5. Component and Subsystem Level Testing Specifications

The following information is intended to complement the information presented thus far and can be used to develop power failure and recovery tests for individual components and subsystems.

5.1. Purpose

Testing at this level is targeted at verifying the proper response of individual components and subsystems to a loss of power.  Success at this level paves the way for testing the integrated response of the component with the system when the system experiences an outage.

5.2. Special Instructions

Include special instructions to the test team where necessary to:

n    Coordinate the test with the operation of the system it serves.

n    Minimize disruption to concurrent building operations.

n    Coordinate the test with the current state of construction.

n    Coordinate the test with the requirements of the manufacturer, including warranty requirements.

5.3. Special Equipment Required

Most testing at this level can be accomplished using standard tools and meters.  See Functional Testing Basics – Basic Tools, Instrumentation, and Equipment for additional information.  Generator tests may require load banks and the associated temporary interconnections.

5.4. Acceptance Criteria

Generally the acceptance criteria for testing at this level include:

n    The power source serving the device is as designated by the contract documents.

n    The power source serving the device is consistent with the operating requirements of the component and the system it serves.

n    The component response to loss of power is as anticipated by the design.

n    The component response to loss of power is consistent with the operating requirements of the system it serves.

n    Reapplication of power returns the component to operation in a manner that does not cause harm to the component.

n    Reapplication of power returns the component to operation in a manner that is consistent with the design and operating requirements of the system it serves.

Note that errors in the contract documents or installation could create some conflicts. For instance, a drawing could have inadvertently shown an interlock circuit to be connected to a normal power source even though the system it serves is connected to an emergency power source and must be completely operational under that condition.  Testing and the related analysis at this level is intended to identify these issues so they can be resolved before proceeding to system and building wide testing.

 

5.5. Precautions

Testing at this level poses the least risk since only one item or subsystem is under test and thus the potential for unstable or destructive interactions to occur is limited.  However, there are still some potential pitfalls that should be considered, some of which are listed in the subsequent sections targeted at specific components.  Generally:

n    Tests with a dynamic component pose more risk than static tests.  For instance the normal (power off) position of a reheat valve on a small coil connected to a pumping system that is not in operation poses less risk than testing the normal position of the outdoor air damper in an air handling system that is operating to provide temporary service.

n    Tests that involve lifting and re-landing wires or tubes pose more risk than tests which can be accomplished by manipulating switches or contacts.  The risk is on two fronts.  One is to the test technician, who may be challenged with working with wires or pneumatic tubes that are active.  The other is to the system since a wire or tube that is removed represents the potential to introduce a problem when it is reconnected if it is erroneously reconnected to the wrong location.

n    Testing may occur in close proximity to elements that will reposition as a result of the test trigger.  For instance, a test that removes air pressure from a pneumatic actuator serving outdoor air dampers will most likely result in the dampers changing position.  Care must be exercised to ensure that the test technicians and equipment are clear of the damper blades an linkages so they can actuate freely without becoming entangled in appendages, clothing, test equipment, or loose tubing, wiring or other materials that are still in the process of being installed.

5.6. Prerequisites

Generally testing the response to a power failure at this level requires that the item under test be fully installed as required by the manufacturer with final power connections in place.  It is highly desirable that the installation be to a point where anything that could impact the power supply, linkage systems, or motion path of the device be in place and in its final configuration.  Otherwise, subsequent construction activities could invalidate the test results.  For example, testing electrically triggered fire and smoke dampers while they are served with a temporary power connection may require some re-testing after final connections are made to ensure that the installers landed the final wiring connections in a manner that still provides the necessary functionality.

5.7. Preparation

Preparation for testing at this level will typically be minimal due to the isolated nature of the test.  Some coordination with other trades working in the area, the equipment supplier and contractor and other interested parties will always be advisable to ensure that everyone is informed and that there is “buy-in” to the process.

5.8. Items to Test, Acceptance Criteria, and Method of Test

The following list highlights important power failure recovery requirements for common building system components and sub-assemblies.  Additional acceptance criteria beyond the general requirements listed previously are listed where applicable.

Many of the verifications listed will be covered in the course of other acceptance tests in a rigorous commissioning process.  However, there are several contingencies that must be considered which may testing or re-testing in the context of power failure recovery appropriate.

n    Situations were a more rigorous commissioning process has not been employed.

