Off-Grid system with back up genset

Hrbie22 · June 2015

Hello all, new to the forum but have been lurking for awhile. As the title says I am in need of help/direction of designing an off grid system for our cabin with generator back up. While I havent figured up our exact needs yet, what we will be running is 5-6 lights, ceiling fan, TV,cable box, outlets that are charging radios and phones and a refrigerator if possible.

The cabin is used sporadically, heavier use during the winter months when hunting seasons are in here in Southern IL. Wood is our heat source and propane is our water heating source as well as cooking. Our biggest draw as far as I can see right now is a deep well pump runs from a cistern into the cabin to charge a pressure tank.

Right now we run a portable generator(7.5 kW) to power everything we use and it does well. Everything in the cabin is wired for 120v except the well pump. I am wanting to design a system that can basically run a couple fans when the cabin is not in use during the summer time to help keep air moving inside but also be able to handle the load when heavier use is called for.

Here the wrench, we have been given a 20kW generac stand-by unit. New and has never been used. I would like to be able to use this in the system even though I know it is big overkill.

Any help would be great, including reading material and PDF files suggestionv to educate myself while designing this system. I have some electical knowledge but this is my first time diving into a venture like this. Thanks in advance for any and all help.

animatt · June 2015

unless there are other large loads. Sell the generator and buy a much smaller one. Sounds like a smaller 3kw generator would be more inline with what you want to run. You will save boat loads of money on reduced fuel costs.

mike95490 · June 2015

So, if you are going to move to batteries, you need to figure your daily watt hour requirements. That sets the size & voltage of the battery bank. Then you figure the charger and then finally, the generator that powers the charger and loads simultaneously.

zoneblue · June 2015

You have a couple of choices.

A. smaller system, sans well pump. Use the genset to run the wellpump once a week to fill a tank / cistern. Shurflo the rest of the way.

B. bigger system capable of running the well pump. Also capable of running an efficient fridge.

Plan B is likely to cost 3 or 4 times more. For cabins, security / theft is something to factor.

You next steps are to work out Wh/day demand needs for both. Then get sunshine hours for your location.

Hrbie22 · June 2015

Thanks for the responses guys. I will.go into a little more detail about the pump and our usage itslef. He cabin sits idle for a lot of the year. Winter time sees the heaviest usage. While the summer months see some use but not as much. The well plumbed I'm line to the cabin. The cistrn holds the water, pump pressurizes lines and bladder. Water is only needed while we are there.

The batteries and solar will only need to run a few ceiling fans and lights. The gen set will hopefully be used to run pump and other high draw items while we are there.

The fans will be on most of the time in summer to help control humidity in the cabin. Would also be able to walk in and hit a light on when needed without running generator.

As far as usages go, we are in the process of updating all lights to LED, and while its not in use, we unplug all other items so there shouldn't be any phantom loads that I can tell.

Alaska Man · June 2015

This is an expensive idea for partial use. Your talking DIY still around $15,000. That buys a lot of genny gas. Unless noise is an issue and even then the new inverter generators like mine are pretty quiet anymore.

Off-Grid system with back up genset

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