EST EST3X - Worksheet Method

Appendix A: System calculations
244 EST3X Technical Reference Manual
Worksheet method
Use this worksheet to determine the maximum cable length of a notification
appliance circuit for a given number of appliances.
Use this worksheet only if all the appliances are regulated. That is, they must
have a minimum operating voltage of 16 V. For other appliances, use the
“Equation method.”
Worksheet 1: NAC cable length
PS10-4B 3-IDC8/4 3-ZA20/40
Total operating current [1]
A
Load factor
×
0.0 0.0 0.0
V/A
Load voltage drop
=
V
Source voltage
22.4 21.3 21.7
V
Load voltage drop
−
V
Minimum voltage
=
V
Regulated appliance voltage
−
16.0 16.0 16.0
V
Voltage drop [2]
=
V
Total operating current
÷
A
Maximum resistance
=
Ω
Wire resistance (Ω/
ft) [3]
÷
Maximum wire length
=
ft
÷
2 2 2
Maximum cable length
=
ft
[1]
Total of the maximum operating currents for all appliances as specified for DC power.
Refer to
the
appliance installation sheets for operating currents.
[2]
This voltage drop is valid for regulated notification appliances only. For special application
appliances,
see “Equation method,” later in this topic.
[3]
Use the manufacturer’s published wire resistance expressed in ohms per foot. For typical
values, see Table 77 on page 245.