Commissioning the BAS

7/29/2019 Commissioning the BAS

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Commissioning the BAS

Following a thorough commissioning process that incorporates bestpractices is essential in delivering a building that meets userrequirements and design intent.

By Mike Eardley, PE, LEED AP, CCP, Cannon Design

10/18/2012

Commissioning of building systems is a process that verifies whether the operational building

that is delivered not only meets the requirements of the building owner, but also the intent

of the design. Successfully demonstrating that a buildings HVAC and building automation

system (BAS) is operating correctly is a key component of the process led by the

commissioning authority (CxA) in the functional performance testing phase.

However, in order for testing to be successful, a number of activities must be performed with

specific processes followed, verifying that all elements are in place and are working together

to support a successful demonstration. During the construction phase, these activities and

processes can include a review of in-progress equipment installation, verification that

adequate air and water flows meet the required heating and cooling capacities, and

documentation of complete equipment installation including all trades before final

confirmation that the HVAC system and related controls are performing according to owner

requirements and design intent.

The HVAC system, like many other building systems, is operated by a BAS that functions

according to a combination of automatic and manual inputs. The BAS is responsible for

controlling a number of individual elements so that they work in concert and function as a

system. Modern controls systems are highly sophisticated and complex even if the intent ofthis complexity is internalso that the net result to the operator is simplicity. The complexity

is due to the hardware that makes up the components of the automation, the controls

theory, the logic that monitors current conditions and predicts the most appropriate

response, and the sequences of operation that are defined by the specifying engineer to

provide functionality, comfort, and efficiency of design. The BAS is therefore a critical part of

the building systems commissioning process.

The BAS affects the commissioning of many other building systems and is a system that, in

itself, requires commissioning for successful operation. As noted, demonstration of successful

operation is just one of the later stages of the commissioning process. To maximize the

benefits of the commissioning process and have the highest positive impact on a building

throughout its lifecycle, commissioning must be performed early on as well as throughout

construction and designeven during the planning phases of a building project.


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Fundamentally, the HVAC system is required to provide adequate temperature, humidity,

filtration, air movement, and air quality to all spaces. The specific levels required of these

metricsduring both occupied and unoccupied periodsshould be documented in the

owners project requirements (OPR). Documentation of these and other requirements is one

of the earliest activities of the commissioning process. The mechanical equipment (boilers,

chillers, fans, pumps, valves, dampers) that modulate and ensure that interior environmental

conditions are met are controlled by the BAS. The BAS is required to sense the status ofbuilding operations based on the various sensors and other inputs that comprise the BAS,

and produce the appropriate response based on pre-programmed logic that modulates and

enables these mechanical components.

Because of the considerable amount of moving parts, the variety of conditions that the HVAC

system will be subject to, and the varying ways in which the HVAC system can respond to

any single condition, commissioning is a critical process that delivers a functioning controls

system and, therefore, HVAC system. Commissioning will test the functionality of individual

components, the operation of individual components working in tandem to achieve the

desired result, and the integration of building systems, such as electrical/mechanical,

emergency power and associated systems, and controls/mechanical.

Owners project requirements

As mentioned, one of the first steps in the

commissioning process is review of the OPR. The OPR includes project goals and the owners

measurable performance criteria. However, because the owner may not know the right

questions to ask or understand specific technical requirements that will be important to the

project, the owner will often require assistance from the design team or the CxA to help

develop this information. Owners of multiple buildings, such as university campuses, will

usually have a better collection of information on which to develop the OPR than an owner of

a single building.

Examples of information in the OPR that will be used in the commissioning of the HVAC and

BAS include temperature setpoints and occupancy schedules for different spaces. As

mentioned, modern controls systems are highly sophisticated, and there is a wide variety ofcustomization that may be available depending on the complexity of the buildings or the

operational goals.

A BAS that requires an exceedingly high level of operator skill or time commitment from the

facility staff reduces the functionality of the building system just as much as faulty

equipment does. For this reason, it is critical to define the level of complexity in interfacing

with the BAS that will operate the HVAC system early in the commissioning process, as well

as to verify that it is appropriately matched with the facilities staff responsible for the

operations of the building.

Factors to consider in this process on the user side are the experience and training of the

current staff, and any planned investment in future facility staff additions or training. Using

this information, the specified BAS should match the ability of the future user in terms of:navigating the graphical interface of the BAS, drilling down into individual components of the


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HVAC system, changing setpoints, modifying the sequences of operation, and setting up and

downloading historical BAS trend data to analyze the operation.

