Whole-building shutdown tests
Properly specifying how to conduct an intentional power outage and recovery reduces risks and increases the likelihood this critical test is performed.
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There’s nothing as frustrating, dangerous, or litigious as a building failing to properly handle a loss of power. People can get stuck in elevators. Healthcare workers may have to rush patients to other facilities. Expensive equipment might get damaged.
To ensure that emergency systems for buildings will function properly when called upon, they have to be tested. In order to test the systems, power to the entire building has to be shut down and then restarted. Every piece of equipment that is electrically powered is involved in a whole-building shutdown test, whether it is on standby power or not. Because HVAC, refrigeration, controls, plumbing, fire alarm and protection, security, telecom, paging, electrical outlets, lighting, vertical transport, and process systems are involved, no other functional test exercises as many different types and pieces of equipment and requires the coordination of more disciplines than dropping the power to an entire building.
Experience has shown that the designer, contractor, and operations staffs often have very different understanding of what should actually happen during a power outage. These expectation differences occur primarily because the construction documents are not clear. Confirming these expectations through a formal test is critical to ensure that life safety, product and equipment protection, comfort, and O&M staff convenience are not compromised during a power outage.
Whole-building shutdown tests
The whole-building shutdown test is not intended to confirm the standby generator functions. That test is completed sometime prior to the shutdown test. During the whole-building shutdown test the electrical power to the entire building is shut off to imitate a “street power” outage. The standby electrical generator is allowed to start normally, and later normal (street) power is restored. During the loss and restoration of power, equipment reaction is observed and documented against the specifications and event matrix. An event matrix is a table that lists each piece of equipment and how it responds to power loss and restoration. The matrix should be provided by the designer, but often isn’t generated until mid-construction by the commissioning provider.
The following questions and more need to be verified for each piece of equipment during the test.
What equipment is on standby power?
What equipment is on a UPS?
Did the equipment go to any required special positioning at power down (dampers, valves, fan speeds, pressure set points)?
Upon power restoration (standby or normal), did the equipment come up automatically or did it require a manual reset as specified?
Did all special sequencing or permissive safeties function properly?
Did the local and network controllers stay “live” on UPS to execute any special restart commands?
Were all time delays to restart accomplished?
Were there any adverse interactions with the building comfort and process systems during the event?
Specifying outage responses
Because the response to power loss involves so many disciplines, coordination is essential. It also requires a champion. The lead mechanical or electrical engineer is suited for this job, but the better party is usually the commissioning provider, as he or she has a more global perspective and is more apt to manage cross-discipline issues to resolution. In order to fully specify the response to a power outage in the specifications and drawings, the design team or the commissioning provider should complete the following. This can be accomplished by creating a blank event matrix and then having the mechanical and electrical designers fill in the blanks. The building operations staff and ideally a controls contractor should also review and comment.
Individual equipment features not controlled by the central BAS (even when other features of that equipment are controlled by the BAS) should state in their respective equipment specification how the piece of equipment will respond upon loss and restoration of power. Providing this information applies to all HVAC, refrigeration, controls, plumbing, fire alarm and protection, security, telecom, paging, vertical transport, and process systems. Examples include:
A chiller may have an internal timer that restricts restart for 10 to 30 min after a loss of power.
A boiler may require a local manual reset button to be pressed even if the BAS is giving it a command to start.
An elevator smoke screen will drop after 7 to 8 s without power and automatically rise once standby power is started.
A packaged rooftop unit may not require any intervention, but will restart automatically.
The controls equipment section of the specifications should include language specifying whether the network peer-to-peer controllers and unitary controllers are on emergency power and whether they have batteries in the panel to ride through the 8 to 10 s dead zone between loss of street power and the generator starting. An outlet in the room assigned to the operator’s work station should be specified to be on a standby power circuit and have a local UPS/battery backup attached to it.
Sequences of operation: For each piece of equipment, provide an article in the sequences of operation in the BAS specification section dedicated to power-loss response or mode. In the article, describe the response the BAS will provide or initiate. Here are some examples of articles for a laboratory setting:
The supply and exhaust fans shall be reduced to 25% speed when on standby power.
Upon loss of power, an air handler will “coast” with dampers remaining as-is until standby power is provided and then the flying-start function of the VFD will resume control of the fan without stopping.
Upon loss of power, an air handler will coast with dampers remaining as-is until standby power is provided. Then the fan, not on standby power, will coast to stop and, after 3 min, the standby powered isolation dampers will close.
Generally, it helps contractors, O&M staff, and others to understand what happens during a power outage by providing a short narrative description in the preface to the sequences or in an article in the common sequences area. The narrative should describe the responses to power loss by the HVAC system and related systems. The narrative should include the objectives for, reasons for, and actions of equipment during a power outage and list interactions among different pieces of equipment. This narrative can go a long way in tying together separate statements in different specification sections.
Drawings: Lack of coordination between what the electrical designer is planning for and what the mechanical designer or building operators are expecting is the most common reason for failed tests and change orders. To coordinate, ensure the one-line electrical ladder diagrams and the electrical panel schedules are consistent with the technical sections specifications for what equipment is stated to be on standby power and the UPS.
Standby power response matrix: The key to successful power outage, standby, and restoration response is to use a detailed standby power response matrix. This matrix lists all equipment that uses electrical power, regardless of whether it is on standby power. Be sure to include any data network devices in the UPS/standby power circuitry such as Ethernet switches (hubs) and serial communication repeaters, especially if the BAS is not included on the building LAN.
