Each car shallbe equipped with two identicalunits to provideHeating, Ventilation and Air Conditioning (HVAC) to the car. The HVAC units shall be removable and self-contained, and shall utilize scroll compressors and R400-series refrigerants forcooling. Temperature control shallbe provided by a microprocessor-based integrated HVAC control systemthat monitors ambient outsideand inside temperatures and adjusts the system’s coolingand heating functions to maintain a comfortable inside temperature and humidity level throughout the range of environmental and climatic conditions identified in PRIIA Specification 305-912. Dampers on the fresh air intake vents shall control the amount of outside air taken in by the HVAC system. To adjustand maintain equaltemperatures on both levels, diversion dampers at each end of the car shall proportion the amount of conditioned air delivered to the upper and lower levels. Heating shall be provided by overhead heat in the HVAC units, with additional heating provided by floor heaters along the base of the side walls in the car interiors. Freeze protection shall be provided on the side door thresholds and all fresh water system components that may be exposed to freezing conditions.
General Requirements The HVAC system shall providea comfortable temperature controlled environment of the interiorareas of all cars as follows: · The cars shall be designed to operate in all environmental and climatic conditions identified in PRIIA Specification 305-912. · The car’s interior temperature, including the engineer’s cab, shall be maintained to the specified value (68°F - 76°F) under all specified circumstances. · The lower level shall receive adequateairflow from the HVAC to maintain the specified interior temperature and be able to restore the interior temperature after the side entrance doors are opened and the interior temperature is impacted by the ambient outside temperature without affecting the upper level temperatures. If necessary, and withcustomer approval, auxiliary duct heaters may be used. · Passenger load shall be assumed to be AW3 for cooling load calculations. · Heat and cooling requirements shall include the opening of both sets of lower level side doors on alternating sides of the car every 15 minutes and held open for 2 minutes, to simulate passenger loading and unloading in all outside ambient temperatures identified in PRIIA Specification 305-912. · Ambient conditions as specifiedand heat lossesdue to train motion shall be includedin HVAC system performance evaluation. · Air flow losses due to door and carbody leakage shall be included in the HVAC system performance evaluation. A microprocessor-based, integrated HVAC system shall be provided. The system shall be designed to maintain the specified interior passenger area temperature and humidity and to also assure adequate interior ventilation. The Contractor shall prepare, and submit for the Customer's approval during design review, a detailed heating and cooling load analysis along with recommended heating, cooling and ventilation capacities. In no case shall the heating capacity be less than 40 kilowatt (kW) not including the forced air control cab heater, nor shall the refrigeration capacity be less than 244,000 BTU/Hr. The HVAC unit manufacturer shall conduct qualification testing to verify that the units provide the design heating and cooling capacity per ASHRAE Standard 37-05. This testing is further discussed in Chapter 19. The HVAC system shall be powered primarily from the 480VAC, 3-phase, 60 Hz supply. The temperature controls shall operate from the 120VAC, 1-phase, 60 Hz supply, and the freeze protection circuits shall operate from the 120VAC,3-phase, 60 Hz supply. The HVAC systemshall be designedto perform at the nominal voltagesand operate withinthe voltage and frequency tolerance ranges specified in PRIIA Specification 305-912. To minimize the effects of motor inrush currents on the head end power system, the controls shall incorporate a method to provide staggered starting of the refrigerant compressor motors. The start up timing shall be set to stagger the startup of the A/F-end unit at least 15 seconds before the B-end unit.
Electric baseboard floor heaters, mounted behind stainless steel guards, shall be provided along both side walls, upper and lower levels. Baseboard heaters shall also be provided in the engineer’s cab in addition to the forced air heater described in Chapter 16. Freeze protection is an essential function of the heating system. Freeze protection shall turn the heaters on when ambient outside temperatures drop below 40°F, and shut off when temperatures rise to 50°F. The HVAC system shall be controlled by a microprocessor temperature control using a sufficient number of temperature sensors to properly regulate heating and cooling in response to temperature changes inside and outside the car. Temperature sensors in the car body shall be located to accurately reflect temperature changes without beingunduly influenced by external heat sources or solar radiation. HVAC system circuit breakers and temperature control adjustment devices shall be located in the electrical locker and be accessible only to the operating crew. Circuit breakers, controls and relays shall be inaccessible to the passengers. The HVAC unit shall be a fully hermetically sealedsystem, without threadedcomponents, or other non- welded fittings, except for two service ports equipped with high quality industrial Schrader valves. Pressure transducers shall be provided to allow the microprocessor to monitor both the discharge and suction line pressures. A technician using a laptop/PTU shall be able to monitor both pressures without the use of pressure gauges. The performance of the entire assembled HVAC system as installed in a completedcar shall be verified at the Climate Room Test specified in Chapter19.
The following parameters are to be assumed in the design of the cooling system:
The following temperatures shall be maintained within the car’s upper and lower levels (including toilet rooms and cab) when the associated ambient outside temperatures are present:
During all modes of air conditioning, the interior relative humidity shall not exceed 60%. Except within the area of the side doors and vestibules, the HVAC system shall maintain a temperature variation, within both the upper and lower levels, of the following: · Vertical variation: (On any vertical line, 4 in. above floor to 43 in. above floor, not closer than 6 in. from walls, and not closer than 20 in. from doors): 5°F maximum difference between end points of the vertical line. · Horizontal variation: (horizontal planes measured 4 in., 43 in. and 67 in. from floor, not closer than 6 in. from walls and not closerthan 20 in. from doors.):The temperature at any point within each plane should not exceed ± 3°F from the average temperature in that plane.
· The average car temperature, including the upper and lower levels, shall recover within 2°F of the required interior car temperature within three minutes maximum following a two minute door opening on one side of the vehicle. It shall be demonstrated that this requirement can be met during two hours of continuous door cycling of two minutesopen and 15 minutes closedat the design conditions in both heating and cooling modes.
Temperature variation between the upper and lower levels shall not exceed 4°F at any time.
The overall HVAC system shall be designed to minimize noise in the passenger and crew areas of the car. The noise level from the HVAC system shall not exceedthe values in the following table. Particular care shall be required at the return air grilles, cab supply vents and galley ceiling air diffusers.
With the car stationary and the HVAC unit in its loudest cooling mode: