Wiring Schematics and Generator Sizing
Please contact our service department for all technical questions:
Emerson 2-71gm generators 1-800-387-4972.
WITH A GENERATOR, SIZE MATTERS

The first thing you need to do is determine what size generator would work best for your particular
needs.  When purchasing a generator, it's important that you select one that's capable of meeting
your requirements.

*   You must match the rated output of the generator to the maximum anticipated power to be used.

WARNING:  Electrocution, severe personal injury or death can occur:  Do not connect any
generator to any building's electrical system unless an isolation switch has been installed by an
electrician.  Refer to the Generator Owner's manual.

CAUTION:  Property damage can occur:  Do not connect any generator to any building's electrical
system unless an isolation switch has been installed by a licensed electrician.  Refer to the
Generator Owner's manual.

TAKE IT STEP-BY-STEP
Follow these steps when determining your energy needs:

1.  Identify the wattage requirements for the tools and appliances that you want to power.  The power
requirements for the tool or appliance can be found on its identification plate or in the Owner's
manual.  If the power requirements are given in amps, multiply the amps times volts to derive the
required watts.

2.  Add up the required watts of all the tools and appliances you expect to operate simultaneously.

3. The total watts derived in step 2 is the size of generator you need. These three simple steps will
"size" a generator. Normally, you won't need to consider motor starting requirements when using a
generator. When a generator is properly sized for a tool's or appliance's running requirements, surge
capability or 3 times the rated output for three seconds usually is sufficient to handle the motor's
starting surge needs.

The Additional Guidelines section explains the procedures to calculate and size for motor starting.

This chart lets you immediately add up all of the appliances you will most likely utilize:

G EN E R A T O R   W O R K S H E E T
  RUNNING
WATTAGE REQUIREMENTS
ADDITIONAL STARTING
WATTAGE REQUIREMENTS
TOTALS
HEATING/COOLING:
   
Furnace Fan, gas
or fuel oil furnace
   
1/8 horsepower
300
500
1/6 horsepower
500
750
1/4 horsepower
600
1000
2/5 horsepower
700
1400
3/5 horsepower
875
2350
Central Air Condition
   
10,000 BTU
1500
2200
20,000 BTU
2500
3300
24,000 BTU
3800
4950
32,000 BTU
5000
6500
40,000 BTU
6000
6700
HEATING / COOLING
  SUB-TOTAL:
     
KITCHEN
   
Refrigerator, Average
600
2200
Dish Washer - Cool Dry
700
1400
Dish Washer - Hot Dry
1450
1400
Clothes Dryer - Gas
700
1800
Clothes Dryer - Electric
5750
1800
Microwave Oven, 750W
750
800
Washing Machine
750
2300
Coffee Maker
850
0
Toaster 2-Slice
1100
0
Toaster 4-Slice
1650
0
Electric Skillet
1500
0
Electric Range 6-in. Element
1500
0
Electric Range 8-in. Element
2100
0
Freezer
2500
220
KITCHEN
  SUB-TOTAL:
     
BATHROOM
   
Hair Dryer
800-1700
0
Curling Iron
1200
0
BATHROOM
  SUB-TOTAL:
     
OTHER APPLIANCES
   
Lights - Wattage
Actual:
 
VCR
50
0
Heating Pad
65
0
Radio
100
0
Television - Black & White
100
0
Television - Color
300
0
Dehumidifier
400
0
Electric Blanket
400
0
Garage Door - 1/4 HP
550
1100
Garage Door - 1/3 HP
725
1400
Wet Pump - 1/3 HP
750
1400
Wet Pump - 1/2 HP
1000
2100
Sump Pump -1/3 HP
800
1300
Sump Pump - 1/2 HP
1050
2150
Vacuum Cleaner - Standard
800
0
Vacuum Cleaner - Deluxe
1100
0
APPLIANCES
  SUB-TOTAL:
     
COMMERCIAL PRODUCTS
   
1/4"  Drill
300
300
Jigsaw
300
300
Electric Weed Trimmer
500
500
Router
1000
1000
Belt Sander
1000
1000
Disc Sander
1200
1200
Chain Saw
1200
1200
Worm Drive Saw
1560
3100
12" Concrete Cutter
1800
3600
7 1/4" Circular Saw
1500
3000
Disc Grinder
2000
4000
Air Compressor, Average
2000
4000
COMMERCIAL PRODUCTS
  SUB-TOTAL:
    GRAND TOTAL:
Counter
Copyright©1995
Emerson & Matkin
Call Us Toll Free:  1.800.387.4972

The formula for voltage drop is:  Vd = 2K x L x I / Cm
Vd = Voltage Drop
I = Current in Conductor (Amperes)
L = One way Length of Circuit
Cm = Cross Section Area of Conductor (Circular Mils)
K = Resistance in ohms of one circular mil foot of conductor
K = 12.9 for Copper Conductors @ 75 degrees C
K = 21.2 for Aluminum Conductors @ 75 degrees C
/ = Divided by

