Monday, September 16, 2019

Fire Alarm Wiring Based on NEC Article 760

A common topic for discussion in the fire alarm industry involves fire alarm wiring. This article will cover all aspects of fire alarm wiring including but not limited to separation, conduit fill, strapping, mechanical protection and marking.

Fire Alarm Circuits


The definition of a fire alarm circuit is as follows: "The portion of the wiring system and connected equipment powered and controlled by the fire alarm system. Fire alarm circuits are classified as either nonpower-limited or power-limited."

I'm sure you have heard these two terms in the industry before so let's break them down.

Non-Power Limited Fire Alarm Circuits

A non-power-limited fire alarm circuit commonly referred to as NPLFA, can operate at up to 600V and the power output isn't limited.

Power-Limited Fire Alarm Circuits

A power-limited fire alarm circuit commonly referred to as PLFA, must have the voltage and power limited by a listed power supply that complies with NEC 760.121. Based on this section, a power source can be either (1) a listed PLFA or Class 3 transformer, (2) a listed PLFA or Class 3 power supply or (3) listed equipment marked to identify the PLFA power source. A few examples of listed equipment would be fire alarm control panels with integral power sources and circuit cards listed for use with PLFA sources.

The two tables below provide the listing requirements for power-limited fire alarm circuit sources:

NEC Table 12a and 12b Power Source Limitations

Power Sources for Power-Limited Fire Alarm Circuits

Power-Limited fire alarm equipment must be supplied by a branch circuit that supplies no other load and is NOT GFCI or AFCI protected. The branch circuit overcurrent device (breaker) must be identified in red, accessible only to qualified personnel, and identified as "FIRE ALARM CIRCUIT". The red markings cannot damage the overcurrent protective device or cover any manufacturer's markings. The lock pictured below is available from Space-Age Electronics.

Fire Alarm Circuit Breaker Lock


Equipment Marking for Power-Limited Fire Alarm Circuits

The fire alarm equipment that supplies power-limited fire alarm cable circuits must be marked to indicate each circuit that is a power-limited fire alarm circuit. Per NEC article 760.30, the fire alarm circuits must be marked at terminal and junction locations.

Wiring Methods for Power-Limited Fire Alarm Circuits


Power-limited fire alarm circuits shall be installed in accordance with NEC article 760.46 and conductors shall be solid or stranded copper.

Cable splices or terminations shall be made in listed fittings, boxes, enclosures, fire alarm devices, or utilization equipment. If the circuits are installed exposed, the cables shall be adequately supported and installed in such a manner that maximum protection against physical damage is afforded by building construction. The thought here is that nails from baseboards, door frames, drywall, etc. may penetrate deep enough to damage the wire. To avoid this, make sure to install your fire alarm cables no closer than 1 1/4" from the edge or the framing.  If this is not possible, use 1/16" thick steel plate for protection [NEC 760.24(A)]. Where cables are installed within 7 feet of the floor, said cables shall be fastened in an approved manner at intervals of not more than 18 inches.

steel plate to protect cables in framing


Power-limited fire alarm cables are NOT permitted to be strapped to the exterior of any raceway as a means of support. Exposed cables must be supported by the structural components of a building so that the cable will not be damaged by normal building use. Cables must be supported by straps, staples, hangers, cable ties, or similar fittings designed and installed in a manner that will not dame said cable. If the calves or raceways are installed above a suspended ceiling, they must be supported by independent support wires attached to the suspended ceiling.

Cables passing through a wall or floor. Both Power-Limited and Non Power-Limited Fire Alarm Cables shall be installed in metal raceways or rigid nonmetallic conduit where passing through a floor or wall to a height of 7' above the floor, unless adequate protection an be afforded by building construction. Keep in mind if the cables pass through a fire barrier, you must provide fire caulking to insure the integrity of the barrier.

fire caulk penetration with metal raceway
Fire Caulk Plugs for Cables


Power-Limited Fire Alarm Circuit Separation


This is a topic that a lot of designers and technicians constantly go back and forth on.  To better understand the separation requirements, I believe it is important to know what the 3 different circuit classification are.

Class 1 Circuits. 

