PDX DCEO Qualification Card

Discuss how a basic PID loop works

A PID loop, or Proportional-Integral-Derivative loop, is a feedback control loop that uses three mathematical terms to adjust a control system to minimize error between a desired setpoint and a variable.

• Proportional: Produces an output value that is proportional to the current error value
• Integral: Proportional to both the magnitude and duration of the error, which is important for long-term accuracy
• Derivative: Computed based on the rate of change of the error, which can help predict future error

Basic operation of a PID loop is as follows:
• Calculate error: The PID loop calculates the error value by comparing the measured variable to the desired setpoint
• Adjust control variables: The PID loop uses the error value to adjust control variables to minimize the error
• Repeat: The output is measured again, and the process is repeated.

Discuss what readings are needed from EPMS to calculate site PUE

PUE= Total Load/IT Load KW reading from USB Main PXM and KW reading from PDP IQ Main. Other calcualtions for buildings without PDP boards can be found on Inframaps>Select PDX>Select Building> Select Calculation details

Explain system activity logging and its use

System activity logging is essentially an audit trail for BMS. You can see what Action was made at what point, what date and time, if comment were made etc.

Explain the dynamic plotter and its use

Used to view trends, graphs or historical data fora point in BMS

What events can cause a PID loop to become unstable?

Too much proportional gain will result in proportional response overcorrection. This creates an unstable feedback loop.

Why is it important to know which points are in BN08?

The point in manual over ride stops BMS from automatic operation. Too many points in BN08 will effect the PID loop.

At what temperature do air handlers enter evaporative cooling mode?

Varies by site.

PDX4:

PODs - 81 degrees
ERMs - 72 degrees

Describe how failed temperature cold aisle probes affect air handler controls operations.

A probe indicating too hot will result in greater cooling being applied (during winter, this may result in subcooling).

A probe indicating too cold may result in less cooling being applied and overheating the area.

Temp sensors that have failed or are out of range will not be used in any calculations by the controllers.  

A temperature sensor is considered failed or out of range if it is below 20 or above 120°F.

Describe how the air handler responds to a loss of BMS connectivity

The Air handler will default to HAND operation and determine its own mode of operation

Discuss the appropriate PPE required to perform water samples

Latex gloves and eye protection.

Discuss the effects of High or low water flow on air handler operations

High water flow will cause moisture carryover from the evaporative media into the supply air- resulting in higher humidity and lower temperatures.

Low water flow will result in inadvertent media dryout- resulting in lower humidity and higher temperatures.

Discuss the expected response for the following alarms: air handler leak alarm

Note which detector is alarming. Place machine HOA to off. Inspect area for source of water leakage and correct. Clean and dry leak detector. Remove water from area and dry. Place machine HOA to run and monitor for further leakage.

Discuss the expected response for the following alarms: air handler sump pump failure

HOA to off. Open Main disconnect. Inspect for tripped breakers or blown fuses.  Before turning unit OFF, check status of motor protection overload; if it is OPEN and water level is above the low level switch, try re-energizing the pump by turning ON the motor protection switch. If the pump overload triggers again, there is likely damage to the pump, or pump wiring.

Discuss the expected response for the following alarms: Cold aisle hotspots.

Escalate, Investigate condition of Mechanical equipment supplying air in that aisle.

Deploy fans or porta coolers as needed.

Verify hot aisle containment meets standard.

Verify temp sensor in working correctly.

Discuss the expected response for the following alarms: Damper feedback mismatch

Intervention is required to investigate and take actions as necessary. Check damper wiring and functionality. If necessary, replace the damper actuator as per the O&M manual.

Discuss the expected response for the following alarms: Flood alarm

Unit must be inspected immediately as a flood may be imminent or water damage to the CRAH unit may occur. Check sensor wiring and functionality. Ensure sensor is configured for N.C. relay operation.

Discuss the expected response for the following alarms: High SAT

Shut unit off, check sump for water, check floats, bypass valve positions, damper positions, etc.

Discuss the expected response for the following alarms: High/low MAT

Shut unit off, check sump for water, check floats, bypass valve positions, damper positions, etc.

Discuss the expected response for the following alarms: CRAHU mains power lost

General: Take HOA to Off. Check all fuses, wiring, and connections. Replace faulty components as necessary.

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Check fuses FU8 and FU9 status and wiring. Check fuses FT6 and FT5-2 status and wiring. Check relay R2 wiring and connections as well as mains power and disconnect switch status and wiring. Check fuses FU6, FU7, and FT3 status and wiring as well as PW3 connection to controller input ID15. Replace faulty devices as necessary.

Discuss the expected response for the following alarms: Purge alarm

Escalate. Investigate reason for purge condition, remedy the issue then reset purge at the purge panel.