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Issue 77 December 2010-News

n Introduction

n Fault Detection for Packaged Units

n Automated Fault Detection andDiagnostics

n FDD for Central Air-Handling Systems

n FDD Limitations

n AirCare Plus

n FDD Case Study

n Codes and Standards

n Whats Next?n Training Highlights

n About e-News

With the trend towards increasing complexity of the lighting and

mechanical systems of todays buildings, there is a broad gap

between the design intent and the actual operational perfor-

mance of buildings. Even when buildings are commissioned, systems

do not work optimally and problems often go unnoticed. Packaged

rooftop units (RTU) for light commercial buildings are checked only peri-

odically and maintenance staff that cover several campuses of buildings

normally do not have time to do anything more than basic checks. For

larger buildings that contain central plants, major equipment such as

chillers or boilers are routinely tested and maintained, but distributed

equipment such as VAV terminal units are not. It is not practical to test

all airside equipment in large buildings.

A technology that has emerged over the last few years to address this

problem is fault detection and diagnostics (FDD). Products are avail-

able that test both packaged rooftop units and larger air handlers

and central plants. The better FDD systems test for both operational

faults (stuck valve or damper) and efficiency degradation (low refriger-ant charge). These products allow maintenance staff to respond more

quickly to problems while reducing inspection requirements.

Fault Dtction for Packagd Unit

Packaged rooftop HVAC units (RTU) are

commonly used to heat and cool small to

medium size commercial and retail build-

ings. They offer a simple installation, and

a number of small units can provide good

temperature control of individual spaces.

Packaged rooftop units serve nearly half

the floor space of commercial buildings inCalifornia. These systems often operate at a

much lower efficiency than their rated condi-

tion. It is estimated that RTUs waste 10%

to 30% of cooling energy due to common

problems that prevent units from operating

at their rated efficiency.

Figure 1 shows that improper economizer

operation, improper refrigerant charge and

Enrgy Dign Rourc -N December 201

(continued on page 2)

Th Doctor I Alay In

Maintaining Optimum Performance with FaultDetection and Diagnostics (FDD)

Introduction

Figure 1 - Common RTU FaultsFrequency of problems observed in the field.Economizer failure and improper charge are themost common problems found in small rooftop

units. Source: Public Interest Energy ResearchProgram, 500-03-082

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restricted airflow affect a significant portion of units in

the field. The Small HVAC System Design Guide estimates

that faulty economizers increase cooling energy by 37%

on average. Some premium equipment has built-in

diagnostics capability, but most equipment will require

add-on hardware to test refrigerant cycle temperatures

and pressures.

Automatd Fault Dtction and Diagnotic

New products have been developed that operate in a

similar fashion to the Service Assistant, but they are

permanently installed at the rooftop unit for continuous

monitoring and diagnostics. Automated fault detection

and diagnostics (FDD) has recently become available for

packaged rooftop units. The automated data acquisi-

tion system includes sensors embedded in the unit to

measure system temperatures and pressures. With some

products data and alarms can be transferred to remote

servers for processing and email reporting. Common

features include refrigeration diagnostics, detection ofrefrigerant charge problems, low condenser heat transfer

(fouling or fan problems), expansion device problems,

and economizer diagnostics to verify proper outdoor

airflow and economizer operation. As an emerging tech-

nology, it is not yet commonly available as a standard

option in off-the-shelf products, but plans are underway

to integrate FDD into packaged HVAC units.

FDD for Cntral Air Handling Sytm

Analogous products available for detecting operational

faults and diagnosing problems for central HVAC systems

use trend data that is available from energy managementsystems. The product can be used, for example, on a

large central plant system consisting of variable-volume

air handling units and VAV terminal units. For such a

system, it is difficult to perform checks on the large

number of terminal units in the system. The FDD product

implements a set of rules to determine when a part of the

system is not functioning as designed. Operational prob-

lems such as stuck economizer dampers, leaking valves,

unstable control, schedule programming errors or chiller

sequencing problems can be detected and reported. The

rules can be based on first principles (i.e., energy bal-ance to determine economizer dampers are sequencing

correctly), a heuristic approach (i.e., SAT off from the SAT

setpoint by more than 3 degrees for a period of five min-

utes), statistical metrics, or a combination of approaches.