We will assume you are going to use copper conductors and your temperature is @ 75 degrees C.  
Reasonable operating efficiency is achieved if the voltage drop of a feeder or a branch circuit is
limited 3 percent.  However, the total voltage drop of a branch circuit plus a feeder can reach 5%
and still achieve reasonable operating efficiency (210.19(A)(1)FPN No. 4 or 215.2(A)(4)FPN No. 2).
8 AWG = 50 amps @ 75 degrees C = 16510 Cm
Vd = 2 x 12.9 x 377 x 50 / 1650 = 30 volts
30 volts / 24 volts = 0.125 = 12.5% = Not Acceptable
6 AWG = 65 amps @ 75 degrees C = 26240 Cm
Vd = 2 x 12.9 x 377 x 50 / 26240 = 19 volts
19 volts / 240 volts = 0.079 = 7.9% = Not Acceptable
4 AWG = 85 amps @ 75 degrees C = 41740 Cm
Vd = 2 x 12.9 x 377 x 50 / 41740 = 12 volts
12 volts / 240 volts = 0.05 = 5% + Not acceptable - This is not acceptable because the 5% voltage
drop is at your sub panel.  If you were to run any wire beyond the sub panel, your voltage drop would
exceed 5%.  We are assuming you are going to install a light and some receptacles.
3 AWG =100 amps @ 75 degrees C = 52620 Cm
Vd = 2x 12.9 x 377 x 50 / 52620 = 9 volts
9 volts / 240 volts = 0.038 = 3.8% = Acceptable
Your equipment grounding conductor (ground wire) is sized off of table 250.122.  You need to run a
10 AWG equipment grounding conductor (ground wire).

Tip:  Plan for voltage drop at 100 feet and increase one wire size for every 100 feet thereafter.

VOLTAGE DROP TABLE






























* The table above applies to the single phase systems, in steel conduit, at a conductor operating
temperature of 75 degrees C.  It assumes a power factor of one.  The table may be used for
systems using non-steel conduit, but actual results for these conditions may result in a greater
voltage drop.
** Type NMB cables may not be used for a 100 amp load.
*** Must use 6 gauge if using NMB or UFB.

WARNING!  Installation of electrical wire can be hazardous, if done improperly, can result in
personal injury or property damage.  For safe wiring practices, consult the National Electrical Code
and your local building inspector.
ADDITIONAL GUIDELINES

CONVERTING AMPS OR HORSEPOWER INTO WATTS            Horse Power required to start motor
If necessary, use these formulas:

Watts = Amps x Volts                                                                      HP/1.341=KW Requirement
Running Watts* = Horsepower x 932** (for motors)                HP * 2.4 amps = per leg requirement

Remember, this worksheet lists average power requirements — a particular manufacturer's
device may use more or less than the listed wattage.

*   Add a 10% correction factor to your totals to help overcome this uncertainty.

If your customer plans to operate devices that use electric motors, list
both the starting and
running
requirements of each.

*   
Starting requirements of some devices maybe significantly higher than their running
requirements
. This higher demand must be considered when estimating your power needs.
Some small, universal motors — which do not draw a heavy starting load (drills, small saws,
blenders, etc.) — require very little extra current for starting.

When listing items that use motors, take them in the order of highest - to - lowest starting
requirements, as shown in the example below. Motor A, for instance, has a
starting requirement
of 2,600 watts, so it's listed first, followed by Motor B at 1,300 watts, and Motor C at 1,000 watts.











Once you have compiled an accurate list of what you will be operating, you can calculate the
maximum power requirements. There are three different calculations you can make, depending
upon the kinds of tools and appliances on the list, and their intended use:

*     No electric motors.
*     One motor running at a time.
*     More than one motor running at a time.

NO ELECTRIC MOTORS
If your list does not include any devices that use electric motors, simply add the power (running)
requirements of all the items on your list to obtain the maximum power needed.

*   For example, if you intend to use only an electric skillet, a 100-watt light and a heating pad (as
shown below), the maximum power requirement would be 1,655 watts. In this case, a generator  
that can produce 2,500 watts rated output, is recommended.














Footnotes:
*   Running Watts is the amount of power a motor consumes once it has started to run at normal
speed.
**   932 is the factor used to convert motor horsepower ratings to needed electrical energy. It takes
into account normal losses in utilizing that power.
DEVICE
WATTS
Electric Skillet
1500
Light
100
Heating Pad
65
Total:
1665
MOTOR / DEVICE
STARTING WATTS
RUNNING WATTS
Motor A
2600
850
Motor B
1300
600
Motor C
1000
750
Wire Size Selection for Long Runs
110 Volts, Single Phase, Max 3% Voltage Drop*
  25'
50'
100'
150'
200'
Amp Load
Copper
14
12
8
6
6
15 AMP
Copper
12
10
8
6
4
20 AMP
Copper
10
8
6
4
3
30 AMP
Copper
3**
3**
1
2/0
3/0
100 AMP
Aluminum
2
2
2/0
4/0
300
MCM
100 AMP
Copper
3/0
3/0
3/0
MCM
350
MCM
200 AMP
Aluminum
4/0
4/0
300
MCM
400
MCM
600
MCM
200 AMP
220 Volt, Single Phase, Max 3% Voltage Drop*
Copper
14
14
12
10
8
15 AMP
Copper
12
12
10
8
8
20 AMP
Copper
10
10
8
6
6
30 AMP
Aluminum
8
8
6
4
4
30 AMP
Copper
8
8
8
6
4
40 AMP
Aluminum
8
8
  4
3
40 AMP
Copper
8***
8***
6
4
  50 AMP
  6
6
4
3
  50 AMP