Design Narrative.pdf

New Air-Cooled Chiller/Distribution Piping Improvements IFB Design Narrative USDA/PSDEL

STV Incorporated i 07/29/11

I:\Projects\3014689\3014689_0005\80_Reports & Studies\Other\IFB Design Narrative 7-29-2011\Contents.docx

TABLE OF CONTENTS

Page

1. INTRODUCTION 1-1

2. CIVIL/SITE DESIGN 2-1

2.1 Codes and Standards 2-1

2.2 Project Location 2-1

2.3 Existing Use and Site Improvements 2-1

2.4 Existing Topography and Site Drainage 2-1

2.5 Land Development & Project Permitting 2-1

2.6 Proposed Use 2-2

2.7 Proposed Grading and Drainage 2-2

3. ARCHITECTURAL 3-1

3.1 Codes and Standards 3-1

3.1.1 Jurisdiction 3-1

3.1.2 Applicable Codes and Standards 3-1

3.1.3 Use and Occupancy Classification (IBC Chapter 3) 3-1

3.2 Design Approach 3-2

3.2.1 Background 3-2

3.2.2 Project Approach 3-2

4. HVAC SYSTEMS 4-1

4.1 Design Conditions and Standards 4-1

4.1.1 Design Criteria 4-1

4.2 Existing Chilled Water System Description 4-1

4.3 Proposed Permanent Chilled Water System Description 4-2

4.3.1 Direct-Primary with Variable-Volume Pumping System 4-3

4.3.2 Flow Circulation Enhancements to Piping Distribution Loops 4-4

4.4 Building Automation System 4-5

5. ELECTRICAL SYSTEMS 5-1

5.1 Codes and Standards 5-1

5.2 Equipment Sizing Criteria 5-1

5.2.1 Secondary Design Voltages 5-1

5.2.2 Equipment Sizing Criteria 5-1

5.3 Normal Power Services and Distribution 5-1

5.3.1 Design Criteria 5-1

5.4 Standby Emergency Service and Distribution 5-1

5.4.1 Design Criteria 5-1

5.5 Grounding System 5-2

5.5.1 System Description 5-2

5.5.2 Distribution 5-2

IFB Design Narrative USDA/NPGQC

STV Incorporated 1-1 07/29/11

1. INTRODUCTION

USDA has requested engineering design services addressing the installation of a new 375 air-cooled ton chiller to supplement the two existing 150 ton McQuay air-cooled chillers’ capacities and enhance the National Plant Germplasm Quarantine Center’s (NPGQC) operational capabilities, improving response to, and control of, conditioned space requirements. During preliminary design for the new chiller, flow limitations for the existing chilled water distribution piping were identified as ultimately restricting the effectiveness of the new chiller, and a study was completed presenting recommendations for associated piping improvements. Main piping and secondary distribution will be upgraded in both the Support Building, and the High Containment Laboratory and Greenhouse. USDA has incorporated these piping improvements into the project’s design requirements. Replacement of the 6” chilled water supply and return piping beneath the driveway separating the Support Building and the containment spaces is not included in the project.

The High Containment Laboratory and Greenhouse work is an alternate deduct item, and implementation may be delayed if operational requirements will not allow the disruption of research activities within these facilities. Chilled water supply pumps’ replacement will occur to utilize direct-primary, variable-volume chilled water pumps with variable frequency drives (VFD).

STV’s technical approach will include disconnecting one of the existing McQuay 150-ton chillers from the emergency power service and powering it from normal power only. The new chiller will be tied into a new 800A automatic transfer switch and emergency power.

The new chiller location will be adjacent to the existing units. Some sitework will be required to relocate existing affected stormwater management piping and drains.

Existing controls will be modified to accept the new chiller. A 150-ton temporary air-cooled chiller will be utilized during construction to ensure adequate chilled water is available during low flow months while construction proceeds.

Proposed enhancements to the existing chilled water distribution system noted below will enable an estimated 60 to 75 tons of cooling load to be added to the present system capacity. To accommodate the installation of the recommended direct-primary variable volume system, the following modifications and alterations will be incorporated into the design package:

a. Replace existing constant volume pumps with larger pumps and motors equipped with variable frequency drives (VFD).

b. Replace chillers’ 6.0 inch common supply and return piping headers with 8.0 inch headers.

c. Replace chillers’ 3.0 inch chillers bypass line and valve assembly with 4.0 inch assembly to accommodate chillers’ minimum flow requirement.

