Potter SLCLoopPerformanceApp

SLC Loop Performance the 2013 edition of NFPA 72 there wasn a requirement to include SLC loop isolation modules when addressable fire alarm systems Unless there was a mandated wiring style Class A Style 7 Class X required isolators they often weren included in the system design Depending on the make and model of fire alarm panel a single SLC could support hundreds of addressable devices Without loop isolation devic a single short on the SLC would result in a loss of communication with all devices on the loop the 2013 edition of the NFPA 72 Handbook there are substantial losses mentioned due to the shorting and of an SLC damaged by fire before an alarm could be activated In addition there were concerns that SLC caused inadvertently in part by building operations and activities could result in an alarm system failure if fire occurs before the trouble conditions are repaired These concerns prompted the adoption of a new require that limits the number of addressable devices that can be lost due to a single fault on an SLC loop the 2016 edition of NFPA 72 the limits were changed from 50 devices to one 1 zone of addressable There was also clarification that the intention of the requirement applied to both short circuit and open faults Module PAD100 IM loop isolation module provides required circuit protection to limit the number addressable devices affected by a single fault When using a Class B wiring scenario module provides two 2 isolated of the This limits the number of addressable devices to each leg and facilitates code compliant design 1 of 2 UpdatePotter Electric Signal Company LLC St Louis Missouri Tech Support 866 240 1870firealarmresources com 72 2013 72 2016 A single fault on a pathway connected to the devices shall not cause the loss of more 50 addressable devices A single fault on a pathway connected to the devices shall not cause the loss of the in more than one zone Handbook provided a few methods to accomplish requirement including the following Installing SLC loops with no more than 50 devices per circuit T a class B signaling circuit into a with loop isolator modules installed the first device after each T tap and keeping the Class B T tapped legs of the circuit to fewer 50 devices Handbook provided the following designations zones By floor where an SLC would not span multiple By floor area where a large floor would be split into zones based on a maximum floor area By fire barrier or smoke barrier compartment which an SLC would not cross By maximum length or circuit where an SLC not be longer than a predetermined length Floor Isolated SLC Devices Floor Isolated SLC Devices Floor Isolated SLC Devices Floor Isolated SLC Devices 72 2016 Paragraph 23.6.1.3 2 allows an un isolated in metallic raceway that does not exceed 3 feet in length Conduit Isolator Isolator B wiring example using IPA series alarm control panel and PAD100 IM isolation modules 2 of 2 UpdatePotter Electric Signal Company LLC St Louis Missouri Tech Support 866 240 1870firealarmresources com