The National Institute of Standards and Technology (NIST)

has developed FDD tools suitable for embedding in com-

mercial air handling units and VAV box controllers. Sev-

eral control manufacturers are working to incorporate the

control logic into their products. The technology is only

applicable to programmable box controllers; controllers

that are merely configurable are not candidates for FDD.The faults for a single duct air handler, for example,

include the following:

n Outdoor air damper is in incorrect position and

not utilizing outdoor air efficiently.

n System is simultaneously heating and cooling.

n System is operating in manual (not controlled

by BAS schedule).

n Hot water and chilled water valves are se-

quenced incorrectly.

n A sensor is out of calibration or in a fault con-dition.

AirCare Plus

AirCare Plus, a program developed by PECI and re-

cently implemented by California utilities, facilitates

diagnosis and correction of rooftop unit operational

faults. The program has been successfully imple-

mented by PG&E and Southern California Edison

utilities. The program provides training to techniciansand contractors on the use of the Service Assistant,

a handheld tool used for the diagnosis of problems

with rooftop units. The Service Assistant guides the

technician through the process and helps the techni-

cian detect and correct faulty economizers, insufficient

or excess refrigerant charge, and insufficient airflow.

Data is collected through the use of a personal digital

assistant (PDA), eliminating paperwork. This addi-

tional service is provided at no additional cost to the

customer beyond the cost of the regularly scheduled

maintenance. Benefits of the tune-up include reduced

system downtime, additional cooling capacity, in-

creased energy efficiency and increased operating

lifetime of the unit. Through increased efficiency, peak

demand can also be reduced.Since its inception in 2002, the program has covered

the service of over 20,000 RTUs, with an average sav-

ings of 2,200 kWh annually for an average unit capac-

ity of 6.5 tons. With an average maintenance cost of

$400, this results in a simple payback period of less

than 2 years . AirCare Plus services are typically pro-

vided as an add-on to existing service contracts. After

completion of the service, contractors receive rebates

intended to cover the additional labor required.

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n Oscillating (hunting) valves and dampers .

n Oscillating modes, i.e., switching between heating and

cooling.

For VAV boxes, some of the automated FDD systems record anoma-

lies or faults in real-time, but restrict reporting of faults based on

accumulated errors over time. Other FDD tools that automate the

analysis of trend log data report faults as they occur.

As with FDD for packaged units, FDD for airside equipment in centralplants provides several benefits: it reduces time spent analyzing

trend logs, detects sequencing problems, controls tuning problems

or sensors out of calibration, and identifies related issues that

waste energy, even when occupant comfort is not affected. FDD

also streamlines operations and maintenance and reduces the time

required for scheduled PM checks; it increases equipment perfor-

mance and reduces frequency of major equipment overhaul. Some

applications of the technology have even included integrating the

FDD system with the work order process.

Limitation

There are several limitations of FDD systems used for central plant

systems. Often the analyzed data can be used to detect a fault; how-

ever, it often cannot verify the root cause of the fault (i.e., whether

it is a faulty VAV box damper or some equipment failure upstream of

the VAV box). Secondly, the product necessitates that trend data is

available for a large number of points; in practice, this data is often

not available unless explicitly specified during the design phase, and

even then it is sometimes value engineered out of a project. When

used in central plant systems, FDD components require significant

customization after the initial install to prevent false alarms from

occurring. Sensors out of calibration can also cause false alarms.

Automated fault detection algorithms have not been developed for

non-standard HVAC systems such as radiant cooling. FDD does not

Rlatd Rourc

nSmall HVAC System Design Guide:

http://newbuildings.org/sites/default/

files/A-12_Sm_HVAC_Guide_4.7.5.pdf

nAir Care Plus program:

http://www.aircare-plus.com

nFor more on automated fault detection anddiagnostics, see:

http://www.archenergy.com/pier-fdd/

nLawrence Berkeley National Laboratory(LBL) on A Specifications Guide for Perfor-

mance Monitoring Systems:

http://cbs.lbl.gov/performance-monitoring/

specifications/

nFault Detection and Diagnostics: Automat-ed, Ongoing Commissioning Functionality for

Large and Small HVAC Systems:

http://www.peci.org/ncbc/

proceedings/2006/17_Cherniack_NCBC2006.

pdf

The Phillip Burton Federal Building in San Francisco is a

22 story, 1.4 million square foot, high-rise office build-

ing with nearly 1,200 dual-duct VAV boxes served by

eight AHUs. The EMCS is a hybrid DDC system with an

Alerton BACTalk system serving as the front end, control

of the air-handling units and the majority of the zone

controls. The facility was chosen for a pilot study to test

the effectiveness of the NIST automated FDD algorithms

for air handling units and VAV boxes. Tuning of the FDD

algorithms was done in conjunction with debugging and

testing of VAV box control algorithms. Tuning is required

to reduce the frequency of false alarms, so that opera-

tional faults more closely predict actual equipment or

controls issues. After tuning was complete, the number

of VAV box alarms was reduced to approximately 30 per

day. The building engineers investigated these faults

and found problems with 11 boxes.