Obviously, if the power failure recovery test is being used as a “catch-all” method of assessing system integration, verification of the integrity and response of critical components is desirable if no prior testing has been performed.

n    Situations were component level testing occurred very early in the testing process, prior to substantial completion of the systems. 

In this case, ongoing work may have compromised the results of the original tests.  For instance, interlock circuits that were installed and tested for temporary operation may not have reflected the final configuration.  If wires were disconnected and reconnected in the course of making final connections, the integrity of the original circuit may be questionable, making spot checks and additional testing based on the results of the spot checks desirable.

n    Situations were the failure of a component to respond as intended could cause significant damage to the system.

This is a variation on the old adage “measure twice, cut once”.  If the failure of one component to perform as intended in a critical situation could cause significant problems or lead to significant damage, a second verification, just to be sure, is usually time well spent. 

Valves

n       Control Valves

Additional Acceptance Criteria:

Valves spring return to a normal position if required.  Not all actuators include a spring return feature, especially electric actuators and double acting pneumatic cylinder actuators.

Upon removal and reapplication of power, verify the rate at which the valve actuates is not so fast that water hammer or adverse piping system pressure relationships will be induced.  This can be especially critical for valves serving steam systems.[1]

Testing functionality with and with-out flow may be necessary to ensure reliable performance under all operating modes.

Method of Test:

Remove and re-apply power to the actuator and observe and document the results.

n       Service and Isolation Valves

Additional Acceptance Criteria:

For service valves that also function as two-position control valves, verify that the manual override capability functions and that when the manual override is released, the criteria listed for control valves are met.

Method of Test:

Engage the manual override feature and manually actuate the valve.  Disengage the manual override feature and verify control valve functionality.

n       Seismic Shut-off Valves

Additional Acceptance Criteria:

Many of the criteria listed for control valves and service and isolation valves apply.

It may be necessary to have this test witnessed by a code authority in some jurisdictions.  Pre-testing to verify functionality prior to witnessing is highly desirable.

Method of Test:

Test per the requirements of the authority having jurisdiction or the manufacturer.

Dampers

n       Control Dampers

Additional Acceptance Criteria:

Dampers spring return to a normal position if required.  Not all actuators include a spring return feature, especially electric actuators and double acting pneumatic cylinder actuators.

Testing functionality with and with-out flow may be necessary to ensure reliable performance under all operating modes.

Upon removal and reapplication of power, verify the rate at which the damper actuates is not so fast that air hammer or adverse duct system pressure relationships will be induced.  See the supplemental information to Chapter 18 – Distribution for additional information on air hammer.

For dampers with manual override capability, verify that the manual override capability functions and that when the manual override is released, the criteria listed above is met.

Method of Test:

Remove and re-apply power to the actuator and observe and document the results.

Engage the manual override feature and manually actuate the damper.  Disengage the manual override feature and verify control damper functionality.

n       Back-draft and Isolation Dampers

Additional Acceptance Criteria:

For dampers that function as code required isolation dampers in addition to back-draft dampers, verify that the back-draft feature is functional irrespective of the isolation feature and visa-versa.

Some of the control damper criteria listed above may also apply depending on the exact nature of the damper and its actuating system and the service it provides in the system.

Method of Test:

Initiate a normal shut down and verify that the back draft function works.  Re-verify after initiating a smoke management triggered shutdown.

See also the test methods listed for control dampers.

n       Fire and Smoke Dampers

Additional Acceptance Criteria:

Many of the criteria listed for control dampers and back-draft and isolation dampers apply.

It may be necessary to have this test witnessed by a code authority in some jurisdictions.  Pre-testing to verify functionality prior to witnessing is highly desirable.

For systems served by normal and emergency power sources, it may be necessary to test the functionality of the fire/smoke management and control functions, including failure modes, under normal and emergency power.

Method of Test:

Test per the requirements of the authority having jurisdiction or the manufacturer.

Humidifiers

While focused on a component, some of the items associated with these test targets cross the line from a component focus to a system and building-wide focus.

Additional Acceptance Criteria:

Loss of power to the air handling system or the humidifier control system may not necessarily impact the steam system, gas system or electrical system serving the humidifier.  In most instances, it is desirable to verify that the humidifier is positively shut down if there is a loss of control power or a loss of airflow, including a loss of airflow due to a power failure.  If the humidifier remains active without airflow, it can fill the fan casing and duct system with steam or water vapor.  The condensing vapor can lead to water damage both inside and outside of the fan system during an extended power outage and/or when the system restarts.  Filters, particularly HEPA filters are very susceptible to damage by moisture and are often found in AHUs that are equipped with humidifiers.  The condensation also can set the stage for IEQ problems down the road. 

