Environmental Chambers Guidelines
Current PDF Version of This Guideline
Walk-In Coolers, Freezers, Warm Rooms, Incubators
- Noise levels inside the chamber may not exceed 80 dBA.
- Specify environmental cold rooms furnished as a complete functional unit.
- Assembly: All metal and other materials shall be shaped and sized as required with all angles sharp and true. All surfaces shall be finished smooth. Punching and shearing shall be neatly done. Permanent connections shall be riveted or bolted. All exposed welds shall be ground smooth and flush with adjacent surfaces. Welded connections in stainless steel shall be polished to match adjacent stainless steel.
- Panel Construction: The room shall be constructed of prefabricated metal skinned urethane panels, with exterior surfaces constructed WHITE STUCCO GALVALUME, interior surfaces of stainless steel. The panels shall be constructed of high quality components with 100 percent of each panel exclusive of its metal supports as being comprised of urethane insulation. Panels shall have tongue and groove construction with vinyl stripping fitted on the exterior and interior of each panel to provide moisture and vapor tight gasketing. Each of the rooms corners shall be performed 90 degree angles. All construction shall comply with Factory Mutual Standard 4880 for insulated wall construction. Contractor shall furnish filler panels of matching metal to extend from the exterior of the chamber walls to the building walls and lay-in ceiling. Insulation in the panels shall be a minimum of 4 inch thick rigid, poured in place, urethane foam. Foam core of panels shall be Underwriters Laboratories certified as having a flame spread of 25 or lower when tested in accordance with ASTM E-84-76. Panels shall be approved by Factory Mutual as a Class 1 building type. They shall not use CFC, HCFC or HFC blowing agents. Insulation shall remain stable at an operating temperature range of –67 to 94 degrees C (non-humidified). Panels – including floor panels – must be constructed not using any wood materials and must be all metal panel and structural support.
- Floor: The floor panels shall be clad in the interior with stainless steel and the exterior with GALVANIZED and utilize 4” thick urethane insulation. The floor panels shall be able to withstand loading to 600 pounds per square foot.
- Door: The door shall be fitted flush with a minimum free span of 36 inches wide and 78 inches high with the same material finish and insulation as adjacent walls. Anti condensate heater wiring shall be concealed behind the (removable) metal edge of the door jamb on all four sides. Heaters shall be connected to a temperature control to provide sufficient heat to prevent the formation of condensation and frost at various temperature and humidity conditions. The door shall utilize a minimum of two hinges of the spring loaded self closing type with plated steel pins and Delrin cam type bearings. Designer shall consider preference to have cam action rather than spring action. Hinges and latches shall be suitable high strength steel and not “pot metal.”) The door latch shall be designed to open the door easily by breaking the force of the magnetic door gasket. The door shall be able to be opened with an easily accessible pull handle. The latch shall have a cylinder lock, keyed to match existing lockset, (PK 625 KEY number) and include provisions for padlocking. The latch shall also include an inside safety release handle. Door interior/exterior materials shall be equal to adjacent panel construction.
- Observation Window: Provide a manufacturers standard, heated observation window. The window shall consist of three panes of glass with sealed vapor spaces between them. Window shall be 14” x 24”.
- Pressure Relief Port: Pressure relief ports shall be utilized for all chambers operating at -10 degrees C or lower.
- Chamber Size: The exterior size of the chamber shall be as large as possible fitting in the free area of the building location. The Contractor shall verify the free space available after the completion of the site preparation by the University and General Contractor.
- Painted Finish: Finish shall be factory applied baked on enamel/polyester. Paint shall be chemical resistant and odorless. Paint shall be sprayed on and not applied with a roller or a brush to achieve a uniform texture and appearance. Paint thickness shall be a minimum of 1 mil. Color shall be white.
- Electrical Receptacles: Receptacles shall be corrosion resistant track type. (must be Hospital grade and have gasketed covers) Receptacles shall be 8 inches above bench surface and shall be on 12 inch centers along the entire length of the bench. Receptacles shall be fed by TWO separate 20 amp, 120 volt circuits each feeding every other receptacle, with two circuits per side of enclosure, connecting to panel indicated on the drawings.
- Sleeves/Pass-throughs Ports: Sleeves for service piping, refrigerant lines, cables and drain water lines shall be cylindrical in cross section, formed of 1/8 inch or 3/16 inch PVC and sealed to chamber from both ends with silicone sealant. The void between the service line and the sleeve inside and out shall be sealed with a sealant that remains flexible. Caps shall be provided to seal pass-throughs used for equipment line passage when not in use. Provide flange on both sides of pass-through for cap to slide onto.
- Ceiling Grid: Lay in ceiling grid shall be provided on a 2 foot by 2 foot perforated Lexan lay in ceiling grid supported by 1.5 inch by 1.5 inch anodized aluminum tees to form a positive pressure plenum at the chamber roof with return air duct or plenum below the ceiling grid to the chamber floor area.
- Single point electrical connection with lockable overcurrent protection and disconnection means.
- Automatic main power overcurrent protection and independent overcurrent protection for the fans, heaters control circuits, steam heaters dryers and receptacles.