Prior to the implementation of automated FDD, techni-

cians would have to physically inspect several boxes

a day to meet annual inspection requirements. The

automated FDD system has reduced the amount of time

required for some preventative maintenance tasks,

allowing staff to focus on equipment that needs mainte-

nance.

Problems such as fouled airflow sensors, stuck actua-

tors or dampers, and loop tuning issues have been

identified. The Chief Engineer at the facility has been

pleased with the effectiveness of fault detection and

diagnostics: I can put my maintenance people right

where they belong.

While the algorithms do require some tuning at each

site, mainly to prevent false alarms, they can be readily

implemented by programmable controllers.

FDD Ca Study

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California utilities offer outstanding educational opportunities thatfocus on the design, construction and operation of energy-efficientbuildings. Listed here are a few of the many upcoming classes andevents; for complete schedules, visit each utilitys website.

Optimizing Air Conditioner Performance in Californias Climate

This class is for HVAC technicians who regularly perform repairand maintenance work. Major topics include:

- Why Californias climate needs something better than thenational average air conditioner.

- How you can get the airflow performance of a premium furnaceout of a standard furnace.

December 9, 9:00 am-3:00 pm, Stockton--ETC http://www.pge.com/mybusiness/edusafety/training/pec/classes/index.jsp?reqType=detail&ID=4505&db=PEC4505.csv&pageTitle=ClassDetails and Registration&postback=yes

Sustainable Building Envelopes

Designers, architects, and others will learn about the integrated

design process and explore passive building measures forhigh performance green buildings. Topics such as buildingorientation considerations, high performance glass, advancedwall systems, cool roofing, and building integrated photovoltaic(BIPV) systems will be discussed. (4 AIA/HSW/SustainableBuilding Learning Units).

December 9, 8:30 am-12:30 pm, Frontier Project,Rancho Cucamonga, CA https://www.sce.com/ECR/EnergyCenterClassSchedule.aspx?ORG=CTAC,OTHER

Building Operator Certification Training - Level II, BOC 214 -Introduction to Building Commissioning

Introduces the building commissioning process for new andexisting buildings. Topics include an overview of commissioningtypes, the elements of a successful project, working with acommissioning service provider, and the building operators rolein a commissioning project.

January 5, 8:30 am-4:30 pm, Camp Pendleton https://seminars.sdge.com/iebms/coe/coe_p1_all.aspx?cc=coe&oc=05

Enrgy Dign Rourc 4 -N December 201

20042010 Energy Design Resources. All Rights Reserved.

eliminate the role of O&M staff, but it does help streamline the mainte-

nance process.

Cod and Standard

Title 24 recognizes the importance of verifying equipment performance.

In the performance compliance method, a compliance credit is given for

package rooftop systems that use automatic fault detection and diagnos-

tics: the assumed efficiency of the unit is degraded by 10% from the rated

efficiency if FDD is not installed. Similarly, the performance of air-side

economizers and VAV boxes is degraded in the compliance calculation if

FDD is not installed.

What Nxt?

Working groups involved in FDD development agreed that there is a need

to develop a consensus standard to seamlessly integrate the technology

with the different control systems that the control vendors supply. While

there are challenges, most agree on the benefits of FDD. Developers of

fault detection and diagnostics products or protocols are developing

a protocol that can be used to measure and verify savings. As ASHRAE

moves towards establishing both asset (as designed) and operationalratings and energy labels, the value of FDD in establishing savings that

persist over the buildings life cycle should become more apparent. It is

possible, if not likely, that the use of FDD will be a requirement of future

energy codes.

Training Highlights

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e-News is published by Energy Design Re-sources (www.energydesignresources.com),an online resource center for information onenergy efficiency design practices in California.

Savings By Design

(www.savingsbydesign.com) offers design as-sistance and incentives to design teams andbuilding owners in California to encouragehigh-performance nonresidential buildingdesign and construction.

Energy Design Resources and Savings By De-sign are funded by California utility customersand administered by Pacific Gas and ElectricCompany, Sacramento Municipal UtilityDistrict, San Diego Gas and Electric, Southern

California Edison and Southern California GasCompany, under the auspices ofthe CaliforniaPublic Utilities Commission.

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