Method of Test:

Verify the operating mode of the humidification source when the air handling system experiences a localized power failure.  Include provisions for verification of the humidifier air flow interlock when testing at the system level.

Heating Coils

While focused on a component, some of the items associated with these test targets cross the line from a component focus to a system and building-wide focus.

Additional Acceptance Criteria:

Loss of power to the air handling system may not necessarily impact the hot water, steam, gas or electrical system serving as the heating source.  For heating coils located with-in the air handling unit casing, it is desirable to verify that the control valve fails to full heat in most situations. Such a provision will help to protect the coil and system from freezing in the event of a power outage during sub-freezing weather (assuming the supply of heat is unaffected by the outage).  This failure mode may not be possible or desirable for electric coils or gas fired furnaces due to the tendency to overheat and trip off on safety limit switches without air flow.

When implemented, failing to full heat can introduce other complications.

n    Coils with-in line of sight of a fire damper or combination fire/smoke dampers can activate the fusible link in a manner similar to that described under terminal equipment below.

n    The warm slug of air created in the air handling unit casing during the outage can make the system difficult to restart.  The issues are similar to those described in Chapter 5: Economizer and Mixed Air in Section 5.5.4.1. Freezestat Control Sequences.

n    The warm slug of air created in the air handling unit casing during the outage can trip fusible links down stream from the unit.  This is usually only an issue for systems where the coil is served by steam or hot water with a temperature in excess of 165°F (the standard fusible link rating applied to fire and combination fire and smoke dampers).[2]

n    This failure mode may not be possible or desirable for electric coils or gas fired furnaces due to the tendency to overheat and trip off on safety limit switches without air flow.

Method of Test:

Verify the operating mode of the heating source when the air handling system experiences a localized power failure.  Monitor the temperatures achieved in the plenum during an extended outage and assess the potential for the problems listed above. 

Cooling Coils

While focused on a component, some of the items associated with these test targets cross the line from a component focus to a system and building-wide focus.

Additional Acceptance Criteria:

Loss of power to the air handling system may not necessarily impact the chilled water or refrigeration systems serving as the cooling source.  In most instances, it is desirable to verify that the cooling source is positively shut down if there is a loss of airflow, including a loss of airflow due to a power failure. If the cooling source remains active without airflow several problems can occur, especially over the course of an extended outage.

n    The surface temperature of the cooling coil approaches the chilled water temperature, leading to heavy condensation.  This is usually not an issue except for systems that are intended to provide sensible cooling only.  Recirculation systems in clean rooms are a good example.  Systems of this type may not be provided with a drain pan on the cooling coil, or the drain pan may not be piped to a drain.  As a result, condensate can accumulate in the casing, leading to water damage and other moisture related problems.  This water can be blown through the system when it restarts, causing damage down stream, including damage to filters sensitive equipment or processes located in the area served.  The moisture also sets the stage for IEQ problems down the road.

n    The wide open chilled water valve represents a thermal short circuit from the perspective of the cooling plant.  This can be an especially critical condition for central chilled water plants that are based on a primary/secondary variable flow design.   A localized power failure that shut down several major air handling systems in a large complex served by a variable flow chilled water plant could create an over-flow problem at the central plant, compromising its ability to perform and meet the needs of the remaining loads that were unaffected by the outage.  Figure 17 in Chapter 18 – Integrated Control and Operation illustrates this problem in greater detail.

n    Under certain conditions, direct expansion refrigeration equipment that remains in operation serving a coil with no airflow can lower the surface temperature of the coil below freezing.  When this occurs, the coil ices up if the local humidity is high enough.  The iced coil further reduces the heat transfer from the refrigerant and may result in liquid refrigerant making it through the coil and back to the compressor where it can cause damage.  The frosted coil can also significantly restricts airflow when the system restarts, slowing the recovery time.

Method of Test:

Verify the operating mode of the cooling source when the air handling system experiences a localized power failure.

Terminal Equipment

n       Reheat

Additional Acceptance Criteria:

A localized power failure that shuts down the air handling system may not impact the steam or hot water distribution system serving the reheat coil.  For units that are located with in line-of sight of fire and combination fire/smoke dampers, it is desirable to verify that the radiant heat from the coil will not melt the fusible link when there is no air flow.  This is especially important for units that have valves that fail open and/or units that are served by high temperature hot water or steam. 

