Notes on Power and Cooling in Lisbon

June 7, 2017

This is r162 of documentation found in the repository svn://svn.cs.miami.edu/csadmin.


POWER IN THE CSC SERVER ROOM

document history:
26 june 2015, created bjr
29 june, update
26 july, update

OVERVIEW

A 200A 3ph line comes from the generator, via operations, to the electrical panel
on the back wall.

The individual breakers in the panel provide power to wall outlets and to CRAC's (AC's).
The large bottom breaker provides power to the UPS.

The UPS works with the distribution cabinet, next to the UPS. The distribution cabinet
has 10 30A 3ph lines running, 2 to each rack; and 3 20A 1ph lines (branches A, B, and C)
running to the networking rack.

The UPS is accessible from a web browser on the servers vlan (VLAN 20) as fatty-arbuckle.

COOLING IN THE CSC SERVER ROOM

OVERVIEW

Two CRV units at the ends of the room are water-chilled. The water lines are from
operations, and they will be switched to an auxiliary DX if the main chiller is
unavailable.

There are a number of valves above the dropped ceiling. Closest to the chase wall
are two pairs of pipes: supply and return operations water (LHS when facing chase wall)
and supply and return house water (i.e. that which goes to the air handler on the roof).

Normally, supply and return for operations are both on, and supply and return for house
are both off.

In unusual circumstances it might be that supply and return for operations are both off,
and supply and return for house are both on.

Do not have both on supply house and operations, or both on return house and operations.
The house loop and operations loop are normally at different pressures, according to the
master pumps. All air handling devices are driven by these pipe pressures.

The two CRV's are accessible from a web browser on the servers network (VLAN 20) as
laurel (for the CRV closest to the corner) and hardy (for the CRV closest to the doors).

The CRV's work in tandem, and they share settings - if you set source temperature
(the temperature of the cooled air exiting) on laurel, that will also be the source
temperature for hardy. They share information by four ethernet wires, which must be on
an isolated network. The old 2900-series switch in the networking rack connects together
these four wires.

TEMPERATURE CONTROL THEORY AND PRACTICE

We are running hot-aisle containment. The waste air is contained in the hot-aisle, and
drawn by fans through the CRV where the heat is transfered to chilled water.

CRV's have two controls: fan speed and chilled water flow. The flow is by percentage
of the total possible flow. The water is not pumped but relies on the pressure
differential between supply and return pipes.

The CRV has three sensor inputs:

* return temperature - temperature of the air entering the unit.
* source temperature - temperature of the air exiting the unit.
* temperature at the face of the server cabinets, read by remote sensors mounted
in the rack front panels and averaged.

In hot-aisle containment schemes:

* The fan is controlled by return temperature. The higher the temperature, the faster the
fan. The target temperature of the hot aisle is 90 to 95 degrees.
* The chilled water flow is controlled by source temperature. We want to set an exit
temperature for the water so the fan speeds of the servers balance in those of the
CRV, and the air quantity is in balance.

We must avoid competition with the house air; we had asked that the house air be disabled,
but that is not completely possible as there is a requirement of air exchange, that there
must be a minimum flow of new air into the room.

posted in Uncategorized by admin

 
Powered by Wordpress and MySQL. Theme by Shlomi Noach, openark.org