Csdrhrt

At my office we have two UPSs, The Big one has 10x 12v Batteries with 50Ah capacity connected to it, and a smaller 600VA Desktop UPS.

The Big one has 8 Desktop Computers connected to it and the smaller one has the Internet Connection's Fiber to Ethernet Devices connected.

Once there is a power failure, the desktops (whatever is loaded on the main ups) can go off whenever it has to, but the Internet Equipment (which is on the smaller UPS) should go off last.

The Little UPS has a load of 0.5-1W, so it was a question if, the smaller UPS could be plugged into the other UPS's Output?

The First UPS gives a Sine Wave output. Is there a chance of blowing up anything?

It is possible to do that provided the output of the big UPS is sine (and not modified sine or square). While it really results in lower efficiency, it may be cheaper to buy two smaller UPSs than one big one or if you already have the USPs and want to extend the runtime of the smaller one as much as possible.

If the output of the big UPS is not sine, the small UPS will most likely not accept it (and switch to battery immediately after the big UPS does so) negating the entire point of having two UPSs in series.

I personally have three UPSs in series. A big one, another big one (most of my equipment is connected to it) and a smaller one (stuff I want to last as long as possible). This is my way of making sure the important stuff turns off last, while the other equipment still lasts as long as possible. I bought the UPSs at different times so this way is cheaper for me than getting a really big UPS.

In general, I would not feed one UPS from another.

There are a few things to consider here.

1. What is the run time of each UPS during a power failure?




2. If there is so little load on the small UPS, why do you have it?

From what you have said, it looks as if the run time on the smaller UPS is far longer than the run time of the large UPS. Therefore, why would you want to increase the load on the large UPS by powering the small UPS from it?

Depending on what the wave-shape coming out of the larger UPS, it is barely possible that the small UPS might be damaged by cascading it from the large UPS. I do consider this to be unlikely but there is a possibility it might happen.

Nothing would explode. But the smaller one would not discharge its battery until the larger one is exhausted.

It would be better, if your load is fairly mixed, to just plug them both into the wall and split the cables between them. Efficiency loss from AC/DC conversion would eliminate a lot of the added runtime, and by reducing stress with a second wall-plugged PSU you'll still gain runtime.

Don't do it. It will not blow up but it's a waste of energy as efficiency is very low.

To put it into perspective, your main UPS will use AC power to charge it's battery and waste some energy in the process, then when power goes out it will use the battery to make AC power for your equipment and waste some more energy, then your second UPS does the same, then your power supply inside your equipment does the same.

IF you need to add more capacity there are specialized UPS systems that connect in parallel to ensure maximum efficiency, or you can get workstations and servers with dual power supplies, connecting each one to a separate UPS.

I have an off-grid solar system - and use a Go-Power 30amp automatic transfer switch between solar (AIMS Inverter pure sine wave) and shore (power company). I have a 3000 watt APC UPS downstream of the automatic transfer switch powering a 15amp circuit of plugs thru the house to smooth out the transfer between solar/inverter and shore power. The transfer occurs twice a day (inverter on and inverter off).

In my office I have a 1500 APC UPS and my wife as a 2nd one in her office - plugged into the circuit powered by the 3000 APC UPS. The purpose of these 2nd ones was to allow work on the 3000 APC UPS / circuit without killing our computers upstairs as I fool with the Solar system.

The one in my wife's office works OK. BUT... the one in my office went crazy and cycled on/off rapidly and actually smoked itself. I replaced it with another/different 1500 APC UPS and it also cycled on/off - once per second continuously until I switched back to Shore power.

**I would be careful!!!