Class 1 remote-control and signaling circuits typically operate at 120V, but the NEC permits them to operate at up to 600V [725.21(B)]. You must install these circuits within a wiring method listed in Chapter 3 of the NEC, which includes raceways, cables, and enclosures for splices and terminations [725.25]. Remote-control circuit. These circuits, which control other circuits through relays or equivalent devices, are commonly used to operate motor controllers in moving equipment, mechanical processes, elevators, and conveyors.

Class 2 Circuits.

Class 2 circuits typically include wiring for low-energy (100VA or less), low-voltage (under 30V) loads such as low-voltage lighting, thermostats, PLCs, security systems, and limited-energy voice, intercom, sound, and public address systems. You can also use them for twisted-pair or coaxial local area networks (LAN) [725.41(A)(4)]. Class 2 circuits protect against electrical fires by limiting the power to 100VA for circuits that operate at 30V or less, and 0.5VA for circuits between 30V and 150V.

Class 3 Circuits. 

Class 3 circuits are used when the power demand for circuits over 30V exceeds 0.5VA, but is not more than 100VA [Chapter 9, Table 11]. We often see Class 3 signaling circuits for security systems and public address systems; voice, intercom, and sound systems; and some nurse call systems.
Higher levels of voltage and current are permitted for Class 3 circuits (in contrast to Class 2 circuits).

Fire Alarm Cable Separation based on Circuit Classifications


PLFA with Class 1 Circuits

NEC 760.136 (A) Power-limited fire alarm circuits must not be placed in any enclosure, raceway or cable with conductors of electric light, power or class 1 circuits.

NEC 760.136 (B) If the circuits are separated by a barrier, power-limited fire alarm circuits are permitted with electric power conductors.

NEC 760.136 (D) Power-limited fire alarm circuits can be mixed with electric light, power and class 1 circuits in enclosures where these other conductors are introduced solely for connection to the same equipment and a minimum of 1/4" separation is maintained from the power-limited fire alarm cables.

Power-limited fire alarm circuits shall be separated by not less than 2" from insulated conductors of electric light, power or Class 1 circuits. Exception: If the electric light, power, class 1 circuit or power-limited fire alarm circuits are installed in a raceway, metal-sheathed, metal-clad, nonmetallic-sheathed or underground feeders.

PLFA with Class 2 and Class 3 Circuits

NEC 760.139 (A) Two or more PLFA Circuits. Power-limited fire alarm circuits, communications circuits or Class 3 circuits can be installed in the same cable enclosure, cable tray, raceway or cable routing assembly.

NEC 760.139 (B) PLFA and Class 2 Circuits. Power-limited fire alarm circuits and Class 2 circuits can be within the same cable, cable tray, cable routing assembly, enclosure, or raceway provided the Class 2 circuit insulation is not less than that required for the power-limited fire alarm circuits.

NEC.139 (C) PLFA and Low Power Network Communication. Low-powered network powered broadband communication circuits hall be permitted in the same enclosure, raceway, cable assembly, or cable tray.

NEC 760.139 (D) PLFA and Audio System Circuits. Power-limited fire alarm circuits and audio system circuits using Class 2 and Class 3 wiring methods shall not be installed in the same raceway, enclosure, cable routing assembly or cable tray. Please not this does not apply to voice evacuation and mass notification speaker circuits controlled by a fire alarm control unit or amplifier.

Fire Alarm Cable Substitutions


NEC 760.154(A) The following fire alarm cable substitutions are permitted as long as the wiring requirements of NEC Article 760 Parts I and III apply.

FPLP (Fire Power-Limited Plenum) ------------> CMP
FPLR (Fire Power-Limited Riser) --------------> CMP, FPLP, CMR
FPL (Fire Power-Limited) -----------------------> CMP, FPLP, CMR, FPLR, CMG, CM

Fire Alarm Conductor Size


NEC 760.142. Conductors of 26 AWG shall be permitted only where spliced with a conductor listed as suitable for 26 AWG to 24 AWG or larger conductors that are terminated on equipment or where the 26 AWG conductors are terminated on equipment listed as suitable for 26 AWG conductors.

Single conductors shall NOT be smaller than 18 AWG.

How to Figure Conduit Fill


Conduit fill requirements can be found in the NEC Annex Table C.  This is toward the back of the book and is broken up into different sections based on the type of raceway being used.  In this example, we will use table C.1 for EMT (Electrical Metallic Tubing).  Take a look at the table below and try to locate the maximum number of 14 AWG THHN conductors permitted in 2 1/2" EMT raceway. The answer is 241.








