STATEMENT OF WORK.docx

Statement of Work Replace NAL Boilers for Bldg Heat and Hot Water A. Goals and Needs:

This project is a design-build contract to replace three existing ~5000 (1000 BTU’s per hour) (MBH) boilers with new high efficiency boilers. It will provide the final design to size the boilers, pumps, and hydronic system, lay out the equipment and piping, replace the domestic hot water system and eliminate the full height boiler stack.

B. Existing Conditions:

The building consists of high-rise “tower” and a low-rise “wing” sections of the building. The tower and wing sections of the building have a basement, ground floor and first (1st) floor, and the tower has second (2nd) through fourteenth (14th) floors with a mechanical equipment penthouse above the 14th floor.

The basement level is mostly unfinished and is primarily composed of mechanical, electrical, storage, and shop space, along with a janitor’s office and engineer’s office.

The roof is a low-slope, single ply roof membrane with a masonry parapet penetrated by numerous vents, stacks, pipes, and hatches. It holds multiple pieces of rooftop equipment and a rooftop penthouse structure. A roof replacement was performed on the building in 2009.

C. Scope of Demolition:

Demolition work planned for this project includes removal of existing boilers and appurtenant mechanical equipment, piping, and accessories, removal of an existing chimney stack on the roof, as well as its support structure and guy wires, removal of an existing domestic water heater and stack, demolition of existing concrete equipment pads in the basement, and cutting/modification of an existing grate on the exterior of the building.

D. Scope of New Work:

Work planned for this project includes installation of new boilers and appurtenant mechanical equipment, piping, and accessories, capping of roof curbs, construction of new concrete equipment pads, and infill of opening in existing exterior concrete wall.

E. Project Schedule Projected schedule for completion of the project, from design and review to construction completion and closeout, is approximately 12 months.

F. Owner Furnished or Installed Items:

None anticipated.

Environmental Management

15. Executive Order 13101 of September 14, 1998, Greening the Government through Waste Prevention, Recycling, and Federal Acquisition; and Executive Order 13123 of June 3, 1999, Greening the Government through Efficient Energy Management H. Existing Mechanical Conditions

1. The facility has three existing ~5000 MBH boilers providing both heat and domestic hot water; two burn either natural gas (primary fuel) or No 2 fuel oil (alternate fuel) and the third boiler burns #2 fuel oil only.

2. The two dual-fuel boilers were installed as part of the original building construction, with boiler nameplates identifying the manufacture year as 1968. The third fuel-oil boiler was added later, and its nameplate identifies the manufacture year as 1974.

3. The facility generally only needs one boiler running to provide heat and domestic hot water during the year. The second boiler is brought online when approaching a design heating day. Three boilers never operate concurrently.

4. Building HVAC controls are digital for most equipment, with pneumatic actuators. Siemens is the control system vendor.

5. The facility prefers to burn natural gas whenever possible. The natural gas is provided via a utility rate/plan that includes curtailment, so the dual fuel capability is important.

6. The majority of the building is heated by air handling units that force airflow across heat (HW) heating coils and into a variety of supply duct systems for delivery of heated air to the building. All occupied office areas (Ground-4th and 14th floors) also have separate HW radiant heaters along perimeter walls and in some overhangs below occupied floors. The radiators on the book stack floors (floors 5-13) were removed and capped off.

7. The record drawings show the boilers producing primary heating HW at 230°F with a 50°F HW temperature drop across coils and heat exchangers served directly from the primary HW system. Much of the building is served by two HW-to-HW heat exchangers. Those heat exchangers produce secondary HW at lower temperatures that vary depending upon the heat exchanger or heating coil scheduled. The secondary HW supply temperatures range from 150°F to 210°F, with water temperature drops across coils and heat exchangers ranging from 20°F to 50°F. The facility staff reports that all three boilers no longer make 230°F HW and more commonly make HW with a maximum primary HW supply temperature setpoint of approximately 200°F, with secondary HW supply temperature setpoints of approximately 180°F on heat exchange (HX)-1 and 140°F on HX-2.