- All control and switch functions clearly labeled with non-fading polycarbonate labels and thus no stamping of silkscreen markings that wear off. Panel labels shall be logically organized for ease of operation.
- Removable laminate covered side panels for protection of main control panel housing. Access panels shall be color coordinated with building color scheme and shall be replaceable if damaged.
- Durable non painted brushed stainless steel fronts for impact resistance and durability. These panels shall be lockable and hinged for convenient access when servicing the control panel.
- Lockable acrylic view window to prevent unauthorized to control and alarm set points.
- Anodized aluminum interior construction with offset mounting rails to produce a natural cooling plenum behind the control panel for heat dissipation.
- Low power level switching and indication for longevity of switches and indicators.
- Accurate and NIST traceable temperature sensing hermetically glass sealed platinum Resistance Temperature Detectors (RTD).
- Central wiring location and grouping for efficient trouble shooting.
- Plug-in components where feasible.
- Specify control panel mounting height of 72” maximum to top of panel. Mount on the latch side of the door to prevent damage from door openings.
Provide refrigerated dehumidification integrated into the pressurized supply air plenum. Electric reheat dehumidification will NOT be accepted. Capable of maintaining chamber relative humidity at 60% when operated at 4° C with accuracy of +/- 1%. Humidification during high temperature operation shall not be required. The system shall control humidity through a microprocessor based digital controller with readout in percent RH. The RH sensor shall be a variable capacitance sensor or a hygroscopic plastic foil sensor, temperature –compensated and calibrated over the entire range of the chamber. The sensor shall be located within the chambers airflow to provide maximum sensitivity and fast response to changes within the chamber. Wet bulb/dry bulb, lithium chloride, gold grid, bulk resistance or similar sensors shall not be acceptable.
- Unit and all system components shall be designed for operation on 134A Refrigerant for coolers designed for 0-10 degrees Celsius and 404A for operating below 0 degrees Celsius. Unit shall be designed for operation on building electrical power. A single 120 volt power supply shall supply power to the control console, the chamber receptacles, lighting.
- Locate condensing units behind or beside the chamber in a chase or mechanical room providing sufficient access on all sides, to facilitate maintenance. DO NOT LOCATE CONDENSING UNITS ON TOP OF CHAMBER. Preferred location is 28” above the floor unless there is room for maintenance and repair and approved by UNC’s Refrigeration Shop.
- A fully proportional modulating refrigerant valve on the hot gas line shall be used for capacity control.
- The condensing unit shall be designed for continuous operation to maximize compressor life, eliminate on/off cycling and minimize RF interference. False loading of the compressor to cause continued operation will NOT be allowed. Unit shall be provided with a modulating water flow valve to regulate head pressure. Provide cleanable shell and tube heat exchanger.
- Provide service lighting and 120V receptacle for service and repair of condensing unit outlet located on the same level and within 10 ft of the condensing unit.
- The compressor/condensing unit shall be linked to a matching evaporator designed to maintain the specified operating conditions. The condensing unit shall have a single point electrical connection point and shall be connected to an appropriate disconnect switch provided by the Chamber contractor.
- Sub Assembly Quality Control: The above mentioned sub-assemblies: condensing unit, evaporator, and plenums, shall be evacuated to <500 microns and held for > 5 hours prior to precharging with 150 PSIG of dry nitrogen. The unit shall be tagged with the dry nitrogen charge pressure, ambient temperature, date and the testing technician’s initials. Units shall be shipped with the test charge in tact and pressures evaluated after installation. Upon start-up, unit shall be evacuated of nitrogen and charged with the proper refrigerant charge. Evacuation shall be witnessed by UNC Refrigeration Shop.
- Chamber Dehumidification: Chamber shall be equipped with dehumidification capabilities which utilize a refrigerated dehumidification coil designed as an integral part of the evaporator plenum. This dedicated coil will be housed inside of the evaporator plenum for condensate removal to a double wall stainless steel drain pan system. The dehumidification coils will be provided with specific valving to obtain the temperatures necessary to maintain the required humidity levels for the chamber. The control shall be through a separate solid state microprocessor based digital controller mounted on the control panel. Dehumidification by desiccant or refrigeration and reheat shall not be acceptable.
- Temperature Fluctuation: Room temperature swing during normal operation with the door remaining closed shall be less than ½° C.
- Temperature Range: All chambers shall be designed to operate AND PERFORM AS ABOVE at any setting between 0 to 10° C.
- Uniformity: Room temperature shall remain uniform within +/-2 degree C. for 24 hours and tested with a multi port recorder with at least 12 sensors over the entire range of operation (0-10 degrees C.) Specify that test results are to be submitted to the University.
- Capacity: The refrigeration system and all related components shall be capable of maintaining the temperature within the specified limits without operation at full capacity more than 80 percent of the time.
- Humidity Control: The chamber shall be designed to be capable of lowering the relative humidity to 65% during low temperature operation. Humidification during high temperature operation is not required.
- Training: The manufacturer shall provide 1 day (8 HRS) of onsite training for the preventive maintenance, calibration, repair and operation of the chambers. The manufacturer shall also include at least one seat in their factory training school for each chamber supplied to the university at no charge. To be used as university work load permits.