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  1. Join Date
    Oct 2002
    Posts
    21,244
    #1
    We're opening a new business soon and today, we're testing the power load on the genset. One of the 2.5hp inverter type A/C won't turn ON. The aircon technician then told us we cannot operate the inverter A/C on genset power.
    Is this true?

  2. Join Date
    Jan 2009
    Posts
    5,576
    #2
    I can't imagine why it shouldn't work. The genset may not be providing clean power, like if the AC frequency (normally at 60Hz) and/or voltage is out of range for the airconditioner's switching power supply.

    The genset should be running at near or precisely the correct speed of 3,600 RPM (for 60Hz). All are designed to provide roughly 220V at this RPM.

  3. Join Date
    Oct 2002
    Posts
    21,244
    #3
    It's really weird. Yesterday, the aircon technicians can't make the aircon to turn ON. Today, we were able to turn it ON just by pressing the power on the remote, and still on genset power.

  4. Join Date
    Jun 2006
    Posts
    2,605
    #4
    Weird. Your A/C should run. Wont matter if its grid power or generator power, as long as you get 220v 60hz you should be good to go.

    Things I would look at:

    1. make sure your generator is pumping out 220v constantly. If your generators rpm is fluctuating, your voltage and frequency will be erratic. Easy enough to do, just use a tester on an outlet.

    2. Could it be that your load is too much for your generator?

    What brand is your a/c and genset? How many kw or kva is your genset?

  5. Join Date
    Oct 2002
    Posts
    21,244
    #5
    The A/C is a Panasonic split type 2.5hp. The genset is 8kVA china branded. Only 1 2.5hp aircon, lights, water heater, signage lighting, and a few outlets are connected to the genset. During the time that the aircon won't turn ON, only a few lights were ON.

  6. Join Date
    Jun 2006
    Posts
    2,605
    #6
    If only a few lights were on power for your generator should be able to provide sufficient for the a/c. Since it ran today, just observe it for now.

  7. Join Date
    Jan 2009
    Posts
    5,576
    #7
    Inverter appliances are actually as close to an ideal load for generators as they do not have a high starting or in-rush current. In other words, they don't behave like a typical inductive load, like AC motors do.

    An inductive load will require a starting current that is 3-4x the rated current for a few seconds. That's why you'll need to take your appliances' starting current into consideration when sizing a generator. But with inverter appliances, these no longer apply. Inverter appliances do not have a steep starting current. When powered on, they start gradually from zero or a very low current and then crawls up to its rated current.

    We don't have power right now with Meralco currently rehabilitating a nearby transformer, so my 4.5kW (5kW peak) genset is providing power to two inverter A/Cs.... a 1.5HP and a 2.5HP split, concurrently. We also have some lights, my servers, PC, son's laptop, hot/cold water dispenser, inverter ref, and home theater turned on, among a few others.

    With all that, they're all pulling around 3.2 to 3.3kW at 16A. I don't intend to run both A/Cs at the same time. I am just load testing.


  8. Join Date
    Jul 2013
    Posts
    5,465
    #8

  9. Join Date
    Jan 2009
    Posts
    5,576
    #9
    Power is back up after 6-7 hours. Nice.... a 4.5kW generator works fine for us as a whole-house genset. The only breakers I had turned off were the two shower heaters. These max out at 4.5kW and 3.5kW, respectively. Though, I doubt we're reaching those limits, it's best to play it safe.

    Being able to run the A/Cs made the wifey forget the price tag.

    So again, no need to compute for in-rush or starting current IF the appliance in question is an inverter (ie. A/C, ref, washing machine, etc.) Just use the rated current and power requirements and add them up.
    Last edited by oj88; October 16th, 2021 at 04:54 PM.

  10. Join Date
    Oct 2012
    Posts
    27,626
    #10
    In my industry we call this "soft start" it will not "excite" the supply/Genset

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Inverter type A/C not to be used with genset?