HPF24S Series Power Supplies —
P/N 52751:D3 5/11/2010
39
Calculating the System Current Draw
Power Supply Requirements
•
Secondary
refers to the power supply’s backup batteries.
•
All currents are given in amperes (A). Table 6.2 shows how to convert milliamperes and
microamperes to full amperes.
6.3.2 How to Calculate System Current Draw
Use Table 6.3 on page 40 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 6.3 on page 40.
Following are the types of current that can be entered into Table 6.3 on page 40
–
Calculation Column 1
- The primary supply current load that the power supply must
support during a non-fire alarm condition, with AC power applied
–
Calculation Column 2
- The primary supply current load the power supply 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
To convert...
Multiply
Example
Milliamperes (mA) to
amperes (A)
mA x 0.001
3 mA x 0.001 - 0.003 A
Microamperes (
A) to
amperes (A)
A x 0.000001
300
A x 0.000001 = 0.0003 A
Table 6.2 Converting to Full Amperes
