cfan73
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Power supplies, PoE, input power
The question regards power input, and the affect on this on PoE capability. The following is from an HP datasheet regarding 1500W power supplies for several of their chassis switches:
"Standard PoE+ power supply for zl series switches. Supplies 300W for PoE+ power at 110-127 volts, 900W for PoE+ power at 200-240 volts, and 600 W for switch power. "
These are 1500W switches. According to this, they can/will supply chassis power at 600W, but the PoE budget will triple based on the input power (110 vs. 2x0).
Please explain why(if) this is true. I've always thought it was a simple formula, where voltage (x) input power (=) watts. If a power supply is rated at 1500W, then why would input power affect the amount of power the supplies could provide for PoE device support?
Thank you - as always, reference links/docs are appreciated.
"Standard PoE+ power supply for zl series switches. Supplies 300W for PoE+ power at 110-127 volts, 900W for PoE+ power at 200-240 volts, and 600 W for switch power. "
These are 1500W switches. According to this, they can/will supply chassis power at 600W, but the PoE budget will triple based on the input power (110 vs. 2x0).
Please explain why(if) this is true. I've always thought it was a simple formula, where voltage (x) input power (=) watts. If a power supply is rated at 1500W, then why would input power affect the amount of power the supplies could provide for PoE device support?
Thank you - as always, reference links/docs are appreciated.
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@aleghart - HP was on a con-call to discuss all of this yes... oddly, they couldn't explain it either. I also had a UPS/power provisioning sales rep on the call and he had the same questions I did.
It comes down to this - if the datasheet is correct, and 240 allows a power supply to provide 3x the available power for PoE devices, then we'd obviously want to run 240 in every closet. This is non-standard (based on my experience) for non-data center closets, which are typically always 110. Converting them to 240 is crazy expensive, so I'm needing to determine if this is really a true statement.
I look at datasheets for Cisco equipment, and I've never seen anything like this. A 3750-X switch w/ an 1100W power supply will provide 800W of PoE power, regardless of 110 or 240 input power.
It comes down to this - if the datasheet is correct, and 240 allows a power supply to provide 3x the available power for PoE devices, then we'd obviously want to run 240 in every closet. This is non-standard (based on my experience) for non-data center closets, which are typically always 110. Converting them to 240 is crazy expensive, so I'm needing to determine if this is really a true statement.
I look at datasheets for Cisco equipment, and I've never seen anything like this. A 3750-X switch w/ an 1100W power supply will provide 800W of PoE power, regardless of 110 or 240 input power.
Tell them for a fraction of the cost of new electrical drops, you can install NETGEAR PoE switches with RPS and UPS, and have money left for a vacation in Hawaii.
They might track down the tech writer and engineer who wrote that spec.
They might track down the tech writer and engineer who wrote that spec.
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Additional research beyond this thread answered my question fully.
needs so that sufficient power is available in
the switch. When the peak power needs of the
powered devices (PDs) connected to the switch
exceed the PoE power available from the
supplies, the PoE power priority in the switch
is used to determine which ports lose PoE
power.
Ports that lose their PoE power will
not be powered again to prevent them from
turning on and off, unless the loss of power
was due to a power supply failure.