Division 15 Mechanical
- Provide access doors for all maintenance items above inaccessible ceilings and into inaccessible walls. If necessary, fire rated access doors shall be used to preserve wall fire rating.
- Locate roof hatches equipped with ladder or near a wall with a permanent ladder installed on wall.
- Accessible doors to crawl spaces shall be located as close as possible to mechanical equipment under floor.
- Locate filter boxes and other maintainable equipment outside of critical areas served, such as operating rooms, so that items can be serviced without disrupting operations in the room or releasing contaminants into space.
- Locate humidifiers, fan coil units, terminal boxes, and other equipment containing water over hallways rather than occupied or critical spaces wherever possible. Where necessary to locate such equipment over such spaces, provide secondary drain pans.
- Provide adequate roof access wherever serviceable equipment is roof mounted.
- Provide control air compressor/filter-dryer for each building. Utilize plant control air where available as a redundant backup.
- In atriums or other multi-story open to roof areas, maintenance and accessibility should be a consideration when mounting fans, lights and other equipment above the floor.
- Primary manufacturer/model number to be specified for various types of mechanical equipment is specified herein. Provide a minimum of two additional and equivalent valve manufacturers and model numbers for each primary manufacturer and model number listed.
- Provide bound, indexed operation and maintenance (O&M) manuals. Manuals shall be organized by systems and fully indexed by equipment type. Must contain original manufacture’s bulletins and manuals, copies are not acceptable.
Pipes and Pipe Fittings:
- ABS piping is unacceptable.
- Do not install heating hot water or other similar service piping susceptible to freezing in overhanging soffit areas.
- Include sufficient zone isolation/shut off valves in cold/hot water, heating hot water, chilled water, steam and other service piping to allow maintenance and replacement of terminal equipment without shutting down entire building.
- Install valves on all lines that penetrate the floor from below.
- Install valves on all branch lines off of main lines.
- Install valves on all lines at locations such that each floor can be isolated independent of main building.
- Any equipment such as showers, darkrooms, etc., requiring mixing of hot and cold water shall utilize a pressure compensated mixing valve rather than a temperature compensated mixing valve.
- Install control valves where they can be reached from the floor where possible. If above a ceiling tile, then identify the location with a small label on the ceiling tile.
- Include a valve schedule on the construction documents that describes type and location of valve.
- Avoid use of gate valves. When possible use ball valves.
- Provide sufficient air vents in chilled and hot water piping systems to easily bleed entrapped air.
- Pipe chases should be provided in sufficient size to accommodate maintenance personnel (at least three feet wide). Do not locate pipe chases in custodial closets.
Provide differential pressure indicator (manometer) for all serviceable filters and locate the indicator where it can be readily observed. Mark on the indicator the "clean" and "replace filter" points.
- Provide parallel stand-by pump for all primary pumped building systems, such as chilled water, heating and domestic hot water, etc.
- Pumps shall be Bell & Gossett or equal.
- Avoid designing custom variable speed drives in panels. Provide standard, readily available surface mounted VSDs.
- Mark location of air handlers, fan coil units, mixing boxes, etc., above ceilings with identifying "buttons" to facilitate maintenance through ceiling.
- Tag roof top exhaust fans and associated fume hood to facilitate maintenance and identification.
- Utilize standard tag or placard to mark all major equipment. Tag all valves and provide valve chart for each floor.
- Utilize standard Commonwealth of Virginia color coding for various building service piping and ductwork. Mark each with name of service, direction of flow, and associated unit served where appropriate.
- All systems handling hazardous materials must have appropriate marking and visual or audible alarms to protect building occupants and maintenance personnel. Mark exhaust fans on roof which handle hazardous fumes with appropriate color code.
- Mark air handling units with large letters and numbers.
- All fire dampers shall be numbered and identified on chart in mechanical room.
Mechanical Rooms and Equipment Locations:
The Architect/Engineer shall, in the earliest stages of design development, be responsible for establishing and/or verifying programmatic requirements for mechanical rooms in order to:
- Provide adequate safe access and manufacturer’s recommended working clearances for all equipment.
- Provide for replacement of the largest piece of equipment without removing permanent walls, large items of equipment or equipment essential to the principal on-going day to day building use.
- Provide direct access from the exterior for major mechanical rooms exceeding 100 net square feet.
- In phased projects mechanical rooms shall be sized to include equipment for all the phases.
