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Equipment Hub: On-farm power generation

Andy Overbay for Progressive Dairyman Published on 06 November 2018

My parents instilled a mantra in me I am sure many of you have as well: “Hope for the best, but plan for the worst, and everything in between is gravy.”

No one ever hopes for a power disruption, but they happen, and they are usually accompanied by far-from-favorable conditions.

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The ability to generate power on the farm is pretty much essential to most dairy operations. The fact generators are not used regularly makes them susceptible to being the weak link during the times they are called upon.

Winter weather here in Virginia is easy to predict. We will have somewhere between record heat and record cold with either above- or below-normal moisture. Joking aside, winter seems to always test our ability to keep our animals’ lives as normal as possible when just about everything else isn’t normal at all.

Adding to our misery (and many of you as well) is: Without power, we also have no water. Keeping the lights on and the water flowing are critical in our mission of maintaining the health and safety of our animals, so it just makes sense to review our preparedness before the ice and snow come.

Again, on-farm power generation is all but essential anymore, and keeping the generator ready to go is a great place to start as we begin to prepare for winter storms. Generators can lose their efficiency over time when left unused, so it is a good idea to not only run them periodically but also have them checked and serviced by a qualified electrician.

Spiders can be especially tough on generators. The waste and webs left behind can foul connections and decrease efficiency to the point of the generator being dangerous. We often think about the danger of high-voltage situations, and that is a concern; however, when it comes to running a generator, low voltage levels are a real danger.

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If you are using a generator that is not providing the proper voltage to your breaker box, fires can be a real possibility. Most of our electrical needs on the dairy farm are from electric motors that have starter switches which kick in to begin to turn the motor. When the motor is at full power, the starter disengages, and the power needed to spin the motor is cut in half.

Without a high enough supply of power, a motor’s starter will stay engaged, essentially doubling the amperes used by the motor. This high amp draw will result in a motor generating a tremendous amount of heat and, over time, will at the very least ruin the motor, but it also stands a great chance of burning your facility to the ground.

So what size of generator does your operation need? That can be a difficult question to answer. Utility providers will provide you with your kilowatt usage but stop short of making recommendations as to how many kilowatts your generator should provide. One thing that is known is the horsepower need for power takeoff-powered generators.

For every kilowatt of power your generator is rated to provide, your tractor must supply 2 HP at the power takeoff. For example, if you have a generator rated at 60 kilowatts, then your tractor needs to be at least 120 HP at the power takeoff. This is especially important to remember, as most of today’s tractors’ rated horsepower is engine HP at the flywheel.

Once you have your generator ready to go, you really need to consider the connection you have to the facility or home’s electrical circuits. Transfer switches can seem very expensive at first glance, but they can help prevent many unfortunate accidents that accompany on-farm power generation.

At their most basic form, transfer switches are either manual or automatic. Which switch you need or should use is best determined on an individual basis and should include a consultation by a professional electrician.

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During a blackout, a manual transfer switch easily and safely allows you to connect your generator to your home by switching between the “line” power source and “back-up” power. Once the generator is running, you can choose which circuits to energize by simply flipping the switches.

The most common automatic transfer switch is a contactor-style transfer switch utilizing a mechanism to switch contactors from one power source to the other. Usually this switching will be between a utility power source and a generator set, but there are switches capable of switching between alternate utility feeds or multiple generators. These types of switches have proven to be robust with mechanisms that are tried and true and, since they are the most economical, are the most common.

Keep in mind: With a manual switch, the proper sequence of hooking up the generator is vital and totally dependent on you. The recommended sequence for manual connection is as follows.

During a power outage:

1. Turn off all the circuits in the transfer switch.

2. Connect the generator and transfer switch using a gen cord.

3. Start the generator and let it warm up outside.

4. Flip the main breakers in the transfer switch from “line” to “generator” power.

5. One at a time, turn on the circuits you want to power, ensuring the generator doesn’t get overloaded.

When power is restored:

1. Turn off the main breakers in the transfer switch back to “line” power.

2. Turn off the generator.

3. Disconnect any cords.

Automatic transfer switches detect power flow and adjust the circuits as necessary to prevent any backfeeds or overloads to the system or the generator. As with any farm operation (especially since this is one that isn’t in the normal daily routine), being mindful of personal safety and the safety of others is always the highest concern.  end mark

Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.

Andy Overbay
  • Andy Overbay

  • Extension Agent
  • Virginia Cooperative Extension
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