BENEFITS OF ALL ELECTRIC SYSTEMS OVER DIESEL TRAILER STORAGE
In addition to the up front cost advantage of using all electric container refrigeration systems over diesel trailer systems, there are many benefits that may help close a deal with a perspective customer.
Refrigeration Machinery Specifications
Unit performance at 100° F (38° C) ambient
The table below contains the cooling capacities and power consumption for three unit-operating conditions. Evaporator fans circulate 3,200 cubic feet per minute (cfm) of air throughout the container while in high speed and 1,400 cfm in low (static pressure dependent).
Heating capacity equates to 19,200 BTU/hr, including evaporator fan heat.
While most specifications are “standard” one will find small variances in the actual measurements.
If a customer is dealing with a requirement which is “border- line” to the dimensions in this table please contact the equipment manufacturer for assistance finding specific units to meet your needs.
Bottom Air Flow vs.Top Air Flow
Containers deliver air to the floor, through “T” channels, and require a specific loading pattern to ensure that air temperature is maintained throughout the container.
Top air delivery systems, as found in trailers, require a ceiling chute to direct air to the rear of the trailer. Not having a chute to maintain could be considered a benefit since they are often damaged during loading and are costly to repair or replace.
See loading practices section details. If loading product as required is a problem for the customer then a container may not meet their needs.
Having the proper electrical service, a safe location for equipment to be placed and the ability to load only pre-cooled or pre-frozen products are strongly recommended.
The following general safety notices supplement the specific warnings and cautions appearing in the manufacturer’s Operation & Service manual. They are recommended precautions that must be understood and applied during operation and maintenance of the equipment.
If you do not have a copy of the manufacturer’s Operation & Service manual, and you or your customer would like one, electronic copies can be found on the relevant manufacturer’s website.
First Aid. An injury, no matter how slight, should never go unattended. Always obtain first aid or medical attention immediately.
• Always were safety glasses
• Keep hands, clothing and tools clear of the evaporator and condenser fans
• No work should be performed on the unit until all circuit breakers and start- stop switches are turned off and the power supply is disconnected.
• Do not work on the equipment alone.
• Be aware of unannounced starting of the evaporator and condenser fans. Do not open fan grille or evaporator access panels before turning power off, disconnecting and securing power plug.
• Do not by-pass any electrical safety devises. Call if system is not operating properly.
• In case of electrical fire, open circuit switch and extinguish with CO2 (never use water).
• In case of severe vibration or unusual noise, stop the unit and investigate.
• Avoid refrigerant coming in contact with eyes. Should refrigerant come in contact with the eyes, wash eyes with potable water for a minimum of 15 minutes and seek medical attention.
• Avoid refrigerant from coming in contact with skin. Should refrigerant come in contact with the skin seek medical attention, it should be treated as if skin has been frostbitten or frozen.
• If container will be operating indoors, be sure ventilation is adequate in case of refrigerant leak, to keep concentration in air below 1000 parts per million.
REFRIGERATION UNIT & CONTROLLER OPERATION
So long as everyone is doing their job properly, and so long as no unforeseen occurrence takes place
during transport, the container will arrive at the site in excellent operating condition.
Container refrigeration systems are very easy to operate. It is important to have someone take a look at the unit on a daily basis.
You should not attempt to make any mechanical or electrical wiring adjustments to the refrigeration system. The only item that may require “customer” adjustment is the fresh air vent.
Refrigeration System Component Layout
Basic Operating Instructions
It is recommended that the Manufacturer’s equipment operating instructions be reviewed with the customer prior to attempting to get the unit started.
Instructions give detailed steps to start a genset (if required), to “Start the Refrigeration Unit”, “Change the Temperature Set Point”, and to put unit into “Manual Defrost”. The “Manual Defrost” feature will be valuable to the user that has a unit with an “iced-up” evaporator coil. Putting the unit into manual defrost overrides the defrost timer and will immediately work to clear ice from the evaporator and restore the refrigeration system’s cooling capability.
Although the instructions include steps to “Perform a Pre-trip” and “Set a Trip Start”, these two functions are completed prior to dispatching the container and are not typically needed by the customer.
User Selectable Controller Function Settings
The controller’s user selectable operational settings should be programmed as follows:
Cd27 Defrost Interval (hours) AUTO or 3 if auto is not available
Cd28 Temperature Units oF
Cd29 Failure Action D (fails to off)
Cd30 In-Range 4 (+/- 3.6 oF, 2oC)
Cd31 Stagger Start Offset (seconds) 0
Cd32 Current limit (amps) 21
If the consequences of making any changes to these settings are not fully understood, please consult technical assistance prior to adjusting the same.
If you have more than one unit in the same yard it is recommended to set different stagger start offset delays (Cd31) on each. This way if the power is lost and suddenly returns, the units will not all start up at the same time, risking loss of power again due to the heavy load put on the utility service.
