2.3.b Outgoing Voltage
1) Determine the following for each load:
a. Power consumption (in Watts). Please note - Total load must not exceed maximum capacity of
the unit. See section entitled “Specifications” for your model’s maximum wattage. If your unit is a
single tap model, please go to step three in this section.
b. Distance from transformer (in Feet).
c. Proper wire size. The wire size is based on power consumption and distance from the
transformer. Use National Electric Code and local regulations to determine which wire size is to
be used.
d. Copper
wire’s
multiplier using Figure 4.
Copper Wire Size
Multiplier (k)
6 AWG
0.000043
8 AWG
0.000065
10 AWG
0.000105
12 AWG
0.000168
14 AWG
0.000265
Figure 4
2) With the load’s power consumption, distance from the transformer and wire multiplier, use the formula in
Figure 5 to determine which voltage tap is to be used. Refer to the wiring diagram on the transformer for
tap locations.
3) Insulate any unused wire taps individually with wire nuts.
4) Add total wattage for all loads and confirm total is under the maximum power rating of the transformer.
12 + (k x W x D) = VT
12
=
Required Voltage for load
K
=
Multiplying factor dependent on the wire gauge of the wire used
W
=
Power Consumption of the load (in watts)
D
=
Distance from the transformer (in feet)
VT
=
Transformer’s Voltage Tap to be used. (12V, 13V, or 14V)
Figure 5
Example:
Load 1:
A model MT-300 transformer is used to connect a 40-Watt light located 50 feet from the
transformer. The local code in this case is stating that a #12 AWG wire size should be used.
(See
local codes for your application.)
The calculation is 12 + (0.000168 x 40 x 50) = 12 + .336 = 12.336 or 12.3,
therefore you can use a 12-volt tap.
(Always rounding up to next highest tap)
Load 2:
A second load, a 60-Watt light, is located 100 feet from the transformer. The local code in this
case is stating that a #12 AWG wire size should be used.
(See local codes for your application.)
The calculation is 12 + (0.000168 x 60 x 100) = 12 + 1.008 = 13.008 or 13.0, therefore you can
use a 13-volt tap.
(Always rounding up to next highest tap)
Total of all loads:
The total wattage of the loads are added together and subtracted from the transformer’s power
capacity. In this example the maximum wattage of the MT-300 transformer is 300-Watts. (
See
Figure 1 for your model’s maximum wattage.)
The calculation is 300 Watts – (40 + 60) = 300 – 100 = 200 Watts available.
Figure 6
