explosion proof air conditioning 

 

       Birdwell

      BIRDWELL MODEL BTBVD

      WALL MOUNT AIR CONDITIONING SYSTEMS

      WITH VARIABLE DAMPER PRESSURIZATION PACKAGE

      INSTALLATION, OPERATION, AND MAINTENANCE INSTRUCTIONS

       

      INTRODUCTION:

      Birdwell environmental control units were originally designed for world-wide use on offshore oil drilling and producing platforms. In approximately twenty years of use in this harsh environment, the rugged corrosion resistance and reliability of the systems were proven to be significantly superior to units that were designed for commercial and residential use. Since that time, users such as refineries, steel mills, chemical plants, pulp and paper plants, ocean going vessels and others having similar problems with corrosion and/or hazardous conditions have found the Birdwell environmental control systems to be tough and dependable.

      The fundamental guidelines used in designing the systems were unrestricted serviceability and ease of installation. Also of prime importance were reliability, safety and resistance to corrosion. As a result of this criterion, many believe these to be the finest units available for the intended market.

      All cabinets and other sheet metal parts are constructed of not less than 16 gauge Type 304 stainless steel (Type 316 stainless optional). Parts most subject to corrosion such as drain pans and exterior grilles are also furnished in stainless steel as standard. Coil coating options include high bake phenolic or epoxy-ester. The units are available in several explosion proof configurations. For a complete list of standard features and options, see the applicable brochure.

       

      RIGGING AND PLACEMENT:

      Provide a wall opening for the supply/return-air throat sleeve. Allow 1/4" for clearance. Make sure the opening is squared. See product drawing for unit dimensions and installation details.

      Install foam gasket material around the sleeve to seal between the sleeve and the wall.

      The unit may be bolted to the wall using the wall mounting angles and (if deemed necessary) set on a user supplied support frame. In any case, be sure the wall anchoring system or the support is of sufficient strength to support the unit weight.

      NOTE: The unit should not be mounted directly on a concrete pad. Pre-trapped 3/4" FIPT drain connection is located on the bottom of the unit.

      The packaged, self contained BTBVD unit has lifting eyes at the top for convenient handling. If the lifting eyes are used to position the unit, attach wire rope slings to the lifting eyes. Lift slightly to check level and security of slings. To mount the unit, position the air throat directly in line with the wall opening. The unit must then be moved very carefully in a horizontal direction to slip the air throat through the opening.

       

      POSITIONING:

      Unit condenser air inlet and outlets may be located in any direction as the unit is not affected by wind direction. Provide adequate clearances around and above the unit for unrestricted air flow, safety and service access. Do not locate the unit near exhaust vents or other contaminated air sources if the pressurization system air inlet is near this location.

      NOTE: If external static pressure port is located where it can be affected by prevailing winds, erratic pressure readings may result. Parallel ports may be required.

      The standard system is provided with a clean air stack connection box on the left side on the unit with an 16" diameter ring mount flange on top.

      The system may be ordered with an optional 16" diameter matching ring flange stainless steel or paint grip steel fresh air stack in various lengths, with rain cap and bug screen.

       

      INSTALLATION:

      CAUTION: Before making any electrical connections or performing any maintenance, make sure all power switches pertaining to this equipment are turned off and locked. In addition to the danger of electrical shock, the fan motors have internal overload protection that could restart a fan without warning and cause serious injury! Also, before energizing any of the electrical equipment or making the initial start up of the pressurization system, make certain the ambient atmosphere is safe (non-hazardous). Although the pressurization blower motor is suitable for the hazardous area, other electrical equipment in the indoor section of the unit have arc making devices (relays, contactors, switches, etc.) that could ignite a flammable gas. This procedure should be observed any time the system has been off and must be restarted.

      Provide two separate power sources to the unit, as indicated on the wiring schematic: one for the pressurization/purge circuit and one for the air conditioning circuit. The voltage and amperage requirements are noted on the data plate.

      If a gas detection system is used, field connect the two wires shown on the schematic to an across the line switch to energize the safety shutdown relay in the controller.

      After the electrical power to both the pressurization and the air conditioning circuits have been connected and tested, flip the power disconnect or breaker to the "on" position. If the building is not immediately pressurized (with all openings such as windows and doors closed), check the rotation of the pressurization blower(s).

      Consult local codes or ordinances for specific requirements regarding installation and the termination point of the condensate drain. If the unit is in a hazardous (classified) location, the drain must be extended to a safe location to preclude the possibility of the trap drying out in the heating season and allowing the entrance of contaminated air.

