Fire Alarm Circuit T-tapping
- Thread starter jkim780
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- Location
- Bremerton, Washington
Re: Fire Alarm Circuit T-tapping
I am not sure what that refers to, but I would start with the national fire alarm code, NFPA 72, or the NECA fire alarm installation standard.
I am not sure what that refers to, but I would start with the national fire alarm code, NFPA 72, or the NECA fire alarm installation standard.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: Fire Alarm Circuit T-tapping
A fire alarm "T-tap" is mearly a parallel tap into the loop. Some manufacturers have regulations regarding this, almost all specifications from engineers have regulations regarding this, but nothing specifically in the code books, unless you have a special type of fire alarm circuit, such as Class A.
[ November 05, 2003, 03:20 PM: Message edited by: ron ]
A fire alarm "T-tap" is mearly a parallel tap into the loop. Some manufacturers have regulations regarding this, almost all specifications from engineers have regulations regarding this, but nothing specifically in the code books, unless you have a special type of fire alarm circuit, such as Class A.
[ November 05, 2003, 03:20 PM: Message edited by: ron ]
Re: Fire Alarm Circuit T-tapping
Most of fire alarm system manufacturers are utilizing communication loop(SLC) for IDC and even NAC in addressable system and their product data sheet says
Quote:
Sophisticated poll and response communication techniques ensure supervision integrity and allow for "T-tapping" of the circuit for Class B(Style 4) operation.
Unquote:
Quote:
...Signaling Line Circuits(SLCs) for both controlling and powering addressible notification appliances. With addressable appliances, class B wiring can be "T-tapped" for both easier wiring and reduced wire run length.
Unquote:
I have believed that T-tap was not allowed in fire alarm circuits. Now, I see this information from manufacturers data sheet, I am confused about fire alarm circuit wiring. What am I missing here?
Most of fire alarm system manufacturers are utilizing communication loop(SLC) for IDC and even NAC in addressable system and their product data sheet says
Quote:
Sophisticated poll and response communication techniques ensure supervision integrity and allow for "T-tapping" of the circuit for Class B(Style 4) operation.
Unquote:
Quote:
...Signaling Line Circuits(SLCs) for both controlling and powering addressible notification appliances. With addressable appliances, class B wiring can be "T-tapped" for both easier wiring and reduced wire run length.
Unquote:
I have believed that T-tap was not allowed in fire alarm circuits. Now, I see this information from manufacturers data sheet, I am confused about fire alarm circuit wiring. What am I missing here?
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: Fire Alarm Circuit T-tapping
In many instances, the manufacturer will allow t-taps for Class B loops. The addressable devices are intelligent and can report a trouble condition through multiplexed comm loops. Even a non-addressable loop can be t-taped if appropriate EOL resistors are used in many instances.
I find them to be more of a headache to troubleshoot, so my specs outlaw them.
[ November 05, 2003, 03:44 PM: Message edited by: ron ]
In many instances, the manufacturer will allow t-taps for Class B loops. The addressable devices are intelligent and can report a trouble condition through multiplexed comm loops. Even a non-addressable loop can be t-taped if appropriate EOL resistors are used in many instances.
I find them to be more of a headache to troubleshoot, so my specs outlaw them.
[ November 05, 2003, 03:44 PM: Message edited by: ron ]
Re: Fire Alarm Circuit T-tapping
In an addressable system supervision is accomplished by the device communicating with the panel. T taps will not compromise this, where as the old "series circuit" type systems relied on the series wiring and end of line resistors for supervision.
If the manufacturer doesn't restrict T taps in a class B addressable installation you are fine.
Note: most audible and visual signals are still series circuits.
Roger
In an addressable system supervision is accomplished by the device communicating with the panel. T taps will not compromise this, where as the old "series circuit" type systems relied on the series wiring and end of line resistors for supervision.
If the manufacturer doesn't restrict T taps in a class B addressable installation you are fine.
Note: most audible and visual signals are still series circuits.
Roger
Re: Fire Alarm Circuit T-tapping
T tapping is not completely prohibited in class A systems, but there are specifics that must be adhered to in doing it, i.e. X number in a given spur off of the loop.
Think about the real reason that a Class A is better and treated different.
In a class B if the device or devices quit communicating a trouble signal occur es but the detection could be completely lost if the circuit had been cut in the middle (or anywhere really)
In a class A a trouble will occur but the possibility that the detection has been lost is greatly reduced being that both ends of the circuit are communicating.
Roger
T tapping is not completely prohibited in class A systems, but there are specifics that must be adhered to in doing it, i.e. X number in a given spur off of the loop.
