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Can you put a GFCI into a circuit with an existing GFCI and what will happen if the two GFCIs are in a series circuit?
Wiki User
∙ 14y ago
Note: The latest types of Ground Fault Circuit Interruptor (GFCI) are also called Residual Current Devices (RCDs).
"Can you put a GFCI into a circuit with a GFCI?" is probably the same question as "What if two GFCI are in series in a circuit?" and the answer is that one GFCI will most likely trip earlier than the other to break the circuit. Which one will trip first depends on the actual difference in sensitivity between the two GFCIs. Leakage currents are measured in mA (1 mA = 1 thousandth of an Ampere) and GFCIs are designed to trip at a certain leakage current with a tolerance of say + or - 3%. So if the basic trip current was 20 milliamps one GFCI might trip at 19.4 mA and the other at 20.6 mA and they would both be within the design specification. The one that trips at 19.4 mA would be expected to trip first. <><><> This question requires answering by a VERY knowledgeable electrician, or an electrical engineer. I am neither, but until the right answer comes along, I will attempt to provide some information which hopefully will allow a better understanding of the issues involved. A GFCI [ground fault circuit interrupter] is much different from, although similar to, a circuit breaker. The DIFFERENCE is WHAT they are designed to detect and react to. The purpose of a fuse or circuit breaker is to detect excess or MASSIVE current flow [ie. a SHORT CIRCUIT, a direct short to ground], and then very quickly turn off the electrical current to the circuit, in order TO PREVENT a FIRE. This is the only thing the breaker is designed and intended to do. This limited capability will not prevent a person from being electrocuted when a fault occurs within an electrical device, if the current flow happens to be low. Voltage and current faults which can kill a person usually will not be detected by a circuit breaker. A ground fault circuit interrupter [GFCI], on the other hand, is designed to, and will, detect those low level currents which can kill a person, BUT which are not great enough to trip a breaker. When a GFCI detects potentially dangerous current it, like a breaker, trips in order to open the circuit. Now as to WHY, when you placed two GFCIs in series [one in the breaker panel feeding one in an electrical receptacle], the first GFCI tripped when the second GFCI is "tested." When you press the TEST BUTTON on a GFCI it puts a high resistance load on the circuit, which simulates a "small" ground fault, and I think both GFCIs "see" the same fault and react as designed and intended. Again, a true professional should "bless" my comments, but I think that there is no danger or hazard in placing two GFCIs in series. On the contrary, I think there is redundant capability in the pairing, with the first GFCI functioning with, and as a backup to, the second. I suggest you contact your local electrial inspection department regarding what the code(s) say about this issue, and also call the tech support people at the 800 number on the packaging for the GFCIs. Another source of information is a local electrical engineer, if you know someone who can help you make contact. Until a more informed answer comes along, I hope this helps you to understand the issues involved. <><><>
As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
Wiki User
∙ 14y ago
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Explain the rules for GFCIs in bathroom wire size wiring?
NEC states that all GFCI's require a 20 amp circuit, the wire size for a 20 amp circuit is 12 gauge.
How do you wire a 120 volt gfci into a 240 volt three wire?
You can't. The 120 volt GFCI is probably just a 2-wire (hot, neutral and ground) You would have to run a new 3-wire (2 hots, neutral and ground). The two hots are how you get the 240 volts (120+120=240). Also you must make sure the wire is gauged properly. #10 wire for 30 amps, #12 wire for 20 amps, etc.
How many gfci outlets can you have on one circuit?
