DPW_Design_guidelines_for_AC.DOC

DPW DESIGN GUIDELINES FOR AIR CONDITIONING & VENTILATION SYSTEMS

Below are mechanical design guidelines for air conditioning and ventilation systems for US Army Garrison, Hawaii, DPW. All new construction and renovation projects shall have as a minimum the following where applicable:

1. All air conditioning units to include roof top air conditioning units and air handlers shall have continuous high output ultra violet (UV) lamps on the downstream side of the cooling coil for improved air quality. Continuous high output UV-C energy prevents microbial growth, fungus and mold, eliminating odors and allergy-causing irritants and will keep the cooling coils and drain pans clean. DPW has many problems with mold, mildew, and keeping the cooling coil and drain pan clean at Schofield Barracks, Wheeler AAF, Helemano, and other U. S. Army facilities and this addition will definitely cut down this problem. Designers should coordinate the electrical engineer for a separate disconnect for the UV-C emitters, which normally uses 120 volts, single phase power.

2. All air handlers shall have 2” double wall construction with solid galvanized steel inner casing.

3. All three phase motors of one horsepower and larger shall be premium efficiency electric motors. This will apply to all air handling units, fans, pumps, etc.

4. Provide a duct thermometer (0ºF to 100ºF) in the supply air duct of each air handling unit and roof top air conditioning unit so that maintenance personnel can check the supply air temperature to see if the unit is operating properly.

5. All pressure gauges and thermometers exposed to the weather shall have either a stainless steel casing, aluminum casing with an epoxy coating, or chrome plated brass case with stainless steel ring and be weatherproof.

6. All chilled water and condenser water pumps shall have a nameplate attached to the bedplate with the GPM, head, and impeller diameter information.

7. All pumps exposed to the weather shall have TEFC electric motors.

8. PVC pipe shall not be used for chilled water piping especially for underground pre-insulated pipe.

9. All air outlets shall be of aluminum or plastic. Steel air outlets will corrode after awhile because of the high humidity.

10. All DDC building and energy management systems shall be native BACnet; no gateways allowed.

11. In the future, all DDC building and energy management systems shall be tied in to the central DDC building and energy managment at DPW headquarters.

12. All training shall have as a minimum at least 40 hours devoted to classroom instructions and one or two days of on-site training. A detailed written sequence of operation manual that will also be used as a training manual shall be provide for each student attending the training with another two copies supplied to DPW as extras.

13. Provide a pressure gauge at the inlet and discharge of each pump.

14. Provide a strainer upstream of each pump and a check valve downstream of each pump (Sump pumps shall not have a strainer).

15. Provide a standby chilled water pump and standby condenser water pump for each chilled water plant that has these pumps. This will provide redundancy in case one pump is out for either system.

16. Provide a water pressure reducing valve with pressure gauge for the cold water makeup for any chilled water system downstream of the reduced pressure backflow preventer. The pressure gauge shall be downstream of the pressure reducing valve.

17. Inlet guide vanes and fan discharge dampers for air handling units or roof top air conditioning units are not allowed for use in variable air volume (VAV) systems as they fail easily and are noisy during operation. Use variable speed drives. DPW has many buildings with inlet guide vanes where they have become frozen and inoperable. For systems with 10,000 cfm and below using forward curve fan wheels, riding the fan curve is acceptable and no variable speed drives are required. For all other types of fans (BI and AF) and systems above 10,000 cfm variable speed drives shall be used.

18. Comply with US Army TI 800-01, paragraph 7c(4) dealing with “Chilled Water Systems” where it states that the cooling capacity of chilled water systems of 350kW (100 tons) and over will be divided between two or more chillers to ensure reliability and constant chilled water supply without temperature fluctuations, to prevent short cycling, and to minimize hot gas by-pass.

19. For packaged equipment below 10 tons and below, a single compressor unit is acceptable. Above 10 tons, units shall have a minimum of two compressors with independent refrigerant circuits; for units using more than two compressors, a maximum of two compressors may be on one circuit. Up to 100 tons, a unit shall have no more than four compressors.