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d. Provide Support Building with new and dedicated 2.5 inch supply and return lines that originate from the Mechanical Room to accommodate chilled water flow to future warehouse and to existing AHU-14. (AHU-14 will be taken-off the Support Building existing 4.0 inch main circulation loop).

e. Provide High Containment Laboratory Building and Greenhouse with new and dedicated 2.5 inch supply and return lines to supplement the existing 4 inch pipe serving AHU-7, 8, 9, 15, 10, FCU-4, AHU-6 and AHU-11.

f. Provide High Containment Laboratory Building and Greenhouse with new and serving AHU-16, AHU-1, Growth Chambers/Cold Rooms and FCU-1.

g. Provide High Containment Laboratory Building and Greenhouse with new and dedicated 1.5 inch supply and return lines to supplement the existing 4 inch pipe serving AHU-2, 3, 4, 5 and PF-14.

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2. CIVIL/SITE DESIGN

2.1 Codes and Standards

· Maryland Department of Transportation – State Highway Administration, Standard Specifications for Construction and Materials, January 2001 or Latest Edition.

· Maryland Department of the Environment – Erosion and Sediment Control Guidelines for State & Federal Projects, January 2004 or Latest Edition.

· Maryland Department of the Environment – Stormwater Management Guidelines for State & Federal Projects, July 2001 or Latest Edition.

· Maryland Stormwater Design Manual Volumes I & II, 2000.

· USDA – ARS Manual 242.1: ARS Facilities Design Standards.

· Washington Suburban Sanitary Commission (WSSC) Plumbing and Fuel Gas

Code.

2.2 Project Location

The project site is located within USDA property, off Powder Mill Road in

Beltsville, Maryland.

2.3 Existing Use and Site Improvements

The project site is the current location of the National Plant Germplasm

Quarantine Center which consists of the following facilities: Germplasm Laboratory, Virology Laboratory, High Security Greenhouse and Laboratory and the PHP Laboratory and Facility Support Building. In addition to the above mentioned facilities, the site contains greenhouses and screenhouses to the south.

Presently, an access road from the main road (Powder Mill Drive) loops around the north, east and south sides of the facility. The project site is located off the main access road within an existing fenced area north of the PHP Laboratory and Facility Support Building.

2.4 Existing Topography and Site Drainage

The project site is generally flat (grades less than 5%). There is an existing stormwater inlet just north of the existing chiller area. This inlet will require removal since the new chiller is to be located in this area.

2.5 Land Development & Project Permitting

Since the project site is located within federal property, neither the City of

Beltsville or Prince Georges’ County have any jurisdiction for review and approval of any proposed land development. Also since the anticipated limits of

STV Incorporated 2-2 07/29/11 earth disturbance will be less than 5,000 sf, a Maryland Department of the Environment (MDE) review of the Soil Erosion and Sediment Control Plan will not be required.

2.6 Proposed Use

A new chiller and associated site improvements are proposed just north of the two existing chillers to serve the NPGQC Facility.

2.7 Proposed Grading and Drainage

Proposed grading for the project site will need to be designed and constructed in such a manner that stormwater runoff is directed away from the proposed chiller and paved surfaces.

Two new storm drain inlets are proposed north of the proposed chiller to collect stormwater runoff from the existing foundation drains surrounding the chiller area and to collect runoff from the west and north. The new inlets will tie in to the existing storm drain system.

New Air-Cooled/Chiller Distribution Piping Improvements

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3. ARCHITECTURAL

3.1 Codes and Standards

3.1.1 Jurisdiction

The NPGQC Beltsville facility is located in Beltsville, Prince Georges County, Maryland.

The campus is on federally owned land and USDA is under federal jurisdiction.

Public Law 100-678 “Public Buildings Amendments of 1988” Section 6, requires that all federal construction projects be coordinated with local officials and comply with local building codes. ARS Manual 242.1: ARS Facilities Design Standards will be used for design guidance. The AHU Replacement & Reroofing project will be designed to local and national building codes and offered to local building officials for review.

