Section 7: Power Supply Calculations; Overview; 1: Overview; Calculating The Ac Branch Circuit - Fire-Lite MS-9200UDLS Manual

Section 7: Power Supply Calculations

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 worst-case system current load on the control panel, when primary (AC) power
is applied, to assure that the limit of the its internal power supply will not be exceeded. This
considers the fire alarm condition only.
3. Calculating the total current load on the batteries (seondary power source) in the event of an
AC power loss. This considers both standby and fire alarm conditions.
4. Calculating the size of the batteries required to support the system if AC power loss occurs,
based on the total batttery current load, plus a regulatory agency mandated derating factor.

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 powered 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
wire with 600 volt insulation for this branch circuit.
Use Table 7.1 , to determine the total amount of current, in AC amperes (A), that must be supplied
to the system.
Device Type
MS-9200UDLS
or
MS-9200UDLSE
CHG-75
CHG-120F

7.3 Calculating the System Current Load

7.3.1 Overview
The control panel's internal power supply must support all connected devices while primary (AC)
power is applied. The continuous system current load is highest during a fire alarm condition. To
caluclate the fire alarm load on the internal power supply, use Calculation Column 1 in Table 7.3 on
page 191.
The secondary power source (batteries) must be able to power the system under both standby and
fire alarm conditions upon loss of primary (AC) power. To calculate the fire alarm load on the
secondary power source, use Calculation Column 2 in Table 7.3 on page 191. To calculate the
standby load on the secondary power source, use Calculation Column 3 in Table 7.3 on page 191.
MS-9200UDLS/E/C Manual — P/N 52750:F 7/26/2010
Number of
Devices
1 X
[ ] X
[ ] X
[ ] X
Sum Column for AC Branch Current Required
Table 7.1 AC Branch Circuit Requirements
Current Draw
(AC amps)
3.00
or =
1.50
2.05 =
2.00 =
[ ] =
=
)
2
Total Current
per Device
189