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February 10, 2002

                             ET News
Volume 2 Issue 6                                       2-10-2002

- News
- ET Journal
- Test Dates
- Class Schedule
- Administrivia



SILVER SPRING, Md. -- A new modification to the Las Vegas Fire & Rescue
(LVFR) policy, stating that LVFR will no longer respond to fire or
emergency calls that are not verified on site by an individual, has
received strong opposition from the National Burglar & Fire Alarm
Association (NBFAA). The policy was made effective Feb. 1 without input
from citizens, business owners or alarm companies, according to the
association. LVFR also says it will begin levying fines against
homeowners, businesses and alarm companies that call in fire or other
emergencies when there is no actual emergency. It says the fines will
range between $250 and $1,000, with the stiffest fines possibly issued
to alarm companies. LVFR has said that false alarm calls have put many
of their fire and rescue teams in compromising situations. According to
a LVFR press release announcing the policy:  "Under the new procedure,
someone will have to actually verify that a fire is in progress before
crews will respond." NBFAA President Bart Didden says the new
modification to LVFR policy causes a new host of problems for alarm
companies and could have effects on fire and rescue teams across the
United States. "This change in policy will result in delayed fire
department response to actual fire events," he says.  "The alarm
industry will also have great difficulty in complying with both state
regulation and the new local modification. When people's lives are at
stake, we must work together. It is the only way that policies and
procedures can truly be effective." Nevada state code requires
compliance with National Fire Protection Association (NFPA) standards.

Source: Security Control Panel


NICET(r) Fire Alarm Systems Element 31006 BASIC ELECTRICITY

"Understand D.C. circuits, use of Ohm's Law, series and parallel
circuits, resistance of wires, voltage drop calculations,
use of VOM (volt-ohm-milliammeter), and A.C. circuits."

31006 is a General-Core work element.
To qualify for certification at Level III & IV, you must pass all Level
I General-Core work elements.

None given.
May I suggest 'Delmar's Standard Textbook on Electricity 5e' ISBN

"Understand D.C. circuits...
Direct Current is current that is always flows in the same direction.
The voltage and current can fluctuate up and down, but the polarity of
the voltage remains the same.

Ohm's law states that it takes one volt to push one amp through one ohm.
In a DC circuit the current is directly proportional to the voltage and
inversely proportional to the resistance.

"...use of Ohm's Law...
The four basic units of electricity:
[E] Electromotive force or voltage, expressed in Volts
[I] Intensite or current expressed in Amperes
[R] Resistance expressed in Ohms
[P] Power expressed in Watts

Ohm's Law:

E=IxR  E=P/I  E=sqrt(PxR)

I=E/R  I=P/E  I=sqrt(P/R)

R=E/I  R=P/I^2  R=E^2/P

P=IxE  P=I^2xR  P=E^2/R

"...series and parallel circuits...
A series circuit can be identified by the following characteristics:
-There is only one path for current
-The voltage will drop across each resistor
-The total resistance is the sum of the individual resistances
-The total power is the sum of the individual powers

A parallel circuit can be identified by the following characteristics:
-Voltage is the same throughout the circuit
-Current splits into each individual branch
-Total current is the sum of the branch currents
-Total resistance is smaller than the smallest branch resistance
-Total power is the sum of the individual powers

"...resistance of wires...
The size of a wire is determined by its cross-sectional area. The unit
of measure is the mil. One mil is equal to .001 inch. The
cross-sectional area of a wire is measured in circular-mils or cmil.


A -> cross-sectional area
pi -> 3.1415926...
d -> diameter of the wire

Resistivity of wire, expressed in ohms, is the resistance of a one-foot
length of wire that has a cross-sectional area of one mil.

Resistivity of material:
Silver - 9.8
Copper - 10.37
Gold - 14.7
Aluminum - 17.02


R -> resistance in ohms
rho -> resistivity
L -> length in feet
A -> area in circular mils

Determine the length of wire in this example using NFPA 70 and a
            |<-------------  d = ? feet ------------>|

+-----------+      .-.  .-.    .-.  .-.    .-.  .-.     
|+----+   + +--.  /   /     /   /     /   /       
||VOM |     |   /    /    /    /    /    /    `x-<-Twisted
|+----+   - +---'   /     /   /     /   /     /   together
+-----------+     `-'    `-'  `-'    `-'  `-'    `-'     
Model 260 VOM                              

R = 4 ohm
d = wire run distance
L = length of copper wire (two times d)                                

The wire is 10AWG 7-strand uncoated copper.

Step 1)
If I pull wire on a job site and need to know the wire run length (d) I
just installed, I can twist the pair together at one end, attach my
trusty Simpson(r) Model 260 volt-ohm-milliammeter to the open pair to
determine the resistance in ohms represented by the pair of wires.

Step 2)
In this example, I read 4 ohm of resistance on the meter.