- Air handling units, zone control devices, such as VAV boxes, mixing boxes, reheat coils, etc., shall also be located and installed to provide unobstructed access to filters, manual valves, zone control devices, replacing motors, and automatic control equipment.
- Mechanical rooms shall be ventilated by a thermostatically controlled fan.
- Mechanical rooms shall have a floor drain.
- Access to ducted fan coil units on occupied floors shall be from corridors, rather than through offices, classrooms, laboratory ceilings, or other occupied spaces.
- The installation of any air handling units with cooling coils above the ceiling level shall include an emergency drain pan installed beneath the unit. This emergency drain pan shall be piped so the occupant can detect any condensate that collects in the emergency drain pan. Such a flow tube should terminate ½ inch below finish ceiling and match the finish of the ceiling.
Outside air intakes shall not draw in exhaust air from adjacent systems, loading docks, parking lots, emergency generators, chemical storage, sewer manholes, etc.
All air conditioning shall use chilled water. Glycols and other heat transfer fluids shall only be used in limited systems such as heat recovery loops, or thermal storage systems which serve only a single central station AHU. Use only after specific approval by CPCC.
Water-cooled condensing units using domestic, potable water on a single-pass cycle are prohibited.
Installations shall be complete with dryers, sight glasses, thermostatic expansion valves and thermostatically controlled solenoid valves for pump-down operation (except for capillary tube units). Refrigerant liquid and suction piping shall be type “K” hard-drawn copper. Suction lines shall be insulated. The need for defrosting is not limited to electrical units. In larger installations, hot gas defrost is required. Installation shall be provided with necessary protective devices, including, but not limited to, electrical overload devices, low suction-pressure cutouts, oil traps, crankcase heaters, anti-cycling timers and head pressure control.
Main piping fittings for dryers, sight glasses, expansion valves and controls shall be flared. A nitrogen purge shall be maintained while soldering all joints. Copper-to-copper joints shall be evacuated to 29.5 inches (water) gauge vacuum and held for at least 24 hours under this vacuum prior to charging the system with refrigerant. Refrigerant shall be approved by Plant Services.
Cooling Coil Condensate
- Cooling coil condensate shall be piped to sanitary drains.
- Pumped condensate systems shall not be used.
- Cooling coil condensate lines shall have cleanouts which allow access of all branches of the condensate drain system.
- Cooling coil condensate lines shall be minimum 1 ¼ inch ID.
- Lines less than 1 ½ inch shall be copper instead of PVC.
The Architect/Engineer shall coordinate with the Owner as to the required specifications for chemical cleaning and equipment to be furnished by the Contractor. The chemicals to be used by the Contractor for the specified initial treatment shall be furnished by the Owner. All chemical treatments shall be performed by the Owner after systems have been cleaned, flushed, and filled.
After cleaning and chemically treating the HVAC system, the Contractor shall furnish CPCC in writing, the following information:
- Date of initial treatment
- Type of chemical(s) used for treatment
- Estimated date that further treatment or testing will be required.
Piping and HVAC insulation should be provided in accordance with the NC Building Code.
Fire Protection Systems
- In buildings with sprinklers, fire pumps and/or standpipes, separate water service for fire protection shall be provided, and shall not be through the domestic metered water service. Also provide a separate meter for irrigation water service.
- In all buildings with fire alarm systems, all control valves, including post indicator and wall indicator valves, shall be electrically supervised by the fire alarm panel. At all locations that control valves are concealed above ceilings or behind access doors, a sign shall be provided on the ceiling below the valve or the access door indicating the location of the control valve.
- Control valves shall only be installed in corridors, stairwells, mechanical rooms, fire pump rooms and sprinkler valve rooms and shall be easily accessible. The control valves shall be accessible with the use of no more than a six foot stepladder. Provide 24” x 24” access door for valves located above inaccessible ceiling types.
- Control valves shall not be installed, above or below ceilings in classrooms, offices, or conference rooms.
- Each control valve shall be supplied with a sign indicating the area of the building that is served by the valve.
- At all locations that inspector test valves (ITV) are concealed above ceilings or behind access doors, a sign shall be provided on the ceiling below the valve or on the access door indicating the location of the ITV.
- Inspector test valves shall only be installed in mechanical rooms, corridors, stairwells, fire pump rooms, sprinkler valve rooms and custodial closets and shall be easily accessible. The ITV’s shall be accessible with the use of no more than a six foot stepladder.