8. The original primary HW from the boilers serves:

a. HW coils in air handling units AHU-4 and AHU-5

b. Secondary HW loop heat exchangers HX-1 and HX-2

c. Wing building perimeter radiation heat

d. The 1st floor Reading Room overhang

e. Unit heaters and air handling units located mostly on the basement level.

f. The domestic hot water system.

9. The primary HW loop heats two secondary HW loops via the heat exchangers. Heat exchanger HX-1 primarily serves tower coils, including preheat coils in tower air handling units AHU-1 and AHU-2 and duct mounted reheat coils in the duct system served by AHU-1 and AHU-2. Heat exchanger HX-2 primarily serves tower radiant heaters located in the tower perimeter areas and in 3rd floor overhangs and penthouse mechanical room radiant heaters.

10. Domestic hot water is generated in the basement using a heat exchanger that extracts heat from the heating HW system and transfers it into domestic water. The system uses a domestic hot water storage tank also located in the basement. Equipment nameplates do not contain enough information to estimate capacity, and record drawings are not available. The capacity is assumed to be 2,030 MBH from the size of the relief valve, which approximately equates to 14 gallons per minute (GPM) (at 30°F assumed heating HW temperature difference).

11. The HW system is served by HW pumps P-5 through P-19, as follows:

a. Pumps P-16 and P-17 circulate primary HW through the boilers, to secondary heat exchangers, to the domestic water heater, and to higher temperature heating coils (e.g., at basement air handling units such as AHU-4 and AHU-5), with P-17 being a stand-by pump to back-up P-16.

b. Pumps P-10 and P-11 circulate secondary HW from HX-1 to the preheat coils in AHU-1 and AHU-2, reheat coils in supply duct systems from AHU-1 and AHU-2, and to various other tower air handling units (e.g., AHU-3 for Multipurpose Room and AHU-6 for Special Collections), with P-11 being a stand-by pump to back-up P-10.

c. Pumps P-12 and P-13 circulate secondary HW from HX-2 to perimeter radiation heaters on the north side of the tower, to toilet room heaters, and to 3rd floor overhang radiant heaters (the overhang system also relies upon tertiary HW pump P-18 on the 2nd floor).

d. Pumps P-14 and P-15 circulate secondary HW from HX-2 to perimeter radiation heaters on the south side of the tower, to stair heaters, and to 3rd floor overhang radiant heaters (the overhang system also relies upon tertiary HW pump P-19 on the 2nd floor).

e. Pump P-7 is a stand-by pump that circulates secondary HW from HX-2 to back-up pumps P-12, 13, 14, or 15.

f. Pumps P-5, P-6, and P-8 circulate HW to wing perimeter radiation heaters, with P-5 serving southwest wing, P-6 serving northeast wing, and P-8 is a stand-by pump to back-up either P-5 or P-6.

g. Pumps P-9 circulates primary HW to 1st floor Reading Room overhang radiant heaters.

h. Pumps P-4.27 and P-4.28 circulate HW to a stair pressurization fan located in penthouse mechanical room.

12. The boiler room was originally provided heat by AH-2, and the unit is also intended to provide combustion air for boilers, since the unit is ducted to draw-in 100% outside air from the below grade areaway containing the generator. Unit AH-2 has been inoperable for an extended period of time, maybe decades. Combustion air is also intended to be provided by an operable damper on a screened exterior wall penetration also located near the generator. This damper is generally and manually left closed in winter and opened in summer. Combustion airflow rate may be inadequate. (The chiller room is heated by AH-1, which was replaced in the last few years and has a capacity exceeding the capacity of AH-2. Since some doors between the boiler and chiller rooms are typically left open, AH-1 has most likely been providing the make-up air required for boilers, since the time that AH-2 became inoperable.)

