Provide chiller packages with centrifugal compressors, or screw compressors, and water cooled condensers.
Design the chiller plant with at least two chillers if the total capacity is more than 400 tons. Size one chiller for 1/3 of the load and the other chiller for 2/3 of the load.
Include equipment KW/Ton and APLV values in a selection criteria.
Basic Equipment Requirements
The equipment shall be furnished as a complete factory assembled package, including hermetically sealed compressor, variable speed drive and motor, evaporator, condenser, lubrication and purge systems, capacity controls, instrumentation and control panel, power and control wiring, refrigerant piping, full charges of R-123 or R-134a.
The control package on the chiller must be capable of controlling chilled and condenser water pumps, the cooling tower, and interface to the building automation system via the BACnet or LON control protocols.
Chiller room ventilation is required in accordance with the Uniform Mechanical Code and ASHRAE 15. Include refrigerant sensors, control systems, only required for HCFL or HFC refrigerants and air handling equipment in any existing chiller rooms to be upgraded to bring them in full compliance with current codes.
The equipment shall be rated in conformance with the latest ARI Standard 550-88 and shall conform to the latest ANSI/ASHRAE 15 Safety Code.
The condenser and evaporator shall also conform to the ANSI B9.1 Safety Code for mechanical refrigeration and to the ASME Code for Unfired Pressure Vessels where applicable.
Electrical components and assemblies shall bear the UL or ETL label, where applicable, and electrical requirements, including control requirements, must be coordinated with available utilities.
The starter may by unit mounted or free standing, but shall be designed specifically for the characteristics of the chiller and shall be furnished with the chiller by the chiller manufacturer.
The temperature control system shall be provided with interface devices and a terminal block to allow remote adjustment of the chilled water temperature set point.
Equipment selection, including evaporator and condenser size and configuration, shall be based on the chilled water system requirements. Coordinate the choice of chillers and system requirements to provide the optimum selection of equipment vs. flow rates, temperatures and temperature changes.
Provide computerized analyses from the manufacturer for at least three different selections. Data should include part load performance in kW/ton based on ARI 550 test conditions, including condenser water relief in 10% increments from 10% to 100% of machine capacity. Base selections on 0.0005 fouling factors for both the evaporator and condenser.
Specify that cooling towers shall not be filled until chemical treatment is operational and that only treated water shall be used in the system.
Isolate the cooling tower from all pipe flushing and cleaning operations.
Use only induced draft cross flow cooling towers located on the roof of the building. Forced draft cooling towers and cooling towers located at grade are not acceptable to OSU.
Towers shall be constructed of non-combustible materials.
Cooling towers to be selected for maximum efficiency at the selected operation point and are to be sized for an additional 20% capacity.
Equalizer connections between basins shall be specified on multiple open evaporative tower applications. Equalizer connections and piping between tower basins shall be separate from any other piping systems. Evaluate the impact of sound upon surroundings.
Cooling towers shall meet the following minimum criteria:
The towers shall be factory assembled, induced draft, cross flow type with a vertical air discharge.
The basin and casing up to the top of the fill shall be constructed of 304 stainless steel.
The casing above the fill shall be constructed entirely from fiber reinforced plastic or stainless steel panels supported by a fiber reinforced plastic or stainless steel angle and channel framework; all finished inside and out with zinc achromatized aluminum.
The basin shall have a connecting weir for equalization of water level and a by-pass connection. A brass, float-operated make-up valve shall be provided complete with a large diameter plastic float, arranged for easy adjustment. The float valve is to be sized for the worst possible conditions of basin fill rate.
Basins shall be provided with provisions for a winter bypass to the sump when the system is expected to operate during winter conditions.
Basins must have a bottom outlet with a strainer and an anti- cavitation device. Do not select a side outlet configuration.
Inlet louvers shall be of fiberglass or galvanized steel construction, and equipped with inlet screens.
The fill material shall be PVC and have a flame spread rating of 5 per ASTM Standard E84-77A and shall be impervious to rot, decay, fungus, or biological attack.
Drift eliminators shall be constructed of PVC and shall limit drift to less than 0.2 percent of the total water circulated.
Fans shall be a fixed pitch, heavy duty, cast aluminum, multi-blade type, protected by a fan guard and each driven though a gear box or power belt reducer by a TEAO (totally enclosed, air over), 1800 RPM, motor, ball bearing type designed specifically for cooling tower service. The motor shall be the high-power factor and high- energy efficient type and have non-fused disconnects located at the motor. The motor shall be furnished with special moisture protection windings, shafts, and bearings. The fan and shaft shall be supported by re-lubricatable ball bearings with special moisture seals, slingers, and housings designed to prevent moisture accumulation. Provide a vibration cut-out switch.
