M-4 Narrative.pdf

HVAC Alternative #M-4 Narrative

General Description of Alternative: Large capacity heat pump air handling units, geothermal well field for total load of building, new high efficiency geothermal supplied hot water boilers with pumping and piping, new dedicated energy recovery air handling systems.

System Components:

1. Air Side Systems

a. Variable Air Volume Heat Pump Air Handling Units – General Requirements

• All new heat pump air handling systems serving the occupied areas shall be factory constructed custom central station air handling units located in existing mechanical fan room areas throughout the facility. Units shall be broken down into sections to allow for entry into the building areas and then reconstructed in-place with factory witness of re-assembly. The heat pumps shall be packaged DX systems utilizing the geothermal condenser water piping system as a source for heat of rejection in the summer or heat extraction from the condenser water source in winter operation.

• The heat pump air handling units shall be provided with the following components:

1) Economizer damper section to operate dampers for enthalpy economizer control.

2) Provide separate duct connections for minimum outdoor air from dedicated heat recovery makeup air unit (described in separate section below).

3) Return/relief fan section.

4) 30% MERV 8 prefilter/85% MERV 13 final filter section.

5) Direct expansion coils for cooling.

6) Reversing valve.

7) Integral or split condenser section.

8) Supply Fan Section with centrifugal fans.

9) Discharge air section.

10) Ultraviolet lights in all air handlers.

• All heat pump air handling units to deliver 55 F. supply air (summer) with reset of discharge temperatures in winter (up to 60 F.) based on space zone temperatures.

• Air from the heat pump air handling units shall be distributed to fan powered variable air volume boxes with reheat coils throughout the facility for zone control.

• All heat pump air handlers shall be ducted with pre-conditioned outdoor air at a capacity required for minimum outdoor air requirements for people plus an additional amount necessary for pressurization of the building. This pre-conditioned outdoor air shall be supplied by the dedicated energy recovery units. This air shall be ducted from the ERU’s in the mechanical rooms to each air handler. Preconditioned outdoor air for occupants and makeup air will be provided by the “house” energy recovery units identified below under “Dedicated Outdoor Air/Energy Recovery Systems – General Requirements”.

• All air handlers shall be ducted for full outdoor and relief air to existing or new louvers on the mechanical floors for full enthalpy controlled economizer. The outdoor air dampers shall be fully closed when economizer operation is not possible. The relief damper shall modulate to maintain space pressures based on average of the floor served.

• Provide the following heat pump air handling systems:

1) B-1: 25,000 CFM – Located in 2nd floor mechanical room. Serving basement.

2) B-2: 25,000 CFM – Located in 2nd floor mechanical room. Serving basement.

3) G-1: 25,000 CFM – Located in 2nd floor mechanical room. Serving ground floor.

4) G-2: 25,000 CFM – Located in 2nd floor mechanical room. Serving ground floor.

5) G-3: 25,000 CFM – Located in 2nd floor mechanical room. Serving ground floor.

6) G-4: 25,000 CFM – Located in 2nd floor mechanical room. Serving ground floor.

7) 1-1: 25,000 CFM – Located in 2nd floor mechanical room. Serving first floor.

8) 1-2: 25,000 CFM – Located in 2nd floor mechanical room. Serving first floor.

9) 1-3: 25,000 CFM – Located in 2nd floor mechanical room. Serving first floor.

10) 1-4: 25,000 CFM – Located in 2nd floor mechanical room. Serving first floor.

11) 1-5: 25,000 CFM – Located in 2nd floor mechanical room. Serving first floor.

12) 2-1: 15,000 CFM – Located in 2nd floor mechanical room. Serving second floor.

13) 2-2: 15,000 CFM – Located in 2nd floor mechanical room. Serving second floor.

14) 3-1: 22,500 CFM – Located in Penthouse mechanical room. Serving third floor.

15) 3-2: 22,500 CFM – Located in Penthouse mechanical room. Serving third floor.

16) 3-3: 22,500 CFM – Located in Penthouse mechanical room. Serving third floor.

17) 4-1: 22,500 CFM – Located in Penthouse mechanical room. Serving fourth floor.

18) 4-2: 22,500 CFM – Located in Penthouse mechanical room. Serving fourth floor.

19) 4-3: 22,500 CFM – Located in Penthouse mechanical room. Serving fourth floor.

20) 5-1: 22,500 CFM – Located in Penthouse mechanical room. Serving fifth floor.

21) 5-2: 22,500 CFM – Located in Penthouse mechanical room. Serving fifth floor.

22) 5-3: 22,500 CFM – Located in Penthouse mechanical room. Serving fifth floor.

23) 6-1: 22,500 CFM – Located in Penthouse mechanical room. Serving sixth floor.

