10 Engineered Systems March 2012

We are at month three of this B2B energy retrocommissioning test series. This entire series is an extension to the October-November-December B2B series addressing K-12 school building HVAC applications. January’s test focused on the addition of a dedicated outdoor air system (DOAS) and three of the several sequences of operation. The second test focused on the testing, adjusting, and balancing of the new DOAS unit and its associated duct distribu-tion. This third month is focused back on the DOAS and three more sequences of operation. The test this month is “On-Maximum Heating, On-Nominal Heating, and On-100% Airside Econo-mizer.”

When beginning a retrocommissioning initiative, it is important to not jump to the answer without following time-tested, quality assured steps that lead an energy conservation team to the optimum answer(s). To comply with this approach, it is important to begin first with data collection followed by data analysis, solution plan-ning, solution implementation, and then monitoring, measuring, and benchmarking the original performance data.

Not included in this test, but still an important part of the overall HVAC building system performance, are the following individual room energy retrocommissioning features:

• Unit ventilators operating as needed during unoccupied cycles to maintain reduce room thermostat setpoint (heating season) and raise room thermostat setpoint (A/C season). During the unoc-cupied cycle, the DAOS unit shall be off so that no unnecessary outdoor air is introduced to the unoccupied space.

• Unit ventilator space heating and space sensible cooling is provided via the room thermostat setpoint. The heating setpoint is 68˚F with a 4˚ temperature dead-band with the cooling setpoint of 72˚, although a more energy conservation initiative setting the thermostat cooling setpoint at 76˚ will save more energy throughout the A/C season.

• Relative humidity-high limit setpoint within the space works in sequence with the DOAS unit dehumidification mode of operation, should space humidity exceed space comfort level. On a call for dehumidification from one or more space high limit humidistats, the DOAS discharge air shall be reset down from 60˚ to 55˚, resulting in additional moisture being removed from the outdoor supply air. An alternate to the DOAS unit providing overall dehumidification control is to have each unit ventilator capable of providing indi-vidual room dehumidification control based on the unit’s cooling capacity, as it also has reheat capabilities within the unit ventilator. A drain pan in the unit will also be needed to allow condensation to be removed. It is important to note that this type of terminal reheat feature is not available when using chilled beams in lieu of unit ven-tilators. In this case, condensation could occur on the chilled beam if a dehumidification mode of operation were to be used.

• Individual room CO2 sensors sequenced are designed to close

down the associated DOAS two-position outdoor air terminal based on adequate CO2 level within the room. The approach provides a reduction in energy consumption by cutting back on outdoor air when not needed. It is important to note that consid-eration needs to be given to state codes relative to acceptable ven-tilation requirements, as well as consideration towards maintain

space pressure within the room and the building to prevent the building from going under negative pressure that would result in unconditioned air entering the building.

With the energy conservation initiatives agreed upon, the energy retrocommissioning team has gone forward with implementing these enhancements (B2B, October 2011) and replacing the existing auto-matic control system with a direct digital computerized BAS comput-er to monitor, measure, and benchmark the past energy performance to the new high-performance energy retrocommissioned system.

Leading up to the energy retrocommissioning test, the TAB engi-neer rebalanced the new DOAS installation, as well as the existing unit ventilator system, associated exhaust system, and the central chilled water and hot water systems and documented the results in the TAB system flow diagrams.

The energy retrocommissioning team shall document each sequence of operation on page two of this B2B. The ATC system will be demonstrated using the FPT Cx-3 software, with the “reaction” device-by-device embedded into the system flow diagram below the associated device. The HVAC installing contractor will demonstrate the new DOAS installation working with the school’s ATC operator and the retrocommissioning engineer facilitating the process. Each sequence shall be confirmed via each control device “passing” per the specific ATC reaction to confirm the new DOAS ATC/FPT is operating per the design intent. The answers can be found at www.esmagazine.com.

When the energy retrocommissioning team has completed the ATC/FPT process, all “failed” device reactions will have automati-cally been inventoried into the Cx-3 software’s corrective action log requiring further action by the technician. For this system, there will be several other sequences of operation, plus verification of alarms and safeties that are not part of this B2B test.

The commissioning engineer’s ATC/FPT system flow diagrams, sequence-by-sequence of operation results shall be included in this opera-tor handbook with the TAB design-to-actual results. Operating instruc-tions will have occurred prior to the energy retrocommissioning imple-mentation project and during the retrocommissioning of the systems.

Here again, the operator handbook provided for this energy ret-rocommissioning initiative will include the current basis of design document to ensure future reference data is available for any new operating personnel and to recommission the system.

The CMMS system operator should update her asset database and PM workorder to ensure these units will receive the required care based on new components and equipment. See “The Facility Files” column for a sample PM workorder for a DOAS unit.

As part of the project closeout, existing record drawings should be updated with the additions, deletions, etc., to these systems. The team should also submit the necessary paperwork for any available utility company rebate(s), having received early approval of the util-ity rebate incentive in the solution plan phase of this project.