Basis of design

The basis of design (BOD) is the design teams response to the OPR. It is critical that the

BAS have a well-developed BOD. It should present the environmental assumptions, such as

climate data used to size the HVAC system, as well as summarize how the elements in the

design meet the OPR. The BOD should be broken down by system for easy reference.

Specifics to include in the BOD, with regard to controls, include the specified manufacturer,

the other building systems to be integrated into the BAS, capabilities for remote connectivity,

communication protocol such as BACnet or LON, integration requirements, type of sensors

included in the design (as well as the required accuracy), trending capability, and other

criteria for selection of various control components. Requirements for remote alarming may

also be specified, including the details of who should be given remote access and if

connection by mobile devices is desirable.

Design review

Once the OPR and BOD have been documented and the design progresses, the CxA willperform a design review against the OPR and BOD to verify that the progression of the

design is consistent with this information. Toward the end of the design phase, controls

diagrams are developed and will be subject to focused review by the CxA to confirm not only

that the specified components are adequate to meet the OPR and BOD, but also that the

controls points necessary to successfully and efficiently operate the building are provided and

integrated into the BAS.

Review will also include sequences of operation and alarm inputs. Many of the problems

encountered by the design engineer, owner, and integrator that cause many of the

shortcomings after installation, even though it conforms to original design intent, can be

eliminated during the design process.

Specifications

Specifications are critical components of the

documents that will be included in the design review. The controls section of the

specifications will be reviewed along with the sequences of operation for consistency with the

OPR and BOD. Issues to be identified throughout the review of BAS specifications include

adequate capacity for control points, memory and appropriate timeframes and frequency for

storing trends, and any desired remote access interface for the owner or any consultants the

owner may wish to provide access to (including the CxA). Server performance is also an area

that will certainly impact the performance of the BAS. In addition, any issues regarding


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integration and protocol for various control components and subsystems that will be required

to work in tandem will be identified.

Submittal review

The submittal review phase is a necessary part of any commissioning scope. The automatic

temperature controls (ATC) submittal is, in many cases, reviewed at a higher level of detail

than any other by the design engineer and CxA. The submittal process allows the design

engineer to verify that any substitutions are at least equal to that specified. The CxA does

not review with this specifically in mind, because the CxAs scope with regard to design

review is typically to conduct an assessment against the OPR and BOD. The ATC submittal is

highly relevant to the CxA because many controls-related details arent fully developed until

the submittal phase. Design specifications may provide an overview of how the system is

intended to function, but it is the ATC submittal that fully develops the sequence of operation

to be programmed into the BAS, and provides all of the necessary specific hardware

components.

The final approved submittals are also the basis for developing the commissioning

prefunctional checklists (PFC) and functional performance test (FPT) plans. Other control

elements, such as control valves, will receive focused review during the submittal processfrom the CxA. For instance, a valve working at above rated pressure might function for a

short period of time, but will fail prematurely. Too high of a pressure drop for control valves

is often ignored as long as the flow is reached. Cavitation will be an issue with upper limit

pressure drops across the valve.

Commissioning meetings

A difficult characteristic about BAS commissioning is that this system is one of the last

systems to be installed and finalized. This means that progress occurs slowly, if at all, early

in construction and rapidly toward the end, when all other systems and the building as a

whole is preparing for turnover. It is, therefore, very important that an elevated level of

communication occurs between the controls contractor, CxA, and the entire construction

team.

It is also important that the controls contractor attend and participate in regularly scheduled

commissioning meetings, even in the early stages of the controls installation. This

encourages communication and often leads to the identification and resolution of particular

issues before they become significant.

Another key point is that between the time of original design and equipment delivery, there

may be desirable enhanced features that have been incorporated into the controls

components to be delivered. During these commissioning meetings is an excellent time to

review such cases and determine whether to incorporate new features into the system

configuration with minimal effort.

Prefunctional checklists


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PFCs are a fundamental component of thecommissioning process and its documentation. All equipment in the commissioning scope is

required to have an associated PFC. The PFC verifies that the equipment has been fully

installed by all trades. Once the PFC is complete, the component is ready for final verification

testing. Each PFC with a controls component will have controls items on the checklists. And

the BAS itself may have a dedicated PFC, documenting that head-end graphics are complete,

applicable systems being controlled are fully integrated, and trends have been enabled.

Point-to-point verification is a critical task to be completed and verified. Control points

include the conversion from volts, amps, or pressure measurements into other variables

used by the BAS. There is, of course, opportunity for error in these conversions and formulas

and they must be verified so that the actual temperature, pressure, position, etc., matches

the conversion as recognized at the BAS.