24) 6-2: 22,500 CFM – Located in Penthouse mechanical room. Serving sixth floor.

25) 6-3: 22,500 CFM – Located in Penthouse mechanical room. Serving sixth floor.

Note: Air handling unit locations are based on conceptual information and may be located to an alternative mechanical room location depending upon the space available in the existing mechanical rooms.

b. Special Area Air Handling Systems All special area air handling units will be factory built heat pump air handling units provided with the following components:

1) Economizer damper section to operate dampers for enthalpy economizer control.

2) A separate duct connection for minimum outdoor air from a dedicated heat recovery makeup air unit (described in section c. below).

3) Return/relief fan section (where required).

4) 30% MERV 8 prefilter/85% MERV 13 final filter section.

5) Hot water coil section (where required for 100% makeup air).

6) Supply Fan Section with centrifugal fans.

7) Ultraviolet lights in all air handlers.

• Mail Room: Provide a separate constant volume unit, nominal 12 ton capacity heat pump air handling unit B-3 with full outdoor air capability for economizer and 100% exhaust requirements. This unit shall be the sole source of air to and from the mail room. The unit may be located in the 2nd floor mechanical room (or at the mail room) with duct distribution to and from the room. The mail room shall be provided with an emergency exhaust system to purge the space upon command from the occupants. Outdoor air from a louver shall be ducted directly to the mail room air heat pump for 100% outdoor air capability for economizer and makeup air.

• Kitchen/Cafeteria/Hood Makeup Air System: Provide a Kitchen makeup air handling heat pump unit G-5, approximately 18,000 CFM capacity at 100% outdoor air capability.

The unit shall be located in the 2nd floor mechanical room. The unit shall be supplied with the capability of providing of up to 100% outdoor air when kitchen hoods are in use. Route outdoor air and relief air to existing louvers. Route supply and return air from 2nd floor to the kitchen areas. The unit shall control the position of outdoor air and return/relief air dampers, supply and return fans based on space pressure relative to adjoining spaces to provide the required makeup air and to maintain a slight negative condition. The unit shall be a packaged heat pump air handling unit, variable air volume with supply and return fans, packaged heating/cooling compressor system.

• Auditorium: A variable air volume heat pump air handling unit G-6 shall be provided to serve the Auditorium areas. This unit may be located in the 2nd floor mechanical room.

The unit shall be sized to achieve approximately 10,000 CFM. The unit shall be a variable volume heat pump air handling unit. The unit shall be provided with outdoor air from the energy recovery systems and will adjust the amount of outdoor air based on carbon dioxide sensors located in the space to adjust the amount of outdoor air based on actual occupancy loads.

• Loading Dock: Provide a separate constant volume heat pump air handling unit G-7 for the temperature control of the loading dock area and to provide 100% makeup air for the exhaust systems. The unit shall be provided with ducted makeup air for up to 100% outdoor air capabilities for makeup and economizer modes of operation. The minimum air required will be provided by the energy recovery system. Outdoor air for 100% makeup during full exhaust will be routed from a louver on 2nd floor (or other location) directly to this unit. The exhaust of the loading dock shall be provided by exhaust duct inlets located to one side of the space near the floor to remove carbon monoxide/dioxide concentrations. The exhaust system shall be ducted to a fan on 2nd floor in the mechanical room. Exhaust shall be energized through an automatic sensor system located in the loading dock area.

• Main Lobby/Entrance: A heat pump variable air volume air handling unit 1-6 shall be provided for the main lobby/entrance vestibule. This unit shall be located in the 2nd floor mechanical room. The unit shall be sized to achieve 7,500 CFM. The unit shall be a variable air volume heat pump air handling unit. This unit shall have supply and return fans, hot water heating and chilled water cooling coils and shall have the capability of operating up to 100% outdoor air to maintain a positive pressure in the lobby/entrance relative to the rest of the building.

• Elevator Equipment Room: Provide a heat pump unit for this room. The unit shall be approximately 6 ton capacity and shall be located in the penthouse mechanical room.

• Fire Command Centers, Building Control System (BAS) Control Rooms, Security Monitoring Rooms, Voice/Data Rooms, Computer Rooms: Dedicated 24/7 heat pump cooling systems for these rooms. Redundant units will be provided where required.

c. Dedicated Outdoor Air/Energy Recovery Systems – General Requirements

• Exhaust from toilet rooms, janitors closets, loading dock and general exhaust for the kitchens/break rooms and other areas will be collected and routed through total energy recovery heat pump air handling systems (recovery of energy from grease producing exhaust systems cannot be achieved due to the grease contamination and fire potential).

The energy recovery units will be located in the mechanical rooms located on 2nd and the 7th floor penthouse mechanical rooms.