Step 3)
Using Table 8 'Conductor Properties' in NFPA 70-1999 (Chapter 9 page
567) I see that 10AWG 7-strand uncoated copper has 1.24 ohm per 1000
feet (at 167 degrees F) or;

1.24 ohm
1000 ft 

Step 4)
Determine how long this wire run is using the information we've

L = 4 ohm x 1000 ft  = 4000 ohm-ft = 3226 ft
            --------   -----------
            1.24 ohm   1.24 ohm
Step 5)
Remember that L is the total length of copper and d is the wire run
distance or L/2;

    3226 ft
L = ------- = 1613 ft

"...voltage drop calculations...
What is the minimum 7-strand, uncoated copper wire size in AWG permitted
by NFPA 70-1999 in the following example:

    |<---------------- 2000' ---------------->|

+---+      .-.  .-.    .-.  .-.    .-.  .-.   +-------+
| + +--.  /   /     /   /     /   /   `--+ +++++ |
|   |   /    /    /    /    /    /      | +++++ |
| - +---'   /     /   /     /   /     .-+ +++++ |
+---+     `-'    `-'  `-'    `-'  `-'    `-'  +-------+
NAC Power Supply                              (10) Horn
Class 2 Power Limited                         .050A ea.
24Vdc nominal                                 21-28Vdc

Average ambient temperature = 75 degrees centigrade.

Step 1)
The minimum wire size is dependent upon the maximum permitted voltage

The manufacturer specifies that the horn will operate properly at a
minimum of 21Vdc and at a maximum of 28Vdc. Comparing the NAC power
supply voltage (24Vdc) with the minimum voltage at which the horn will
operate (21Vdc), we can determine the maximum voltage-drop permitted.

24Vdc - 21Vdc = 3Vdc = Ed (Maximum Volt-drop)

The manufacturer also specifies a current requirement of .05A each time
10 horns.

I = .05A x 10 = .5A

Step 2)
Use Ohm's Law and solve for R, which is the maximum resistance allowed
under the maximum voltage drop allowed, 3V:

R = Ed/I
R = (24v-21v)/.5A
R = 3V/.5A
R = 6ohm

Another way to look at this answer is;
The maximum amount of resistance permitted by the circuit conductors is
The example is a 2000' 2-conductor circuit or;

a 4000' 1-conductor or;

The maximum amount of resistance permitted by the 4000' round-trip
circuit is 6ohm or;


Step 3)
NFPA 70-1999 Chapter 9, Table 8, page 567, Conductor Properties, is
where you will find the smallest conductor size permitted, which will
not exceed 1.5ohm per 1000', which turns out to be 10AWG, which has
1.24ohm per 1000'. 

"...use of VOM (volt-ohm-milliammeter)...
Learn how to use and read an analog VOM, especially a Simpson(r) Model

"...and A.C. circuits."
-Alternating Current is current that changes polarity periodically due
to voltage changing polarity. Probably the biggest advantage of AC is
the fact that AC current can be transformed and DC current cannot. A
transformer permits voltage to be stepped up or down.

-Sine wave values of AC include peak-to-peak, peak, RMS, and average:

-Peak-to-peak is measured from the maximum value in the positive
direction to the maximum value in the negative direction.

-The peak value is measured from zero to the highest value obtained in
either the positive or negative direction. The peak value is one-half of
the peak-to-peak value.

-RMS stands for root-mean-square, which is an abbreviation for the
square root of the mean of the square of the instantaneous currents. The
RMS value can be found by dividing the peak value by the square root of
2 (1.414) or by multiplying the peak value by 0.707 (the reciprocal of
RMS = peak x 0.707
Peak = RMS x 1.414 

-Average values of voltage and current are actually direct current
values. The average value must be found when a sine wave AC voltage is
changed into DC with a rectifier. The average value of voltage will
produce the same amount of power as a nonpulsating source of voltage
such as a batter. For a sine wave, the average value of voltage is found
by multiplying the peak value by 0.637 or by multiplying the RMS value
by 0.9.
Average = peak x 0.637
Average = RMS x 0.9

The information in ET JOURNAL is provided as a guide only and is
intended to assist you in preparing for an exam. The references herein
are not intended to be inclusive of all information included on a test.


PCC Sylvania, Portland;
Test 4/20/02. Postmark deadline 3/2/02.
Test 7/27/02. Postmark deadline 6/8/02.

Clackamas Community College, Oregon City;
Test 6/22/02. Postmark deadline 5/4/02.
Test 9/14/02. Postmark deadline 7/27/02.

Bates Technical College, Tacoma;
Test 2/23/02. Postmark deadline 12/1/01.
Test 5/18/02. Postmark deadline 3/30/02.

Walla Walla Community College;
Test 4/20/02. Postmark deadline 3/2/02.
Test 7/27/02. Postmark deadline 6/8/02.

Spokane Community College;
Test 2/23/02. Postmark deadline 12/1/01.
Test 5/18/02. Postmark deadline 3/30/02.

For a complete list of all test centers and test dates, visit


The Washington Burglar & Fire Alarm Association (WBFAA) is sponsoring a
16-hour NICET(r) Test Preparation Seminar:

>> 2-28-2002 8am - 5pm NICET(r) Certification application process and
Fire Alarm Systems Level I Element Review.

>> 3-1-2002 8am - 5pm Fire Alarm Systems Level II Element Review.

Stella McDonald, WBFAA Executive Director
(800) 248-9272

Pierce County Fire District #3
University Place Fire Department
3631 74th Avenue
University Place, WA 98466

Dean Reed, CET
(206) 935-8950


Clackamas Community College is sponsoring a 16-hour NICET(r) Test
Preparation Seminar:

>> 4-6-2002 8am - 5pm NICET(r) Certification application process and
Fire Alarm Systems Level I Element Review.

>> 4-13-2002 8am - 5pm Fire Alarm Systems Level II Element Review.


Clackamas Community College

Michael B. Baker, CET
(503) 209-7345


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