This question requires answering by a VERY knowledgable electrician, or an electrical engineer. I am neither, but until the right answer comes along, I will attempt to provide some information which hopefully will allow a better understanding of the issues involved. A GFCI [ground fault circuit interrupter] is much different from, although similar to, a circuit breaker. The DIFFERENCE is WHAT they are designed to detect and react to. The purpose of a fuse or circuit breaker is to detect excess or MASSIVE current flow [ie. a SHORT CIRCUIT, a direct short to ground], and then very quickly turn off the electrical current to the circuit, in order TO PREVENT a FIRE. This is the only thing the breaker is designed and intended to do. This limited capability will not prevent a person from being electrocuted when a fault occurs within an electrical device, if the current flow happens to be low. Voltage and current faults which can kill a person usually will not be detected by a circuit breaker. A ground fault circuit interrupter [GFCI], on the other hand, is designed to, and will, detect those low level currents which can kill a person, BUT which are not great enough to trip a breaker. When a GFCI detects potentially dangerous current it, like a breaker, trips in order to open the circuit. Now as to WHY, when you placed two GFCIs in series [one in the breaker panel feeding one in an electrical receptacle], the first GFCI tripped when the second GFCI is "tested." When you press the TEST BUTTON on a GFCI it puts a high resistance load on the circuit, which simulates a "small" ground fault, and I think both GFCIs "see" the same fault and react as designed and intended. Again, a true professional should "bless" my comments, but I think that there is no danger or hazard in placing two GFCIs in series. On the contrary, I think there is redundant capability in the pairing, with the first GFCI functioning with, and as a backup to, the second. I suggest you contact your local electrial inspection department regarding what the code(s) say about this issue, and also call the tech support people at the 800 number on the packaging for the GFCIs. Another source of information is a local electrical engineer, if you know someone who can help you make contact. Until a more informed answer comes along, I hope this helps you to understand the issues involved.
Why do gfcis trip?
GFCI's trip on an un balance between the current on the "hot" wire and the current on the neutral wire
Is it possible to run a 240V heater and two 120V outlets from one line of 3 wire 12 gauge romex?
It's possible. It's not right though. Run a separate wire for your 110v circuit. To follow NEC (National Electrical Code) guidelines you need two separate branch circuits: 240V and 120V.Each circuit should have its own breakers of the correct size. Wire sizes will depend on the length and ampacity of each cable.The outlet types required for each circuit will depend on the appliances to be served and, according to their locations, GFCIs may be necessary too. As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
Explain the rules for GFCIs in bathroom wire size wiring?
NEC states that all GFCI's require a 20 amp circuit, the wire size for a 20 amp circuit is 12 gauge.
How do you wire a 120 volt gfci into a 240 volt three wire?
You can't. The 120 volt GFCI is probably just a 2-wire (hot, neutral and ground) You would have to run a new 3-wire (2 hots, neutral and ground). The two hots are how you get the 240 volts (120+120=240). Also you must make sure the wire is gauged properly. #10 wire for 30 amps, #12 wire for 20 amps, etc.
How many gfci outlets can you have on one circuit?
This question requires answering by a VERY knowledgable electrician, or an electrical engineer. I am neither, but until the right answer comes along, I will attempt to provide some information which hopefully will allow a better understanding of the issues involved. A GFCI [ground fault circuit interrupter] is much different from, although similar to, a circuit breaker. The DIFFERENCE is WHAT they are designed to detect and react to. The purpose of a fuse or circuit breaker is to detect excess or MASSIVE current flow [ie. a SHORT CIRCUIT, a direct short to ground], and then very quickly turn off the electrical current to the circuit, in order TO PREVENT a FIRE. This is the only thing the breaker is designed and intended to do. This limited capability will not prevent a person from being electrocuted when a fault occurs within an electrical device, if the current flow happens to be low. Voltage and current faults which can kill a person usually will not be detected by a circuit breaker. A ground fault circuit interrupter [GFCI], on the other hand, is designed to, and will, detect those low level currents which can kill a person, BUT which are not great enough to trip a breaker. When a GFCI detects potentially dangerous current it, like a breaker, trips in order to open the circuit. Now as to WHY, when you placed two GFCIs in series [one in the breaker panel feeding one in an electrical receptacle], the first GFCI tripped when the second GFCI is "tested." When you press the TEST BUTTON on a GFCI it puts a high resistance load on the circuit, which simulates a "small" ground fault, and I think both GFCIs "see" the same fault and react as designed and intended. Again, a true professional should "bless" my comments, but I think that there is no danger or hazard in placing two GFCIs in series. On the contrary, I think there is redundant capability in the pairing, with the first GFCI functioning with, and as a backup to, the second. I suggest you contact your local electrial inspection department regarding what the code(s) say about this issue, and also call the tech support people at the 800 number on the packaging for the GFCIs. Another source of information is a local electrical engineer, if you know someone who can help you make contact. Until a more informed answer comes along, I hope this helps you to understand the issues involved.
GFCI circuitry checks for what?
