mikejrc
Active Member
I have a copy of the NFPA72, I obtained a Nevada State Fire Marshal Certificate of Registration type F for Fire Alarm Protective Signaling Systems, I also have a Nevada photovoltaics installer license and soon in may I will be getting my Electrician's license from the State of Nevada.
There is no need to go into credentials or education we all know what we know by education or experience in one way or another. But I must say this...
when it comes to 2 wire 4 conductors fire loop you are dead on wrong and against code.
Section 6.4.2.2.2 of your NFPA 72 book says, "where CLASS A circuits (not class D there is no such thing) are installed, the outgoing and return conductors must be physically separated to prevent total failure of the circuit ...." that means you CAN NOT install a 4 conductor cable.
Its recommended a separation of one foot where run vertically and four feet where run horizontally.
There is one exception to Class A requirements, outgoing and return conductors can be together within 10 feet of a device, appliance (not a kitchen appliance, a notification appliance ex. a siren) or equipment.
The EOL is designed to provide a path for monitoring current. So the occurrence of an open or ground will be detected and reported. Most signaling line circuits (meaning addressable devices) do not require the use of an EOL since they monitor by polling devices rather than current. Class A circuits require a separate pair of return conductors from the last device to the control unit in order to provide power and signaling for the entire circuit under a fault condition. However the circuit must contain special controls that sense the fault conditions and provide power and communications in two directions ( meaning you can have missing device/s but the others will be operational).
All that means... by having the EOL supervision at the last device you could maintain the integrity of the rest of your circuit (if designed for it) and it will allow you to find a faulty device or fault condition in the field, by splitting your circuits in halves or sections and testing with your meter which is another ball game.
Most security control panels with fire capabilities use a 2 conductor cable that supplies both power and signal (class "B") or a 4 conductor cable 2 wires for signal 2 for wires for power (somewhat Class A) and looking at my elk's diagrams it shows both UL listed "EOL supervision Relay" and a 2.2k ohm resistor installed at the last device not the panel which is consistent with figure A.5.4.7("B") Wiring Arrangements for 4 wire detectors page 72-132 on the latest edition NFPA 72 book.
Thats why when it comes to fire alarm and in order to be code compliant, i would never advice anyone to mess with all this theory unless you hire a professional. Stick to a) wireless smoke/heat detectors b)use 110V detectors with the disadvantage of not being able to monitor those with your alarm or c) 1 wire 2 conductor detectors.
The NFPA72 has nothing to do with security systems at all, it only says that security systems could be combined with a fire control panel if it's listed for that purpose. Only the fire capabilities of the alarm panel have to follow NFPA72.
Now back to security, a simple 1 wire 2 conductors circuit for security is what most people do, specially someone that does not have the experience or knowledge like we have. For 1 wire 2 conductor supervision for security it's recommended installing the EOL In a manner that is accesible etc, hence my misinterpretation of what you said as far as location or placement in places that later you can't get to.
A double EOL for a 1 wire 2 conductor circuit is another option. Many control panels (ELK, Ademco, DSC) support them.
it would be another way to do accomplish what a 4 conductor circuit could do allowing you to monitor 4 states (short, 2.2k ohms, 4.4k ohms, open, page 9 of the Elk's manual).
This post was created by someone that needed advice on wiring, someone trying to do some DIY work, if we start adding more complexity to what he is trying to do then we are failing to provide useful real life information for his particular application.
In the end, EOL supervision could be done in any way you want but it is a subject that can not be treated equally for fire and burglary applications, and it's dependent on the end user's application, residential or commercial and industrial may have different requirements when it comes to supervising your circuit status.
Let's keep it simple for those who need simple help and then elaborate if more info or details are requested.
There is no need to go into credentials or education we all know what we know by education or experience in one way or another. But I must say this...
when it comes to 2 wire 4 conductors fire loop you are dead on wrong and against code.
Section 6.4.2.2.2 of your NFPA 72 book says, "where CLASS A circuits (not class D there is no such thing) are installed, the outgoing and return conductors must be physically separated to prevent total failure of the circuit ...." that means you CAN NOT install a 4 conductor cable.
Its recommended a separation of one foot where run vertically and four feet where run horizontally.
There is one exception to Class A requirements, outgoing and return conductors can be together within 10 feet of a device, appliance (not a kitchen appliance, a notification appliance ex. a siren) or equipment.
The EOL is designed to provide a path for monitoring current. So the occurrence of an open or ground will be detected and reported. Most signaling line circuits (meaning addressable devices) do not require the use of an EOL since they monitor by polling devices rather than current. Class A circuits require a separate pair of return conductors from the last device to the control unit in order to provide power and signaling for the entire circuit under a fault condition. However the circuit must contain special controls that sense the fault conditions and provide power and communications in two directions ( meaning you can have missing device/s but the others will be operational).
All that means... by having the EOL supervision at the last device you could maintain the integrity of the rest of your circuit (if designed for it) and it will allow you to find a faulty device or fault condition in the field, by splitting your circuits in halves or sections and testing with your meter which is another ball game.
Most security control panels with fire capabilities use a 2 conductor cable that supplies both power and signal (class "B") or a 4 conductor cable 2 wires for signal 2 for wires for power (somewhat Class A) and looking at my elk's diagrams it shows both UL listed "EOL supervision Relay" and a 2.2k ohm resistor installed at the last device not the panel which is consistent with figure A.5.4.7("B") Wiring Arrangements for 4 wire detectors page 72-132 on the latest edition NFPA 72 book.
Thats why when it comes to fire alarm and in order to be code compliant, i would never advice anyone to mess with all this theory unless you hire a professional. Stick to a) wireless smoke/heat detectors b)use 110V detectors with the disadvantage of not being able to monitor those with your alarm or c) 1 wire 2 conductor detectors.
The NFPA72 has nothing to do with security systems at all, it only says that security systems could be combined with a fire control panel if it's listed for that purpose. Only the fire capabilities of the alarm panel have to follow NFPA72.
Now back to security, a simple 1 wire 2 conductors circuit for security is what most people do, specially someone that does not have the experience or knowledge like we have. For 1 wire 2 conductor supervision for security it's recommended installing the EOL In a manner that is accesible etc, hence my misinterpretation of what you said as far as location or placement in places that later you can't get to.
A double EOL for a 1 wire 2 conductor circuit is another option. Many control panels (ELK, Ademco, DSC) support them.
it would be another way to do accomplish what a 4 conductor circuit could do allowing you to monitor 4 states (short, 2.2k ohms, 4.4k ohms, open, page 9 of the Elk's manual).
This post was created by someone that needed advice on wiring, someone trying to do some DIY work, if we start adding more complexity to what he is trying to do then we are failing to provide useful real life information for his particular application.
In the end, EOL supervision could be done in any way you want but it is a subject that can not be treated equally for fire and burglary applications, and it's dependent on the end user's application, residential or commercial and industrial may have different requirements when it comes to supervising your circuit status.
Let's keep it simple for those who need simple help and then elaborate if more info or details are requested.