Friday, May 17, 2019

NICET Facebook Group Post Answers



If you are looking for the answers to the NICET for Fire Alarms Facebook group posts, then you are in the right place!  If you have stumbled upon this article and want to have these questions pushed to your phone or PC instantly, then please by all means join the greatest Fire Alarm forum online.

If you have a questions you want dissected, email us and we will throw it out there.

Question from post on 5-15-19

Based on the International Building and Fire Codes, a fully sprinklered two story office building with a group B occupancy and 11,000 sq' of floor space per level requires what type of fire alarm system?

The 2015 International Building Code table 1004.1.2 states that business type occupancies requires 100 sq' of space per occupant.  11,000 sq' divided by 100 = 110 occupants per floor. The 2015 International Fire Code section 907.2.2, a group B occupancy with greater than 100 persons on a floor above or below the level of exit discharge, a manual fire alarm system shall be required. Since this facility is sprinkled, only one manual pull box would be required in an approved location IF the waterflow activates the occupant notification appliances.

Thursday, May 2, 2019

Smoke Detector Spacing with Beams

Smoke Detector Spacing for Smooth Ceilings


Let's start with the basics of smoke detector spacing.  Based on NFPA 72, there is not a listed spacing and you are instructed to consult with the smoke detector's published documentation.  However, NFPA 72 2016 edition section 17.7.3.2.3.1 states the following, "In the absence of specific performance based design criteria, one of the following requirements shall apply:

  1. The distance between smoke detectors shall not exceed a nominal spacing of 30 feet and there shall be detectors within a distance of one-half the nominal spacing, measured at right angles from all walls or partitions extending upward to within the top 15 percent of the ceiling height.
  2. All points on the ceiling shall have a detector within a distance equal to or less than 0.7 times the nominal 30 foot spacing.
What does this mean?

Number 1 above states you must have a smoke detector within one half the nominal spacing from walls.  One half of 30 feet is 15 feet.  In the image below you will see a total of six yellow circles each with a 30 foot diameter.  These circles represent the area covered by a spot type smoke detector based on a nominal spacing of 30 feet. As required by NFPA 72, we have spaced each detector at 15 feet from walls and 30 feet apart.    

smoke detector spacing for smooth ceilings
Smoke Detector Spacing with a Smooth Ceiling

What about the white areas not covered?

If you notice in the image, there are areas not covered by the yellow circles representing the smoke detector coverage.  This is where NFPA 72 2016 edition section 17.7.3.2.3.1 criteria number two comes into play.  

With a nominal spacing of 30 feet, you must insure that all areas of the ceiling have coverage within 0.7 times this 30 foot amount.  To find this distance, simply multiply 30 feet by 0.7 to get 21 feet.

If you use Pythagorean's Theorem you will come up with a surprising result.  Remember Pythagorean's Theorem is used to find the unknown side of a right triangle and is expressed as A squared + B squared = C squared.  In this case we have a right triangle in each quadrant of the yellow circles.  Each quadrant is 15 feet our and 15 feet up.  We can write this equations as:

15 squared + 15 squared = C squared 
225 + 225 = 450 squared
450 squared = 21.2132 feet

In the image below you will see a cleared depiction of how this all comes together. With this, it is clear that we have met the intent of the standard by mounting our smoke detectors 15 feet from the walls, 30 feet apart and still achieve 0.7 times the nominal spacing (21 feet) coverage at all points of the ceiling.
smoke detector spacing template for 30 feet
Smoke Detector Coverage for 30 Feet

NFPA and Smoke Detector Spacing Distances


The Annex of NFPA 72 provides us with a diagram to assist in smoke detector spacing. Note that smoke detectors are not listed for spacing.  Use the smoke detector's published installation documents and the spacing breakdown below to assist in your design.

NFPA 72 Smoke Detector Spacing Irregular Areas
NFPA 72 Smoke Detector Spacing Diagram



For areas/corridors 10 feet wide, smoke detectors can be spaced at 41 feet.
For areas/corridors 15 feet wide, smoke detectors can be spaced at 39 feet.
For areas 20 feet wide, smoke detectors can be spaced at 37 feet.
For areas 25 feet wide, smoke detectors can be spaced at 34 feet.
For areas 30 feet wide, smoke detectors can be spaced at 30 feet.