13. Known problems with the heating hot water system include:

a. The boilers and most HW pumps have been in use for 44-50 years and have exceeded a normal operating life expectancy. (Some HW pumps and heat exchanger HX-1 have been replaced, but all replaced equipment is believed to have been in service for at least 20 years.)

b. Boilers have existing control system deficiencies, such as the boilers do not reliably and automatically shut down upon loss of water flow.

c. The boilers do not automatically change lead/lag/stand-by assignments to equalize runtime accumulations; this is done manually.

d. The use of the HW boilers with no HW temperature reset schedule in mild temperatures is inefficient.

e. The use of so many different HW pumps is complicated and difficult to understand.

f. The use of these HW pumps at constant speed is inefficient.

g. The pumps do not automatically change operating/stand-by assignments to equalize runtime accumulations.

h. The HW piping system insulation was tested and found to contain asbestos fiber.

i. Combustion air for boilers is potentially inadequate.

14. Electric service to the building is 3,000A, 480/277V, 3PH, 4W. Electric service to existing boilers and pumps are from existing Motor Control Centers MCC-1, MCC-1-SB and local branch panels in the boiler room.

I. Scope of Demolition:

1. Prior to beginning demolition, existing hydronic flows and pressure profiles are to be measured at each pump and heat exchanger and at each hydronic piping riser or zone. Measurements are required to be collected at conditions that simulate maximum heating. Removal of insulation and the use of ultrasonic flow measurement devices will be required in locations where there is no existing and functional balancing valve available.

2. Demolish three boilers. Concrete pads may be re-used.

3. Demolish boiler vent and vent stack piping to the maximum extent practical in boiler plant and on roof. Vent piping concealed inside masonry chase in tower may be abandoned in place.

4. Demolish all plant HW pumps and concrete bases (i.e., for constant speed basement HW pumps P-5 through P-17, excluding P- 9 and heat exchangers and supports (i.e., for HX-1 and HX-2). Demolish all associated supports made obsolete by this project.

5. Demolish associated HW piping in boiler plant, but the majority of piping outside of the central plant to coils and heaters is to remain. Make HW piping ready for reconnection to replacement boilers and pumps.

6. Demolish fuel oil and natural gas piping (plus natural gas system vent piping) at boilers and make all such piping ready for extension and reconnection to replacement boilers.

7. Demolish disabled combustion air heater (i.e., AH-2) and associated intake louver located above roll-up door. Wall penetration remaining (60”x36”) is to remain for re-use.

8. Demolish disabled combustion air intake damper from rear of screened opening.

9. Demolish domestic water heater and the minimum possible domestic cold, hot, and recirculated hot water piping at this equipment. Domestic hot water recirculation pump is to remain for re-use. Remove all associated hydronic HW piping.

10. Carefully remove control air compressor and save for relocation and re-use.

J. Scope of New Work:

1. Replace all three boilers with high efficiency condensing boilers, which would alternate lead and lag assignments to equalize runtime accumulation and satisfy the base load. All three boilers have a similar capacity to existing boilers. The boilers are to be modern, dual fuel, 125 PSIG, condensing hot water boilers with a rated fuel input capacity as scheduled.

2. Provide a variable primary flow, variable secondary flow pumping system to vary HW flow from the boiler plant out to the building to match the HW demand. Pump capacities are to be as scheduled.

3. HW is to be produced at temperatures following a schedule that resets with outdoor air temperature, or with actual HW demand, which could be determined from monitoring the difference between supply and return HW temperatures. The boilers are to supply the variable flow primary HW system at 120°F supply HW temperature at periods of lowest heating demand and would be capable of increasing the primary supply HW temperature up to 200°F with a 30°F water temperature difference (from supply to return) at periods of peak heating demand. These peak temperatures will approximately match the HW system design used currently, since heating coils are not replaced as part of this project.

4. Replace existing basement HW pumps identified above with one set of three 50 percent capacity variable speed primary pumps, which would circulate HW flow through all boilers and one set of three 50 percent capacity variable speed secondary pumps, which would circulate HW flow out to the various existing HW supply branches throughout the building. Each variable primary pump would be designed for 50 percent of the total peak HW flow required at boilers. Each variable secondary pump would be designed for 50 percent of the total peak HW flow required in the building and for the worst-case pump head pressure through the path of most resistance. All boilers and pumps are to be in use or standing by, such that the maximum of two boilers, two primary pumps, and two secondary pumps are in operation at any time.

