Appendix B: Worksheets
212
EST iO64 and iO500 Technical Reference Manual
Equation method
Appliance operating voltage and current
Regulated notification appliances have an operating range from 16
V to 33 V. Use 16 V as the minimum appliance voltage when using
regulated notification appliances.
When using special application notification appliances, refer to the
installation sheets to determine the minimum appliance voltage
required.
What if there are different types of appliances in the NAC, and each
type has a different minimum operating voltage? In this case, use
the
highest
minimum voltage required by any appliance.
The total current requirement for the appliances will be the sum of
the individual maximum currents drawn by each appliance when
using FWR power. Use the maximum current for the appliance over
the 16 V to 33 V range.
If all appliances draw the same maximum current, the total current
is the maximum current multiplied by the number of appliances. If
different appliance types have different maximum currents, the total
current is the sum of the maximum current for each appliance type
multiplied by the number of appliances of that type.
Wire resistance
Typical wire resistances are shown in the following table.
Table 1: Typical wire resistances
Wire
gauge
Resistance
1-strand uncoated copper
Resistance
7-strand uncoated copper
Ω
per foot
Ω
per meter
Ω
per foot
Ω
per meter
12
AWG
0.00193 0.00633 0.00198 0.00649
14
AWG
0.00307 0.01007 0.00314 0.01030
16
AWG
0.00489 0.01604 0.00499 0.01637
18
AWG
0.00777 0.02549 0.00795 0.02608
When performing these calculations, always refer to the actual
cable supplier documentation and use the actual
Ω
/ft. (or
Ω
/m) for
the cable being used.
Calculating cable length
To calculate the maximum NAC cable length:
1. Calculate the total current (Itot) as the sum of the maximum
operating currents for all the appliances.
