load resistor

Discussion in 'Dump Loads' started by gvabish, Oct 12, 2009.

  1. gvabish

    gvabish WindyNation Engineer

    i have 500 pma, what kind of load resistor i should have and installation instruction, thanks.
  2. windy_question

    windy_question WindyNation Engineer

    Depending on the voltage of your system, the installation instructions are available at the following URLs:


    You'll notice that each product listing on our store has a link titled "Technical Specifications" which shows you specs of the resistors plus instructions. So you can link to this page directly from the Store.

    For a 500W PMA, the kind of load resistor will depend on the voltage of your system. If you are using 12V batteries, then you'll use the 12V resistors. The number of resistors depends on how much power you expect you'll need to dissipate. This is a function of how many batteries you have (the more batteries you have, the less likely you will have excess power to dissipate).
  3. windyguru

    windyguru WindyNation Expert

    One thing should be stated more clearly. The amount of dump load wattage you need is determined by how much energy your alternative energy system is capable of generating.

    For a the 500 Watt PMA, you would want to have about 600 Watts of dump load capability (two 300 Watt resistors wired in parallel). You need to be able to dump at least as much as your system can generate.

    For this scenario, you would need two 40 amp relays on the Windy Nation charge controller. One would handle the 500 Watt PMA and one of the 300 Watt dump loads. The second 40 amp relay would take care of the second 300 Watt dump load. Even though there would be no wind generator or solar panel running through the second relay, it would still be able to control dumping to the second resistor as long as the 40 relay is hooked up to the charge controller. Instructions on how to do this are shown on the wiring diagram

  4. gvabish

    gvabish WindyNation Engineer

    thanks for the info.,but i do not see 40 amp relay in your store, just 30amp ?...
  5. windyguru

    windyguru WindyNation Expert

    Oh yes, you are right. They will be up in a day or two. Sorry about that.
  6. WindyFAQ

    WindyFAQ WindyNation FAQ Staff Member

    I recently purchased a Windtura 750. I am using the WN 80 amp 3 phase rectifier and a diversion controller. I am charging 2- 12 volt, 126 amp-hour deep cycle batteries.Can you tell me in terms of ohms, how much resistance should be used when the controller is diverting to the load? I am using water heater elements for the diversion load. I can series or parallel them to achieve varying resistance.
    In a storm, should the generator stay on the diversion load?
    Will shorting hurt it?
  7. windyguru

    windyguru WindyNation Expert

    I would recommend about a 600 Watt diversion load for the Windtura 750 on a 12 volt battery bank system. It is better to have the diversion load "dump" off of the battery. If you have the relay on the charge controller just switch the entire wind turbine load to the dump load, then this is similar to shorting out the wind turbine.

    Our 12 volt/300 Watt dump loads are 0.73 ohms. Using two of them in parallel will give you a 600 Watt/12 volt dump load. If you want to use your own dump load (e.g. water heating element) then your dump load set-up should factor in ohms law using the same approach as we do.

    You can short out the turbine if you prefer but you will have to fuse it or risk burning the stator out. A much better approach in my opinion is to fabricate a furling mount like we use on our Complete Windtura 750. Or if you do not want to fabricate one, you can purchase our mount. Not only does a furling mount protect the wind turbine from overspeeding, it also limits the amp out. With this approach the diversion load will protect the battery from overcharging and keep the wind turbine under a load. And the furling mechanism will keep the wind turbine from overspeeding and the amp output in a safe operating range.
  8. WindyFAQ

    WindyFAQ WindyNation FAQ Staff Member

    I do have the full Windtura 750 kit with the furling mount and windgrabber blades. Does that change your recommendations regarding the diversion load?

    If I understand your response correctly, the 750 output would stay connected to the batteries at all times and the controller would simply turn on the diversion load in parallel with the batteries when they are charged. Is this correct?
  9. windyguru

    windyguru WindyNation Expert

    Yes, this is correct. It is generally accepted that it is better to dump off of the battery than to short the wind turbine. This keeps the wind turbine's load operating in the region it was designed for. Connecting the wind turbine directly to the dump load can be done but it very similar to shorting the wind turbine. In high winds, you risk overheating the stator if you are shorting the stator. If you choose to go this route, you will need to have a fuse between the dump load and the wind turbine.

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