Commissioning personnel should perform a sensor-to-controller-readout calibration accuracy

check sampling to confirm that the correct temperature is displayed. Actual measurements

should be done. A commonly observed issue is the interpretation of an analog signal to a

graphical value. For instance, a variable frequency drive for a fan or pump is displaying one

speed on the graphics, but the actual speed at the drive panel is different. The way in which

points are bound to the user interfacewhether directly or through some sort of

conversionimpacts the risk of this error.

Functional performance testing

FPTs are the most demanding part of the commissioning effort. FPT plans are developed by

the CxA based upon design documents, submittals, the OPR, and the BOD. FPTs are then

executed by the contractor and witnessed by the CxA for acceptance. Like PFCs, FPTs will

have strong controls components for most equipment and systems. The FPT generally

includes a demonstration of the expected sequence of operation as specified, alarms and

safeties, schedules, and setpoints for variables to be maintained such as temperature, flow,

and pressure.

Final FPTs are performed through the BAS with complete graphics. It is essential that all

work, including balancing of air and water systems, is complete before final FPTs are

performed. The CxA also should determine a list of points to be trended. The trends should

be made available before any functional performance testing occurs. Any anomalies observed

should be resolved before testing.

Issues log

The commissioning issues log is maintained through design, construction, acceptance, andeven the post-occupancy period. Controls-related issues, which are likely identified during

acceptance and post-occupancy, often include installation work not being complete, an


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operational sequence not occurring as expected, or graphical representations not matching

what is physically occurring in the controlled system. As with other items on the

commissioning issues log, items are tracked until resolution.

O&M training

Operations and maintenance (O&M) raining on the BAS is a major effort that must be

scheduled prior to turnover for the operator to effectively control the building. The training

should include a demonstration of the system through the BAS, but also allow the operator

being trained to take control and navigate the system in order to validate the capability for

operation after the contractor and CxA have completed their scope. A comprehensive agenda

should be developed for training, and it is not intended to be an open question and answer

session.

Post-occupancy, seasonal testing and warranty

While the goal is that all issues be resolved before project turnover, often problems are

identified only after a building has been occupied for a period of time, and when the seasonal

environment has altered the load on the building. Post-occupancy commissioning activities

include monitoring the building operation, occupant and operator interview, and analysis of

short-term trend data that is available through the BAS. This analysis of trends, createdduring the acceptance phase, is especially useful during the first heating and cooling seasons

when the HVAC system is first tested with the full force of the natural environment. Any

issues that arise can typically be addressed under the system warranty, and should be back-

checked prior to the commissioning end-of-warranty review.

Sensors

Sensor location is critical to successful

HVAC and control system operation. A sensor takes a measurement at a specific point that is

intended to be representative of a larger condition. For instance, the outside air sensor

provides a critical measurement that may drive a large number of subsystems within the

HVAC system. If this sensor is providing a measurement that is not true, the HVAC system

will perform inefficiently and inconsistently with the design intent. Reasons for inaccurate

readings may include locating a sensor near a false load such as an exhaust outlet, locating a

sensor in a place that receives varying amounts of sun throughout the day, or simply that

the sensor has not been properly calibrated.

Other sensors that can have significant impact are the air and water differential pressure

sensors in the ductwork and piping systems. These sensors are representative of the system

as a whole, and meeting pressure setpoint is intended to confirm that all air and water flow

capacities are met at each load. Typically, the design engineer will specify a general location

for such sensors, such as two-thirds of the distance down the duct or piping system. The

contractor then determines the specific location. For critical locations, it may be more

desirable to specifically locate such sensors in the design documents, or hold an on-site

meeting with the contractor and engineer to locate them.

Control points need to be verified to control the appropriate equipment. For example, roomtemperature that is specified to control the discharge air temperature of its associated air


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handling unit may be programmed to the wrong unit. These issues will not always show on

the BAS graphics as they may be buried in the control programming, but they may have a

significant effect on system functionality and energy consumption. The CxA should determine

a list of points that might be susceptible to such errors and need verification.

Control loop adjustment

Tuning of control loops is a process in the controls checkout and commissioning process that

may require a period of operation, monitoring, and trial and error adjustment. This tuning

process should be performed prior to project turnover and not during the post-occupancy

period. Any controls system generally requires input, decision, action, and feedback. For a

given set of inputs and outputs, the tuning process changes the proportional, integral,

derivative (PID) variables of the control loop to achieve the most effective system response.

