KMC Controls XEE-6311 - Manual (Page 8)

KMC Controls
AN0604D Revision B
Tips for connecting 24-volt power
Calculating voltage drop
1–22
Calculating voltage
drop
Inadequate voltage caused by voltage drop may result in erratic network
problems or controller failure. Voltage drop occurs when power flows along a
length of wire. To minimize the effects of voltage drop, connect transformers as
close to their connected controllers as possible. The size of the connected load and
the gauge of the connecting wire has a significant effect on an acceptable distance
between the transformer and the controller.
Use the following formula to calculate voltage drop based on the length and size
of wire and the load presented by a controller. Limit the voltage drop at each
controller to no more than 5% or 1.2 volts AC.
Example:
Wire Size–AWG, stranded Ohms / 1000 ft (at 77°F)
Voltage drop = Amps x (length of circuit in ft) x 2 x (ohms per 1000 ft) / 1000
= I x L x 2* x R / 1000
Table 1 Wire resistance
22 16.46
20 10.35
18 6.512
16 4.095
14 2.576
12 1.620