System calculations
B.12 EST3 Installation and Service Manual
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 rated voltage is the theoretical operating minimum for the
power supply, and is calculated as 85% of 24 volts.
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’ll 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 circuit (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.
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