Current Imbalance: GFCIs continuously monitor the current flowing in the "hot" (live) wire and compare it to the current returning in the "neutral" wire. If there is a difference of as little as 4-6 milliamperes (mA) between these currents, indicating that some current is not returning through the normal circuit path, the GFCI will trip and disconnect the power. Leakage to Ground: GFCIs are designed to detect any unintended flow of electricity to ground, which could be potentially hazardous. This can occur when there's a fault in an electrical device, damaged wiring, or when someone comes into contact with a live wire or conducts electricity to the ground. Rapid Response: GFCIs are engineered to respond quickly, typically tripping within milliseconds when they detect a ground fault. This rapid response helps prevent electric shocks and electrical fires.
Why do gfcis trip?
GFCI's trip on an un balance between the current on the "hot" wire and the current on the neutral wire
Can I install several GFCI outlets on one circuit as it would be difficult to find the first plug on the line?
Generally, no, as GFCIs are designed for one to be a "master" and have the others feed off of it.
What happens to voltage during a short to ground?
Basically, the same as if you had a short to neutral, since the neutral and ground are tied to the same bus bar in the breaker panel. The breaker should trip, or the fuse should blow. Supply of voltage then stops.See the answer to the Related Question about GFCIs - shown below - for information about circuit protection when even a small current flows to ground.
Is it possible to run a 240V heater and two 120V outlets from one line of 3 wire 12 gauge romex?
It's possible. It's not right though. Run a separate wire for your 110v circuit. To follow NEC (National Electrical Code) guidelines you need two separate branch circuits: 240V and 120V.Each circuit should have its own breakers of the correct size. Wire sizes will depend on the length and ampacity of each cable.The outlet types required for each circuit will depend on the appliances to be served and, according to their locations, GFCIs may be necessary too. As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
Do you need a special waterproof TV in your indoor swimming pool area?
Answer for USA, Canada and countries running a 60 Hz supply service.Before you use any mains electrical appliance, such as a TV, in a swimming pool area be sure to check the electrical wiring code for your locality (town/state) because the area will be subject to water spray as well as generally damp and humid conditions.Your local wiring code will give detailed instructions about its installation requirements for such conditions.In addition, depending on the locality and the actual installation site, some wiring codes will require - for personal safety reasons - that any socket outlet supplying a mains electrical appliance must be fitted with a safety device such as a Ground Fault Circuit Interrupter (GFCI) or Residual Current Device (RCD).If the local wiring code requires one of these protective devices you must fit one into the circuit to be compliant to the code.For information about GFCIs or RCDs and what such devices constantly check for, please see the answer to the Related question shown below.Before GFCIs were available you had to use an isolation transformer.As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
Why would two GFICI breaker outlets that are tapped off of an outside GFI on its own line and breaker not work?
GFCI receptacles are extremely sensitive, there are any number of reasons this may not be working for you. The first thing you can do is to make sure that the wire feeding your 2 other outlets off of the outside GFCI are connected to the line side of the device. There are 2 sides to any GFCI: the "line" and the "load" side. The line connections are typically at the bottom, and the load at the top.The load side is protecting all the downstream receptacles on the circuit. Be sure you have the blacks ("hot" or "line") and whites (neutrals) all on the correct side. Any receptacles downstream don't need to be GFCIs because they will automatically be protected if connected to the load side of the first GFCI.If you want to use GFCIS for the two new receptacles then you should make sure they are both connected to the line side BEFORE the outside GFCI so they will work independently of the outside one.As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
How does an earth-leakage circuit breaker or ELCB work?