3.1.2 Applicable Codes and Standards

The applicable Building Codes and Industry Standards that are pertinent to the Installation of a New Air-Cooled Chiller and Improvements to the Chilled Water Distribution Piping System project can be summarized as follows:

General Building: 2009 International Building Code (IBC)

Maryland Building Rehabilitation Code (MBRC) incorporating 2006 International Existing Building Code (IEBC), Accessibility: Maryland State Accessibility Code MAC (acceptable substitute: American Disabilities Act - ADA requirements)

Life Safety: 2009 NFPA 101 Life Safety Code

Energy Code: 2009 International Energy Conservation Code (IECC)

Other: ARS Manual 242.1: ARS Facilities Design Standards

3.1.3 Use and Occupancy Classification (IBC Chapter 3)

The Occupancy Use of the facility is categorized as:

B - Business; Laboratory and Testing

3.1.3.1 Classification of Work (IEBC Section 403)

The Scope of the project area is the removal and replacement or the covering of existing materials, elements, equipment, or fixtures using new materials, elements, equipment, or fixtures that serve the same purpose; the Work is be classified as Level 1 Alteration.

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3.1.3.2 Energy Conservation (IEBC Section 607)

Level 1 Alterations to existing buildings are permitted without requiring the entire building to comply with the energy requirements of the IECC. The alteration work shall conform to the energy requirements of the IECC as they relate to new construction only.

3.2 Design Approach

3.2.1 Background

The facility is composed of several buildings constructed at different times. The first buildings which make up the facility were the Headhouse and the Greenhouse Connector that were built to serve the greenhouses. The Old Mechanical was constructed in 1983 to house three boilers. Virology Laboratory was constructed in 1986. The addition of the High Containment Laboratory and Greenhouse Building to the north and east of Virology Laboratory and the Inspection Station, and the Breezeway leading to the Headhouse were constructed in 1999. There have been numerous renovations over the years to portions of the buildings.

3.2.2 Project Approach

Architecturally the project will consist of the required work to support the installation of the new chillers and piping. The work will include ceiling removal and installation to access above ceiling areas, new and enlarged penetrations thru existing floors and partitions, and finish painting in exposed areas. The areas of the building which will be affected by work of this project have ceilings which are either exposed structure or suspended acoustical panel ceiling system. Partitions in the affected areas are typically masonry constructed with a few areas having a stud and gypsum board construction.

Floors are concrete slab.

The approach to the project will be for smaller required access areas to remove the existing acoustical ceiling panels and snap-in ceiling grid from the suspended acoustical panel ceiling in localized areas to install new piping and perform above ceiling work.

This will be accomplished in areas where the removal of a few panels will provide sufficient space for above ceiling work. The panels and grid will be reinstalled at the completion of the above ceiling work in each area. Existing damaged panels or grid will be replaced with items matching existing adjacent items. This is anticipated for all required areas of this project.

Wall pipe penetrations through existing partitions will be reused where appropriate and where of a size to handle the new pipe to be installed. Any unused pipe penetrations at removed pipe of this project will be patched and finished with materials compatible with the existing partition construction. Any existing partitions which are fire rated will be sealed in accordance with appropriate Underwriters’ Laboratory approved details and

STV Incorporated 3-3 07/29/11 materials for the fire rating of the partition. Fire rated partitions are indicated on the Drawings.

Floor pipe penetrations through the existing floors will be handled with the same methodology as described for the wall penetrations. Floor sealant will be traffic bearing rated sealant.

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4. HVAC SYSTEMS

4.1 Design Conditions and Standards

The HVAC systems will be designed in accordance with the codes as detailed by the requirements of ARS 242 and with the following guidelines and standards:

• International Mechanical Code (IMC) 2006

• International Energy Code (IEC) 2006

• Maryland State Code (Adheres to the IMC 2006 with interpretations)

• Maryland Occupational Safety and Health (MOAH)

• Local Codes Prince George County

• National Fire Protection Association (NFPA)

• ASHRAE 15 Safety Code for Mechanical Refrigeration

• NFPA 90A Installation of HVAC Systems

• National Electric Code

4.1.1 Design Criteria

The HVAC system for the permanent chiller installation shall be sized using the following criteria.