Method of Test:

Verify that the fusible link rating exceeds the surface temperature of the coil when it is supplied with water or steam at the design temperature/pressure condition.

n       VAV and VAV/Reheat

Additional Acceptance Criteria:

See criteria listed above for reheat terminals

Method of Test:

See criteria listed above for reheat terminals.

n       Fan terminals

Additional Acceptance Criteria:

Some fan terminal unit designs are subject to problems with the fans spinning backwards if they are placed across the line with air from the air handling unit that serves them is active and blowing through them.  The issue is described in detail in Chapter 18, Section 18.8.2.- Integrating the supply fan start-up with the start-up of the museum fan powered terminal units. This could occur if the AHU restart on a recovery from a power failure were not properly coordinated with the start-up of the fan terminal unit fans.

Method of Test:

Simulate a power outage at the air handling unit in a manner that does not shut down the terminal units and then allow the system to recover.  Verify that the fan terminal unit fans are operating and spinning in the right direction.

Sensors

Additional Acceptance Criteria:

Active sensors are becoming more common and often are powered from local sources rather than the controller reading their input.  Some of these sensors can be critical to the process they serve and if the process is on emergency power, they also need to be on emergency power.  Or, if a power outage affects the sensor but not the process it serves, significant problems could be created.  Thus it is essential that the power supplies serving locally powered sensors be coordinated with the process and system(s) they serve.

Method of Test:

Verify power supply coordination by measurement and/or test. 

For critical sensors, simulate a power outage to the sensor and verify that the process served is not impacted in a negative manner. 

For systems served by emergency power or UPS power, transfer the system to the alternate power source and verify all sensors remain active and reporting good data.

Control and Interlock Systems

Additional Acceptance Criteria:

Verify that the controller has a suitable means to detect a power failure in the system(s) served.

Verify that the power sources for control and interlock systems have been coordinated with the sources serving the system(s) they served.

Verify that the power sources for the various network level devices (operator work stations, repeaters, routers, network controllers, etc) have been coordinated with the system(s) served.

Verify that the power sources for the various network level devices (operator work stations, repeaters, routers, network controllers, etc) and the programming handling network level activities has been configured in a manner that will maintain functionality to the extent necessary when local power failures impact network level devices.

Verify that programs that rely on data that is passed over the network can tolerate a loss of current data due to the impact of local power outage on the network.

Verify that programming has been arranged to detect a loss and reapplication of power and respond accordingly with logic that returns the system and building to service in a coordinated, safe, and stable manner.

Method of Test:

Testing by inspection may be adequate in some situations and is a desirable starting point in all situations.

Testing system wide and building wide recovery logic via simulated local and building wide power outages will provide positive verification of the assessment of programming logic by inspection and is desirable in most situations due to the dynamics of HVAC systems and processes.

Testing network integrity by simulating random power outages at known critical points in the system and observing the results will provide positive verification of the assessment of the network integrity by inspection.  Mission critical facilities may require the simulation of a power failure at all network level devices, one at a time  and in combination.

Drive systems

n       Belts and couplings

Additional Acceptance Criteria:

Facilities groups frequently deem the detection of a coupling or belt failure by the control system proof of operation logic to be desirable. 

Method of Test:

Positive verification requires verifying that proof of operation is shown as positive with the equipment under test operating under all normal operating conditions, including minimum load.  Once this is verified, the belt or coupling can be removed.  When the equipment is commanded back on, the motor will start, but a failure should be indicated since the motor will not be driving the equipment.

n       Contactors/Starters/Motors

n    Phase rotation

Additional Acceptance Criteria:

Motors that can be served by two different power sources (normal power and emergency power for instance) should see the same phase rotation from either power source

Method of Test:

Verification by test with a phase rotation meter.

n    Multi-speed starters

Additional Acceptance Criteria:

Verify that the time delay and high speed/low speed interlocks are arranged in a manner that will ensure the low speed contactor is not re-engaged while the driven load is still coasting down from high speed after a momentary outage.[3]

Method of Test:

Verification by inspection is adequate in most situations.  Assessment of the interlock logic and the exact response of time delay relays and/or control logic after a momentary outage are critical.  It may be easier to design the system in a manner that ensures that a time delay long enough to allow the driven load to coast to a stop occurs any time there is a power interruption. Simulating a momentary power interruption can be difficult.

n    Programmable electronic starters

Additional Acceptance Criteria:

Verify the response of the starter to momentary outages to ensure that it provides the required level of protection without creating nuisance trip problems due to short (a few cycles) power disruptions.

