Automatic transfer switch & Load shedding.

[Dsg319]

What kind of load shedding devices do you all prefer, and use for 20kw and smaller residential generators?

Feel free to explain how they work and what they are. Just looking to learn about them.

 

[ATSman]

I can't speak for residential as commercial and industrial is my forte but willing to learn.

 

[LarryFine]

What kind of load shedding devices do you all prefer, and use for 20kw and smaller residential generators?

Feel free to explain how they work and what they are. Just looking to learn about them.

They're either modules within the ATS that automatically interrupt power to loads that you don't want to start or run when on generator power, and allow you to manually add them when you're around to supervise.

Or, they automatically interrupt power to loads when other loads consume enough power that the generator can not supply enough power for everything, and automatically add those loads back when there is enough headroom.

Either way, the controlling is done through low-voltage contacts that can control loads with LV control, like HVAC, or other loads through added contactors. That's my understanding of how they work.

 

[brantmacga]

The Generac load-shedding is frequency based, and there is a hard limit of 8 load shedding devices; that includes the relay contacts built into the transfer switch. So if you used two of the internal HVAC relays, you could only use 6 additional load shedding modules.

The load shed modules each have an 8-position dial to set priority. When there is a power loss, all of the modules will open their contactors. Once the generator is running at 60hz, they’ll close. If the frequency drops below 60hz they will sequentially drop out starting at #8 until 60hz is maintained.

You could technically use more than 8 modules, but because they only measure 8 different frequencies, you would have multiple modules opening and closing at the same time. The relay contacts break the t-stat power. The modules have 2-pole contactors rated at 50A and 100A.


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