Summer: Dry-Bulb Temperature = 93°F Wet-Bulb Temperature = 78°F

(Based on 0.4% dry-bulb and 0.4% wet-bulb temperature for Baltimore, published by 2005 ASHRAE Fundamentals.

(105°F will be utilized as ambient temperature in the selection of the air-cooled chiller).

Winter: Dry-Bulb Temperature = 12°F

(Based on 99.6% dry-bulb conditions for Baltimore as published by 2005 ASHRAE Fundamentals.)

4.2 Existing Chilled Water System Description

Currently, the facility has two (2) existing 170 ton nominal air-cooled chillers providing cooling to the Support Building and to the High Containment Laboratory Building and Greenhouse facilities. The two (2) existing chillers lack adequate cooling capacity during summer hot/humid days. The existing chilled water distribution system is served by three parallel constant-flow, frame-mounted, end suction pumps that discharge flow into a common main supply header. Each of the three existing pumps is sized to match the flow of each one of the existing chillers. The chilled water pumping distribution system operates as a single direct-primary constant volume piping loop with a minimum flow bypass line and control valve distributing chilled water to two main supply branch legs.

The first leg serves the Support Building HVAC systems (AHU-12, AHU-13, AHU-14, STV Incorporated 4-2 07/29/11 and a total of nine Growth Chambers/Cold Rooms). The second leg serves the Containment Laboratory Building HVAC systems (AHU-1 thru AHU-11, AHU-15, AHU-16, FCU-1 thru FCU-5, PF-14, and a total of five Growth Chambers/Cold Rooms).

Additionally, there are two separate piping take-off connections from the main header in the Mechanical Room that serve Treatment Room #SF-149 HVAC systems (systems:

#SF-17 and Waste Treatment Sterilizer Power Supplies and Magnetrons).

Each of the two pumps in the mechanical room is sized to handle a total flow of 385.0 GPM at 90.0 feet of head pressure drop through the chilled water piping distribution loops for a total flow of 770.0 GPM. The facility total chilled-water system connected load is 842.0 GPM (862 including future warehouse).

The total connected load of each loop is as follows:

1) Support Building HVAC Systems: 242.0 GPM (262.0 GPM including future warehouse).

2) High Containment Laboratory Building & Greenhouse HVAC Systems: 507.0 GPM.

3) Treatment Room #SF-149 HVAC Systems: 91.0 GPM.

Most of the existing 6” main pipe distribution loop and other branch pipes are operating at higher than the recommended standard maximum design values for flow rates, pressure drops and velocities due to the system differential flow rate between the design and connected loads.

4.3 Proposed Permanent Chilled Water System Description

The two (2) existing facility 170 ton nominal air-cooled chillers (150 ton net) will remain intact and will continue to operate and provide the required cooling demand.

A new permanent 417 ton nominal air-cooled chiller (380.0 ton net) located on grade north of the existing chillers’ yard will be installed and integrated into the existing chilled water system to enhance the National Plant Germplasm Quarantine Center’s (NPGQC) operational capabilities by providing a chiller system redundant to the current existing chillers. The new chiller will become the facility primary cooling system and will operate to provide the required cooling demand during summer peak load conditions.

The temperature control set point of the chilled water leaving the chiller will be 42°F, with a water temperature rise of at least 10°F.

A temporary “rental” 170 ton nominal packaged air-cooled chiller (150 ton net) located on grade east of the chillers’ existing mechanical room will be installed and integrated into the existing chilled water system. The temporary chiller is packaged with a single pump and isolation valves and will be the facility main cooling source until the installation of the permanent chiller is completed.

Increasing the flow rate capacity through the existing chilled water piping distribution system is feasible in some of the system piping loops. Some could handle an additional flow at the industry standard normally recommended design range criteria (water velocity

STV Incorporated 4-3 07/29/11 range between 5 to 10 feet per second for general service piping). A maximum water velocity of 6 feet per second with maximum friction head loss of 6 feet of water per 100 ft of equivalent clean pipe length will be utilized in determining new system pump head loss calculations. The additional flow increase to the supply and return piping loops and to the system total flow rate will require replacement of the existing chilled water pumps and modifications to selected piping segments in order to handle the modified system corresponding flows and pressure drops.

