTest to place a full 15 ampere load on the line without interrupting any equipment on the circuit. By comparing this load to a no-load condition you get a true voltage drop measurement. In addition, it will measure the ground impedance all the way back to the panel, verify isolated grounds with the isolated ground adapter, and identify false grounds. Some models will even measure harmonic distortion. All by simply plugging the unit into an outlet. SureTest Circuit Analyzer with AFCI Basics of Branch Circuit Testing

Infrared Temperature Meter
Checks for hot spots in breakers and panels Laser point sighting to target device under test 15 to 1 angle of view ability 15 inches from panel will measure temperature across 1 inch circle Hot spots on a panel can be easily and safely identified with an infrared temperature meter. IEDAL’s has a laser point sighting to target an individual breaker. The angle of view ability specification is an indication of the range of the unit. A 15/1 ratio indicates that at 15 inches away from an object, the unit is measuring the temperature across a 1 inch circle. At 15 feet, the measurement point is 1 foot in diameter. Most of the units on the market have an 8/1 ration forcing you closer to the panel for the same precision. Basics of Branch Circuit Testing

Earth Testers Ideal/Megger 3 pole Testers IDEAL/Megger 4 pole Testers Self powered - no need for hand crank Low power consumption Compact and lightweight Quick battery check Limited lifetime warranty Basics of Branch Circuit Testing

Earth Testers Ideal Ground Resistance Clamp Ground Resistance Ground Leakage Current Auto ranging Audible indication < 40 ohms Open jaw indication Data hold Basics of Branch Circuit Testing

SureTest Circuit Tracers
Series Tracers Open/Closed Tracer Superior tracing technology inside case Operates from 0–600V AC/DC Rugged hard case UL Listed to Cat III-1000V Basics of Branch Circuit Testing

Branch Circuit Testing

Similar presentations

Presentation on theme: "Branch Circuit Testing"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Branch Circuit Testing

Similar presentations

Presentation on theme: "Branch Circuit Testing"— Presentation transcript:

Similar presentations

About project

Feedback