6.3.5 Equipment Sizing/Space Requirements

Provide heat pump split system with low ambient control to -20°F and condensate pump for MDF spaces. Active humidification not required. Unit controls shall be stand alone. Setpoint 75°F. Provide BAS space temperature sensor for alarming out of range (85°F). In addition, provide a separate exhaust fan set at 80°F as backup to the split system. Fan may discharge to an adjacent plenum return ceiling to avoid the need to bring in outside air during fan operation. Fan shall be on the BAS.

Kilns are typically electric. Provide kiln exhaust fan accessory. Duct to the outdoors. Where a kiln is provided post construction, provide duct infrastructure for future connection. Provide a separate dedicated exhaust fan above kiln as a backup to space conditioning set to ensure space temperature does not exceed 85°F. Typically, primary space conditioning is shared with adjacent art room zone system. Do not locate fire protection sprinkler heads directly above the kiln due to accidental discharge when the unit is opened immediately after use.

• Field: The Geo-exchange Field shall be coordinated with the Civil Engineer and Architect. The field shall be located in an area with ease of access for the manifold housing (vault) and allow for future maintenance without major removal of essential elements (Do not route below the building. Avoid routing below parking lot/paved areas). The Path of Travel from the building to the field shall also be considered for ease of future access. Tracer cabling and warning tape shall be provided above all outdoor horizontal piping and vertical wells. Provide GPS coordinates for each well on as built drawings. The addition of leak detection equipment shall be considered. Review field sizing with CPS.
  Typically, a hybrid system is provided in which the field is sized for approx 70 to 80% of total yearly energy load, not 100%. Provide supplemental boiler/tower/chiller for final 20 to 30%. Design field distribution so that a leak downstream of the vault/pit (field side) in a branch/well results in no more than a 5% loss in system capacity. Obtain CPS approval for redundancy requirements based on a project by project basis.
• Heat Pump: Where possible, utilize centralized heat pumps/reversing chillers to create chilled water and hot water for distribution to traditional HVAC equipment/terminal devices rather than individual compressorised terminal equipment spread throughout the building.
• Valve Vault/Pit: Where geo-exchange field is located directly adjacent/close to associated building mechanical space, consider homerunning the well branch lines into the building and locating the individual well branch differential pressure gauges/thermometers/isolation/balance/P&T taps, drain valve assemblies in the building basement or within an indoor pit. Basement or pit valve assembly area shall be along the exterior wall of the building. Pit shall include permanent ladder, sump pump, lighting and walkable grating. Provide a walkable clearance area in front of assembly for maintenance. Where exterior vaults are more appropriate for the site layout, provide prefabricated HDPE vaults with ballast and two manhole entrances at opposite ends. Vaults shall include permanent ladder, sump pump/pit, lighting, electric heater, vent fan with intake and discharge goosenecks, GFI convenience receptacle, factory fabricated/installed main headers and well branch piping with trim similar to indoor installation described above. Entire assembly shall be factory wired allowing for a single point power field connection. EOR shall determine the number/size and location of vaults. Vault detail shall be shown on design drawings.
• Pumps: Hydronic pumps shall be redundant with VFDs.
• Thermal Storage: The use of thermal storage medium shall be considered for all new systems. Storage medium shall be chosen based on availability, cost and be environmental inert. The most common medium is water or a water-based solution. Typically, 20% PG solution is utilized.
• Additional Heating/Cooling: Provide additional systems (electric boiler, cooling tower, dry cooler, reversing chiller) as required to maintain acceptable space conditions throughout all spaces. These additional systems shall be designed per these Design Guidelines.
• Controls: The Geo-exchange System shall be fully controlled by the BAS. The Geo-exchange System shall be the primary means of both heating and cooling for the building, with additional systems only being brought online if there is a need based upon field fluid temperatures.

