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UPS with Generator and ATS | Smart-UPS & Symmetra LX / RM

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UPS with Generator and ATS

Discussion in Smart-UPS & Symmetra LX / RM started by Jan , 7/22/2019 4:45 AM
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Posted in: General

UPS with Generator and ATS

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  • JC1987

    After browsing most of this forum I found below thread explaining my situation best (the second answer):


    It is exactly what I want to achieve. however, there are a few differences. This setup has to placed in Indonesia where there are blackouts 2x per week on average. We intend to start the generator automatically (if the model allows it) or manually if that's the only option. So our situation will be as follows:

    - Main utility power goes out
    - UPS detects blackout, switches to battery within 16ms (computer load)
    - (Automatic?) Transfer switch triggers generator auto-start or manually go to generator and turn on
    - Generator spins up (from mains power blackout to stable generator power will be around one minute)
    - Transfer switch changes from mains AC to the generator
    - UPS detects good AC, switches back to line power (being fed from the generator).
    - Main utility power returns
    - Transfer switch changes from generator back to mains AC. Turns off generator.
    - UPS detects a disturbance, transfers to battery for 10s or so.
    - UPS switches back to wall power (now fed from main utility).

    regarding hardware, we already have the following generator model: https://www.tokopedia.com/atlindonesia/genset-bensin-wolf-2500watt-1
    This generator has always been used to power the whole network when there is a blackout. Computers, printers, etc running fine on it... But I am not sure how the UPS will react to it...

    There is not much information available for this generator model as I could not find any technical sheet.

    For the UPS I was looking at the following model: https://www.apc.com/shop/id/en/products/APC-Smart-UPS-SC-620VA-230V/P-SC620I

    We don't need much power and for only a short time (several minutes). One computer and a few routers is all.



    - the physical location of the generator would be quite far away from the UPS (50-100m), is that a problem?
    - has anyone come across a more detailed wiring diagram for such setup?
    - what is a good ATS for this setup? I have no experience with ATS yet...
    - Do I need 2 or 1 UPS?

    All info is more than welcome...

    Thanks in advance





  • JC1987

    Found some schematics:

  • JC1987

    Can anyone help me with this?

  • s.v.s

    Hi Jan,

    Taking into account the distance between the generator and the UPS, some voltage drop should be expected, depending on cable material and diameter. This should be best worked out with an electrician familiar with local regulations, taking expected load current into account, but this application guide may also come in handy.

    APC ATS models are intended for IT load and are typically connected downstream to a UPS rather than upstream to it. These are pluggable, rack-mounted ATS models, rather than hard wired - I'm including our ATS brochure and a link to our ATS product pages for further specs. Based on your description and schematic, it looks like you might want an ATS that allows hard wiring input into utility AC feed and generator feed, and hard wiring output to the distribution board where you can then pick up the UPS input feed.

    The SC620I is a 390W max capacity UPS that provides step approximated sinewave output when operating on battery - you mentioned a PC and some routers are the planned UPS load - I recommend reviewing their max power draw to ensure the UPS can support that load.

    Generators output can at times be distorted which in turn can cause complications with a UPS in terms of the UPS staying on battery even when the generator is providing output. The generator is recommended to be able to supply the peak current required by the load, not only the average current. UPS and generator compatibility wise, the general suggestion is to ensure the generator has at least 3 to 5 times the rating of the entire load connected to the generator (not just to the UPS). However, due to wide differences in output impedance for generators, it is not possible to specify an oversizing factor that guarantees compatibility with all systems.




  • JC1987

    Thanks for your insight. In the meantime, I worked out a schematic myself in order to publish my specific situation. This setup is placed in Indonesia where there are barely any rules concerning electricity installations. That's why we are trying to improve it...

    Please refer to the attachment for my schematic.

    Some thoughts:

    - The generator will be far away from the ATS and electricity board. In the schematic you can see it's around 100m, will that create problems?

    - The first double pole circuit breaker right after the ATS is there because I took it from this schematic but since the electricity meter from the supplier already has a 6A circuit breaker, I think it is not necessary, correct?

    - What about the RCD, is that needed?

    - If there is a 6A or 10A connection, what are is the values for the circuit breakers for lamps or sockets? I know in Belgium (where I am from) lights are secured at 10A and sockets at 16A but that is for a 60-ampere connection...

    - Concerning the choice of the APC UPS I have taken a low watt one because it only needs to power a PC monitor, a NUC PC and a router for a few minutes. Until the genset is turned on. I think consumption will be around 40W (screen) + 10W (router) + 60W (NUC) = 110W which is pretty low for a 260W UPS (not even 50% load). Is this going to degrade the UPS faster? Or any other disadvantages?


  • JC1987

    Anyone can shine a light on this?

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