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   Before you go out and buy a generator you first must determine what size you may need. This process is started by figuring out what appliances you will need in the case of emergency, and which ones you could live without. Plan on having the power outage for one week. Power consumption (in the US) is based upon watts, that is how you are charged by your electric company, and that is how generators are rated. (There is no need to explain a watt here, it is just a unit of measure).

 

There is a simple formula that is used to determine wattage:

 

                                 Volts X Amps = Watts

 

Example: A refrigerator is rated at 10 amps and connects to a regular 120 volt circuit- 10 amp X 120 volts = 1200 watts 

 

 For a 240 volt circuit the amps are again multiplied by the line voltage to get the watts:

 

Example: An air conditioner is rated at 20 amps and connects to a two pole 120 amp circuit making it 240 volts total-20 amps X 240 volts = 4800 watts

 

If you have the horsepower of a motor, say for a furnace fan, or a refrigerator the formula is approximately:

                          

                             Horsepower X 746 = Watts   

 

Below is a list of appliances and estimated wattage they require. These are only estimates and should be used only to estimate the size of generator you might need. Do your own calculations with the appliances you will be powering,most will have watt usage on a label.

APPLIANCE                                                     RUNNING WATTS                 SURGE WATTS

 

Refrigerator                                                             800                                      1600

Freezer                                                                         800                                      1600

Central Air Conditioner                                   3750                                      6235                              

Window Air Conditioner 8k                             800                                      1600 

Flat screen TV 46"                                                  180

Coffee maker                                                          1200

Electric Dryer                                                         5400                                     6750     

Electric Fan                                                                   85                     

Microwave                                                                1500

Heat Pump                                                                4700                                    12000

Electric Oven                                                          3400

Furnace Fan                                                                875                                      2300

Electric Blanket                                                       400                    

Desk Top Computer                                               150

1/2hp Well Pump                                                  1000                                      3000

Electric Water Heater                                        4500

 

 

                         PUTTING IT ALL TOGETHER

    Now let's put some of this together. Let's say you have a refrigerator,freezer, furnace ,a couple of 60 watt lights and you want to watch TV,that is as long as your dish or cable still

work.

                     APPLIANCE                      RUNNING WATTS                SURGE WATTS

                      

                      Refrigerator                          800                                         1600

                      Freezer                                     800                                          1600

                      Furnace                                    875                                          2300

                      2- Lights                                   120

                       TV                                                180

                                                                   _______                                    ________

           TOTAL WATTS                                 2775                                            5800

 

  So, what is needed in this example is a generator with no less than a 5800 watt surge power even though the running watts are 2775watts. Again, I remind you to add up your specific appliance wattage, for they may vary greatly from this example! Damage to the generator or appliance may result. Also, the surge power is what the generator can handle for short periods of time, it is not meant to run continuously under this condition.

 

 

 One more example using a Nexus Smart Switch:

 

     APPLIANCE                                    RUNNING WATTS                              SURGE WATTS

 

 Refrigerator                                         800                                                      1600

 Freezer                                                     800                                                      1600

 Water Heater                                      4500                                                     4500

 Heat Pump                                            2500                                                     5000

 Heat Coils                                            12000                                                   12000

 TV                                                                   180                                                         180

 2-60 watt lights                                    120                                                          120

                                                                 ________                                        _________

Total Watts:                                        20900                                                   25000

           

  Without a Smart Switch or a DML you would need a 25KW generator which carries a high initial cost and higher fuel consumption.

But with The Nexus Smart Switch these high load circuits would be monitored and switched on and off when the generator can handle them.

 For this example, let's pick the heat system as priority #1.

The surge for the heat pump and air handler are 5000w.

The heat coils are run at the same time the heat pump turns

on because it is below 30 some degrees outside and they are rated at 12000w. Therefore we can lower the size of the generator to 17KW.  A great savings!  But wait! You want to be able to watch TV and have some lights on. OK, Make the heat coils #2 priority, that way they will wait for the heat pump surge to be over before turning on, thus,there is an added 2500w which will even run the freezer or refrigerator which are #3 priority. When the heat system is done with its cycle then the water heater may want to turn on - priority #4.

If you are running on a heat pump especially with electric

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back-up coils, you should ask the advice of your HVAC con-

tractor for wattage requirements and hook=up procedures.

 

 

 Unless you are familiar with the National Electrical Code (NEC),it is recommended that you consult with a qualified professional, such as a licensed electrician in your area. They may need to update themselves on the NEXUS SMART SWITCH however.