Smoke Detector Spacing with Beam Construction


If your ceiling configuration involves beams, your smoke detector coverage can get a bit more tricky.
NFPA 72 2016 edition section 17.7.3.2.4.2 deals with level ceilings with beams. In a nutshell, this is how it breaks down:
  • If the beam depth is LESS than 10% of the overall ceiling height, then smooth ceiling spacing for smoke detection can be applied.  Also note that in this scenario, you can choose to install the smoke detectors on the ceiling or the bottom of the beams. Reference the above text and images for smooth ceiling spacing.
  • If the beams are are equal to or greater than 10% of the overall ceiling height, two scenarios are possible:
    • If the beam depth is equal to or greater than 10% but less than 40%, use smooth ceiling spacing PARALLEL to the beams and one half spacing PERPENDICULAR to the beams.  With this scenario, the smoke detectors can be mounted on the ceiling or the bottom of the beams.
    • If the beam depth is equal to or greater than 40%, a smoke detector shall be placed on the ceiling within each beam pocket.  Keep in mind that more than one smoke detector may be required to cover a given beam pocket.

How to Calculate Smoke Detector Spacing with Beam Construction 


To calculate the beam depth for smoke detector spacing, convert your overall ceiling height into inches.  For example, if your ceiling is 12 feet it would convert to 144 inches.  Take 144 and multiply it by 0.1 to get 10%.  144" x 0.1 = 14.4".  In this case, ant beam depth of 14.4" or more would require an altered smoke detector lay out.  If you want an easier way to work this cal and remember what spacing requirements go with the different percentages, we have you covered.  Download a FREE copy of our Excel Fire Alarm Calculation Tool and use the "SD BEAMS" tab.  All you need to do is input your ceiling height and beam depth in inches and the calculator will give you a color code for which spacing requirement is required (see image below).  Email us with any questions.   




Smoke Detector Spacing in Corridors with Beams 


What do you do if you have a corridor that is equal to or less than 15 feet in width with beams running perpendicular to the length of the corridor?  Consult NFPA 72 2016 section 17.7.3.2.4.2 (4).  This section of the standard allows you to use smooth ceiling spacing and the smoke detectors can be mounted on the ceiling, bottom of the beams or on the sidewall.

Smoke Detector Spacing in Rooms 900 Square Feet or Less


NFPA 72 2016 section 17.7.3.2.4.2 (5) allows the use of smooth ceiling spacing for smoke detection coverage in rooms that are equal to or less than 900 square feet.  You can also install the smoke detector on the ceiling or bottom of the beam. 

Monday, April 22, 2019

Using a Manometer to Test Duct Smoke Detectors

A Manometer is an electronic device commonly referred to as a liquid column hydro-static instrument.  A Manometer measures pressure and vacuum between the actual duct smoke detector's sample tubes. These manometer units can be used with other manufacturer's duct detectors but for this example we will stick with the System Sensor DNR. 

Manometer Testing Duct Smoke DetectorThe Manometer we chose to use for this article is the Duct Checker manufactured by SDI.  The Duct Checker is light weight, portable and battery operated making it easy to get to areas duct smoke detectors are commonly found. Simply connect the two provided hoses with variable size end plugs and power it on.  Once the unit turns on, press down the "hold" button for three seconds to zero out the machine.  Sort of like a scale.  Now press the "unit" button until you arrive at the selection of "inH2O" on the bottom left of the screen.

The Duct Checker comes with two hoses that are designated for specific ports.  One tube is marked as negative and the other positive.  Make sure to place the hose end of the positive into the actual sample tube inlet.  The negative tube will go into the exhaust port. 

With the System Sensor DNR duct detector you will be looking for a reading of anywhere between 0.01 min and 1.11 max.

Duct Checker Manometer from SDi


With this requirement clearly required in NFPA 72 2016 Table 14.4.3.2 section 17 (g)(5), as well as most manufacturer's documentation, you can expect to come across these at some point in your career.  They are not too pricey so I suggest grabbing one from SDi and placing them in your inspection crew's service vehicles.

Voltage Drop For Fire Alarm Circuits

·     Code Requirement for Voltage Drop Calculations?

