Back up power supplies: Read this before you buy

TheCapn;1769462 said:

In aeroponics, we often have timers that turn on water pumps periodically, saturating our roots with nutrient solution. If you're growing DWC, it is CRITICAL we don't lose air flow to the root system. Recently, I've been using methods that are more resilient to power outages, but in the past, there has been many a power outage where the plants were in trouble, and I had to take action in order to keep them from drying out or choking on oxygen reprieved water.

You might grow in an area where power outages are rare. But don't count on it. Let's say you're away from your grow, and your neighbor calls you to say the power is out? Do you panic? If so, a UPS (UN-interuptable power supply) might help.

You've probably seen a "UPS" at your local office supply store. They are usually designed to keep a computer running for 5 minutes, just long enough to shut it down gracefully. We use a UPS a little differently. We use it to keep air and water pumps running for a certain amount of time. The biggest UPS at the office store might not be big enough.

But read this before you buy. There are two types of these power supplies available. There are "Stepped sine wave / modified sine wave (same thing)" and there are "smart / pure sine wave" supplies.

If your system is running a plain, non-digital timer, yes, the $100 UPS at the office supply or electronics store will work. But if you have a CAP ART DNE digital timer, (and I believe any digital timer) these regular UPS's will not work. You MUST buy a PURE sine wave UPS with digital timers. IF it doesn't say what kind of sine wave it is, believe me, it's not pure. If it is pure sine wave, they make it a point to advertise this.

Bad news.... A pure sine wave UPS costs much more than stepped.

Believe it or not, 10 years ago, you could get a pure sine wave UPS cheaper than you can today. It seems these companies are getting cheap on us. I was able to find a APC brand, "SMART UPS 700" used, for $90, and it had two new batteries in it. Your best bet is to do like I did and look for a used APC "smart" ups, and put new batteries in it. With the APC brand, "SMART" means "pure sine wave".

Why won't a regular UPS work? The modified sine wave messes with the way the digital timer calculates time. I found, when using the cheaper stepped sine wave UPS, the digital timer just sits there, never turns on. Then, if I manually push the button to reset it, it turns on and then never turns off!!!!

Here you can see my pure sine wave UPS, powering two timers, one digital, one not.

Now, how long do you need the UPS to last? That depends on your set up, and how often your pumps run. If you are running RDWC, you're going to be using a couple hundred watts, if you count your air pumps and constantly running water pump. Or, you could only put the air pumps on the UPS. It's up to you. You can make a GUESS by calculating the total watts your air pump or water pump needs, and comparing that to the rating of the UPS.

The stepped sine wave UPS I bought (before I bought the smart UPS) now keeps my wireless router going, so I never lose access to 420mag.com

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