20. Equipment Procurement: Use the following language in the General Mechanical specification section or in the body to the technical mechanical specification section “The equipment shall be furnished by a factory authorized supplier within a distance of 500 miles of the installation site which shall include but not limited to: (a) Replacement units up to 10 tons; (b) Adequate replacement parts inventory of compressors, indoor fan housings, wheels, shafts, bearings, condenser fan blades and motors, factory OEM accessories such as circuit breakers, relays, timers, and microprocessor controls unique to the manufacturer; (c) Factory trained engineers to provide field support and training (minimum 10 years experience); (d) local warranty administration to expedite warranty issues in a timely manner.”

21. Provide solid state phase monitor relay or internal phase monitor for every separately mounted three phase motor to prevent phase failure and phase reversal damage to the electrical motors.

22. Provide a reverse phase and phase failure relay for every motor control center (MCC). Wire this unit into the primary circuit serving the control center through properly selected fuses. Upon a detection of a 10% phase unbalance or a reverse phase condition, all motors stop. Provide a green pilot light located on the starter section labeled “Power Normal”. When a power failure occurs on any phase, light is de-energized and rings an alarm located in the motor control center. This panel is not required for starters with internal phase monitor.

23. Factory Coatings

· All air cooled condensing unit, air cooled water chiller, air cooled condenser and all outdoor packaged unit casings shall have a baked powder coated finish capable of withstanding a minimum 5,500-hour salt-spray test, in accordance with ASTM B-117

· All air cooled condensing unit, air cooled water chiller, air cooled condenser, and all outdoor packaged unit shall be provided with copper tube/aluminum fin condenser coils with either a factory applied epoxy-phenolic coating or locally applied aluminum impregnated polyurethane protective coating. Either coating shall be capable of withstanding a 4,000 hour salt-spray test, in accordance with ASTM B-117 and a 4,000 hour acid-salt spray test, in accordance with ASTM B-287. The total dry film thickness of the coating shall be a minimum 1 mil (25 microns). Locally applied protective coating shall provide a 3-year conditional warranty for the coating.

24. Condenser Water Treatment Systems [1] The condenser water treatment system shall be chemical free. The system shall do the following:

· Mitigate scale, corrosion and bio-fouling without discharge of tower water or chemicals.

· Shall have zero tower blowdowns.

· Shall permit operation with high TDS.

· Shall have corrosion and scale inhibition at up to 150,000 TDS tower water.

· Shall be capable of monitoring 24/7 assuring performance and reliability.

· No chemical handling and storage allowed.

· No scale shall form on heat transfer surfaces.

· Heat transfer efficiency shall not be reduced in any way.

25. Insulation

All chilled water, hot water and reheat water piping, and all ductwork shall be insulated per Unified Facilities Guide Specification for Thermal Insulation for Mechanical Systems. The R values for the insulation shall follow the latest requirements per the latest version of the International Building Code. It is preferred that the chilled water pipe insulation not be fiberglass but cellular glass or better. Polyurethane is acceptable for pre-insulated piping.(E)

All insulated piping exposed to the weather shall have an aluminum or PVC jacket. All insulated ductwork with outside wrap and exposed to the weather shall have a galvanized or stainless steel outer shell or have an aluminum jacket. No ponding will be allowed on the top of any ductwork. Aluminum foil is not allowed.

Rubatex insulation shall not be used on any type of piping, pipe fittings, and ductwork. Only in instances where access to a valve, strainer, etc. is required for maintenance will Rubatex be allowed.

26. Piping

Condenser Water

In most cases, the condenser water piping is an open loop. Condenser water piping is not required to be insulated since there will be negligible heat gain or loss and sweating will not occur. If the piping is exposed to cold ambient conditions, however, it shall be insulated and heat traced to avoid freezing.

Condenser water piping shall be pressure tested to 1-1/2 times working pressure and held for 24 hours. Allowances for temperature rises/falls shall be factored into the higher/lower pressure readings.

All condenser water piping shall be flushed until the effluent is clean and contains no visible particulate matter. Clean all strainers upon the completion of flushing.