The three existing pumps will be replaced with three larger primary pumps (one standby pump) with variable frequency drives. A differential pressure transmitter between the water supply and return mains will be used to vary the speed of the pumps via the variable frequency drive to maintain a constant pressure differential between the piping mains. Primary building pumps will circulate chilled water throughout the facility. The building chilled water system will be a variable volume system utilizing the existing modulating 2-way control valve at each cooling coil. The chilled water piping will be run in copper piping up to 2-1/2 inches in size and in steel pipe in sizes 4 inches and larger.

The pumps will be placed in the location of the existing chilled water pumps in the mechanical room. The chilled water system will utilize a 30 percent ethylene glycol mixture for freeze protection.

4.3.1 Direct-Primary with Variable-Volume Pumping System

The existing chilled water system has undergone numerous upgrades since the original installation of its direct-primary constant-volume pumping system. Responding to the various demands of operation, equipment, and the drive for more efficient system, a direct-primary variable-volume pumping system is the logical choice for the chilled water plant. The direct-primary variable-volume system allows much greater flexibility in providing chilled water where it is needed in the most efficient manner possible.

However, this system is a little more complex and requires an understanding of how it is to operate in order to function most efficiently.

A direct-primary pumping system with variable flow through the chillers will use less energy over a single cooling season than the current direct-primary constant flow system.

Operating the chillers to their full potential saves a significant amount of energy over the life of the chiller plant operation. In addition to the savings in chiller operation, a single loop with variable flow will inherently result in a net energy savings in pumping power.

Because the chilled water flow rate follows the cooling load, the flow rate being pumped is matched to what is actually needed in the buildings (the limit to this savings is the minimum flow required through the chillers).

The chilled water system would consist of a single variable volume chilled water loop, which combines the chilled water chillers and distribution systems. In order to vary chilled water flow to match the cooling load (position of two-way valves), this variable pumping allows the flow through the chillers to adapt to varying distribution conditions instead of having an independent secondary loop. The pumps would be equipped with

STV Incorporated 4-4 07/29/11 variable frequency drives (VFD) to vary chilled water flow within the system to met operating conditions. This will require varying the flow through the chiller evaporator.

Careful attention must be given to the existing chillers’ allowable limiting tube velocity and rate of exchange in evaporator flow.

Some of the advantages of a direct-primary variable-volume system include:

• The system pump flow rate is better matched to the cooling load within the distribution system.

• The adjustable chiller flow allows the flow through the chiller to vary above or below normal design flow gives the option to optimize flow to the chiller and match the system ∆T. This maximizes the output of a given chiller and eliminates the need to start additional chillers and pumps prior to reaching nameplate capacity.

• Generally this approach yields lower energy and operating costs per year (fewer pumps and less mechanical space) as compared to a constant flow primary system.

Some of the control challenges of a direct-primary variable-volume system include:

• Control of the system would require that chillers are not inadvertently shutdown during simultaneous flow and load changes.

• Controlling the low flow bypass – normally closed valve that opens under low load conditions to maintain the minimum chiller evaporator flow rate. The control of the system is dependent upon the accurate measurement of chilled water flow and proper selection/operation of the bypass control valve. The inability of the bypass to properly open and close may result in the chillers tripping due to low flow.

• When an additional chiller is needed to be brought online, the sudden drop in flow through the lead chiller may cause it to trip offline on low flow. A control strategy is required to first unload the lead chiller, start the next unit and ramp them back up together.

4.3.2 Flow Circulation Enhancements to Piping Distribution Loops

The following enhancements to the existing chilled water distribution system will enable an estimated 75 tons of cooling load to be added to the present system capacity. To accommodate the installation of the recommended direct-primary variable volume system while realizing the enhancements, the following modifications and alterations will be incorporated into the design package:

1. Replace existing constant volume pumps with larger pumps and motors equipped with variable frequency drives (VFD).

2. Replace chillers’ 6.0 inch common supply and return piping headers with 8.0 inch headers.

STV Incorporated 4-5 07/29/11

3. Replace chillers’ 3.0 inch bypass line and valve assembly with 4.0 inch assembly to accommodate chillers’ minimum flow requirement.

