Mod 2
Student Name: _____________________
Wire Sizing Worksheet
Description:
In this worksheet you are going to determine: wire sizing, over current sizing, and disconnect sizing for
multiple questions on the sample data below. Additionally, you will be using actual manufacturer specs to
size all of the above
LEGEND
RLA – Rated Load Amps
LRA – Lock Rotor Amps
OFM – Outside Fan Motor
IDF - Indoor Fan Motor
FLA – Full Load Amps
MCA – Minimum Circuit Amps
MOCP – Max.*Overcurrent
COMP - Compressor
Note: For ampacity calculations of a multi-motor assembly, 25% is added
only to the largest motor.
So if the compressor has a RLA of 10 (almost always the largest load is the compressor) then you multiply the RLA by 1.25 to get the
total amperage for the compressor. You then add that number to the remaining loads to determine the total amp rating of the unit.
Sample Electrical Data:
Comp Amps: 10(RLA)
IDF Amps: 2.0 (FLA)
ODF Amps 1.5 (FLA)
Finding total amperage:
Compressor is the largest load so: 10 amps X 1.25 = 12.5 amps
then you just add that to all the remaining loads: 12.5 amps (compressor) + 2.0 amps (IDF) + 1.5 amps (ODF) = 16 amps total
Finding Conductor Size:
From your wire size chart, you round up to the amperage shown in chart. Look for the corresponding wire size.Through
using this chart you will soon memorize the most common sizes
Instructor - Dave Van West
Page 1 of 1
WyoTech HVAC
Mod 2
Student Name: _____________________
Wire Sizing Worksheet
Wire Amps
Size
14
15
12
20
10
30
8
55
6
75
4
95
2
130
1
150
1/0
170
2/0
195
3/0
225
Instructor - Dave Van West
Using the wire sizing chart:
1. With the given amps you round up to get the correct wire size.
As an example, if you have a load that requires 17 amps, you would install
#12 wire, because #14 wire only goes to 15 amps, 2 amps shy of the required.
2. If you know the wire size you have, then you are able to determine maximum
allowable amperage
Things to keep in mind:
1. This is the amp ratings for THHN / THWN insulated wire. If the ambient
temperature goes up, the allowable amp rating goes down. Almost all of
the wire that we use is the dual rated THHN / THWN.
2. Another consideration is how many wires you are installing into one
piece of conduit, known as the conduit fill. By code you can only install
a fixed number of wires into a conduit.
Page 1 of 1
WyoTech HVAC
Mod 2
Student Name: _____________________
Wire Sizing Worksheet
Directions: From the data plate pictured below, answer the following questions:
1. Sample Electrical Data:
3. Sample Electrical Data:
Comp Amps: 11.2 (RLA)
IDF Amps: 2.4 (FLA)
ODF Amps 1.8 (FLA)
Comp Amps: 35 (RLA)
IDF Amps: 8 (FLA)
ODF Amps 3.5 (FLA)
1. What is the total amperage (running) on this unit?
1. What is the total amperage (running) on this unit?
2. What size wire is necessary to run this unit?
2. What size wire is necessary to run this unit?
3. What size fuses are necessary for this unit?
3. What size fuses are necessary for this unit?
2. Sample Electrical Data:
4. Sample Electrical Data:
Comp Amps: 21 (RLA)
IDF Amps: 3.4 (FLA)
ODF Amps 2.8 (FLA)
Comp Amps: 4.5 (RLA)
IDF Amps: 1.1(FLA)
ODF Amps 0.8 (FLA)
1. What is the total amperage (running) on this unit?
1. What is the total amperage (running) on this unit?
2. What size wire is necessary to run this unit?
2. What size wire is necessary to run this unit?
3. What size fuses are necessary for this unit?
3. What size fuses are necessary for this unit?
Instructor - Dave Van West
Page 1 of 1
WyoTech HVAC
Mod 2
Student Name: _____________________
Wire Sizing Worksheet
Directions: From the data plate pictured below, answer the following questions:
1. What is the total amperage (running) on this unit?
2. What size wire is necessary to run this unit?
3. What size fuses are necessary for this unit?
Instructor - Dave Van West
Page 1 of 1
WyoTech HVAC
Mod 2
Student Name: _____________________
Wire Sizing Worksheet
Directions: From the data plate pictured below, answer the following questions:
A. Model 38GK... 5 TON
C. Model 50YX... 2 TON
1. What is the total amperage (running) on this unit?
1. What is the total amperage (running) on this unit?
2. What size wire is necessary to run this unit?
2. What size wire is necessary to run this unit?
3. What size fuses are necessary for this unit?
3. What size fuses are necessary for this unit?
B. Model 38TDB... 4 TON
D. Model 38CE...
1. What is the total amperage (running) on this unit?
1. What is the total amperage (running) on this unit?
2. What size wire is necessary to run this unit?
2. What size wire is necessary to run this unit?
3. What size fuses are necessary for this unit?
3. What size fuses are necessary for this unit?
Instructor - Dave Van West
Page 1 of 1
WyoTech HVAC