Rooftop Units:

All packaged Rooftop Air Handlers (RTU) shall meet or exceed all applicable energy codes and meet the current CPS Specifications. All units shall include full 0-100% Economizer operation, outside airflow measuring station, modulating power exhaust or modulating return fans with space pressure control, stainless steel drain pans, a non-fused disconnect switch and separate power for convenience outlets and interior lights (provide interior lighting and access door viewing glass on large units (+10,000 CFM / +25 tons). Doors shall be hinged and open against pressure. Provide an alarm at the building automation system for when the outdoor airflow value varies by 15% or more from the outdoor airflow setpoint.

Heating shall be provided for all units. The preferred heating type shall be Natural Gas. Gas heating shall include fully modulating controls and be sized to allow proper distribution temperatures at minimum outdoor air rates at winter design temperatures. Distribution temperatures may differ based on the type of system being designed. Electrical heating shall only be used when no other type of heating is available, Electrical coils shall include SCR controls for full modulation. The use of hot water (30% PG) or steam heating shall be allowed with the addition of circulation pumps and other freeze protection measures.

For units with cooling, all units greater than 7.5 Tons shall include multiple compressors. Exception: inverter compressor units shall include a single compressor up to 25 tons. The use of a digital scroll or inverter compressor shall be provided for discharge air temperature control and project energy efficiency requirements. The combination of all new and existing base building HVAC&R equipment shall comply with the LEED ozone depletion and climate change formula for all projects.

Unit controls shall be factory installed for all packaged units, with the addition of a BACnet control card for integration to the building BAS. EOR shall confirm that all required control points are supplied by the Manufacturer and add any optional sensors, devices, controllers or other items as required to meet CPS Control Standard Diagrams, sequences and Specifications.

All RTUs shall include optional items required for proper system maintenance, protection from environmental conditions, and allow for full unit controls. These may include an insulated roof curb, insulated vibration curb (provide with all compressorized units), insulated plenum vibration curb (avoid where possible), hail guards, smoke detectors, and field-installed cottonwood screens for the condenser coils.

Fan Arrays may be provided with project specific approval by CPS. Where arrays are provided, individual fan status shall be monitored by the BAS and a means of closing off a failed fan (backdraft damper, blankoff plate, etc) shall be provided to avoid air recirculation through failed fan when unit remains in operation.

Makeup Air Units:

Makeup Air Units (MAU) shall be provided when a large exhaust system is designed for a specific space. This is most common in Kitchen and Culinary Arts Labs, and in Shop areas where large exhaust systems are used for dust collection or fume exhaust.

These units shall be heating only systems in existing Kitchen/shop applications and shall provide 10% less supply CFM than the local exhaust system in order to keep the space at a negative pressure to the rest of the building. Heating shall be provided by Natural Gas when available. The use of other heating types may be used if gas is not available. New construction shall include mechanical cooling.

These systems may be constant volume, as they are only to operate along with the associated exhaust systems. MAU shall be interlocked with the exhaust system and connected to the BAS for monitoring of systems status, alarms and unit discharge temperature.

Pool Dehumidification Units: 

All new pool and replacements for existing pool air handlers shall use a Pool Dehumidification Unit (PDU). This unit shall be specifically designed for use in a pool environment and shall be designed to meet CPS Specifications Section 23 84 16.

