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Current draw of RM3000SM2U (208 volts) during recharge? | Server Room & Data Center Design Best Practices

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Current draw of RM3000SM2U (208 volts) during recharge?

Discussion in Server Room & Data Center Design Best Practices started by Brent , 10/4/2011 7:49 PM
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Current draw of RM3000SM2U (208 volts) during recharge?

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  • FlyboyData

    I need to move a data rack which has an RM3000SM2u, 208 volt UPS to a generator-backed circuit.

    I'm trying to help the building manager guarantee that we're not going to exceed the generator's output load.

    The generator takes about 10 seconds to start from a lights out event.

    The UPS is currently running at about 38% of capacity, which uses 5.3 amps at 208 volts.

    What kind of load can we expect the UPS to create when power is restored? I realize the current draw is probably going to be above our usual 5.3 amps, as some of the current draw of the device is going to be recharging the battery. I would hope that the device doesn't take on the full 20 amps available in the circuit it is plugged into ;)

  • Wwallender

    Watts Are Watts

    12 Watts At 1.5 Volts Is The Same As 12 Watts At 1000,000 Volts

  • ipicKedawinna

    if this is an [SUA3000RM2U|www.apc.com/resource/include/techspec_index.cfm?base_sku=SUA3000RM2U] as I'd suspect, then it uses 175W to charge.

    here are a few notes you need to consider for the power consumption during charging.

    Internal Power Consumption is the amount of power coming into the UPS that does not leave to support the load, and is due to internal conversion to either heat or stored battery charge. Internal power consumption is equal to the inefficiency times the Watt rating at full load

    Example: SURT5000XLI (full load) is rated at 3500 watts and 92% efficiency.The internal consumption is equal to 3500 watts * (100%-92%)=280 watts

    As far as calculating the extra power consumption when the batteries are fully charging, you would add the charger watt rating to the internal power consumption. However, calling this internal power consumption may not be theoretically correct since the energy is being stored for later use, not dissipated and lost. There is a percentage of the charger energy that is also lost due to inefficiencies and secondary electro-chemical processes, but getting into this detail is not practical.

    Battery charger for SURT5000XLI: 341 W

    Total current drawn without load and with fully discharged batteries:
    (280W+341W) / 230V (Mains Voltage) = 2.7A

    efficiency is on the apc.com link i showed and i gave you the charger rating now :-)

  • FlyboyData

    Close...it's the 208 volt model (not the 120 volt model) ;)

    208 is a common voltage in American office buildings (well, for supplying large amounts of power to server rooms and HVAC, you usually don't go strolling down the hallway and into cubicles and see 208 volt outlets). It is apparently a very easy voltage to produce from a 480 volt three phase transformer.

    http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SUA3000RMT2U&total_watts=50&tab=models

    Can't find anything on the effeciency specs, though, for the 208 model... :(

  • ipicKedawinna

    alrighty. i asked around and did not have an exact figure but was told ~92%. the charger is still max 175 watts but it can vary based on certain conditions (battery temperature, etc). i think the most accurate number for total consumption of the unit while charging the batteries is close to 275 watts.

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