4. Provide Support Building with new and dedicated 2.5 inch supply and return lines that originate from the Mechanical Room to accommodate chilled water flow to future warehouse and to existing AHU-14. (AHU-14 will be taken off the Support Building existing 4.0 inch main circulation loop).

5. Provide High Containment Laboratory Building and Greenhouse with new and serving AHU-7, 8, 9, 15, 10, FCU-4, AHU-6 and AHU-11.

6. Provide High Containment Laboratory Building and Greenhouse with new and serving AHU-16, AHU-1, Growth Chambers/Cold Rooms and FCU-1.

4.4 Building Automation System

HVAC control will be accomplished utilizing a direct digital control (DDC) Building Automation System. The control system shall be direct extension of the existing American Auto-Matrix/Tridium-Niagara (JACE 6000). The provided Building Control System shall be compatible with American Auto-Matrix/Tridium’s Niagara Direct Digital Control System framework, designed and installed in accordance with the center design standards.

The DDC Control System existing throughout the center is American Auto-Matrix/ Matrix/Tridium-Niagara (JACE 6000). Therefore, notwithstanding any other provision of the Contract, all controllers and programming shall be compatible with American Auto-Matrix/Tridium-Niagara (JACE 6000). The units control system shall communicate with the main workstation JACE #4 located in the Support Building. The system shall provide communication with the existing front end in the Support Building for all new and modified control work. New and modified work shall function seamlessly with the center system, both locally and remotely.

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5. ELECTRICAL SYSTEMS

5.1 Codes and Standards

The electrical systems will be designed in accordance with the following codes:

• International Building Code 2009

• National Electrical Code 2008

• International Energy Conservation Code 2009

• USDA ARS-242 Design Standard

5.2 Equipment Sizing Criteria

5.2.1 Secondary Design Voltages

• Chiller Motors– 480V, 3 phase

• Pump Motors- 480V, 3 phase

5.2.2 Equipment Sizing Criteria

Feeder Load Calculations

• Motors – 125% of Motor FLA

Demand Factors

• Fixed Equipment – 100% of total VA installed

5.3 Normal Power Services and Distribution

5.3.1 Design Criteria

USDA has requested that the new 375 ton chiller and one existing 150 ton chiller be connected to the emergency power system. Therefore, one existing 150 ton chiller (CH-2) will be disconnected from a transfer switch (ATS-6) and connected to the normal service. The purpose is to limit changes to the emergency power switchboard controls.

5.4 Standby Emergency Service and Distribution

5.4.1 Design Criteria

A 600 amp transfer switch will need to be removed and replaced with an 800 amp transfer switch for the 375 ton chiller. New circuit breakers and feeders will be required. Since the 375 ton chiller can run on emergency power, the chiller load

STV Incorporated 5-2 07/29/11 will need to be manually operated by USDA to avoid overloading and will only be able to operate when on normal power or both generators are operating in parallel. The two existing emergency generators are each rated at 750 kW, 480/277 volts, three phase and are located in the Support Building generator room. The two generators provide emergency and standby power to the entire facility.

The chilled water pumps are increasing in size, and will be controlled by variable frequency drives. The variable frequency drives shall be wall mounted. The power for the chilled water pumps will originate in the MCC where the existing pumps are connected. The existing starters will be disconnected, the existing circuit breakers will need to be changed and the branch circuits will need to increase in size.

A temporary chiller will need to be supplied in order to limit the downtime to the chilled water system. The temporary chiller will need to be connected to the emergency power system. The existing transfer switch ATS-6 can be used to supply power to the temporary chiller, however the new chiller will require the 800 amp transfer switch in order to operate.

5.5 Grounding System

5.5.1 System Description

All feeders will be provided with an equipment ground conductor. Under no circumstances will the raceway system be used as an equipment grounding conductor.

5.5.2 Distribution

A separate equipment ground conductor will be provided for all circuits.