Kidde VM-1 Technical Reference Manual

Appendix A: System calculations
180 P/N 3101890-EN • REV 006 • ISS 21JUN18
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 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 DC 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 72: Typical wire resistances
Wire gauge
(AWG)
Resistance
1-strand uncoated copper
Resistance
7-strand uncoated copper
Ω per foot Ω per meter Ω per foot Ω per meter
12
0.00193 0.00633 0.00198 0.00649
14
0.00307 0.01007 0.00314 0.01030
16
0.00489 0.01604 0.00499 0.01637
18
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 CAB cable length:
1. Calculate the total current (Itot) as the sum of the maximum operating currents for all the appliances.
Itot = ΣIa
Where:
Ia = appliance maximum current
Refer to the appliance installation sheets for Ia. Remember to use the maximum operating current specified
for DC power.
2. Calculate the minimum voltage (Vm).
Vm = Vr − (Itot × K)
Where:
Vr = source voltage
Itot = total current (from above)
K = load factor
For the power supply, Vr is 22.4 V and K is 0.0 V/A.

Kidde VM-1 Specifications

General

Brand	Kidde
Model	VM-1
Category	Fire Alarms
Language	English