5. Required pump head pressures are estimated as scheduled for these bridging documents based upon existing record drawings. Pressure requirements must be verified during final design of these modifications, using the data collected from the pre-demolition hydronic flow and pressure measurements collected as required by these bridging documents.

6. Modulating 2-way control valves are to be added at individual HW system piping zones, as indicated on piping schematics, to reduce HW flow when HW demand decreases. The control valves would be modulated based upon the difference in supply and return HW temperatures to automatically open as the need for heating creates a larger temperature difference. These modulating control valves allow the variable speed secondary HW pumps to reduce speed when heating demand decreases, which saves pump energy at reduced heating load. Each of the vertical piping branches with multiple coils and/or radiation heaters has distribution piping installed in a reverse-return arrangement, so the reduction of flow created by control valve modulation is not expected to significantly and adversely affect HW flow balancing within that piping zone as HW flow varies.

7. Combination flow measurement and balancing valves are also to be added on each piping riser/zone to balance hydronic flows. Existing balancing valves may also be utilized.

8. Replacement of hydronic accessories such as HW air separators, strainers, plant valves, and controls is required.

9. The DB contractor will non-destructively test the existing expansion tanks for soundness. If the tanks are found to be sound, they can be re-used. Associated make-up water stations may be re-used since many have recently been upgraded.

10. Piping will be modified as required in the basement to connect the new main distribution piping to basement branch piping serving existing heating coils and radiators.

11. HW supply temperature will be allowed to vary with either outdoor temperature or actual heating load.

12. Since the variable HW supply temperature would no longer serve as a good energy source for generating domestic hot water, the DB contractor should determine how the domestic water heater should be replaced. The new water heater must be reconnected to existing domestic cold, hot, and recirculation hot water piping.

13. The project must be completed in multiple phases to prevent a complete HW system outage of extended duration. Multiple partial HW system outages would be required to replace equipment and modify the existing system. Refer to phasing instructions provided elsewhere in these bridging documents.

14. New digital controls are to be provided for all boiler plant equipment and integrated with the existing Building Automation System, although the front end software and workstation are to be upgraded to current software versions and hardware requirements.

K. Technical Analysis and Requirements:

1. HVAC Load Calculations:

a. As part of a separate study performed in 2017, a computer model of the tower and wing buildings was generated to calculate building peak heating and cooling loads using Trane Trace 700 Version 6.3.2.2.S software. Record Drawings were used to model the building footprint and envelope, and staff interviews were used to model the number and location of building occupants.

b. The calculated peak heating and cooling loads from the computer model of existing conditions was compared with the capacity of the existing system, as reported by the facility staff (i.e., approximated, by how many chillers and boilers operate and by how loaded the facility staff believes them to be), to verify that calculated loads represent reasonably accurate results. Refer to Appendix A for actual load calculation input/output. Tables 1 below shows the results of this comparison.

2. Heating HW Calculations:

a. Heating HW flow and pump head information was gathered from a combination of record drawings, pump nameplates, and manufacturer pump curves for non-custom pumps.

b. Table 2 shows a summary of data collected, without any assumed reductions for diversity. All loads are assumed to peak simultaneously. The table also adds scheduled flows, with no correction for different original entering water temperatures, which is done primarily because the boilers have not made 230°F HW for many years.The increase in HW design flow from 670 GPM to 1,025 GPM on pumps P-10, 11 cannot be fully explained. Added preheat coils on penthouse AHU-1 and AHU-2 are the only known added loads.

c. Tower reheat/recool coil flow rates are as scheduled on original drawings, which applied to cooling flows with a smaller temperature differential, which is no longer applicable. No correction was made for heating HW flow with a higher temperature differential.

d. The total flow of 1,256 GPM in Table 2 equates to a heating capacity of more than 12,500 MBH, which is approximately double the assumed capacity of two existing boilers, which have a capacity of about 6,500 MBH, so the calculated total flow in Table 2 is very conservative.

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