745 Clark Ave. Bristol, CT Toll Free: Fax: General Air Dryer Installation Guidelines and Design Considerations

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1 Page 1 of 4 Subject: Applicable To: General Air Dryer Installation Guidelines and Design Considerations All McIntire Air Dryer Systems 1.0 General This bulletin presents general central office installation guidelines and design considerations for McIntire Air Dryer Systems. The information presented includes heat generating and environmental temperature considerations, sound levels, electrical power requirements, general environmental considerations and related operational and performance design considerations. The information is intended to serve only as a guide since many variables influence and affect the data presented. However, in many cases, this information can be utilized in conjunction with related field experience to provide a sound basis for environmental design criteria, installation practices and selection of McIntire Dryers. In general, air dryers located in clean, well ventilated rooms and with proper electrical power supply will enhance life and reliability. In addition, implementation of preventative routine maintenance procedures will assure reliable, trouble-free service and extend dryer life and reliability. 2.0 Power Requirements The tabular summary of power requirements (Table I), outlines electrical input service including kilowatt consumption. For optimum performance, proper supply voltages are required for maximum operating efficiency and reliability. It is recommended that input voltage variations within 5% of nominal specified values be maintained. Voltage variations in excess of 5% will not only reduce the compressor motor life, but will result in increased heat rejection. The maximum input voltage tolerance should not exceed 10% of the nominal specified air dryer voltage. For installations where the input voltage varies beyond the 10% tolerance, a buck-boost transformer (PN M ) must be utilized to provide the proper voltage. Some older central offices have input power voltages on the order of 245/250 volts. For installations where the building power voltage exceeds 230 volts, we recommend installation of transformer stabilization kits. Call McIntire Sales/Service department for details. 3.0 Sound Level Data The sound level data presented in Table I should be used only as an installation consideration guide. Sound levels are very dependant on many variables such as room size, room acoustics, type of construction, bac k- ground noise, etc. It should be noted that the OSHA limit for an 8 hours exposure is 90 DbA or less.

2 Page 2 of 4 The sound level data are presented for distances of 3 feet and 10 feet from the dryer. A 3 DbA reduction in sound level represents a 50% reduction in sound level as perceived by the human ear. 4.0 Heat Rejection Considerations Air dryers generate a significant amount of heat, most of which is rejected to the ambient surroundings. Calculated heat rejection data is summarized in Table I which also presents recommended ventilation rates of air flow to maintain an ambient temperature rise of about 20 F. The curves on figure I presents approximate ambient temperature rise for an interior room with essentially no forced ventilation or air conditioning as a function of room size (ft 3 ). In most cases, a room area of 300 square feet or more (assuming a 12 foot ceiling; i.e ft 3 ) is adequate for installation of even the largest air dryer without additional cooling. For example, a 25000XE air dryer located in a 30 X 10 X 12 high room will generate sufficient heat to raise the ambient room temperature 20 F. The maximum recommended ambient room temperature range for continuous, reliable dryer operation is 110 F. McIntire air dryers have operated satisfactorily in ambient temperatures as high as 150 F for several weeks. However, the long term effects on dryer reliability and operation under severe ambient temperature conditions are not known. Whenever room size is limited, the following methods of maintaining tolerable room temperatures are recommended: 1. Ventilation via adjacent areas with natural circulation or forced circulation with fans or blowers. 2. Automatic alternation of dual dryer installations. The concept of dual/multiple dryers offers a significant advantage in operational reliability and flexibility and ultimate cable plant protection. Incorporating automatic alternating capability for 2-4 dryers is possible through the use of an alternator. McIntire sells two such devices which offer the following advantages: 1. Provides safety backup capability if one dryer compressor becomes inoperative or if air demand exceeds capability of one dryer or one compressor. 2. Extends dryer life and maintenance requirements. 3. Reduces energy consumption by 50%. 4. Reduces heat rejection in the room by 50%. 5. Reduces sound levels. 5.0 Ambient Environmental Considerations A space of one or two feet between the dryer and the wall should be provided to permit dissipation of heat and permit accessibility. The ambient temperature not only affects life and reliability but also reduces deliverable air capacity. Figure 2 presents the approximate effect of ambient temperature on capacity for the waterseal compressor systems.