- Inspector test valves shall not be installed, above or below ceilings, in classrooms, offices, conference rooms or in any area requiring entry through a classroom, office, or conference room.
- Inspector test valves discharge shall be piped to a drain capable of handling the discharge at full flow or to the exterior of the building.
- Drain valves shall only be installed in corridors, stairwells, mechanical rooms, fire pump rooms and sprinkler valve rooms and shall be easily accessible. The drain valves shall be accessible with the use of no more than a six foot stepladder.
- Drain valves shall not be installed, above or below ceilings, in classrooms, offices, conference rooms, or in any area requiring entry through a classroom, office, or conference room.
- Main drains discharge shall be piped to the exterior of the building.
- Auxiliary drain valves discharge shall be piped to a drain capable of handling the discharge at full flow or to the exterior of the building.
- In addition to building code requirements, in buildings more than two stories tall, all stairways that have an exterior exit shall be provided with standpipes and fire department hose valves on each level.
- Fire control systems shall be compliant with the CPCC FMCS (Facility Management and Control System) and/or approved by the Facilities Services Division, Maintenance.
- Floor Drains; Installed in all restrooms, centrally located with floor slightly sloped toward drain, 4" inlet with 2" outlet, chrome plated brass or nickel bronze.
- Water Closet; Watersaver vitreous china, wall hung, siphon jet, elongated closet bowl with an integral automatic flushing sensor device equal to “AutoFlush”, chrome finish, battery operated, easily installed, 3-year warranty (Technical Concepts, 1-800-551-5155).
- Urinals also shall have automatic flushing. Automatic flushing sensor equal to “AutoFlush”, chrome finish, battery operated, easily installed, 3-year warranty (Technical Concepts, 1-800-551-5155)
- Faucet; Provide a countertop mounted automatic faucet, chrome finish, ADA compliant, battery powered with a top mount sensor, equal to “AutoFaucet” with a 3-year warranty (Technical Concepts, 1-800-551-5155).
Drinking Fountain; provide recessed drinking fountains in main public areas. Provide surface mounted or semi-recessed drinking fountains in other areas. Provide an alcove in the corridor to prevent the surface mounted drinking fountain from protruding into the corridor.
Service Sink: Floor mounted, cast iron or steel with baked enamel covering, acid/chemical resisting plastics, concrete or stone construction material; 28" maximum height from floor to rim, 24" x 24" (minimum size); Faucet - vacuum breaker, integral stops, spout with pail hook and nose end, top single brace, renewable units and valve seats, equal to Eljer 749-1200 or 749-1400.
Drain and waste lines shall be selected for chemical resistance and heat resistance where steam is used as a laboratory medium.
- Shut off valves are required on each floor, on take-offs from all vertical risers, and at the connection to each piece of equipment.
- Dielectric fittings shall be used with connecting piping of dissimilar metals.
- Drain valves shall be installed in accessible locations at all low points in the piping system to permit drainage and servicing.
Heating, Ventiliation, and Air Conditioning (HVAC)
- Indoor design conditions for cooled & heated spaces shall be 74°F dry bulb & 50% relative humidity for summer and 68°F dry bulb for winter. Summer outdoor design temperature shall be 91°F dry bulb and 74°F wet bulb. Winter outdoor design temperature shall be minus (-) 10°F. Design altitude shall be 2150 for all design calculations.
- Design quantities of outside air for ventilation of occupied spaces shall be as per current ASHRAE requirements.
- Ventilation rates (No. of air changes) for spaces such as restrooms, mechanical rooms, etc. shall be as per current ASHRAE requirements.
- Provide adequate freeze proofing for all air handling equipment with high percentage of outside air. Provide coils that can be drained.
- Provide stand-by or redundant equipment, cycled or alternating lead-lag sequence for critical needs (e.g. standby compressors on refrigeration for food storage).
- Use dual independent refrigeration circuits on HVAC equipment where available, particularly when serving critical areas.
- Utilize semi-hermetic compressors rather than hermetic compressors for all HVAC/refrigerant equipment larger than 10 nominal tons, where available.
- Provide minimum 5 year parts and labor warranty on HVAC compressors.
- Any new or renovated building containing more than one chiller shall have a primary/secondary chilled water pumping system.
- Aluminum tubing in HVAC coils is unacceptable.
- All air handlers and fan coil units shall be located with provisions for sufficient space to service units, (e.g., change filters, sheaves, bearings, motors and coils, lubricate components and replace belts).