• Constant Flow System: A constant flow system is a pumping system which does not include a means of modulating flow at the pumps to address load conditions within the building. Constant flow systems typically only contain three-way control valves or have no means of control valve modulation, such as two position unit ventilators operating in a face/bypass control. Constant flow systems are also utilized in the primary loops of primary-secondary pumping systems in order to maintain flow through a system.
• Primary Secondary: A Primary-Secondary pumping arrangement is one which has two pumping loops to provide heating and cooling to a building. The two loops are connected together via a common pipe. The Primary side of the heating or cooling circuit contains the boilers or chillers as well as the primary pumps. In this circuit, the boilers or chillers heat or cool the water which is circulated around by the primary pumps in a continuous loop between the chiller or boiler and a low loss header. The secondary side of the system contains any items which transfer thermal energy into the rooms or equipment within the building. Examples include: Fan Coil Units (FCU’s), Air Handling Units (AHU’s), Chilled Beams, or Under Floor Heating, as well as Radiators etc. The primary and secondary circuits are connected via a pipe known as the “Low Loss Header”, sometimes referred to as the “Decoupler” or “Common Header”. The primary water flows into this to provide heated or chilled water to the secondary circuits.
• Variable Flow: A Variable flow pumping system may be both a primary only or a secondary pumping system. In a variable flow system the flow of heating or cooling water is modulated to match the usage of the buildings terminal equipment. This modulating of flow is typically based on pressure in the system and care should be taken to confirm that minimum flow rates for chillers and boilers are maintained at all times.
• Dual Temperature Systems: Dual temperature systems are used when the same load devices and distribution systems are used for both heating and cooling. In the design of dual-temperature systems, the cooling design usually dictates the requirements of the equipment and distribution piping. The use of control valves to shut-off water flow to heating only equipment shall be reviewed during the design. In addition, control valve selection for heating and cooling equipment shall be reviewed to ensure proper operation during both modes of operation.
• Pumps: The hydronic distribution pumps shall be sized with a full 100% redundant stand-by. In a 2 pump system, each pump shall be sized for the peak calculated flow and pressure loss, not connected flow. In a 3 pump system, each pump shall be sized for 50% of the total fluid flow and full pressure loss. CPS preference is 2 pump design. 3 pump systems require CPS approval.

• Low Pressure: Low pressure steam shall be any steam system below 15 psi. Steam piping shall be run outside of public spaces whenever possible. Pitch piping uniformly down in the direction of steam flow at 0.25 inches per 10 feet of pipe. Piping shall be sized in accordance to ASHRAE Fundamentals.
• High Pressure: High pressure systems shall be any system operating at 15 psi or greater. All high pressure piping shall remain outside of public space and be limited to the Boiler Room and Mechanical spaces/utility corridors. Piping shall be sized in accordance to ASHRAE Fundamentals. No new high pressure systems shall be added. There are only a few high pressure systems that still remain in the CPS system. Where possible and when directed by CPS, those high pressure systems shall be converted to low pressure or replaced with hydronic systems. When converting from high to low pressure all pipe sizes, control valves and coils/terminal units shall be reviewed by the EOR to determine which must be replaced/resized in order to provide proper stable heating. Often connections to boilers, the steam header, branch takeoffs, portions of distribution piping and coils terminal units shall be replaced in addition to the removal of remote PRV stations.
• Steam Traps: Only the use of mechanical type steam traps are allowed. Orifice traps shall not be used. Traps shall include a union of flanged connection on both ends. Provide strainer upstream from the trap. Refer to CPS Standard Details.
• Condensate Return: Condensate return shall be provided with either low pressure return units (gravity return) or Vacuum Condensate Pump systems. No new vacuum systems shall be provided; replacement only. Provide duplex pump units. Include terminal strip for BAS alarm monitoring. These items shall be, at a minimum sized as follows (EOR is responsible for all final equipment sizing):
  
  Condensate Transfer Unit (Gravity Return):
  • Total installed HP x .069 = GPM Evaporation rate
  • GPM X 3 (factor for building return) = Condensate transfer pump flow rate
  • 2 x Evaporation rate = 2 x Total installed HP x .069 = Condensate receiver tank size
  
  Condensate Transfer Unit (Vacuum Return):
  • ((Total boiler HP x 33,400) / .8) / 240 Btu/h per SF of Rad = SF of Radiation
  • SF Rad. x Factor (.3 for tight condensate piping & good traps, .5 for average condensate piping & good traps, .75 for poor condensate piping & good traps) = CFM of air pump
  • Based on the CFM, select a standard vacuum return unit which will then indicate the pump and receiver size. The important parameter here is the CFM to create a vacuum to return the condensate to the receiver.
• Boiler Feed: The Boiler Feed system consists of the Boiler Feed Tank and the Boiler Feed Pumps. Additional items associated with the Boiler Feed include Makeup Water Assembly, Inlet Strainer and System Controls. There shall be 2 boiler feed pumps per boiler, both sized for 100% of the load. Provide duplex pump units. Include terminal strip for BAS alarm monitoring. These items shall be, at a minimum sized as follows (EOR shall be responsible for all final equipment sizing):
  