NFPA 72 2013 Edition Section 7.2.1 - "Where documentation is required by the enforcing authority, the following list shall represent the minimum documentation required for all fire alarm and emergency communication systems, including new systems and additions or alternations to existing systems.", Within this list, you will find #7, Battery Calculations  and #8, Voltage Drop Calculations.

Keep in mind almost all fire alarm control units are 24 volts DC.  Also note that there are a few fire alarm control panels that are 12 volt DC.  Now these panels are typically combination fire and burglar system.  Just remember that the calculations for NAC voltage drops are the same for these systems, however the cut off voltage for a 12 volt system will be roughly half that of a 24 volt system.

·        What is the reason for voltage drop calculations?


NAC voltage drop calculations are critical for determining if your notification appliances will in fact work with the provided head end equipment.  (This is of course based on the installation contractor installing the system per plans and noted wiring distances).  If you perform your NAC voltage drop calculations correctly at the time of design, you will know exactly how many remote power supplies and NAC circuits are needed as well as the wall space requirements and 120 VAC connections required by the electrical contractor.  Keep in mind that this is a requirement of NFPA 72.

·         Voltage Drop Calculation Methods


There are primarily two methods to perform a NAC voltage drop calculation.  These methods are better known as “Point to Point (PTP)” and “End of Line (EOL)”.

·       Point to Point Voltage Drop requires much more math than the “EOL” method.  However, the extra work pays off as this method is more accurate.
  •          Designers generally use this method with a spreadsheet as the math can become tedious
  •          This is the method typically used by panel manufacturers within their own calculation programs
  •          Since it is less conservative of the “EOL” method, it allows for more devices on a circuit.
  •          There are cases of a 30% difference between the PTP and EOL methods
End of Line method is the easiest, quickest calculation
  •          Can be done easily by hand or with a calculator
  •          Results are less accurate that provide lots of head room for future expansion

Starting Voltage and Cut-Off Voltage


UL (Underwriters Laboratories) 864, 9th Edition Standards for Fire Alarm Control Panels:
  •          All panels must have a demonstrated 20.4 VDC panel cut off voltage.

You may be asking, “Where did they come up with 20.4 VDC on a 24 Volt system?”

It is actually quite simple.  20.4 VDC is 85% of 24 VDC. Or like we stated earlier, there are a few 12 VDC systems floating around.  In their case, the demonstrated voltage shall be 10.2 VDC.  Once again, 10.2 VDC is 85% of 12 VDC.

Now, above we mentioned a term “Cut-Off Voltage”.  All fire alarm control units (FACU) have and internal voltage drop.  The voltage at the actual NAC output terminal is always less than 20.4/10.2 volts at cut-off.
  •          This amount of drop varies with every panel.  The variance can be as much as .5 VDC to 2.5 VDC.

Keep in mind that this value is not often found within the panel documentation.  I have found that the easiest way to obtain this value is to contact the panel manufacture and get it in writing.

You now may be asking yourself, “Why is it so critical that I get this value from the manufacturer and not just use the 20.4/10.2 value figured from the 85% set forth by UL 864 9th Edition?”

In order for your NAC voltage drop calculations to be precise and as accurate as possible based on the facts and information provided, you must use the specific panel/power supply terminal cut-off value.

How to determine your NAC Voltage Drop using the End of Line method:

Step #1
Add up the total current draw for your entire notification appliance circuit.  This is based on the manufacture, type (strobe only, horn/strobe, mini horn, audible level, wall, ceiling, etc.)  Make sure to consult with the appliance documentation to get these figures.

Step #2
Add up the total wire length for the run and multiple it by 2 (if class B).  The 2 represents the number of conductors used in the run.

Step #3
Multiply the total wire length times the wire resistance value per foot for a total circuit wire resistance.  The wire resistance per foot can be found in Table 8 “Conductor Properties” in Chapter 9 of the National electrical Code.

Step #4
Using Ohm’s Law we know that Current (I) x Resistance (R) = Voltage (E).  Simply take the total current found in step #1 and multiply it by the resistance found in Step #3.  This will give you the volts dropped.

Step #5
Subtract the volts dropped from the panel/power terminal cut-off voltage to obtain the voltage that will be supplied to the last appliance on the circuit.  This value MUST exceed 16 volts.

