You have just received a call from your supervisor that a portable chiller will be arriving tomorrow for the new production line, which needs to be operational by the end of the week. What do you need to do to set up and maintain your new portable chiller?
First, start by asking some questions:
- Is the chiller air-cooled or water-cooled?
- What are its voltage, amperage and phasing?
- What is the tonnage or BTU rating?
- What is the physical size and weight of the chiller?
- What is the coldest temperature production requires of the chiller-water solution?
Air- or Water-Cooled. If your chiller is air-cooled, make sure that you have at least 800 ft3/min per ton of air exchange in the room or area you want to put the chiller. If the hot air is not removed at that rate, the inlet condenser coil air temperature will continue to rise and cause high pressure trips or excessive refrigeration pressures to the chiller.
If the chiller is water-cooled, a source of water is required to supply the water-cooled condenser. The rule of thumb is to make sure you can provide at least 3 gal/min per ton of water flow coming in and going out of your chiller. This cannot be a recirculation loop. It must be a tower or city water loop that has an average temperature range of 60 to 85°F (16 to 29°C).
Voltage, Amperage and Phasing. Be sure that the voltage is correct. Most portable chillers are either 230 or 460 V, three-phase. Also, ensure that the electrical service for your chiller is sized properly for the full load amps.
Tonnage or BTU Rating. The tonnage or BTU rating will dictate many things. For example, it will tell you what kind of flow rate you need (the design on most chillers is 2.4 gal/min per ton) and what kind of air exchange or tower water needs you will have to provide.
Size and Weight. Most portable chillers are indoor chillers that have casters. They can be moved by human power and can fit in smaller areas where specific cooling is necessary.
Once you know the chiller’s size and weight, you can make some educated decisions about its location. If it is an air-cooled model, make sure that the area in which you are locating the unit has adequate airflow around the coil and intake screen. For both air- and water-cooled systems, be sure the ground is able to handle the weight. You also want to make sure that the chiller is positioned where it can be rolled out easily for service. Service costs can quickly rise if a technician must spend a lot of time simply gaining access to the chiller. Leave extra hose and electrical wiring so that the chiller can be moved and serviced easily.
Coldest Temperature. The answer to this question is important. Most industrial chillers are designed to supply a chiller-water-solution temperature as low as 50°F (10°C) without the help of antifreeze. If your production needs require a supply temperature below 50°F, consider using some type of industrial ethylene or propylene glycol (antifreeze). A good rule of thumb is that the freeze point of the water/glycol mixture should be 20 to 25°F (11 to 14°C) less than the coldest water temperature you are supplying out of the chiller. Remember that the refrigeration coils in the evaporator are much colder than the actual supply water. Of all the maintenance services regarding a portable chiller, this is the most neglected and the most important.
Now you have your chiller properly located, piped up, filled up and electrically wired. Press the button, make sure the pumps, fans and compressors (scrolls) are rotating at the proper speed, and away you go.
Maintenance ScheduleThe next important service you should provide for your portable chiller -- whether new or old -- is to prepare a maintenance schedule and follow it. If left alone, the chiller will quickly age from the inside out. Unlike an air-conditioning or refrigeration system, chillers cool water that is usually never seen. Out-of-sight and out-of-mind can mean service and efficiency problems down the road.
Contracting with a chiller service company is one way to ensure that proper preventive maintenance is performed on your chillers. Between regularly scheduled inspections, in-house maintenance personnel can perform many maintenance services such as those suggested below that will help your chiller have a long, productive life.
Install and Check Daily the Inline Water Filter. Poor water quality is the No. 1 reason for chillers to have poor efficiency or service problems. Filter the water by installing at least a 40-mesh-quality Y-strainer in the return water line from your process. This will catch any physical debris from your process before it enters the chiller tank and exchangers. A “sock” filter may be necessary if your water quality is poor. The Y-strainer will catch debris such as plastic pellets but will not filter out fine mud or minerals that build up from the hard water used in some plants.
The schedule you use in your facility will depend on process-specific factors. When setting up your maintenance schedule, start with daily checks of the strainer and filter. If they are consistently clean when checked on a daily basis, change your schedule to check them weekly. If they are still clean consistently when checked on a weekly basis, update your schedule to check them monthly. Do not extend the inspection and replacement schedule more than a month.
Inspect the Water Hoses and Chiller Pumps Monthly for Leaks or Rusted Fittings. Monthly visual inspection of the water lines, pumps and hoses is the best way to head off a blown water line. Some portables hold as much as 50 gal of water in the reservoir tanks. It is better to head off a rusty clamp or a dry, rotted hose before the production machine shuts down and glycol is all over the floor.
Inspect and Measure the Water and Antifreeze Levels Weekly. A refractometer is a common tool used to do this (figure 1). Water and antifreeze levels can become low due to a hose leak or mold change. This fluid loss reduces the effective cooling of the chiller. Unfortunately, portable chillers often are refilled with straight water when a leak occurs. If you run at 50°F or higher, there is no problem. But if you run temperatures lower than 50°F, then a hidden problem -- internal icing -- can occur and cause serious problems to the compressor and evaporator. If you have ever experienced an internally ruptured evaporator, most likely, icing was the reason.
I recommend that a chiller be drained and flushed once a year. If you have industrial-grade antifreeze and your water quality entering the plant is good, then you may not need to do this as often. In some process facilities though, the inexpensive “car” antifreeze is used. This is the worst thing you can do for your chiller and your process machine. The car antifreeze will break down in a short time (1 to 2 years) and cause slime to form inside the chiller and water lines. This will greatly reduce the overall chiller efficiency and clog small water channels.
Have a Startup and Shutdown Procedure List Mounted on the Chiller Control Panel. This small bit of preventive maintenance will save you many unnecessary late-night calls. When shutting down the system, it is best to make sure that the control switch is shut off only -- never the high voltage. Many portable chillers have high voltage crankcase oil heaters to prevent refrigeration migration when the compressor is not running. Add simple suggestions to the list such as to check the water level before startup, and to check whether the water valves have been shut off mistakenly. If the chiller is water-cooled, then make sure that the tower water valves are open and the person notices a pressure in the gauge before starting the chiller.
Clean the Air-Cooled Condensers on a Weekly Basis. Have an air-pressure connection close by and an air-pressure hose and nozzle already hooked up, ready to use. Some coils get dirty and are not cleared merely because it is a time-consuming job to find and attach the hose and nozzle before you can clean the coil. Make it easy by having it ready for the operator or maintenance crew.
Air-Blow Electronic Equipment and Components Twice a Year. Most of today’s chillers incorporate some type of electronics, and all have contactors and electrical wiring (figure 2). After a few months, dust builds up on the resistors and other electronic components. Electronics do not like dust and debris.
Every six months, take that same air line you hooked up to clean the condenser coil and carefully blow out the electrical cabinets and electronic components. When you do this, be sure to shut off all power, and test the air coming out of the air line for at least 15 sec before you direct it into the electrical panel. Sometimes the air is “wet” due to a problem with moisture removal (air dryer). If this is the case, do not blow clean any electrical components. Adding moisture to the electronics will make things worse rather than better.
Listen to the Chiller. When the chiller is operating properly, go over to the chiller and listen to the sounds it makes. Listen to the fans turning on and off along with the compressor cycling. Listen to the hot-gas or unloaders engage. These simple items will tell you that the chiller is operating normally. Knowing how it sounds when all is well will help you know when something does not sound right, so you can find potential problems before they become something more serious.
Remember, the best way to maintain your portable chiller is to draw up your own preventive maintenance list and incorporate it into your daily production schedule. A little planning and prevention now can save you money later.