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The Voltage Drop Calculator
System Sensor’s Voltage Drop Calculator is a
quick and efficient means for developing voltage drop calculations for fire
alarm
control
panels
and
auxiliary power supplies. It calculates the voltage drops along a System
Sensor Notification Appliance Circuit (NAC) by analyzing each device on the circuit
and
determining if enough operating voltage is available at each device location.
This program provides a means of generating reports listing the
circuit voltages along the entire circuit at specific wire gauges.
Voltage drop
calculations determine whether the gauge of wire selected will introduce
so much of a
voltage drop that notification appliances will not
sound at the required dB noise level.
Additionally, the age-old method of calculating
voltage drops based on the presumption that all
devices are installed at the end of the circuit yields
fast but conservative (and often negative) results.
With the advent of ADA devices, current demands
on control panels rose sharply and system
designers were faced with the need to determine exactly how many
appliances could be supported by a circuit. Voltage Drop Calculator
performs point-to-point circuit analysis, which results in a more accurate
assessment of the circuit’s capabilities, and allows for the mixing of
differing devices on the same circuit.
This web tool includes support for System Sensor’s
newest line of Selectable Output appliances.
Getting Started
STEP 1
Set the NFPA Wiring Style
The National Fire Protection Association (NFPA)
style of wiring a circuit can be selected by the
clicking on the desired style indicator.
Style Y (Class B) wiring is characterized by two wires that
leave the source and are terminated at some distance
away by an end-of-line resistor (ELR). A single break in
the wiring prevents all devices installed after the break
from functioning.
Style Z (Class A) wiring is characterized by two
wires that leave the source and are brought back
to the source from the end of the circuit. There is
no external ELR connected to this type of circuit.
This circuit has the advantage of providing
alternate paths of current to reach installed
devices in the presence of a single break of wire,
allowing each device to function.
A normally-functioning Style Z circuit will have
smaller IR drops than a Style Y circuit because of the dual run of wire for
each leg. However, in the presence of a worst-case two-wire break
(occurring closest to the panel) the IR drops encountered by installed
devices will be greater than those found on a normal Style Z circuit, but
identical to those found on a Style Y circuit of the same length. Voltage
Drop Calculator uses this worst-case consideration to analyze a Style Z
circuit.
This Style setting is just for completeness - it does not affect program’s
calculation routine. Since the program assumes a two-wire break on a
Style Z circuit, it is treated as a Style Y circuit for IR loss calculation.
Wire Gauge
This allows the selection of 12, 14, 16, or 18 AWG wire. The calculator will
display the drop at all gauges. This selection is for highlight purposes
in your final report.
MDL Circuit
Check this box if your circuit will have an MDL sync module. This effects the
starting voltage.
Appliance Circuit
DC or FWR
The type of power supply employed to power Notification Appliances
plays a major role in calculating voltage drops. Most notification appliances
have
differing current draws when powered by a regulated, filtered (DC) power supply
versus a Full-Wave Rectified (FWR) unfiltered power supply. Voltage Drop Calculator
correctly calculates the circuit voltage at each device based upon the filtering
characteristics of specific
power supply selected.
12 or 24 volt supply
This selection made here will determine whether 12 or
24-volt devices will be available in the Notification Appliance drop down menu.
It also
determines the maximum current limit for the power source overload
meter (assuming that the full current indicated is dedicated to that single
Notification Appliance Circuit).
Current (amps)
Choose the amperage of your circuit. This is the only option you may change in STEP 2
Warning: Voltage Drop Calculator assumes that
source power is dedicated for the circuit being developed.
If the power run is T-tapped or shared with
any another device circuit, ignore the Power Meter
and manually calculate system circuit currents.
STEP 2
After selecting all the parameters
in STEP 1. you will be able to select the first set of appliances in your
circuit using the drop down menu displayed. After selecting
a model, you can select the number of units and spacing for each unit in
that group. Once this is done a spreadsheet will appear below showing the
voltage drop at each unit for each gauge of wire. You may choose a different
model or add more of the selected model with different spacing.
Options
Once you have entered in the first unit(s) in your circuit,
a list of options will appear in the upper right portion of the screen.
Below is a description of what each option does. Current Meter
This is a graphical display of the amps used in your circuit. If it is flashing
red, then you have exceeded the amps you specified in STEP 1.
Increase/Decrease current limit
You can increase or decrease your circuit amperage in increments of 0.5 amps
by clicking on the + and - buttons or adjacent links. This will change the
current limit, adding or subtracting 0.5 amps to the specified circuit.
Starting Voltage
As a default this will be set to nominal minus 15% or 20.4 volts for a 24 volt
supply and 10.2 volts for a 12 volt supply. You can change this by entering
your desired starting voltage in the input field and clicking the = button.
You are limited to the operating range of System Sensor units; 16 to 33
volts for a 24 volt supply and 8 to 17.5 volts for a 12 volt supply.
Remove Group
This will allow you to remove any group of units entered in at the left. The
groups are designated by lowercase letters.
Highlight AWG
This will allow you to turn on/off the highlighted column of the wire gauge
you chose in STEP 1.
Go to STEP 3 Print
Click here when you are finished adding units and adjusting the calculator
to move to the next STEP.
STEP 3
Once you have finished creating your spread sheet, click this link to go to
a print friendly representation of your spreadsheet. You will be taken to a
form page where you can enter in any information you wish to be typed in for
you. This will appear at the
top
of
your report. No fields are required. Any field left blank will appear as a
line for you to fill in later with a pen or pencil.
LAST STEP
This is the final report. Simply choose Print from the Browser's
file menu to print your report. You may also want to save this document. If
you save the document you may experience font differences when you
re-open it. To rectify this, choose a smaller text size from your browser's
view menu.
Link
There will be a link at the bottom of your report which will be active for
two weeks. Use this link to make any changes or to forward on to others.
Suggestions
The voltage drop calculator is offered as a free service to System
Sensor customers. We'd like to give our customers the opportunity to help us
make it as useful a tool as possible. Please send any suggestions, bug reports,
or comments to the following email address: suggestions@gruntcreative.com
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