3 Page 3 of 4 Ambient pressure (or altitude) directly affects dryer performance by virtue of compressor air intake density variations. A capacity reduction of about 2% per each 1000 feet of altitude above sea level will result. The ambient relative humidity has essentially no effect of the operation of the McIntire air dryers, especially with regard to drying effectiveness at high relative humidities and maintaining sufficient water in the water-seal compressor type systems to preclude low water alarms at low relative humidities. The drying towers in the McIntire units are designed to operate at full design capacity thereby maximizing the water extracted from the ambient air. We have conducted tests at ambient relative humidities on the order of 5-10% without experiencing low water alarms. The routine maintenance procedures are described in detail in our operating manuals. The semiannual maintenance routines can be accomplished in about 15 minutes without taking the dryer out of service. The entire bi-annual routine maintenance can be accomplished in about hours total time. The preventative routine maintenance program will not only enhance and extend life and reliability of a dryer system, but will preclude critical and expensive dryer/cable plant breakdowns. Model Water Ejected Gal/Day PAD/HDS 2500 (Water returned to air as vapor. CAD/PAD 5000 There is no liquid water dump.) 8000XE XE XE XE 3.7 The water ejected from the PAD/HDS 2500 and CAD/PAD 5000 is dispersed in the form of atomized vapor directly into the atmosphere and requires no provisions for disposal. The liquid water ejected from the 8000XE through the 25000XE series dryer must be disposed either in a suitable container or piped into a building drain. Because the water ejected from the XE series dryers is at a pressure of about 25 PSIG, the system can satisfactorily eject water to an elevation of at least 20 feet above the drain point. 1.0 Piping and Air Distribution Considerations The proper sizing, design and arrangement of the central office piping and distribution of the air from the dryer to the cable vault is essential to obtain maximum pressure capability. This is especially true for large cable plant capacity requirements or for significant peak increases in cable demand. The limiting factor in many central offices is the excessive restriction to flow (pressure loss) due to undersized piping and not air dryer capacity. Generally, a low loss feed system from the dryer to the cable vault can be designed such that dryer output can be set at 11 or 12 PSIG to achieve a cable feed pressure of 10 PSIG at the vault.

4 Page 4 of 4 Table II presents data on pressure drop for various size and types of tubing. The data is presented for 100 foot lengths at a air system pressure of 15 PSIG. The data can be extrapolated for lengths other than 100 feet (e.g. for a 200 foot length double the values indicated; for a 50 foot length, half the value). In general, semi-hard or rigid tubing is more desirable to provide sufficient rigidity and safety against accidental damage or heat deformation which can result in either leaks or severe restrictions due to crimping. Rigid schedule 40 ABS plastic pipe or refrigeration copper tubing is recommended. ABS pipe can be installed, assembled and joined very easily using pipe cement. Rigid ABS provides a reliable, low cost, efficient piping system. Copper tubing provides a very satisfactory system but requires soldering and/or expensive compression fittings, especially in the ¾ piping size. We trust the information and data presented here will be useful in defining your installation requirements. We would be pleased to discuss and assist you with your particular installation requirements. Please feel

5 Table I - Dryer Specification Matrix Application Pole-Mount/Outdoor Indoor/C.O. Portable HDS-2500 HDS-2500P PAD-2500 CAD XE 12000XE 17000XE 25000XE Output Capacity (SCFD) Output Pressure (PSIG) Compressor Type Piston Waterseal Compressors (Qty.) Compressor Horsepower 3/4 3/4 3/4 3/ Alarms High Humidity High Outlet Pressure Low Outlet Pressure Low Water Front Compressor Rear Compressor Overload Power Failure Power Requirements Voltage / Phase Current Draw (amps.) Heat Rejection - BTUH Recommended Ventilation (CFM) Dryer Model Ft Ft Dimensions (D" x W" x H") 15x16x37 21x19x44 15x16x37 20x26x42 22x31x50 22x31x50 25x35x56 25x35x56 Net Weight (Lbs.)

6 Table II - Determining Pressure Drop for Various Sizes and Type of Tubing Pressure Drop (PSI) per 100 Foot Length at 15 PSI Inlet Pressure Air Flow (SCFD) 3/8" OD Plastic (.247ID) 3/8 OD Copper (.305ID) 1/2" OD Plastic (.376ID) 1/2" OD Copper (.430ID) 3/4" OD Plastic (.626ID) 3/4" OD Copper (.680ID) CA 3131 Air Pipe (.625ID) Rigid ABS Pipe 3/4" OD (.824ID) Schedule 40 1" OD (1.049ID) 1 1/4" OD (1.38ID) Less than Note: 1. Pressure Drop (PSI) data is rounded off to the nearest 0.1 PSI 2. For each 90 bend or elbow, the change in pressure is 1/10 that of equivalent size of 100 ft. length of tubing 3. For each 45 bend or elbow, the change in pressure is 1/20 that of equivalent size of 100 ft. length of tubing

7 60 50 Room Temp Rise-Deg. F XE 17000XE 12000XE 8000XE CAD-5000 HDS Room Size-Square Feet Figure I-Heat Rise vs. Room Size Ambient Tempurature Percentage Capacity Loss Figure II-Capacity Loss Due to Ambient Temperature