Keep in mind that this method is not as accurate as the Point to Point method.  This method assumes that the voltage drop at each appliance will be the same when in reality, they are not.

NEC Table 8 Conductor Properties

Below is an example of an End of Line voltage drop calculation:


End of Line Voltage Drop Fire Alarm

Diagram notes:
  • ·        We will assume that the terminal cut-off voltage is .5 volts below the 20.4 VDC giving us a voltage of 19.9.
  • ·         Use the wire lengths shown in the diagram
  • ·         V1=85mA / V2=75mA / V3=115mA / V4=100mA
  • ·         The circuit is using #12 AWG wire
  • ·         Use the Table 8 of the NEC (National Electric Code) provided previously in this document

Using the Diagram and notes above, can you provide the voltage drop for this circuit using the End of Line method?  Give it a try and when you are ready move on to the next page where we will break it down for you.

End of Line Voltage Drop Calculation Break Down:

Step #1
Add up the total current for all four notification appliances within the circuit.  We know that V1 = 85 mA, V2 = 75 mA, V3 = 115 mA and V4 = 100 mA.  The total of all four of these is 375 mA.

Step #2
Add up the total wire length and multiply it by 2.  We know based on the diagram that the first section is 200 feet, the second section is 150 feet, the third section is 25 feet and the final section is 70 feet.  This totals up to 445 feet x 2 = 890 Total Feet

Step #3
We know from the Table 8 “Conductor Properties” we have a value of 1.98 Ohms/1000 feet of #12 AWG stranded uncoated wire.  To find our resistance for our circuit simply take the total wire length (890 Feet) and divide it by 1000.  This gives us a value of .89.  Now take .89 and multiply it by the 1.98 value found in the NEC Table.  (.89 x 1.98 = 1.7622 Ohms of Resistance)

Step #4
Using Ohm’s Law we know that Current (I) x Resistance (R) = Voltage (E).  Take the total current found in Step #1 (.375) and multiply it by the total found in Step #3 (1.7622).  .375 x 1.7622 = .660825 volts dropped.

Step #5
Finally we need to subtract the .660825 volts from our terminal cut-off voltage.  We know from the previous diagram and notes that we have a terminal cut-off voltage of 19.9 volts.  19.9 volts - .660825 = 19.239 Volts at the last appliance.

Point to Point Voltage Drop Calculation Break Down:

Point to Point Voltage Drop Calculation

Diagram notes:
  • ·         We will assume that the terminal cut-off voltage is .5 volts below the 20.4 VDC giving us a voltage of 19.9.
  • ·         Use the wire lengths shown in the diagram
  • ·         V1=85mA / V2=75mA / V3=115mA / V4=100mA
  • ·         The circuit is using #12 AWG wire
  • ·         Use the Table 8 of the NEC provided previously in this document

Calculation Breakdown:

To perform a point to point voltage drop calculation is basically the same as the End of Line method however; we are going to do a breakdown of each path/appliance.

Calculation #1
  • ·         First wire run section resistance multiplied by the total current for appliance V1, V2, V3 and V4
  • ·         Subtract the total from the terminal cut-off voltage to get the voltage drop for V1.

Calculation #2
  • ·         Second wire run section resistance multiplied by the total current for appliances V2, V3 and V4.
  • ·         Subtract the total of V1 from the terminal cut-off voltage to get the voltage drop of V2

Calculation #3
  • ·         Third wire run section resistance multiplied by the total current for appliances V3 and V4.
  • ·         Subtract the total of V2 from the terminal cut-off voltage to get the voltage drop of V3

Calculation #4
  • ·         Fourth wire run section resistance multiplied by the total current for appliances V4.
  • ·         Subtract the total of V3 from the terminal cut-off voltage to get the voltage drop of V4

If this last value is greater than 16 volts, the circuit should work.

Using the Diagram and notes above, can you provide the voltage drop for this circuit using the Point to Point method?  Give it a try and when you are ready move on to the next page where we will break it down for you.