Chilled Water

All chilled water piping is required to be insulated. Chilled water piping shall be pressure tested to 1-1/2 times working pressure and held for 24 hours. Allowances for temperature rises/falls shall be factored into the higher/lower pressure readings.

All chilled water piping shall be flushed until the effluent is clean and contains no visible particulate matter. Clean all strainers upon the completion of flushing.

Any type of “plastic” pipe shall not be used for chilled water carrier piping especially for underground pre-insulated pipe. Carrier pipe shall be steel or copper. This shall include PVC, HDPE, PE, etc. Outer jacket can be HDPE or PVC.

Reheat Water Piping

All reheat water piping is required to be insulated. Reheat water piping shall be pressure tested to 1-1/2 times working pressure and held for 24 hours. Allowances for temperature rises/falls shall be factored into the higher/lower pressure readings.

All reheat water piping shall be flushed until the effluent is clean and contains no visible particulate matter. Clean all strainers upon the completion of flushing.

Refrigerant Piping

Refrigerant piping, valves, fittings, and accessories shall be in accordance with ANSI/ASHRAE 15 & 34 and ASME B31.5. Refrigerant piping, valves, fittings, and accessories shall be compatible with the fluids used and capable of withstanding the pressures and temperatures of the service. Refrigerant piping, valves, and accessories used for refrigerant service shall be cleaned, dehydrated, and sealed (capped or plugged) prior to shipment from the manufacturer's plant.

Copper tubing shall conform to ASTM B280 annealed or hard drawn as required. Joints shall be brazed except that joints on lines 22 mm 7/8 inch and smaller may be flared. No compression fittings allowed. Cast copper alloy fittings for flared copper tube shall conform to ASME B16.26 and ASTM B62. Wrought copper and bronze solder-joint pressure fittings shall conform to ASME B16.22 and ASTM B75M ASTM B75. Joints and fittings for brazed joint shall be wrought-copper or forged-brass sweat fittings. Cast sweat-type joints and fittings shall not be allowed for brazed joints. Brass or bronze adapters for brazed tubing may be used for connecting tubing to flanges and to threaded ends of valves and equipment.

Underground Piping

All underground chilled water and reheat water piping shall be preinsulated piping. The carrier pipe shall be black steel, copper or HDPE. The insulation shall be polyurethane or polyisocyanurate foam and the exterior jacket shall be HDPE or PVC. All joints shall be supplied by the manufacturer of the preinsulated pipe. Acceptable manufacturers are Thermacor, Perma-Pipe or approved equal.

27. Metal Ducts

All metal ductwork shall be manufactured and installed per the latest SMACNA standards. The pressure drop shall be less than or equal to 0.07 inches H20 per 100 ft of ductwork. Provide a manual volume damper with locking quadrant at each duct branch that is tapping off the supply main.

No plenums are allowed in any Army facilities. All supply, return and outside air shall be ducted.

28. Filters

Air filtration elements shall be listed in accordance with UL 900, except that high efficiency particulate air filters and carbon absorbers shall meet the requirements indicated.

Filter racks shall have an access door to remove the filtration element and replace it with another. Access doors shall be double-wall insulated type and fully gasketed to the filtration system housing. Each access door shall be rigid and provided with at least four tie-down latches (with locking hasps).

29. Diffusers, Registers, and Grilles

Noise levels shall not exceed those published in the ASHRAE Guide for the type of space being served (NC level). Air distribution devices shall be fully compatible with the surface in which they are installed and shall be provided will all required mounting accessories for installation in the actual construction at the installation location. All ceiling and wall mounted air devices shall be painted white or off-white unless specified otherwise and all air devices shall be the same color.

Provide diffusers with corrosion resistant treated surfaces and finished off-white baked enamel unless otherwise specified, scheduled, or shown on the Drawings. Provide opposed volume control dampers with supply air diffusers where scheduled. Where applicable, provide adapters with diffusers to permit connection to round supply duct.

Provide registers which contain opposed blade volume damper operable from the face side, unless scheduled otherwise. Supply air registers shall be of the double deflection type, unless otherwise scheduled.