  Boiler Feed Pump:
  • Continuous run pumps (use on boilers >300HP) = 1.25 to 1.5 X Evaporation rate (Appr. 25-30 psig across auto valve plus piping/valve PD) = GPM Boiler feed pump flow rate. (Note 1 Boiler HP = 0.069 GPM of Evaporation).
  • On/Off pumps = 2 x Evaporation rate (Appr. 20 psig PD - 5 psig piping & 15 psig boiler) = GPM Boiler feed pump flow rate. (Note 1 Boiler HP = 0.069 GPM of Evaporation).
  
  Boiler Feed Tank:
  • Number of boilers x HP of boiler = Total installed HP
  • Evaporation rate = Total installed HP x .069= GPM
  • GPM x 30 minutes storage = Boiler feed tank size
  
  Makeup Water Assembly:
  • Capacity = Total of one Boiler Feed Pump for each Boiler
• Water Treatment: Steam System water Treatment shall comply with CPS Specification Section 23 25 00.

• Air Handling Equipment: All units shall include supply and return fans (packaged dx cooling RTUs less than 10,000 CFM may utilize relief fans), coils, filter section, dampers, air mixing sections, and other sections as needed based on the design. Typically, indoor unit return fans shall be in-line mixed flow fans. Additional sections may include energy recovery units as required to comply with code or to meet project energy goals, bypass section and access sections between coil sections. All sections shall include adequate sized access doors (vision glass for indoor units and outdoor units 10,000 CFM and greater), LED marine lights, convenience GFIC receptacle and all required controls sensors and elements. All doors shall be hinged and open against pressure. Each unit shall have proper maintenance space for each section based on manufacturers recommended clearance spaces. Units may share maintenance space in a Mechanical space.
• Supply/Return/Relief Fans: All fans shall be sized based on the connected air distribution system. EOR shall calculate fan external static pressure requirements for all units (new and renovation) to verify the fans have the proper static pressure and air volume capacity. When available as an equipment option, fans shall be direct drive to eliminate belt maintenance. All fans in VAV applications and direct drive fans shall include VFDs or electronically commutated motors controlled per the sequence of operations
• Fan arrays: Arrays may be provided with project specific approval by CPS. Where arrays are provided, individual fan status shall be monitored by the BAS and a means of closing off a failed fan (backdraft damper, blankoff plate, etc) shall be provided to avoid air recirculation through the failed fan when the unit remains in operation. Single unit centrifugal and plenum fans are the CPS standard.
• Coils: Coils shall comply with CPS Specification Section 23 73 13. All coil locations shall be confirmed to include proper clear space for proper maintenance and removal. Cooling coils shall include properly sloped, stainless steel drain pans with properly sized “P” traps, discharging to the nearest floor drain, or collected for Greywater systems, if applicable. The air velocity across the coil shall be:
• Airflow across chilled water coils: 450 fpm maximum
• Airflow across hot water coils: 650 fpm maximum
• Dual Temperature Coils shall be sized at maximum for chilled water coils
• Terminal Units: All terminal units shall be either single zone, variable or constant volume units, or a fan powered series unit. Avoid fan powered units where possible. CPS prefers to minimize the use of terminal units with motors and filters for maintenance and sound issues. Dual duct units shall only be used in replacement of existing dual duct units. Where possible, dual duct terminals and associated AHUs shall be converted to dual duct vav. All units shall include DDC controls. Heating coils shall be provided as required. Terminal units shall not be located above/in learning spaces (classrooms, etc.) and storage rooms (units become inaccessible for maintenance). Maintain all clearance requirements recommended/required by unit manufacturer and controls provider. Refer to CPS Specification Section 23 36 00 for additional requirements.
• Zoning: Provide multiple air handlers within a complex rather than a single larger unit to better meet scheduling needs for the different types of spaces. Displacement ventilation may only be used with prior written CPS approval.
  