- Provide high-limit on steam humidifiers to prevent spraying liquid condensate into duct system.
- Avoid water coils and piping in rooftop air handling units.
- All cooling towers shall be of the induced draft (draw-through) type.
- Air handling unit fans should be specified to mid-range speed instead of near maximum. (Units are coming apart at high speed). Units should be sized so the motor will be smaller horsepower than the maximum allowed for fan size.
- Specify variable frequency drives instead of vortex dampers for air flow volume control.
- Piping and conduit shall be run parallel and perpendicular to building structure (walls, ceilings, floors).
- Drain pans in air handling units and fan coil units shall be double layer insulated, tilted in two directions so it will drain no matter how the unit is set.
- All Hydronic Control Valves shall be selected with a minimum close-off pressure capacity of 45 - 50 psig.
Variable Frequency Drives (VFD)
- Variable Frequency Drives. Three manufacturers to specify – ABB, Allen Bradley, and Square D.
- All VFD’s shall be provided with a manual or automatic type constant speed bypass circuit. The bypass circuit shall be provided in the drive enclosure. A harmonic analysis shall be performed by the drive manufacturer based on the system documentation.
- Provide this information as a part of the submittal.
- Provide isolation transformers in a separate enclosure.
- VFD’s shall include input line reactor.
- Provide standard readily available surface mounted VFDs. Avoid custom assemblies.
- Size restroom grilles and diffusers according to State, Federal and local codes for room size, air quality, etc.; Stainless steel, type 304, or aluminum, satin or brushed finish shall be used.
- Use care in locating outside air intake relative to exhausts, vents, or other discharges. Do not locate near loading docks, parking areas, or other vehicular traffic areas.
- Transferred return air for ventilation (second hand ventilation air) is unacceptable.
- Where fume hoods are present, provision must be made for make-up-air, such as hoods being of the "add-air" or "auxiliary-air" design and including a motor operated shut off valve in the exhaust stack.
- All fire dampers shall have access doors.
- Ceiling returns plenums shall not be used. All return air shall be ducted from conditioned building spaces back to air handling units.
- No interior duct insulation (liner) shall be used.
- Duct insulation shall be exterior duct wrap or
- Factory fabricated double, solid, wall insulated duct or
- Factory fabricated double wall with perforated inner wall wrapped with 2 mil thick Mylar then wrapped with insulation.
- All interior air contact surfaces of duct shall be coated with anti-microbial paint. The metal perforations are not to be bridged with paint prior to assembly of double wall ducts. Painting shall not be done after assembly to prevent bridging sheet metal perforations.
- Double wall air handling units, VAV boxes and terminal boxes shall be specified so that no interior insulation is exposed to the air stream.
- All interior surfaces of air handling units (excluding coils, fins and fan wheels) shall be coated with anti-microbial paint.
- Air filtration shall be minimum 80% efficiency for air handling systems serving general classroom and office spaces. This is typically achieved by using a 30 to 40% efficient 2 inch pleat or panel pre-filter and an 80% efficient final bag or rigid box (cartridge) filter.
- Keep air handling equipment clean during construction:
- If equipment is going to be operated during construction, change filters once/month or more often if needed and install filter media over return grilles.
- Keep fan coil units clean by covering inlet and outlet during construction when not in use.
- Building must be turned over to the College upon project completion with clean air handling equipment and duct systems; including a clean set of air filters installed in the air handling equipment and with a quantity of filters for one additional change left in the building.
- Coat interior surfaces of outside air, supply and return ducts with anti-microbial paint. Dampers, turning vanes and extractors shall be painted.
- Interior surfaces of fan coil units, mixing boxes and convectors, excluding coils and fan wheels, shall be coated with anti-microbial paint.
The cooling tower(s) shall be installed on steel structural support in accordance with manufacturer’s installation recommendations. Steel structure must be hot dip galvanized.
The cooling tower(s) shall have the following design criteria:
Provide appropriate guards meeting all OSHA recommendations for all rotating and/or nip points. Do not provide any cross-draft towers.
Acceptable manufacturers shall be Marley, Baltimore Air Coil, Tower Tech or engineered approved equal.
Provide the following submittal data as part of the bid response: dimension drawings and installation information, structural requirements, electrical service requirements, performance data, and a complete description of corrosion protection for steel components. The cooling tower(s) shall be induced draft, cross flow, vertical discharge, draw through type, factory assembled.