Verify the settings that control the reactivation of the load upon the return of power are coordinated among loads and control system programming to ensure an orderly return to operation.

Method of Test:

Verification by inspection of the response to a momentary power outage is adequate in most situations.  Frequently, it may also be satisfactory for ensuring a coordinated recovery.

Verification of a coordinated recovery via simulation of a system wide and building wide power outage will improve the confidence level over that achieved through verification inspection..

n    Fuses/single-phasing

Additional Acceptance Criteria:

Verify fusing and motor over load settings have been coordinated to take the motor off line in a single-phasing situation.  In mission critical facilities, it may be necessary to assess the penalty vs. benefit of keeping the system operating to allow an orderly shutdown at the risk of damage to the motor.

Method of Test:

Verification by inspection will be adequate in all but the most mission critical situations.

n       Variable Speed Drives

n    Programming

Additional Acceptance Criteria:

Verify programming for issues similar to those cited previously for electronic programmable starters.

Verify DC injection braking settings or similar parameters to ensure that the drives are set up to stop any rotation created by air or water being forced through the machinery by other mechanisms, thereby allowing the drive to accelerate the load from a dead stop.  If these parameters are not set correctly, the voltages induced in the motor as it spins without being connected to the grid can damage the drive when it engages against them.  In addition the inertia of the spinning load can lead to problems similar to those described in the Shear Luck sidebar at the beginning of the chapter.  Systems with belt drives are less likely to have the drive shaft sheared by such an event, but belts can be thrown or broken, leading to a maintenance problem and unreliable performance.

Method of Test:

Verification by inspection is adequate in most cases and good first step in all cases.  Verification by subjecting the system to a local or building wide power failure will improve the confidence level over that achieved by inspection based verification

Elevators

Additional Acceptance Criteria:

Elevators may be required by code or the local code authority to respond in a very specific manner during a power failure.  Many times, service by an emergency power source is required.  Any testing associated with verifying these requirements may need to be witnessed by the local code authority.  Pre-testing to ensure performance as desired before witnessing is highly desirable.

Method of Test:

Verify power sources and emergency power sources are as required by the design and code.

Test per the requirements of the authority having jurisdiction.

Life safety systems

Frequently, there are life safety functions associated with the fire alarm, hazardous gas detection systems, medical gas systems, fire protection systems, and smoke control and management systems that must be coordinated and verified in terms of how the systems respond to a power outage.

Additional Acceptance Criteria:

Life safety systems may be required by code or the local code authority to respond in a very specific manner during a power failure.  Many times, service by an emergency power source is required.  Any testing associated with verifying these requirements may need to be witnessed by the local code authority.  Pre-testing to ensure performance as desired before witnessing is highly desirable.

Method of Test:

Verify power sources and emergency power sources are as required by the design and code.

Test per the requirements of the authority having jurisdiction.

Emergency Generators

Additional Acceptance Criteria:

The connection between emergency generators and power failure recovery testing is obvious.  Typically, the need for a generator is driven by code requirements or Owner requirements which are very specific to the nature of the project or the loads it serves.  It follows then, that the acceptance criteria will also be very specific and driven by the requirements of the code authority and/or Owner.  Typically, the criteria will include:

n    A specification for the response time between when the power failure occurs and the load is assumed by the emergency equipment.

n    A specification for verification of the capacity of the equipment.

n    A specification for verification of the arrangement of the distribution system serving the loads handled by the equipment.

Any testing associated with verifying these requirements may need to be witnessed by the local code authority or Owner.  Pre-testing to ensure performance as desired before witnessing is highly desirable.

Method of Test:

Verify power sources and emergency power sources are as required by the Owner, design, and code.

Test per the requirements of the Owner or authority having jurisdiction.

5.9. Return to Normal

As with any testing process, it is absolutely essential that the systems be returned to their normal operating state.  Temporary connections, provisions and equipment must be removed.  Selector switches and programming must be returned to the normal operating state.  Simulated conditions must be removed.  Documenting this and proactively including the Owner in the process is essential.