Think about the real reason that a Class A is better and treated different.
In a class B if the device or devices quit communicating a trouble signal occur es but the detection could be completely lost if the circuit had been cut in the middle (or anywhere really)
In a class A a trouble will occur but the possibility that the detection has been lost is greatly reduced being that both ends of the circuit are communicating.
Roger
Re: Fire Alarm Circuit T-tapping
Your answer gives me more question. Like you said, class A is better than class B because it keeps system operational during single open condition while class B doesn't.
That's why it makes sense to me that class A can have "T-tapping" and Class B can't. But manufacturers indicate the other way. Manufacturer prohibits "T-tapping" in class A system. Can you tell me why?
Roger,
Your answer gives me more question. Like you said, class A is better than class B because it keeps system operational during single open condition while class B doesn't.
That's why it makes sense to me that class A can have "T-tapping" and Class B can't. But manufacturers indicate the other way. Manufacturer prohibits "T-tapping" in class A system. Can you tell me why?
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Fire Alarm Circuit T-tapping
I could be wrong about this........
A class A circuit is designed to be a series wiring circuit. Do they make addressable modules for Class A?
The class B wiring method can be used as a series circuit or a parallel circuit. A series circuit needs to have an End Of the Line resistor so the FACP can monitor the condition of the wires, not the devices.
When notification devices are used they are always wired in a series circuit.
When initiating devices are used, they can be wired in a series circuit with an EOL and is also known as a "zone system".
OR
They an be wired in a parallel circuit when used with an addressable device so the wires and devices are monitored. In this type of circuit, the FACP will indicate the exact location of the initiation and what type it is. It will also report a wiring fault as well as a device problem. This type of system allows the conductors to be "T- tapped" because the monitoring is accomplished via the addressable units as opposed to an EOL. This type of system is known as an "addressable system".
I could be wrong about this........
A class A circuit is designed to be a series wiring circuit. Do they make addressable modules for Class A?
The class B wiring method can be used as a series circuit or a parallel circuit. A series circuit needs to have an End Of the Line resistor so the FACP can monitor the condition of the wires, not the devices.
When notification devices are used they are always wired in a series circuit.
When initiating devices are used, they can be wired in a series circuit with an EOL and is also known as a "zone system".
OR
They an be wired in a parallel circuit when used with an addressable device so the wires and devices are monitored. In this type of circuit, the FACP will indicate the exact location of the initiation and what type it is. It will also report a wiring fault as well as a device problem. This type of system allows the conductors to be "T- tapped" because the monitoring is accomplished via the addressable units as opposed to an EOL. This type of system is known as an "addressable system".
- Location
- Massachusetts
Re: Fire Alarm Circuit T-tapping
Dave I have not wired any FA equipment in series for a long time now.
We used to put tamper switches in series with the EOL.
Initiating and notification devices are wired in parallel just like light fixtures.
Initiating devices in series would result in an open loop.
Notification devices wired in series would result in insufficient voltage to each device.
As for addressable systems you can get an addressable module to run a class A or B from that module.
An example would be a run of heat detectors run off of one addressable monitor module.
Dave I have not wired any FA equipment in series for a long time now.
We used to put tamper switches in series with the EOL.
Initiating and notification devices are wired in parallel just like light fixtures.
Initiating devices in series would result in an open loop.
Notification devices wired in series would result in insufficient voltage to each device.
As for addressable systems you can get an addressable module to run a class A or B from that module.
An example would be a run of heat detectors run off of one addressable monitor module.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Fire Alarm Circuit T-tapping
Bob,
What brand are you installing?
I was not aware that horn/strobes were addressable.
Bob,
What brand are you installing?
I was not aware that horn/strobes were addressable.
- Location
- Massachusetts
Re: Fire Alarm Circuit T-tapping
Dave I am sorry if I gave that impression.
I am not aware of addressable horn strobes.
I do install horn strobes that with only two terminals on them can be silenced but remain flashing,
Dave I am sorry if I gave that impression.
I am not aware of addressable horn strobes.
I do install horn strobes that with only two terminals on them can be silenced but remain flashing,
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Fire Alarm Circuit T-tapping
Bob,
OK!
The horn/strobes these days run off of a "sync" module that also allows the horns to be manually silenced during alarm. However, the strobes can only be reset after the alarm is cleared.
Bob,
OK!
The horn/strobes these days run off of a "sync" module that also allows the horns to be manually silenced during alarm. However, the strobes can only be reset after the alarm is cleared.
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