• Estimated amount of continuous exhaust is approximately 40,000 CFM.

• Estimated minimum outdoor air requirements are based on the amount required for makeup air to supply the occupants and makeup for the volume of air exhausted (40,000) + the amount required for building pressurization (approximately 40,000). Total required makeup air for the facility = 80,000 CFM.

• The heat recovery units shall be mounted inside the existing mechanical rooms and consist of the following:

1) Supply and exhaust fans.

2) Intake and Exhaust louvers and dampers.

3) Total energy heat wheel.

4) Heat pump compressor with reversing valve for supplemental cooling and heating requirements.

5) 30% MERV 8 prefilter/85% MERV 13 final filter section.

6) Unit capable of recovering 80% of the energy from the air being exhausted and transferring this heat energy to the incoming makeup air.

• All energy recovery units to deliver 55 F. supply air (summer) with reset of discharge temperatures in winter (up to 60 F.) based on space zone temperatures.

• Provide the following energy recovery systems:

1) ERU-1: 17,500 CFM – Located in 2nd floor mechanical room.

2) ERU-2: 17,500 CFM – Located in 2nd floor mechanical room.

3) ERU-3: 17,500 CFM – Located in 2nd floor mechanical room.

4) ERU-4: 17,500 CFM – Located in 2nd floor mechanical room.

5) ERU-5: 15,000 CFM – Located in 7th floor mechanical room.

6) ERU-6: 15,000 CFM – Located in 7th floor mechanical room.

7) ERU-7: 15,000 CFM – Located in 7th floor mechanical room.

• Intake and exhaust ductwork from the seven ERU’s will be connected to the existing louvers on each of the two floors. Provide motorized dampers at these connections.

• Exhaust from the basement through 1st floor sources will be ducted directly to the inlets of the four ERU’s evenly split between each unit.

• Exhaust from the 2nd floor through 6th floor sources will be ducted directly the inlets of the three ERU’s in the 7th floor, evenly split between each unit.

• Makeup air from each of the four (4) ERU’s in the 2nd floor mechanical room will be ducted into the ceiling plenums of the basement, ground and first floors. Makeup from the three (3) ERU’s in the 7th floor mechanical room will be ducted directly into the ceiling plenums of the 2nd, 3rd, 4th, 5th and 6th floors.

• The tempered outdoor air at each of these floor locations shall be routed out into the ceiling plenums and discharged within 10’-0 of the intakes of all of the heat pumps throughout the ceiling plenum areas.

• Provide balancing dampers at each of the discharge ducts in the ceiling plenums.

d. General HVAC Systems

• All bathrooms, locker room and janitor rooms will be exhausted at a rate of 10 air changes per hour.

• All break/small kitchen areas on floor x floor locations will be exhausted at a rate to maintain a slight negative condition to adjoining areas.

• Ductwork from shafts serving multiple floors shall be provided with combination smoke/fire dampers at penetrations on to a floor served.

• Interior conference rooms, training rooms, classrooms, seminar rooms or other rooms with larger occupancy will be provided with heat pump(s) and room specific thermostatic control.

The outdoor air from the energy recovery units ducted up to these space heat pumps will be provided with motorized dampers and the rooms served provided with space carbon dioxide level sensors to enable the motorized damper to increase the supply of outdoor air when the room(s) are fully occupied.

• Air distribution shall be through overhead vaned type diffusers. Perimeter zones will be provided with linear slot type air diffusers along the exterior window walls.

• Return air from spaces shall be through ceiling return air plenum.

• Perimeter Heating: All perimeter walls with windows and walls exposed to outdoors with a heating load of greater than 400 btuh/lineal foot of exposed wall shall be provided with perimeter hot water finned tube radiation. Hot water will be supplied at a maximum water temperature of 140 F. at -19 F. peak winter condition. Where heating load is under 400 btuh/linear foot for these same locations, overhead slot type diffusers shall be provided in lieu of finned tube radiation under the windows.

• Thermostatic Zones

1) Interior – open office areas: One zone for similar occupancies up to 1500 sq. ft.

maximum.

2) Interior – private offices: One zone per three offices.

3) Interior – larger conference rooms: One zone per conference room.

4) Perimeter offices – No more than 300 sq. ft. per zone along a common exposure.

5) Perimeter conference rooms: One zone per conference room.

6) Perimeter – corner rooms/offices: One corner room per zone.

2. Water Side Geothermal Condenser Water Systems

• Total building cooling required = 1050 tons.

• A closed loop vertical geothermal well field shall be provided to exchange the heat energy from the heat pump systems in the condenser water loop in the building to the ground outdoors. Estimated vertical wells required = 1050.