By effective, we mean that we want the system to react quickly to any deviation in setpoint

(whether that setpoint is temperature, flow, pressure, etc.). It is also desirable for the

system not to overshoot and not to hunt back and forth excessively in trying to reach the

desired target.

Control components that make up such systems include sensors, valves, dampers, system

fluids, and heat transfer equipment. Each of these components responds differently, atdifferent time delays, thermal capacities, sensitivities, ranges of motion, and rates of change.

These elements are what lead to the complexity in control logic, and necessitate the process

of loop tuning in the commissioning of a controls system. Monitoring of such systems often

includes analyzing historical trend data. Plotting this data against time will demonstrate

whether there is hunting, cycling, overshooting, and other undesirable elements of system

inefficiency and instability. Varying loads and seasonal environmental changes will also

impact BAS response. It is therefore critical that post-occupancy verification, seasonal

testing, and warranty period review should be included in the commissioning scope.

Remote access

Remote access to the BAS has been noted as something

that may be desirable, either to the building operator to monitor or make revisions remotely,

or to the CxA or energy consultant to remotely monitor building operation in an efficient

manner. Most modern control systems are capable of this feature; the system can be

accessed anywhere in the world that is connected to the Internet. However, there is a level

of coordination required between the contractor, owner, information technology

professionals, and the party requesting access. The cooperation on the part of the owner and

information technology professionals has proven critical to success here. Security issues

must be coordinated for access, and it is also important to consider the level of access that isdesired. For instance, the operator may wish to make changes to schedules or temperature

setpoints, while a CxA or energy consultant could typically only be given the rights to


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observe and download historical trend data. Regardless of the specifics of who should have

access at what level, this requirement should be discussed early in the design and

documented in the OPR. If not planned for, this desirable aspect of a BAS that can

dramatically increase the effectiveness of the facility operations team can be difficult to

realize.

Network traffic

An important factor of an extensive control network that is often overlooked is the quality of

the network communication. Network bandwidth analysis and traffic variable configurations

may need special attention depending on the project configuration. Error, collision of rates,

and lost data are common aspects of the communication network, and will occur in a BAS

more frequently on a network with a broadband that is used at a higher percentage for other

uses. A common solution implemented is to increase the speed of the network or install fiber

optics. However, simply controlling the network traffic and reducing or eliminating

interference is a preferable alternative. Also the activity of the BAS as it relates to the HVAC

system can be adjusted. For instance, is it necessary to repeatedly transmit the same

variable that is used infrequently? Is it critical to see a 0.2 F change in temperature when the

precision of a sensor is 2%? The answers to these questions might not only resolve

communication issues but might be crucial for the future expansion of the network.

The CxA should be familiar enough with the control system limitations to foresee wiring

issues that may cause problems, such as separating power and control wiring as much as

possible. It may not be acceptable for a network cable and a power line to be in the same

conduit. Verifying that the proper wiring gauge is used for communication and control is

critical. Also, the process should verify the maximum wiring length between an actuator and

a controller, or the acceptable maximum length of a communication wire. Like many aspects

of commissioning, sampling may be acceptable for project goals and should be targeted

where expected issues might arise. Network traffic is certainly a larger concern with existing

buildings and networks rather than new or modern systems.

Emergency power

One aspect of commissioning and building controls that is not fully taken into consideration is

the aspect of emergency power. Often emergency power is simply thought of as the systems

and equipment that are on an emergency power circuit. While this is certainly important, it is

also true that the associated controls must be part of the emergency power system. For

instance, in the event of a power failure, an emergency generator will activate, energizing

the appropriate circuits for the applicable HVAC equipment. However, if the controls

associated with that equipment are not provided with power, the equipment will either not

operate according to specified requirements or perhaps not operate at all.

Building automation components are also sensitive to disruption and electrical

inconsistencies. Such criteria should be considered in the specification of controls

components, and any requirement for full system response in the event of a power failure for

critical areas should be considered.

Finally, the systems on emergency power should be tested by actually disconnecting power

at the building. This will not only allow the testing of the emergency generator and automatic

transfer switchconfirming that specified system voltage is achievedbut will also confirm

that the required HVAC components and applicable controls respond correctly and in the

required timeframe.

Mike Eardley is associate vice president and director of commissioning services at Cannon

Design where he manages project execution and staff activity on commissioning and energy

consulting projects across the firms 15 international offices. He is president of the Building

Commissioning Certification Board of the BCA (Building Commissioning Assn.) and is a 2012

40 Under 40 award winner.

Commissioning the BAS

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