  Typically separate air handling units are provided for the following zones:
  • Gymnasiums/Lockers
  • Aquatic Centers
  • Cafeterias/Dining/Servery/Kitchens
  • Auditorium/Stage (Large auditoriums may have a separate unit for the stage and seating area.)
  • Administration Areas (Often 1st floor administration and educational spaces are combined into a single system. When possible, provide a separate unit for administrative spaces to allow for off hour operations when other spaces are not in use.)
  • Educational Spaces. Multiple units may be used based on the school area and space layout.
  A Zoning diagram shall be included along with the Schematic Design Narrative.
• Exhaust Fans: Exhaust fans shall be roof mounted if possible. If inline fans are used within the building, verify there is a proper point of discharge from the building. Upblast fans shall be used for all Kitchen or other food service exhaust; chemical resistant centrifugal utility set fans with 10’ vertical extension shall be used for fume hood exhaust. All fans shall include a damper (motorized for fans greater than 300 CFM, no dampers for fume hood and Type 1 kitchen hoods), bird screen and roof curb. Refer to CPS Specification Section 23 34 23 for additional requirements.
• Trash Compactors: Avoid locating indoors. This has been a source of odor issues within schools as buildings often have pressure issues causing the odors to spread throughout the facility. If the unit must be indoors, provide a dedicated room that can be independently exhausted and held under negative pressure. Provide a pressurized vestibule separating this space from the reset of the building. Coordinate with all trades.
• Exhaust Hoods: Exhaust hoods shall be used on a limited basis where required by Code. The most common use of hoods is within the Kitchen. A Type I hood (heat with grease laden vapors) shall be used for all cooking equipment where there is potential of fire due to grease usage, as per Code. Type II hoods (heat with/without moisture laden vapors) shall be used in all other situations, including Warming Kitchens and Receiving Kitchens. Cooking hoods shall be UL 710 compliant/labeled. Cooking hoods shall include temperature/infrared sensors for automatic operation/modulation where required by Code. When modulation is required, smart hood controller, hood exhaust fan/make-up air fan VFDs and bacnet interface card shall be provided with hood. Coordinate with CPS Nutrition Support Services. Obtain list of available points to map into BAS during design and review with CPS. Locate room supply air diffusers as recommended by hood manufacturer to ensure supply air does not negatively impact hood capture. Hoods may also be used in some Shop areas where the equipment and process in use will generate excessive fumes that cannot be contained any other way. This may include welding and soldering stations or painting areas within an Auto Shop. Independent Living Classrooms with residential ranges/ovens shall utilize residential style ducted exhaust hoods (not recirculation type) above each appliance with manual OFF/LOW/HI speed settings.
• Building Pressure: All buildings shall be designed to maintain a positive building pressure to limit infiltration of outside air. An Air Balance Table shall be included in the design drawing to show a minimum of 10% positive pressure (air supplied vs air exhausted) within each building.
• Carbon Dioxide (CO2) Monitors: Monitor carbon dioxide concentrations within all densely occupied spaces (25 people/1000 sf minimum) or as required by Code. CO2 monitors shall be between 3 and 6 feet above the floor. CO2 monitors shall have a visual indicator and include demand control sequence for associated terminal units and associated AHU/RTU. The BAS shall monitor sensor PPM levels and alarm when zone value exceeds setpoint; initial setpoint shall be 900 PPM. Demand control ventilation sequences shall include a manual graphical button on the BAS to enable/disable active demand control ventilation. ASHRAE recommends temporarily turning OFF demand control during a pandemic (COVID-19, etc.).