• Estimated area required for the well field is approximately 300,000 to 350,000 sq. ft. Refer to the attached drawing for the location of well fields in the parking lot areas.

• The vertical well depths will vary between 250’ to 350’ deep to achieve an average heat transfer of approximately 1 ton of energy summer and winter. Note: Conductivity testing of the soil conditions is required before final depths and capacities will be known.

• Groups of fifteen(15) wells shall be collected on sub-main supply and return piping.

Approximately 70 groups of these well system sub-mains will be routed from the well fields under the parking surface to the chiller room to primary manifold supply and return headers inside the room. Each sub-main will be provided with valves and pressure test tappings to enable isolation and periodic testing.

• The “condenser” water from the well fields collecting at the primary headers in the building will be pumped throughout the facility to the heat pumps.

• Two base mounted pumps shall be provided (one redundant) to circulate the condenser water to the “house” cooling loads. The pumps shall be approximately 2850 gpm each at 100

ft. of head. Each pump shall be provided with a variable speed drive to control pump speed based on actual building loads.

• Two base mounted pumps (one redundant) shall be provided and a separate condenser water loop routed for the “24/7” critical loads in the building. The pumps shall be 300 gpm at 100 ft. of head. Each pump shall be provided with a variable speed drive to control the pump speed based on the actual building loads.

• The condenser water system shall be filled with a 40% solution of propylene glycol for freeze protection.

• Provide air separator and expansion tank(s) appropriate for the size of the system.

• Provide makeup water fill and chemical pot feeder systems for this condenser water system.

• Distribute new condenser water supply and return water piping to new heat pump air handling units in locations described in “Air Systems”. All heat pumps shall be provided with modulating two way valves.

Backup “24/7” Condenser Water System

• Provide a backup “24/7” condenser water system to be available for backup of the “24/7” geothermal condenser water systems serving the building fire command/building automation/security type communication rooms, voice/data rooms and computer rooms with dedicated 24/7 critical AC equipment. Provide one evaporative fluid cooler on the roof area above the 6th floor. The evaporative fluid cooler shall be sized for approximately 100 tons of cooling capacity. The evaporative fluid cooler will be provided with finned coils for 100% “free cooling” capability in the winter (below 40 F. ambient conditions) and to minimize any potential for water freezing. The fluid cooler fans shall be controlled with variable speed drives. The fluid cooler shall energize any time the geothermal loop flow fails.

• Route domestic water for fill of the fluid cooler sump for coil spray.

• Provide two condenser water pumps for the fluid cooler (one redundant) in the Penthouse mechanical room. The pumps shall deliver approximately 300 gpm at 75 ft. of head. The pumps shall be based mounted centrifugal. The condenser water system shall be filled with a nominal 40% propylene glycol solution.

• Route the condenser water piping from the 24/7 fluid cooler to the main location of the geothermal loop 24/7 pumps. The connection to this piping shall include a motorized valve to enable operation of the backup system upon geothermal system failure.

3. Boiler Plant

• Total required hot water capacity of plant = 12,000,000 btu

• Boiler Type: High efficiency geothermal supplied heat pump boilers.

• Heat pump boiler system shall operate in a range of 140 F. supply water/120 F. return water (maximum) water temperatures at -19 F. ambient conditions down to as low as 100 F.

supply/80 F. return (minimum) at 50 F. outdoor ambient conditions for maximum efficiency. Provide at least nine heat pump boilers, manifolded together and operating in series to maintain loop temperatures required. One heat pump boiler is provided for redundancy.

• The boiler systems will supply 140 F. hot water, or less, to building system perimeter finned tube radiation, unit and cabinet unit heaters, overhanging areas exposed to the outdoors and makeup air handling unit preheating coils. All heating coils and elements will be provided with modulating two way valves.

• The circulating hot water systems shall be filled with a 40% solution of propylene glycol.

• Provide Clima-Cool, or equal heat pump boilers within the existing boiler room (one boiler is redundant). Each heat pump hot water boiler return water connection shall have a motorized valve to enable shut-off of non-operating boilers at lower load conditions.

• Pumping Systems: Provide a primary/secondary piping and pumping configuration. Provide one dedicated primary pump for each boiler with one backup for the pumps. Primary pumps shall be 130 gpm at approximately 30 ft of head each. Provide two (one redundant) based mounted secondary pumps at 1200 gpm each at approximately 75 ft. of head. Each pump shall have a variable speed drive.

• Provide air separator and expansion tank(s) appropriate for the size of the system.

• Provide makeup water fill and chemical pot feeder systems for this hot water system.

s:\2100\2111\027-00\work\mech\predesign specs and calculations\alternate m-4\alternative m-4 narrative.doc