Section 7: Power Supply Calculations; Overview; Calculating The Ac Branch Circuit; Calculating The System Current Draw - Honeywell NOTIFIER SFP-5UD Series Manual

7.1 Overview

This section contains instructions and tables for calculating power supply currents in alarm and standby conditions. This is a four-step
process, consisting of the following:
1. Calculating the total amount of AC branch circuit current required to operate the system
2. Calculating the power supply load current for non-fire and fire alarm conditions and calculating the secondary (battery) load
3. Calculating the size of batteries required to support the system if an AC power loss occurs
4. Selecting the proper batteries for your system

7.2 Calculating the AC Branch Circuit

The control panel requires connection to a separate, dedicated AC branch circuit, which must be labeled FIRE ALARM. This branch
circuit must connect to the line side of the main power feed of the protected premises. No other non-fire alarm equipment may be pow-
ered from the fire alarm branch circuit. The branch circuit wire must run continuously, without any disconnect devices, from the power
source to the control panel. Overcurrent protection for this circuit must comply with Article 760 of the National Electrical Codes as well
as local codes. Use 14 AWG (2.00 mm
Use Table 7.1, to determine the total amount of current, in AC amperes (A), that must be supplied to the system.
Device Type
SFP-5UD
or
SFP-5UDC/SFP-10UD(C)
or
SFP-10UDE

7.3 Calculating the System Current Draw

7.3.1 Overview
The control panel must be able to power all internal and external devices continuously during the non-fire alarm condition. To calculate
the non-fire alarm load on the system power supply when primary power is applied, use Calculation Column 1 in Table 7.3 on page 111.
The control panel must support a larger load current during a fire alarm condition. To calculate the fire alarm load on the power supply,
use Calculation Column 2 in Table 7.3 on page 111. The secondary power source (batteries) must be able to power the system during a
primary power loss. To calculate the non-fire alarm load on the secondary power source, use Calculation Column 3 in Table 7.3 on page
111.
When calculating current draw and the battery size, note the following:
• 'Primary' refers to the main power source for the control panel
• 'Secondary' refers to the control panel's backup batteries
• All currents are given in amperes (A). Section 7.2 shows how to convert milliamperes and microamperes to full amperes.
Milliamperes (mA) to
amperes (A)
Microamperes (
amperes (A)
7.3.2 How to Use Table 7.3 on page 111 to Calculate System Current Draw
Use Table 7.3 on page 111 to calculate current draws as follows:
1. Enter the quantity of devices in all three columns
2. Enter the current draw where required. Refer to the Device Compatibility Document for compatible devices and their current draw
3. Calculate the current draws for each in all columns
4. Sum the total current for each column
5. Copy the totals from Column 2 and Column 3 to Table 7.4 on page 112
Following are the types of current that can be entered into Table 7.3 on page 111:
 Calculation Column 1 - The primary supply current load that the control panel must support during a non-fire alarm condition,
with AC power applied.
110

Section 7: Power Supply Calculations

2
) wire with 600 volt insulation for this branch circuit.
Number of
Devices
[
[
Sum Column for AC Branch Current Required
Table 7.1 AC Branch Circuit Requirements
To convert...
µ
A) to
Table 7.2 Converting to Full Amperes
Current Draw
(AC amps)
1 X
] X
] X
Multiply
mA x 0.001
µ
A x 0.000001
SFP-5UD & SFP-10UD Series Manual— P/N 52879:C6 6/12/2018
1.00 =
3.90
2.20
[ ] =
[ ] =
=
Example
3 mA x 0.001 = 0.003A
µ
300 A x 0.000001 = 0.0003 A
Total Current per
Device