Structural components of the tower, including the cold water basin, framework, mechanical equipment supports, casing, hot water basins, fan deck, and fan cylinder shall be fabricated of heavy gauge steel (basin and floor shall be a min. 16 gauge and sides shall be a min. 11 gauge), and be protected against corrosion by G-210 galvanizing, or equivalent, that meets the requirements of salt fog testing in accordance with ASTMB 117. Factory welded components shall be hot-dip galvanized after completion of fabrication to a zinc thickness equivalent of G-210. Cold galvanizing will not be acceptable.
- Minimum 16 USSG galvanized steel
- Cold water basin with side outlet connections consisting of suction, overflow, and drain piping. Heat tape shall be installed on manual sump drain piping.
- Condenser water outlet connections with a clog resistant, lift out strainer with perforated openings sized smaller than spray nozzle orifices, mounted in assemble with an anti-cavitation device.
- Reduce partitions in sump to facilitate filtration.
- Provide single fan propeller type with corrosion resistant cast aluminum blades, adjustable pitch, individually attached to a cast aluminum or cast iron hub.
- Provide hot dipped galvanized steel fan cylinder with close, but adequate tolerance for fan blade tips.
- Provide heavy gauge hot dipped galvanized wire grill type fan guard over fan cylinder.
- Provide fan with vibration switch to de-energize fan in the event of excessive vibration.
Heavy duty roller type bearings integral with gear reducer.
Fan shall be driven through helical gear reducer. Gear reducer shall have synthetic rubber oil seals and shall be designed to require oil changes on five year intervals. Speed reducers employing pulleys and belts shall not be acceptable unless manufacturer warrants such speed reducing equipment to be maintenance free for a five (5) year period.
Motor(s) shall be TEFC, 1.15 service factor, variable torque, and specially insulated for cooling tower duty. Motor shall operate in the shaft-horizontal position and nameplate horsepower shall not be exceeded at design operation.
- Casings shall be heavy gauge steel protected against corrosion by G-210 galvanizing, or equivalent, with lapped joints sealed watertight.
- Provide large galvanized steel access doors located in each end wall casing for entry into the cold water basin and fan plenum area. Access doors shall be operable form inside as well as outside the tower.
- The tower and all its components shall be designed to withstand a wind load of 30 psf, as well as a Zone 4 seismic load, per UBC. Fan deck and hot water basin covers shall be designed for 50 psf live load or a 200 lb. Concentrated load. Fork lift slots shall be provided to facilitate movement at grade level.
- Provide galvanized steel guardrails, handrails and ladder. Guardrails shall be capable of withstanding a 200 lb. Concentrated load in any direction.
Tower fill and drift eliminators
- Tower fill shall be lightweight and manufactured of non-corrosive material.
- Drift eliminators shall be two-pass manufactured of non-corrosive honeycomb type material supported in galvanized steel framing. Maximum allowable drift loss shall be less than 0.2 percent of the water circulated.
- Open gravity type hot water distribution basin using replaceable polypropylene or PVC diffusing type metering orifices. Heavy duty flow regulator valves shall be provided at the discharge into each hot water distribution basin to equalize water flows. These valves shall be disc type with cast iron bodies and stainless steel stems. Valves shall be right-angle type precluding the need for inlet fittings.
- Basin cover(s) shall be removable galvanized steel panel(s) supported by basin sides, top of cover flush with basin. These covers shall withstand loads described in paragraph G (3).
- Tower should be cyclo-sand or similar type filtration. Provide mechanical filtration of water to less than (or equal to) 10 microns. Filter should be auto backwash with easy to change elements and not require more than 10 gpm for backwash cycle.
Provide electric immersion heaters and controls to prevent freezing in the collection basin. One or more stainless steel immersion heaters shall be installed in threaded couplings provided in the side of the basin. A NEMA 4 enclosure shall house a magnetic contactor to energize heaters; a transformer to provide 24 volt control circuit power; and a solid state circuit board for temperature and low-water cut-off shall be provided. A control probe shall be located in the basin to monitor water level and temperature. The system shall be capable of maintaining 40 deg. F. water temperature at an ambient air temperature of –10 deg. F.
Demonstration of Mechanical Equipment
Provide project walk-through, instruction and start-up by Contractor and factory technical representative, where appropriate. Consider video taping instructions for future reference.
In individual buildings, only closed loop systems, such as secondary heating water, shall have chemical treatment (chemical treatment for fluids from central systems will be provided at the heating or chiller plant).