ML2i units have additional user selectable operational settings that are options from the factory.
As with the previous, if an option is available and it is suspected that the customer may benefit from the same, refer to the manufacturer’s operation and service manual prior to adjusting option settings.
Dashes “ – – – – ” present in the data field signify that the option is not available on that specific unit.
Codes 33 through 39 should be set as follows:
Cd33 Dehumidification (option) OFF Cd34 Economy Mode (option) OFF Cd35 Bulb Mode (option) nOr
Cd36 Evap Speed Select (option) a l t
Cd37 Defrost Termination Temp Setting (option) – – – –
Cd38 Secondary Supply Air Temperature (option) – – – –
Cd39 Secondary Return Air Temperature (option) – – – –
Fresh Air Vent Settings
Typically the fresh air vent should remain closed. However, if the customer is storing fresh produce for several days without plans to enter the container, the fresh air vent may be opened 15 to 45 cfm. This allows the container to be replenished with oxygen while at the same time removing ethylene-contaminated air.
* * WARNING * *
Opening the vent over 45 cfm could overwhelm the refrigeration system with hot humid air, ambient dependant, leading to a lack of temperature control.
Temperature Control Methods
Chill Range Operation (set points above 14oF)
When set in the chill temperature range, the unit controls temperature off the supply air temperature sensor, delivering air to the container at set point +/- 0.5oF. Modulating the flow of refrigerant to the compressor controls the cooling capacity. The compressor often runs continuously, in a partial load condition.
In high humidity ambient areas, ice may form on the compressor end bell, which in small quantities is normal. See Manufactuer’s Operation & Service manual or label on unit for unit specific details.
In an attempt to control head pressure and save energy, the condenser fan motor may cycle on and off when the ambient temperature and head pressure are low.
Frozen Range Operation (set points below 14oF)
For frozen set points temperature is controlled off the return air sensor, ensuring the “return air” is at set point +/- 0.5oF. This means the unit may deliver air at a temperature much lower than set point. The unit controls capacity by cycling the compressor on and off as the load demands. A 3-minute time delay protects the compressor from short cycling. Heat mode is locked out for all frozen set points.
When two speed evaporator fans are present, the fans operate in low speed.
In an attempt to control head pressure and save energy, the condenser fan motor may cycle on and off when the ambient temperature and head pressure are low.
System Operating Modes
Cooling Mode – The evaporator fans, condenser fan, compressor and the controller’s cool LED are typically energized while in the cooling mode. In an attempt to control head pressure and save energy, the condenser fan motor may cycle on and off. The exact state of the suction line valve(s) is dependant on the cooling load demand, but suffice it to say if in the cooling mode the valve(s) will be in some state of “open”.
Heat Mode – In low ambient temperatures heat may be required to maintain the desired set point. Container units are fitted with electric resistance heating rods that put out 18,000 BTU/hr of heat. Evaporator fans circulate the heated air throughout the container. Heat mode is locked out when the temperature set point is in the frozen range.
Null Mode – When the box temperature requirements have been sufficiently met, the controller will initiate the null mode. While in the null mode the compressor and condenser fan motor is shut off and evaporator fans continue to run, circulating air throughout the container. The temperature of the air returning to the refrigeration unit is constantly measured and is used to determine when the unit should cycle back into heat or cool mode.
Defrost Mode – Defrost can be initiated via (MD) manual defrost switch (located next to the unit’s (ST) Start-Stop switch, or via the defrost timer. A user selectable defrost interval of 3, 6, 9, 12, or 24 hours can be set via controller Code 27. The controller uses accumulated “compressor-on-hours” to initiate defrost. The actual hours since the unit came out of defrost last may be much more.
Follow these simple steps to ensure product temperature is maintained as close to required setpoint as possible:
1. Pre-Cool or Pre-Freeze product prior to loading
2. Prior to loading, for frozen set points insert (4) floor drain plugs inside container (2 front 2 rear in corners). For chill range set points keep floor drains open (do not plug).
3. Load cargo flush with the front bulkhead; leave no space
4. Do not load past the end of the “T” floor
5. Leave 6” of air space above cargo for return air to circulate. (Do not load cartons above the red line)
Figure 2. Turn off the refrigeration unit prior to opening doors for entry. Operating the reefer unit while loading or unloading does not facilitate the cooling process and can even damage the product you are trying to protect. Hot humid air enters is pulled in to the container, warming product as it makes its way to the refrigeration unit. Moisture condenses out of the air depositing water on the walls, ceiling, product and evaporator coil. The evaporator coil typically ices up and, until the unit completes a defrost cycle, the product may not be protected by adequate refrigeration for several hours.
A 40-foot container can be loaded with 20 pallets (48” x 40”) if pin-wheeled or stagger loaded, see Figure 3 below. Otherwise the easiest way to load pallets is straight in. When loaded straight in only 18 pallets will fit.