An Earth Leakage Circuit Breaker - ELCB for short - was the first name given to what is now called a Ground Fault Circuit Interrupter (GFCI) .The early, original, type of ELCB was designed only to detect a current flowing in the safety "ground" or "earth" wire.Why was that important?If there is no fault anywhere in a circuit supplying single-phase alternating power to a unit such as an electrical appliance, machine or other equipment, the current flowing to the unit at any instant in the "hot" or "live" wire should exactly match the current flowing away from the unit in the neutral wire. Similarly, there should be no current flowing in the unit's safety "ground" or "earth" wire.It is a basic fact of electrical engineering design that all current flowing to an electrical appliance, machine or other equipment from the power generation station via its supply circuit's "hot" or "live" wire should only return to the power station via that same circuit's "neutral" wire.So, as a result of that basic fact, if any current isflowing in the ground wire, it must be caused by a fault condition and the supply of current to the circuit needs to be stopped urgently.Many years ago, before today's electronic RCDs or GFCIs were designed, much simpler electro-mechanical relays called Earth Leakage Circuit Breakers (ELCBs) were invented so that, if any such ground current exceeding just a few milliamps was detected, they would "trip" - meaning "operate" - to break the current supply to the circuits for which they were installed to protect.The original type of ELCB did not check for any difference in current flowing in the live and neutral wires, which is another indication of a very serious fault condition - even if no current can be detected flowing in the ground wire - because the "missing current" may actually be flowing to ground via someone's body!When RCDs were invented, most manufacturers of GFCIs adopted the same technology because it offers so much more protection to users than the original GFCI could ever give.In the US and Canada such devices are still commonly known as "GFCIs" or "GFIs" even though they have the additional "residual current detector" functionality, whilst in Europe and elsewhere the more accurate name of "Residual Current Detector" or RCD has been widely adopted for general use instead of using the name of the much simpler GFCI device.Another answer [Note: this is actually a description of a GFCI, not of an ELCB.]An ELCB works by comparing the input current in the "hot" line feeding a load and the return current in the "neutral" line coming back from that load.If the return current is less than the input current by a quite small amount - usually only about 30mA or less (mA = milliamps, which are thousandths of an amp) - it means there must be a leakage current.That very small difference between the input and return currents is what the ELCB is designed to detect and cause it to trip so as to break the flow of current to the load.As the name itself indicates, an Earth Leakage Circuit Breaker device always checks for any leakage of current. The leakage may be either to the "earth" or "ground" wire or to something else such as the user of the equipment that is being protected by the ELCB device.
How is a Residual Current Device or RCD different to a Ground Fault Circuit Interrupter or GFCI?
Nowadays terms Residual Current Device or RCD and Ground Fault Circuit Interrupter or GFCI refer to the same type of electrical safety device.If there is no fault anywhere in a circuit supplying single-phase alternating power to a unit such as an electrical appliance, machine or other equipment, the current flowing to the unit at any instant in the "hot" or "live" wire should exactly match the current flowing away from the unit in the neutral wire. Similarly, there should be no current flowing in the unit's safety "ground" or "earth" wire.It is a basic fact of electrical engineering design that all current flowing to an electrical appliance, machine or other equipment from the power generation station via its supply circuit's "hot" or "live" wire should only return to the power station via that same circuit's "neutral" wire.So, as a result of that basic fact, if any current isflowing in the ground wire, it must be caused by a fault condition and the supply of current to the circuit needs to be stopped urgently. Many years before today's electronic RCDs or GFCIs were designed, much simpler electro-mechanical relays called Earth Leakage Circuit Breakers (ELCBs) were invented so that, if any such ground current exceeding just a few milliamps was detected, they would "trip" - meaning "operate" - to break the current supply to the circuits for which they were installed to protect.An Earth Leakage Circuit Breaker was the first name given to what is now called a Ground Fault Circuit Interrupter (GFCI) . The original type of ELCB or GFCI was designed only to detect a current flowing in the safety "ground" or "earth" wire.So the original type of ELCB or GFCI did not check for any difference in current flowing in the live and neutral wires, a difference that would be an indication of another type of serious fault condition. Such a fault can be serious because, even if no current can be detected flowing in the ground wire, the "missing current" may actually be flowing to ground via someone's body!After miniature electronic circuits were invented the invention of RCDs became possible: an RCD constantly checks for small differences in the currents flowing in the live compared to the neutral wire and for any current flowing in the earth wire. If any such "fault current" is detected, the device is designed to act very fast to shut off the supply of power to the circuit and the unit(s) it is protecting, because the "missing current" may actually be flowing to ground via someone's body!That is the reason why, when RCDs were invented, most manufacturers of GFCIs adopted the same technology because it offers so much more protection to users than the original GFCI could ever give.In the US and Canada such devices are still commonly known as "GFCIs" or "GFIs" even though they have the additional "residual current detector" functionality, whilst in Europe and elsewhere the more accurate name of "Residual Current Detector" or RCD has been widely adopted for general use instead of using the name of the originally much simpler GFCI device.For more information on all these topics see the answers to the Related Questions and the Related Link shown below.As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
