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Selecting and Locating Batteries
6.3.2 How to Calculate System Current Draw
Use Table 6.3 to calculate current draws as follows and refer to the battery calculation tool on www.silentknight.com or www.farenhyt.com.
1.
Enter the quantity of devices in both columns.
2.
Enter the current draw where required. Refer to the Silent Knight Device Compatibility Document for compatible devices and their
current draws.
3.
Calculate the current draws for each in both columns.
4.
Sum the total current for each column.
Following are the types of current that can be entered into Table 6.3.
Calculation Column 1 - The secondary supply current load that the power supply must support during a non-fire alarm condition,
with DC power applied
Calculation Column 2 - The secondary supply current load the power supply must support during a fire alarm condition, with DC
power applied
Table 6.3 contains two columns for calculating current draws. For each column, calculate the current and enter the total (in amperes) in the
bottom row. When finished, use the data to select the proper size batteries in Tables 6.4 and 6.5.
Device Type
Main Circuit Board - SK-PS6 with all outputs 2k EOL
Main Circuit Board - SK-PS6 with 4.7k EOL
Main Circuit Board - SK-PS6 with 27k EOL
Main Circuit Board - SK-PS6 with all Outputs Aux Power Class B
Main Circuit Board - SK-PS6 with ZNAC-PS Class A option card
with all outputs Aux Power
Main Circuit Board - SK-PS10 with all outputs 2k EOL
Main Circuit Board - SK-PS10 with 4.7k EOL
Main Circuit Board - SK-PS10 with 27k EOL
Main Circuit Board - SK-PS10 with all Outputs Aux Power Class
B
Main Circuit Board - SK-PS10 with ZNAC-PS Class A option card
with all outputs Aux Power
NAC/Output #1
NAC/Output #2
NAC/Output #3
NAC/Output #4
NAC/Output #5
NAC/Output #6
NAC/Output #7
EOLR-1 Power Supervision Relay
Sum each column for totals
6.4 Selecting and Locating Batteries
Select batteries that meet or exceed the total ampere hours determined in Tables 6.4 and 6.5. The power supply can charge batteries from 7
AH to 33 AH range. The power supply cabinet is capable of housing industry standard 7 AH or 18 AH batteries. Other ampere batteries (e.g.
12AH, 26AH, 33AH) will not fit physically inside the SK-PS cabinet and require a separate battery box.
6.4.1 NFPA Battery Requirements
NFPA 72 Local and Proprietary Fire Alarm Systems require 24 hours of standby power followed by 5 minutes in alarm for normal operations
or 15 minutes for mass notification systems.
NOTE: When using carbon monoxide detection, the system must be monitored by a Supervising Station meeting the Standard for the
Installation of Carbon Monoxide (CO) Detection and Warning Equipment, NFPA 720.
SK-PS Series Instruction Manual — P/N LS10227-002SK-E:C 2/2/2022
Calculation Column 1
Secondary, Non-Fire Alarm Current
Qty
1
1
1
1
1
1
1
1
1
1
[
]
[
]
[
]
[
]
[
]
[
]
[
]
[
]
Secondary Non-Alarm =
Table 6.3 System Current Draw Calculations
(amps)
X (current draw) =
Total
X [0.154] =
X [0.139] =
X [0.124] =
X [0.132] =
X [0.142] =
X [0.178] =
X [0.156] =
X [0.135] =
X [0.149] =
X [0.160] =
X [
] =
X [
] =
X [
] =
X [
] =
X [
] =
X [
] =
X [
] =
X [0.020] =
Power Supply Requirements
Calculation Column 2
Secondary, Fire Alarm Current
(amps)
Qty
X (current draw) =
1
X [0.192] =
1
X [0.157] =
1
X [0.137] =
1
X [0.132] =
1
X [0.142] =
1
X [0.232] =
1
X [0.185] =
1
X [0.154] =
1
X [0.149] =
1
X [0.160] =
[
]
X [
] =
[
]
X [
] =
[
]
X [
] =
[
]
X [
] =
[
]
X [
] =
[
]
X [
] =
[
]
X [
] =
[
]
X [0.020] =
Secondary Alarm =
Total
39
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