If fresh produce and will be stored in the container it is recommended to cover the floor between pallets with cardboard, dunnage or air bags. This will help force the air up and through the cartons rather than allow it to “short circuit” around them.
When Frozen product is loaded into a container maintaining a blanket of cold air around the cartons is desirable. Block stow the pre-frozen product in the container.
It is important that both electrical power and physical site requirements are met prior to receiving equipment. Site preparation work is the responsibility of the customer (renter/lessee) and should be coordinated and paid for by the same.
It is the customer’s responsibility to ensure that all electrical work completed on their property meets local codes. The customer should question any system requirements that are not understood. It is recommended that the customer contract a local licensed electrician to ensure power/service requirements are met by the facility.
Units operate on 460/480 VAC, 3-phase, 60 Hz power with a maximum electrical load, under rated operating conditions, not to exceed 18.75 kVA. The power consumption shall not exceed 15kW.
If 460/480 VAC is not available it is the customer’s responsibility to determine the power voltage available and communicate the same to you. You should dispatch equipment fitted with a step-up power transformer to meet the customer’s needs. Step-up transformers to accommodate either 208VAC or 230/240 VAC, 3-phase, 60 Hz power.
If the customer plans to invest in new electrical service in for this application, 460/480 VAC would be the more economical choice.
Since the compressor motor, which is the only 3-phase component on the refrigeration system, can rotate in either direction, having the proper “phase” sequence is not an issue. Fan motors are single phase.
Reefer Unit Circuit Breakers
FYI – These breakers are built into the reefer system.
460/480 VAC (25 amp) circuit breaker – must trip at 29 amps (standard) 230/240 VAC (50 amp) circuit breaker – must trip at 62.5 amps (optional) 208 VAC (70 amp) circuit breaker (optional)
Hardwiring vs. Use of Receptacles
There are two ways to connect the unit’s voltage power cable to electrical service.
1) Hardwiring – which typically requires that a licensed electrician connect each of 3 power legs and one ground connection to an electric service panel.
2) Receptacles – if unit will be connected and disconnected frequently this may be the best method to connect the unit to power.
There are two plug designs on the market that can be used with this equipment, a marine and a domestic type plug.
Marine plugs CEE-17:
All refrigeration systems should be provided with a 460/480 VAC marine design power plug. If the customer plans on using 230/240
VAC power, then the 460/480 VAC plug is necessary, it connects to the unit’s step-up transformer, see diagram at right.
If customer will operate on 460/480 VAC and plans to hardwire the same, they can have their electrician remove the supplied plug upon arrival at their site. This plug should be reinstalled when returned. Missing plugs should be charged back
to the customer for both parts and labor.
Marine Plug Specifications:
For 460/480 VAC power use 380/440 VAC, 32 AMP, 3-Pole, 4 Wire plug For 208/230/240 VAC power use 250 VAC, 50 AMP, 3-Pole, 4 Wire plug
Plug/Receptacle source – ERO Electric Reefer Outlets http://www.eroinc.net,
Trailer refrigeration systems with electric stand-by typically use a domestic type of plug. If the customer requires a domestic plug they will need to arrange for the purchase and installation of the same.
Domestic Plug/Receptacle Source – HUBBELL http://www.hubbell-wiring.com The customer’s electrician should determine if Hubbell’s TWIST-LOCK® devices (3 Pole, 4 wire ground plugs and receptacles available in both 480VAC, 50A, 3φ and 250VAC, 50A, 3φ) meets their local requirements.
Land Site Preparation
If unit will be placed on the ground, without a chassis (wheels), note the following points:
• Ensure there is sufficient space for a tilt-bed delivery truck or crane to safely unload the container.
• The surface that the unit will be placed on must be level and free of accumulating water.
• Unit must be placed within 50 feet of a power receptacle or service box.
• Containers are designed to be supported by their (4) corner castings. If the container cannot be placed on a level concrete surface where only the corner castings are touching the ground, use railroad ties or paving stones to support the corner castings. Never attempt to support the container from any other points on the bottom of the frame.
• Position the machinery end of the container no less than 3 feet from a wall or other objects that may block the airflow.
• Units have 4ft wide, bi- fold swing rear doors. Ensure there are no physical obstructions to prevent doors from opening fully before “placing” unit.
• Units should be operated in areas with ambient temperatures below 100oF, and never exceeding 122 oF.
• Save on energy expenses by placing the refrigeration unit in a shaded area.
• If planning to operate container indoors, defrost drain line may need to be routed to a pail or collection devise to meet OSHA standing water requirements. Additionally, the space may need to be ventilated to control the ambient temperature and limit the heat load on the refrigeration system.
If the container will remain on a chassis while in use at the customer’s facility, the unit can be treated like a trailer. The only caveat being, the container must be unplugged from its stationary electrical power outlet and the 60’ cable properly coiled up and secured before moving the chassis.