Split Systems: Split System Heat Pumps shall be used where supplemental cooling only is required. As these systems do not offer the ability to provide Code required outdoor air, any occupied space requiring supplemental cooling shall receive its required flow of outside air from a separate system. The outdoor portion of the Split System shall be placed on the roof if possible. Any other location needs to be approved by the Project Design Manager and CPS. The indoor fan coil shall be placed above or within the ceiling unless that is not possible.

These systems are not required to be connected to the BAS, however, if the unit has a BACnet connection available, it shall be monitored for status, alarms and room temperature. A room temperature sensor shall be provided and connected to the BAS to monitor and trend space temperature, with an alarm set up for prolonged time outside of set temperature range.

• Split Systems: Split Systems shall be used where supplemental cooling is only required. As these systems do not offer the ability to provide code required outdoor air, any occupied space requiring supplemental cooling shall receive its required flow of outdoor air from a separate system. The outdoor portion of the Split System shall be placed on the roof if possible. Any other location is required to be approved by the Project Design Manager and CPS. The indoor fan coil shall be placed above or within the ceiling unless that is not possible.
  
  These systems are not required to be connected to the BAS, however, if the unit has a BACnet connection available, it shall be monitored for status, alarms and room temperature. A room temperature sensor shall be provided and connected to the BAS to monitor and trend space temperature, with an alarm set up for prolonged time outside of set temperature range.
• PTAC Units (CPS approval required on a project by project basis for use): Packaged Terminal Air Conditioners (PTAC) shall be used in areas that are required to have access to cooling year round and require low levels of outdoor air. Typically, these shall be thru wall units, mounted close to the finished floor level, and only placed in small office spaces. Units shall include an outdoor air damper and heating coil, utilizing the building hydronic system or electrical resistance heating. If required, system may be heat pump type for additional heating based on the load of the space.
  
  These systems are not required to be connected to the BAS, however, if the unit has a BACnet connection available, it shall be monitored for status, alarms and room temperature. A room temperature sensor shall be provided and connected to the BAS to monitor and trend space temperature, with an alarm set up for prolonged time outside of set temperature range.
• Window AC: Window units shall only to be used as replacements for existing units on major renovation projects, where the addition of central cooling of the spaces in question cannot happen for some reason.

• Finned Tube/Radiators: Finned tube/Radiators shall be avoided wherever possible due to vandalism/damage from students, low heat output due to low condensing hot water supply temperatures, and lost wall space that could be used for future teaching aids/shelves. Typical applications include large curtain wall areas. If approved by CPS on a case by case basis, the associated control valve shall work in conjunction with the local air system zone controller and BAS. The system will modulate to maintain space temperature. Coordinate elements and covers with the AOR.
• Radiant Panels: Ceiling/Wall Radiant panels shall be avoided wherever possible due to low heat output when utilizing condensing boilers. Where approved by CPS on a case by case basis, possible locations may include: public toilet rooms along exterior wall or with roofs directly above, and curtain wall areas if supply water temperature if adequate for effective heating. At approved locations, the associated control valve shall work in conjunction with the local air system zone controller and BAS. The system shall modulate to maintain space temperature. Coordinate elements and covers with the AOR.
• Unit Heaters: Unit heaters shall be provided in all spaces requiring supplemental heating, especially where there is a lack of ventilation or forced air systems. This included Vestibules, points of entry for the building, Mechanical and Electrical Rooms, and exterior spaces.
  
  All cabinet type unit heaters shall be recessed within the wall or ceiling. Suspended unit heaters shall be located based on unit throw to achieve complete coverage of the area or point of cold air entry.
  
  Recessed/wall mounted unit heaters shall have local stand alone integral vandal proof thermostats. Cabinet Unit Heaters shall include stand alone controls with remote programmable thermostats and vandal proof covers. Suspended unit heaters shall include remote mounted programmable thermostats with vandal proof covers.