The matrix should be included in the electrical section of the specifications or on the electrical drawings and referenced from the mechanical sections and Division 1. Should the matrix not be detailed enough, or not be included in the construction documents, the commissioning provider usually is tasked with developing a format for it and pushing until the design and construction team fill it in. Figure 1 is a sample of portion of such a matrix.
Managing the test
The requirement for the contractor to conduct a whole-building power shutdown test should be referenced from the general mechanical and electrical divisions and in Division 1 because of the multidisciplinary nature of the test (see sidebar on page 25, Example of shutdown test requirement).
A test plan should be developed as early as possible during construction. The plan provides an overview and objectives, a list of the test prerequisites, and the role of each player. The plan should also give a general chronological list of what will happen on test day and a specific test schedule (by hour and minute) for the events.
Pre-testing: Prior to the whole-building shutdown test, the generators should have been successfully tested through startup and load-bank testing, along with any UPS integration and testing. There also should be two levels of equipment pre-testing. The first consists of each subcontractor testing the response of their equipment individually by tripping breakers or feeders. Secondly, there should be a pre-test of the whole-building shutdown by actually shutting down the power to the building while the contractors observe their equipment responses relative to what is specified in the response matrix, though this test need not be formally documented.
For complex sequences, such as a staggered equipment startup, the commissioning authority should review the programming code of the sequences prior to the test being scheduled.
Test day preparation: Prior to test day, set up any alarms and trend logs to document the test . Also, be sure to list and obtain any test, safety, and communication equipment that is needed, and coordinate with witnesses representing the owner, operators, tenants, inspectors, or designers.
Roles and responsibilities: Among participants, there are three primary roles: Executing the test (dropping street power, running the BAS, etc.), documenting the results, and being available to deal with any glitches with equipment. A test may only require the electrician, controls technician, and commissioning authority to execute the test and document the results, but it is strongly recommended to have a representative on-site for every piece of equipment that is being tested or that can affect the tests. Without these parties on-site, a small problem that could be easily fixed by the right person may turn into a failed test and a required repeat for a half-dozen or more contractors.
Initiating the test: Having a test-readiness and coordination meeting the day before the shutdown test will help ensure the test is properly conducted. On the day of the test, make sure everyone has a copy of the test hourly schedule and the response matrix where they can record results. Just prior to dropping street power, verify in the field that all VFDs are in normal or auto mode. From the BAS, go through each screen and see that all systems are in auto/normal mode. Run an alarm report on all equipment to ensure none is in alarm mode. Verify that each automatic transfer switch and generator is in normal mode.
Recording observations: When street power is dropped, make an announcement over the radio that all parties should make their assigned observations. When staggered starts are not involved, the test is fairly simple, with only a few parties making the observations by walking around to each piece of equipment and through the BAS. They record what state the equipment is in and whether it matches what was specified in the response matrix. After the documentation is complete, parties meet and assess the success of this part of the test, noting any items that need correction or adjustment.
Then, normal street power is restored and participants again record the status of the equipment, comparing the results to what is specified in the matrix. Noting the actions, if any, required to restart equipment at this point is critical. Too often, equipment that was supposed to restart automatically requires manual intervention. After the documentation is complete, parties meet again and assess the success of this part of the test, noting any items that need correction or adjustment. Plans for making corrections and for retesting are then made.
Before initiating the test, instruct participants to write down all relevant observations, particularly unexpected ones. Even if timing is not critical, recording the exact time of each person’s observations can assist in trouble shooting problems that may arise.
Documentation: Documentation will normally consist of the response matrix filled in with checks and initials of the party witnessing the event. These are compiled and merged onto one final test form by the commissioning authority. Using trend and alarm logs to document these tests may also be appropriate.
Standby Power Response Matrix
|Stum, principal at Summit Building Engineering, has more than 14 years of experience in commissioning. He specializes in large, complex facilities and in commissioning controls. He is a past recipient of the Benner Award and is a frequent speaker at the National Conference on Building Commissioning and at ASHRAE events.|
This article describes how a shutdown test should be specified by engineers in their design and construction drawings. It is based on a paper presented at the 2009 National Conference on Building Commissioning (NCBC), April 2009. The full paper, which includes how to manage the test, is available at no cost in the conference proceedings at www.peci.org/ncbc .
Example of shutdown test requirement
Whole-building integrated shutdown tests shall be conducted. This is not the test of the generator, which has been tested and accepted prior to this test. The objective of the building shutdown test is to verify that all equipment responds according to the power response matrix, including delays, timers, reset requirements, and all sequences of operation when power is dropped from the entire building or portion thereof, and when power is restored via the standby generators, and later when normal street power is restored.
Each installing subcontractor shall be responsible for pre-testing its equipment during a loss of power upstream from the local disconnect. Auto-resets and the actual procedures for manual resets shall be pre-tested.
The test shall be repeated for redundant equipment that was not tested during the first test by assigning the lag equipment as lead. This equipment may include chillers, cooling towers, pumps, CRACs, AHUs, XD units, and piping. That is, the test shall be conducted twice (assuming no deficiencies), though the second test of redundant equipment will document results only for the redundant and related equipment.
Documentation: The results shall be verified for most equipment by visual verification in the field. For some equipment like numerous small terminal unit controllers, queries and trend logs in the control system shall be acceptable. Written documentation shall be provided for all verifications on test forms and for lighting and electrical outlets on the electrical drawings.
Test process: The power is dropped from the building, the generator starts, and verification documentation continues until complete, confirming whether equipment responded according to the standby power response matrix. Then the normal power is restored and another round of verification is documented.
The entire test shall be repeated until all equipment functions properly.
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