       

      ELECTRICAL:

      Field wiring must comply with the latest applicable articles of the National Electrical Code and the requirements of the United States Coast Guard in the case of offshore drilling/producing platforms or oceangoing vessel use. Wiring should be performed only by a qualified electrician.

      In hazardous locations install and pour seals between the unit and all connecting conduit. Refer to articles 500 and 501 in the National Electrical Code for specific requirements.

      Size conductors using the data supplied on the nameplate. Use only stranded copper conductors. Be certain the available voltage matches the data on the nameplate. A disconnecting means must be within sight and readily accessible from the unit.

      The unit must be securely grounded to the grounding lug provided in the main control panel.

       

      DUCTING:

      The duct system (if required) should be installed in accordance with the American Society of Heating, Refrigerating And Air Conditioning Engineers, Inc. (ASHRAE) standards.

      NOTE: External static pressure (ESP) loss should not exceed 0.1" WC.

       

      AIR CONDITIONING SECTION OPERATION:

      The single compressor Birdwell Model BTBVD series of air conditioning units are single packaged self contained systems. These systems are designed for one stage cooling and optional one or two stage electric heating.

      After the unit, ductwork, fresh air stack, and power supply wiring have been installed, set the thermostat system switch to the "off" position. Switch the pressurization / purge circuit power "on" after referring to the "caution" paragraph under the installation heading. And, after it has been determined that the area is "safe" for operation, switch the air conditioning circuit power "on".

      If compressor has crankcase heater, do not start unit during cold weather for a period of twenty-four hours to allow time for the heater to vaporize any liquid refrigerant that may have accumulated in the crankcase during storage. CAUTION: Failure to observe this precaution could result in serious damage to the compressor valves and/or bearings. After the twenty-four hour period has elapsed, the unit may be started in the cooling mode.

       

       

      AIR CONDITIONING SECTION START UP PROCEDURE:

      This procedure should be performed only by a qualified air conditioning technician.

      Step 1: Double check the voltages supplied to both the pressurization circuit and air conditioning circuit to insure that they match the data plate requirements.

      Step 2: Check the pressurization / evaporator blower motor(s) for correct rotation.

      Step 3: Set the thermostat system switch to the "cool" position.

      Step 4: Set the thermostat to a setting slightly below the indoor temperature, then check to see if the compressor is running.

      Step 5: At this point amperage readings should be taken on the compressors and motors to confirm that they match data plate ratings.

      Step 6: Set the thermostat system switch to the "heat" position (if the unit has this option).

      Step 7: Set the thermostat above the room temperature, then check to see if the heat is operating.

      Step 8: Set the thermostat to desired mode of operation (heat or cool), then set for the desired operating temperature.

       

      AIR CONDITIONING SECTION MAINTENANCE:

      NOTE: All maintenance should be performed by a qualified air conditioning/heating mechanic.

      MOTORS All fan and blower motors on the system are the sealed bearing type and permanently lubricated, therefore no maintenance of the motors is required.

      BLOWERS The blowers and fans on the standard units are direct drive, so there are no belts to service. It is recommended that at least once a year (more often in very dirty locations) the blower wheel be inspected and cleaned if necessary using a wire brush and vacuum cleaner.

      FILTERS Filters should be checked at least once per month or more frequently in dirty air conditions and cleaned or replaced as necessary.

      COMPRESSOR The compressor is hermetically sealed and factory charged with oil, therefore no maintenance is necessary.

       

      CONDENSER/ The condenser coil should be cleaned at least once a year

      EVAPORATOR (possibly more often in dirty locations) using a good commercial

      COILS coil cleaning agent. This is very important to maintain top efficiency and to prolong compressor life by keeping operating pressures within normal limits. The evaporator coil should be inspected at the same time and cleaned in the same manner if needed.

      CONDENSATE The condensate drain pan and drain line should be checked and

      DRAIN cleaned a minimum of once yearly, or more often if found to be necessary.

      REFRIGERANT The system is factory charged with refrigerant and should not re-

      CHARGE quire adjustment. The sight glass will show some bubbling in very hot or very cold conditions and is not necessarily indicative of a need for additional refrigerant.

      If at any time the system should need an addition of refrigerant, it should be added very carefully and only by qualified personnel. Use only refrigerant 22!

      NOTE: Whenever maintenance is being performed on this equipment whereby the refrigerant system may be opened up to the atmosphere, proper procedures for handling system refrigerant must be followed according to the Environmental Protection Agency (EPA). Please refer to Title 40 of the Code of Federal Regulations, Part 82 for EPA regulations.

      If the system is low on refrigerant and still has considerable pressure, the entire piping circuit should be checked and the leak located and repaired before any refrigerant is added.

      If the system is completely void of pressure, it should be pressurized, the leak located and repaired, then a new liquid line drier be installed.

