Power Supply Calculations

Calculating the System Current Draw

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 165. The control panel must support a larger load current during a fire alarm con- dition. To calculate the fire alarm load on the power supply, use Calculation Column 2 in Table 7.3 on page 165. 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 165.

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). Table 7.2 shows how to convert milliam- peres and microamperes to full amperes.

Table 7.2 Converting to Full Amperes

To convert...

Multiply

Example

 

 

 

Milliamperes (mA) to

mA x 0.001

3 mA x 0.001 = 0.003A

amperes (A)

 

 

 

 

 

Microamperes (µA) to

µA x 0.000001

300 µA x 0.000001 = 0.0003 A

amperes (A)

 

 

 

 

 

7.3.2How to Use Table 7.3 on page 165 to Calculate System Current Draw

Use Table 7.3 on page 165 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 166 Following are the types of current that can be entered into Table 7.3 on page 165:

Calculation Column 1 - The primary supply current load that the control panel must support during a non-fire alarm condition, with AC power applied.

Calculation Column 2 - The primary supply current load that the control panel must support during a fire alarm condition, with AC power applied.

Calculation Column 3 - The standby current drawn from the batteries in a non-fire alarm condition during a loss of AC power.

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MS-9200UDLS PN 52750:A 11/04/05