[j-nsp] MX960 Power Options

[Chuck Anderson]

No, sorry I was unclear.  You *probably* only need two 30Amp circuits
from the datacenter.  What I was trying to say is that you need to
split each datacenter circuit into 4 outlets via a PDU.  So split the
"A" datacenter feed into 4 outlets and the "B" datacenter feed into 4
outlets.

The dual-input PEMs have a switch that lets you select whether 2 input
feeds are expected or not.  You COULD flip that switch to single-input
and then you would only need 2 "A" feed outlets and 2 "B" feed
outlets.  Of course if you do that, then power capacity is reduced.
But you said you will have "limited cards installed" so maybe that
would be okay.  See here for how the zones work and how to calculate
your power requirements:

https://www.juniper.net/documentation/en_US/release-independent/junos/topics/reference/specifications/calculating-power-requirements-mx960.html

Divide the required input power in Watts by 208V, and then divide that
by the Power Factor to get an approximate circuit total in Amps.  The
exact Power Factor depends on the efficiency and design of the power
supplies, but it is generally safe to assume a value of 0.8.  You can
also input these values here to have it calculate it for you
automatically:

http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm

With the example on the Juniper doc of 3335W, that comes out to about
20 amps.

On Tue, Jan 26, 2016 at 09:50:08AM -0600, Colton Conor wrote:
> So from what I gather, there are 4 AC power supplies, and each AC power
> supply has two plugs. So thats not really going to change, its more what
> power to order from the datacenter.
> 
> So can I get away with one A side 208V/ 30 AMP circuit and one B side
> 208V/30AMP circuit?
> 
> 208V X 30AMP X .80 Max Load = 4,992 watts. That's a lot.
> 
> Are you saying I ideally need double this? Why?
> 
> On Mon, Jan 25, 2016 at 10:20 PM, Chuck Anderson <cra at wpi.edu> wrote:
> 
> > I recommend 4 x 208V.  The MX960 uses "power zones" in a 2+2
> > arrangement where half of the chassis is powered by 2 PEMs, and the
> > other half of the chassis is powered by the other 2 PEMs.  Make sure
> > the 1st PEM for each zone is powered by the A feed, and the 2nd PEM
> > for each zone is powered by the B feed.  For dual-input PEMs, you
> > should put both inputs of a single PEM on the same branch circuit,
> > either A or B.
> >
> > I would use two PDUs to break out the two 208V/30AMP outlets to
> > multiple C19's (plus any C13's you need), and then use C19/C20 cords.
> > Each branch circuit PDU will have 4 C19/C20 cords connected (2 PEMs x
> > 2 inputs per PEM).  Alternatively you could use L6-20 PDU
> > outlets/cords.
> >
> > On Mon, Jan 25, 2016 at 09:25:02PM -0600, Colton Conor wrote:
> > > What are the options for powering a MX960 using AC power? The datacenter
> > > provider is offering us power  in the following options:
> > >
> > > 120V/20AMP A/B Power
> > > 120V/30AMP A/B Power
> > > 208V/30AMP A/B Power
> > >
> > > We are leaning towards using a MX960 with 4 AC power supplies and limited
> > > cards installed. More than likely we will order the 208V/30AMP A/B Power
> > > from the datacenter, but want to know if this will be enough? What does
> > > Juniper recommend?