Calculation # 1
  • ·         200 Feet x 2 = 400 Feet.  400 / 1000 = .4 x 1.98 = .792 Ohms (From the FACU to V1)
  • ·         .792 x .375 (Current of all Appliances) = .297 volts dropped @ V1
  • ·         19.9 (Terminal Cut-Off Voltage) - .297 = 19.603 VDC @ V1

Calculation #2
  • ·         150 Feet x 2 = 300 Feet.  300 / 1000 = .3 x 1.98 = .594 Ohms (From the FACU to V1)
  • ·         .594 x .290 (Current of Appliances V2-V4) = .17226 volts dropped @ V2
  • ·         19.603 (Terminal Cut-Off Voltage) - .17226 = 19.43074 VDC @ V2

Calculation # 3
  • ·         25 Feet x 2 = 50 Feet.  50 / 1000 = .05 x 1.98 = .099 Ohms (From the FACU to V1)
  • ·         .099 x .215 (Current of Appliances V3-V4) = .021285 volts dropped @ V3
  • ·         19.43074 (Terminal Cut-Off Voltage) - .021285 = 19.40946 VDC @ V3

 Calculation # 4
  • ·         70 Feet x 2 = 140 Feet.  140 / 1000 = .14 x 1.98 = .2772 Ohms (From the FACU to V1)
  • ·         .2772 x .200 (Current of Appliance V4) = .05544 volts dropped @ V4
  • ·         19.40946 (Terminal Cut-Off Voltage) - .05544 = 19.35402 VDC @ V4

Both of these calculations are commonly used and widely accepted by your local AHJs.  As you can see the PTP method came up with a total voltage drop of 19.35402 while the EOL method came up with 19.239.  Remember both of these examples used the same parameters.  I personally recommend using the Point to Point method purely based on its accuracy.

How to Apply for NICET Certification Video

NICET Certification - Where to Start

We have had a lot of member from our Facebook Group ask about the NICET certification process, specific to getting started.  The NICET website can be tricky as it is packed with tons of links and  information. To save our readers time, we have complied a video with a complete walk through including: where to click, what to download and most importantly, how to fill out the application for the NICET exam.

Although this video walk through simply covers applying for the NICET exam, you can also find additional information on our website for NICET Practice Exams, NFPA 72 Tabs for references during the NICET exam as well as general information. 

Be sure to comment below if you have any questions with the NICET application process.

Monday, February 19, 2018

NFPA 72 2016 Chapter 26 Changes

NFPA 72 2016 Chapter 26 - Supervising Station Alarm Systems


The following information contains the changes, updates and additions to Supervising Station Alarm Systems found in Chapter 26 of the NFPA 72 2016 edition.  Remember if you see a * make sure to consult the Annex A for additional information.

All information highlighted in this light blue color is NEW to the 2016 edition of NFPA 72.

  • 26.2.1.1 Alarms signals initiating by manual fire alarm boxes, automatic fire detectors, waterflow from the automatic sprinkler system, or actuation of other fire suppression system(s) or equipment shall be treated as fire alarm signals.
  • 26.2.1.2* Except as permitted by 26.2.2 and 29.7.9.2, all fire alarm signals received by a supervising station shall be immediately re-transmitted to the communications center.
  • 26.2.1.3 Fire alarm signals received at the supervising station by a zone or zones shall be re transmitted by zone to the communications center.
  • 26.2.1.4 Fire alarm signals received at the supervising station that are identified as an individual point or points shall be re-transmitted by point identified to the communications system.
Central Station Service Alarm Systems
  • 226.3.4.7 The authority having jurisdiction identified in 26.3.4.2(5) shall be notified within 30 calendar days of the expiration or cancellation by the organization that listed the prime contractor.
  • 26.3.8.3* Supervisory Signals.  Upon receipt of a supervisory signal that is not prearranged, the central station shall perform the following actions:
    1. *Communicate immediately with the persons designated by the subscriber and notify the fire department, law enforcement agency, or both when required by the authority having jurisdiction
    2. Dispatch a runner or maintenance person to arrive within 2 hours to investigate unless the supervisory signal is cleared in accordance with a scheduled procedure determined by 26.3.8.3(1)
    3. Notify the authority having jurisdiction and the subscriber when sprinkler systems or other fire suppression systems or equipment have been wholly or partially out of service for 8 hours.
    4. When service has been restored, provide notice to the subscriber and the authority having jurisdiction of the nature of the signal, the time of occurrence, and the restoration of service when equipment has been out of service for 8 hours or more.

NFPA 72 2016 Chapter 24 - Supervising Station Alarm Systems



Back to the Beginning - NFPA 72 2016 Chapter 3 - Definitions