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Can I use a UPS instead of generator for backup source 1 on UTS10BI? | Universal Transfer Switch

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Can I use a UPS instead of generator for backup source 1 on UTS10BI?

Discussion in Universal Transfer Switch started by Jesse , 1/17/2021 11:13 PM
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Can I use a UPS instead of generator for backup source 1 on UTS10BI?

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  • I have a UTS10BI coming to me soon, and I have a powerful 240V UPS that I would like to use as backup source 1 instead of a generator. Is it possible to do this? The UPS source says I can only have 15A input on the backup source 2. The wiring is not the issue, but I wanted to make sure that it would be possible to configure it for this. So if the utility power goes out, it would automatically feed from the source 1 as a ups instead of a generator and provide uninterrupted power. I might also have a smaller ups feeding the ups source 2, however if possible to utilize the larger 3KVA for ups that would be better. I have several racks of servers and networking equipment, and 15A may not be enough.


  • I'm trying to do the same thing as Jesse, and I have the same question.  I have a 5K, 240 volt inverter that is powered by a bank of batteries that are kept charged by a dozen solar panels.  I want to use this power backup on the "generator" backup circuit of the UTS10BI.  (Then I don't have to worry about running out of gas with the generator.)  I checked with APC tech support, and they confirmed that the generator backup port on the APC requires a 240 volt circuit (can't use a 125 volt).  Other than that, they couldn't confirm that an inverter could be hooked to the generator port on the transfer switch.  (They thought it ought to work.)

    Originally I thought I would simply hook the inverter/batteries/solar panels to the UPS backup circuit on the transfer switch (which is designed to work with 125 volt), but the UPS circuit is limited to 1800 watts; somewhat less than my 5,000 watt inverter.  But the generator backup circuit can handle up to 12,000 watts, so that is the preferred port.

    I really love my APC transfer switch.  Not only does it load shed, so I don't have worry about overloading any of the backup systems, but by having TWO backup ports, I can use my big inverter on the generator port, and a smaller, 2,000 watt inverter on the UPS port (with its separate bank of batteries).  Then if the solar panels can't keep up with the draw on the main battery bank, the transfer switch will detect the loss of power on the generator port (just as if there was a generator that ran out of gas) and switch to the UPS port with a separate bank of fully-charged batteries waiting to go.  This guarantees I will have power for the essential stuff (lights, microwave, etc.) while I wait for the solar panels to recharge the main battery bank that is used for the heavy-duty circuits.

    Basically I've divided the house circuits into "essential" and "optional" categories, each with its own inverter and battery bank, with a bank of solar panels to keep everything charged up, and the transfer switch handles the switching automatically.

    So I'd really be interested in an answer to Jesse's question





  • My battery backup has a 240V output, so I could hook into it with 240V. How does it work when you connect a generator now? Does it just automatically take over from that generator? If you were to connect the generator to it and just start the generator and shut off the utility, will it just seamlessly transfer over? There is no starting time with a ups, so I would guess if you tried starting the generator and plugged it in ,and then cut the utility power to simulate an outage, that the result would be essentially the same as if it was a ups.

  • Jesse,

    Not quite.  (At least if I've understood your question correctly).  I think you're asking if there is any delay between losing the utility power and restoring power with the generator input (or in your case, a battery backup).  If the grid power fails (or is shut off), there is a delay of a few seconds between losing utility power and acquiring generator power or UPS power on the transfer switch.  For a long time I had a few batteries and an inverter connected to my UPS port.  That way I didn't have to bother hooking up the generator every time the utility power failed for a few hours.  When the utility power failed, the lights would go out for a few seconds, and the computer would reset before the backup power could activate.  Same with my cable box and television.  I finally bought a couple of UPS units and put them on the computer and cable box.  Now when the utility power fails, the UPS units instantly switch on so that neither the computer nor television is disrupted.  Then a few seconds later, when the UPS on the transfer switch kicks in, the small UPS units switch off, and the computer and television are running on UPS power on the transfer switch.  So, yes, there is a noticeable delay.

    One way to get around this is to make the backup circuits "uninterrupible" on the transfer switch.  Then the circuits are ALWAYS pulling their load through the UPS port on the transfer switch, and there is no interruption when the utility power fails.  Hope this answers your question.




  • Is that an option in the settings? It can use the backup circuit as uninterruptible through a settings option? That would work fine for me. My ups is an online double conversion and is heavy duty enough to power all the circuits in full that I'd put on it. I would like the ability to not lose power at all. I'd put lights and other stuff on there. I have several racks of network equipment/servers and other stuff that absolutely cannot lose power at all. But I only need to hold it over until the standby 25kw genset takes over.

  • Yes, it is an option in the settings.  Just select "uninterruptible".  Then it will constantly draw power from that circuit (or circuits).  Then if the main power fails, you're already drawing from your uninterruptible power supply.  Of course you need to keep the power supply charged up.


  • Now what happens if I lose power? If the UTS receives power to operate on 9 and 10, then when the power goes out, there would be no power for it to work, correct? Or does it get that power from the UPS/Generator? And if that's the case, then if I didn't have anything connected to either one and the power went out, then the unit would actually go out then?

  • It seems the uninterruptible ONLY will work using backup source 2. It won't allow me to use backup source 1 as uninterruptible.

    I have a large ups which is connected to a hardwired inlet, so I can provide for a lot more than 1800W using that.

    I also have a 20KW generator outside, so this was only meant to provide power for the short 30 seconds or so until the generator took over.

    I wanted to keep all the lights on in the house during that very short time, and I'm limited to the source 2, which allows less.

    It should be fine for me I guess because I won't have more than 1800W being powered.

    But I have it wired for the 240V so that's pretty much a waste. I wish there was a way for it to use source 1 as uninterruptible too.

    So for anyone in the future who is curious, you can use ups for source 1, but you won't have uninterruptible it seems. If you don't have a standby generator and just want to power lights and whatever using a portable one, then this is pretty awesome. For my needs since I have whole house standby generator, it isn't as useful. Cool item, and I'm not tearing it out, but I wish I could do uninterruptible off source 1 ups. I'm looking at maybe wiring one for my parents house, because they have portable generator, but are limited to only what can be plugged into the generator with actual cords.

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