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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3587
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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I am trying to power an Amana Furnace with a 5500 watt Preditor

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I am trying to power an Amana Furnace with a 5500 watt Preditor gas powered generator. It appears there is some issue with sine wave and clean power. I am plugging the furnace into a 10 guage 50 foot extension and running it to the generator. The furnace will ignite but when the fan comes on, it shuts down. Any suggestions would be appreciated.

Hello name is XXXXX XXXXX I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!


1) Can you provide me with the total wattage of the Amana furnace? The furnace will have a nameplate rating located somewhere on the furnace. The nameplate rating will show the wattage, amps and volts. I need either the wattage or the amps of the furnace. I assume the furnace utilizes 240 volts, correct?


2) Your generator should be labeled with a peak or a surge wattage either on the generator nameplate or within the generator instruction manual. Can you provide me with that wattage? According to my search on the internet, your generator shows a maximum wattage of 6500 watts, is that correct? Please confirm..........Thanks............Kevin!

Customer: replied 3 years ago.

1) The furnace is Amana Model AMH950904CXAC

It is 115 volts,Amps 13.8 and says it is to have a circuit with 15 amp.breaker. There is no wattage listed on the name plate.

2) Yes, the peak wattage of the generator is 6500 watts.


Additional comments: The furnace service tech was here on Thurs. to locate an outlet and plug arrangement so that I can plug the furnace electrical into the cord from the generator. I purchased a 10/3 50 foot extension cord to connect to the generator which is outside. The furnace is in the basement. The furnace tech told me to turn the fan switch on the thermostat to "on" so the fan would run continuously when using the generator. I tried the new cord this morning and it started up like it was going to run, the ignitor lit the burners, the small flue fan was running, and then the main fan motor started and when it reached speed the burners shut down but the fan kept running a couple of minutes. This is what happened when the tech was here and tried it Thursday. He said after checking with his instruments that the "circuit board doesn't like the sine waves of the generator and shut it down, it is a dirty sine wave pattern and not clean current". He said maybe an electrician could put a filter or something to "clean up the sine waves". Does this make any sense? What shall I do next?

Hello John and thanks for the replies.


1) You have a couple of options here. First off, If the generator RPM's are not properly synchronized for a 60 hertz output, that could be one reason as to the cause of the problem. In other words, if the generator output is less or greater than the required 60 hertz frequency, the generator sine wave output will be out of synch and not producing the required 60 hertz frequency. A test instrument such as an oscilloscope can confirm the output sine wave shape, peak-to-peak and RMS voltages. Any local generator maintenance shop can perform this test and advise you as to the output quality of the wave form, etc.


2) Generators are widely known for not providing clean power. The cheaper the generator, the less quality of power will result from it. Depending upon the quality characteristics of the generator, a power line conditioner may assist in the problem. One of the best methods for power conditioning is the use of a UPS. The better solution for your application is to use a Line Conditioner. Please note that some Line Conditioner manufacturers will void the warranty if used on a generator. It appears that the Eaton model Line Conditioners do not limit a warranty on their products when used on a generator.


I would recommend a line conditioner for your application versus a UPS. A UPS is generally used for battery backup purposes such as computers but they do provide quality power conditioning. However, you do not require battery backup for your application.


Since the furnace is rated at 120 volts and 15 amps, you would need a Line Conditioner that is rated at 120 volts and 20 amps. The 125% NEC rule is to compensate for the "in-rush" current upon startup of the fan/blower motor. Thus the reason why I would recommend a Line Conditioner rated at 20 amps and not 15 amps.


Here is a link to the Eaton website for Line Conditioners


Prior to purchasing a Power/Line Conditioner, I would recommend that you contact and visit your nearby electrical supply store. They may have different models and manufacturers and can best assist you in your application.


3) The National Electrical Code requires that the over protection device rating of the electrical supply to be sized @ 125 % of the furnace amperage rating. Therefore, using 13.8 amps times 1.25 = 17.25 amps which is less than the 20 amp over current protected receptacle on the generator. Therefore, your generator can support the furnace load without a problem.


4) In addition, using a 10/3, 50 foot extension cord at 120 volts and a 20 amp load results in a 2.4 voltage drop or an overall 2% VD. National Electrical Code recommends a maximum of a 3% VD, therefore, using the 10/3 cord is OK.


Hope this helps.........If you have any additional questions, let me know and I'll be glad to answer them for you.


Otherwise, don't forget to rate me before you log Off.


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Hello John...... thank you for the excellent service rating...........much appreciated!


If you have any other questions, just let me know.


Take care and have a great weekend...........Thanks again...........Kevin!

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