      After this is done, a good vacuum pump should be connected to the system and a run for several hours to remove any possible moisture that could be present. After the vacuum has been pulled, weigh in the proper charge according to the data on the nameplate.

       

      PRESSURIZATION SYSTEM INTRODUCTION:

      The variable damper pressurization package was designed for minimum maintenance and to meet the National Fire Protection Association, Inc. Standard 496 for Purged and Pressurized Enclosures for Electrical Equipment in Hazardous (Classified) Locations.

      The pressurization package is an intregal part of the self contained air conditioning unit and contains the following components: 1) make-up air inlet stack box (fresh air stack optional); 2) air throat sleeve extension with supply-air diffuser (or duct connection), return-air grille, and pressurization control panel; 3) pressure controller; 4) differential pressure transmitter; 5) motorized opposed blade damper assembly.

      Building pressure is created and maintained by injecting or forcing fresh air from the outside into a building with all doors & windows closed. A positive pressure will occur when the air from the outside exceeds the building leak rate. The amount of make-air taken in is regulated by restricting the return-air inlet - full restriction results in 100% outside air intake. The evaporator blower(s) serve a dual purpose, in that they are used for both bringing in outside air for pressurization / purge, and for recirculating the air conditioned inside air.

      A safety shutdown relay is provided in the gauge/alarm enclosure to deactivate the air conditioning and general purpose controls in the event of gas detection. The gas detection equipment and the electrical connections between the two items are to be provided by the customer.

       

      CONTROLS:

      The pressure gauge is the Magnehelic type. Pressure range is 0.0 to 0.25" WC with an accuracy of two percent of full scale at 70 degrees F.

      The pressure switch operating range is .07 to .15 inches WC.. An alternate explosion proof pressure switch with an operating range of 0.4 to 1.6 inches WC. is used for some Class II applications.

      Time delay relays are the solid state type.

      The safety shutdown relay is single pole double throw 24 volt plug in type. The optional remote alarm relay is single pole double throw type. The optional local alarm bell can be either general purpose or explosion proof (depending on area classification).

      If the system is ordered for standard Class I, Division I (type "X" purging) duty, the off/on switch, the indicator lights, time delay relays, control relay, and optional relays are installed in an explosion proof NEMA 7 enclosure. In addition, the explosion proof motor is wired using mineral insulated cable.

      If the system is ordered for standard Class I, Division II (type "Z" purging) duty, the motor is wired using liquid tight conduit and fittings.

       

      SCOPE OF OPERATION:

      The desired building pressure measured in inches/water column (" WC) is pre-set at the factory (0.15" WC) in the pressure controller. A differential pressure transmitter is used to monitor the building pressure and send instantaneous electrical signals to the controller. The controller compares the set point with the current reading, and converts the difference into a modulating (+ or -) electrical output to a motorized damper motor. When the current reading is higher than the set point the return-air damper starts to open, thereby reducing the amount of make-up air. And, likewise when the building pressure is low the damper starts to shut, thereby increasing the amount of make-up air. The controller sensitivity determines the frequency which the signal is reversed, therefore is factory set to maintain minimal pressure fluctuation.

      The pressure switch is preset to meet the National Fire Protection Association’s 496 code requirement of 0.1" WC. For alarms apply power to pressurization fan to purge

      building; continue purging building until hazardous atmosphere inside building has been removed. After building is purged, turn system switch (located on the pressurization control panel) to the "on" position.

      If the building pressure is at, or above, the predetermined pressure set point (factory set for 0.15" WC), the green light will be energized to indicate normal pressure

      If the building pressure is not at the desired level, check for open doors, windows, and other sources of building leakage; also verify pressure controller set point.

      When clean air (free of hazardous concentrations of flammable vapors and gases, contaminants and any other foreign matter) is induced into the fresh air inlet of the Birdwell pressurization unit, the fan will introduce only enough air into the building (with all doors closed) to provide a positive pressure while making up for normal leakage around doors, etc.

      Should this leakage suddenly increase (as when a door is opened), the motorized damper automatically closes resulting in 100% air from fresh air intake. This minimizes the possibility of contaminated (possibly explosive) air from entering the building. Simultaneously, the red warning light is energized to indicate building pressure loss.

      Should the door remain open, or for any other reason the building loses the predetermined pressure level for a time period of 20 seconds, the optional alarm bell will be sounded or optional relay contacts closed for user’s remote alarm system (type "Z" purging). Or in case of type "X" purging, the contacts may be used to terminate power to the control room.

      NOTE: If any problem is encountered that is not covered in these instructions, or for any question that might arise, call The Birdwell Company in Houston, Texas: (281) 492-1786.