Access doors shall be provided on both sides of the tower for access to eliminators and the plenum section. Safety railing and a ladder shall be furnished with a tower unit requiring a fan and drive service above the fan deck, and shall meet OSHA requirements. Units capable of being serviced from within the unit shall be provided with an internal galvanized steel catwalk for service access.
Lubrication points are to be provided with appropriate lubrication fittings.
Furnish electric immersion heaters factory installed to prevent freeze-up conditions. Include factory installed thermostats and controllers.
Furnish vibration isolator rails for vibration control. Consult with the sound consultant for requirements.
Specify single stage centrifugal pumps for water service.
Horizontal, base mounted, end suction pumps with a common forged or cast, steel base frame (not welded), are preferred for applications up to 1,000 GPM.
Horizontal or vertical split case pumps with a common steel base are preferred for applications larger than 1,000 GPM.
Select the pump motor horsepower for non-overloading conditions.
Small circulation pumps must be a maintenance free type.
Pipe mounted pumps must have a cast iron volute.
Basic equipment requirements
All water service pumps shall be of bronze fitted cast iron with mechanical seals of the carbon-ceramic type.
Impellers shall be bronze, enclosed, statically and dynamically balanced, and fitted to the shaft with a key and locked in place. Motors and impellers shall be easily removed without disassembling the piping.
Specify 1,750 RPM motors. Avoid using 3,500 RPM motors. Motors shall be the premium-efficiency type. Pumps, coupling, and motors shall be factory installed.
The pump shaft shall be fitted with a bronze sleeve and the bearing frame assembly shall be fitted with regreasable ball bearings.
The end suction or split case pump and the motor shall be connected with a flexible coupler fitted with an OSHA approved coupling guard. The pump housing shall have gauge and drain tappings.
PUMP SUCTION DIFFUSERS
Suction diffusers should be considered for all chilled and hot water system pumps with capacities up to 2,500 GPM and installed to maintain minimum pump flow requirements at all times.
Basic equipment requirements
The unit shall consist of an angle type body with inlet vanes and a combination diffuser-strainer-orifice cylinder with 3/16" diameters openings for pump protection.
The orifice cylinder shall be equipped with a disposable fine mesh strainer which shall be removed after system start-up.
A permanent magnet shall be located within the flow stream and shall be removable for cleaning.
The unit shall be provided with an adjustable support foot to carry the weight of the suction piping.
Pressurized diaphragm type, pre-charged with air to the initial fill pressure of the system shall be located on the return side of closed loop systems. The tank shall be ASME stamped and certified for 125 psi and 240 deg. F. Furnish horizontal tanks with saddles and vertical tanks with base mounts.
Specify strainers in all hot water, chilled water, steam, and condenser water systems. Provide manual blow-down valves for strainers in sizes 1 1/4" and larger. Provide Y-type strainers at water supply piping to all chilled water and hot water coils, upstream of all components except the last isolation valve. Size the mesh for service. Provide valving, and allow space to remove and clean the strainer basket or mesh.
Use Y-type strainers for up to 8" diameter. For larger sizes, use basket-type strainers.
WATER FLOW MEASURING STATIONS
Use a pitot tube or Venturi type and specify stations complete with a portable readout meter. Locate the meter in the piping at a point where proper upstream and downstream distances are observed so that accurate readings can be obtained. Differential pressure taps for the meter readout shall be located on the horizontal centerline of horizontal pipes.
Specify stations with shut-off valves and quick disconnects for the portable meter.
Specify air separators in all hot and cold water closed loop systems.
Air separators shall be the centrifugal type complete with removable strainers, drains and support legs or brackets.
Provide an automatic air vent with separator assemblies.
Specify a "Petes Plug" to be installed in piping at the inlet and outlet of all water coils, heat exchangers, chillers, pumps, and at all ports of water coil temperature control valves.
Water treatment systems shall be provided for all open circulated systems requiring a continuous supply of make-up water. The chemical treatment system shall be automatic in operation and shall continuously monitor and control pH, conductivity, and the corrosive tendency of the recirculated water. Chemicals shall come in a solid concentrated form and be specifically formulated for the water on the OSU campus.
All closed loop chilled water and hot water circulating systems shall be provided with chemical feeders across the appropriate pumps.
Specify system components to be furnished by a single supplier. Components shall include, but not be limited to, the following:
A pre-wired control and instrumentation panel mounted in a NEMA 12 enclosure with a key-lock door with a window.
A water meter for monitoring make-up water quantity.
An automatic bleed valve.
Chemical feed pumps (positive displacement type).
Corporation stop and injection assemblies.
Chemical feeding tubing.
Solid concentrated chemical.
Acceptable manufacturers: Chem Aqua, or an equal.
The piping systems shall be designed in accordance with the guidelines established by the latest edition of the ASHRAE Fundamentals Handbook.