At the project closeout meeting, the monitoring, measuring, and benchmarking assignment should be made and a monthly report-ing system mutually agreed upon by the retrocommissioning team.

2Back BasicsBack BasicsBY HOWARD MCKEW, P.E., C.P.E.Based on Cx-3 ATC/FPT and TAB-3 software

12 Engineered Systems March 2012

ANSWERS: TO VIEW AND DOWNLOAD THIS MONTH'S ANSWERS, VISIT WWW.ESMAGAZINE.COM.

UV-Typheating coil

cooling coilUV-LastUV-1st

Hot Water Supply from the Boiler

Chiller Water Supply from the Air-Cooled Chiller

EF-1

DE-1

EF-Typical

DE-Typ

EF-Last

DE-Last

Exhaust From AssociatedRoom Unit Ventilator

VFD

HWP-1

VFD

CHWP-1

Note: Each UV to be retrofitted to havereturn air damper open 100% and existingoutdoor air damper also open 100% toaccept DOA as provided via 2-position airterminal

D-1F-1DOAS

ERC-DOAS PHC-1 CC-1

VFD

SAF-1

ERC-1F-1

ERC-Typ ERC-LastF-1 FDP-

Last

VFD

ERSP-1ERRWTT ERSWTT

Direct Outdoorair Supply

Outdoor AirOAT TT-1 TT-2

SD-1

CO-Typ

RT-Typical

CO-1st

RT-1st

CO-Last

RT-Last

TT-3

RARARHC-1

SH-Typical

DOA-1st

DOA-Typ

DOA-Last

� � Energy Retro-Cx

Device Tag Description Reaction Status Result Status Result Status Result

BAS BAS Interface Monitoring X Pass/Fail X Pass/Fail X Pass/Fail Computer Normal power X Pass/Fail X Pass/Fail X Pass/Fail Emergency power X Pass/Fail X Pass/Fail X Pass/Fail Alarm indication X Pass/Fail X Pass/Fail X Pass/Fail Occupied cycle X Pass/Fail X Pass/Fail X Pass/Fail Unoccupied cycle X Pass/Fail X Pass/Fail X Pass/Fall

D-1 Two-Position OA Damper Closed X Pass/Fail X Pass/Fail X Pass/Fail Open X Pass/Fail X Pass/Fail X Pass/Fail

SAF-1 Supply Air Fan On X Pass/Fail X Pass/Fail X Pass/Fail Off X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

F-1 DOAS Filter Differential Pressure No signal X Pass/Fail X Pass/Fail X Pass/Fail Monitoring X Pass/Fail X Pass/Fail X Pass/Fail High static filter X Pass/Fall X Pass/Fail X Pass/Fall

UV-Typ Typical Unit Ventilator On X Pass/Fail X Pass/Fail X Pass/Fail Off X Pass/Fail X Pass/Fail X Pass/Fail

CC-1 Cooling Coil With Two-way Closed X Pass/Fail X Pass/Fail X Pass/Fail ATC Valve Open X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

PHC-1 Pre-Heating Coil With Two-way Closed X Pass/Fail X Pass/Fail X Pass/Fail ATC Valve Open X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

RHC-1 Reheating Coil With Two-way Closed X Pass/Fail X Pass/Fail X Pass/Fail ATC Valve Open X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

ERC-DOAS Energy Recovery Coil No flow X Pass/Fail X Pass/Fail X Pass/Fail Full flow X Pass/Fail X Pass/Fail X Pass/Fail

CHWP-1 CHW Pump VFD On X Pass/Fail X Pass/Fail X Pass/Fail Off X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

ERSP-1 Energy Recovery System On X Pass/Fail X Pass/Fail X Pass/Fail Pump VFD Off X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

HWP-1 HW Pump VFD On X Pass/Fail X Pass/Fail X Pass/Fail Off X Pass/Fail X Pass/Fail X Pass/Fail Modulating X Pass/Fail X Pass/Fail X Pass/Fail

OAT OA Temperature Transmitter No signal X Pass/Fail X Pass/Fail X Pass/Fail Monitoring X Pass/Fail X Pass/Fail X Pass/Fail Alarm X Pass/Fail X Pass/Fail X Pass/Fail

SD-1 Smoke Detector No signal X Pass/Fail X Pass/Fail X Pass/Fail Monitoring X Pass/Fail X Pass/Fail X Pass/Fail Alarm X Pass/Fail X Pass/Fail X Pass/Fail

On-100% Occupancy On-50% Occupancy- On-100% Airside Economizer & Max Heating Normal Heating

1 2 3

Mode:

Status:Energy RetroCX Airside – New ERUand DOAS Application

D-1

VFD

SAF-1

F-1DOAS

UV-Typ

CC-1

PHC-1

RHC-1

ERC-DOAS

VFD

CHWP-1

VFD

ERSP-1

VFD

HWP-1

OAT

SD-1

Month 3- The Energy Conservation Opportunity:K-12 School Building With New DOAS And Existing Unit Ventilator System Application