EST EST3X - Page 253

Appendix A: System calculations
EST3X Technical Reference Manual 243
Table 76: NAC calculation values
NAC
source Maximum
voltage (V)
Source
voltage (V)
Load factor
(V/A) [1]
Power
supply type
PS10
-4B Power Supply 26.4 22.4 0.0 DC
3
-IDC8/4 Traditional
Zone I/O Module
[2]
26.0 21.3 0.0 DC
3
-ZA20 or 3-ZA40 Zoned
Audio Amplifiers
[2]
25.9 21.7 0.0 DC
[1] The PS10-4B has an onboard boost circuit to keep battery voltage at a required value. If the
battery voltage drops below the required value, the boost circuit activates.
[2] These values only apply when the card is used in an EST3X control panel.
The maximum voltage is the highest voltage measured at the NAC terminals.
This value is not used in the calculations, but is given so you can ensure
appliance compatibility.
The source voltage is the theoretical operating minimum for the NAC source, and
is calculated as 85% of 24 volts [minus the diode drop].
The load factor is a measure of how the power supply voltage reacts when a load
is applied. The load factor measures the voltage drop per ampere of current
drawn by the load.
The power type reflects the type of power supplied to the NAC terminals at
minimum voltage. The current draw of notification appliances can vary
substantially with the type of power supplied: full-wave rectified (VFWR) or direct
current (VDC). It is important to know the power type at minimum terminal
voltage.
You will need to calculate the following values relating to your power supply and
to the NAC circuit current. These are:
• Minimum voltage
• Voltage drop
The minimum voltage is the lowest voltage measured at the NAC terminals when
the power supply is under the maximum load for that loop (i.e. for the appliances
that constitute the NAC).
The voltage drop is the difference between the minimum voltage and 16 V. This
value is for use with the worksheet only.