Welders must be certified in accordance with the American Welding Society Standard Qualification Procedures.
Refrigerant piping installers must be certified under Oregon Mechanical Specialty Code Chapter 11.
A factory trained representative of special items or systems must provide field instruction to the installers.
The piping shall be routed as directly as possible and sloped for venting and draining. Where possible, use routing to accommodate thermal expansion requirements. Locate pipes, vales, and accessories to be readily observable and accessible for modification, maintenance, or repair, except when concealed in finished areas.
Piping runs, manifolds, and connections to equipment should be arranged so the operation and function of the systems and their components are easily understood.
CONNECTIONS TO EQUIPMENT
Arrange pipe, valves and accessories for ease of operation and maintenance. Every item of equipment and every assembly such as pressure reducing stations and flow control/measuring stations shall be provided with isolation valves; a balancing valve equipped with a memory stop may be used as the downstream valve if appropriate. By-pass loops with balancing valves shall be provided where it is desirable to keep the system in operation during shutdown.
Flexible connections shall be provided at equipment to allow for minor misalignment. Vibration elimination connections shall be provided where required. Rigid pipe supports shall be provided on the "outboard" side of flexible connections and vibration eliminators. Avoid strain on equipment.
Provide clear access to all heat exchanger bundles of chillers, boilers, heat exchangers and coils for cleaning, removal or replacing individual tubes. Route connecting piping to clear access space or provide flanged connections to allow minimal removal of piping to gain clear access. In general, the clear access shall be provided at one end only of the heat exchanger bundle.
Where it is not possible to accommodate expansion and contraction by the general routing of the pipe, expansion loops must be used.
Take special care in providing for adequate expansion.
Proper pipe guides are imperative at expansion loops and devices.
Locate properly designed anchors that control the way expansion occurs to ensure the effectiveness of routing devices and to prevent undesired movement at connections to equipment, where pipes are close to structure, etc.
VENTING AND DRAINING
Piping shall be pitched to allow for proper automatic venting of all system high points and manual or automatic draining of all system low points. Use eccentric reducers as required. Provide manual shut-off valves for maintenance of automatic devices.
Extend the vent or drain piping, if required, to allow installation of valves and assemblies at convenient service locations. Extend vent discharge piping to a safe location; extend drain discharge piping to a floor drain or other appropriate location such as the condensate return system for steam traps.
Provide vacuum relief’s at coils, heat exchangers, and other heat transfer devices as required.
HANGERS AND SUPPORTS
Specify hangers and supports with special considerations for vertical piping and connections to equipment. Use vibration eliminating hangers for piping near pumps, fan coil units, and other dynamic equipment for vibration-sensitive applications.
Provide seismic restraints to meet local codes. Use SMACNA Guide restraints where applicable. Attachments to the building structure must be adequate and shall be detailed and/or specified.
Pipe, valves, and accessories "in-board" of flexible connections at vibration isolated equipment must be supported from the equipment inertia base or otherwise isolated with the equipment without putting undesirable stress on the equipment.
In addition to local connections to equipment, provide piping systems with isolating valves to facilitate maintenance and minimize the extent of the system that must be shut down for repairs, modifications, or expansion. In general, provide an isolation valve, ball, gate or butterfly, at all pipe header connections to eliminate total system drainage during future piping modifications.
The valve pressure rating must be a minimum of 1.5 times the working pressure of the system served.
Pipe valve fittings and accessories shall be of good quality. To ensure quality, specify piping by ASTM, AWWA, or other appropriate standard; specify ASME ratings for valves and list brand names as a standard; specify fittings by ANSI or another appropriate standard.
All materials must meet applicable codes. Where standards may not be sufficient to ensure the quality desired, specify a brand name as a means of establishing the quality level. Whatever method is used, be specific. Include pipe joint materials and methods in the specifications.
CLEANING AND TESTING
After installation, all systems shall be properly cleaned by flushing with an appropriate liquid or gas before installation of valves and final connections to the equipment. After flushing, closed heated and cooled water systems shall be cleaned by circulating a solution of trisodium phosphate or a similar agent before the final flush and fill. Untreated water and all cleaning and water treatment chemicals shall be approved by EH&S by going through the OSU Project Manager.
Isolate the cooling tower from all piping flushing and cleaning operations to prevent untreated water from entering the basin.
Before their final acceptance all strainers, drip legs, and similar items shall be thoroughly cleaned.
All tests must be observed by OSU’s Project Manager. In general, test systems at 1-1/2 times the highest system operating pressure for 24 hours.
Any tank for chemicals which may enter the sewage system will be located so it can be easily charged and serviced.
Refrigerant piping to be purged with dry N2 during brazing, and pressure tested using dry N2.
DIRECT BURIED PIPING
Refer to Section 33 63 13 – Underground Steam and Condensate Distribution Piping