When installing a field-fabricated system, such as a walk-in freezer or cooler, an important part of the overall installation that is sometimes rushed or skipped is a thorough system startup. All of the components may be operational, but are they adjusted and working properly as a complete system? A professional installation will include a thorough inspection of the system as a complete unit.
Here are some things to do before leaving the job site:
• Check the system’s operating suction and discharge pressures and verify they are operating within normal parameters;
• Measure the refrigerant’s superheat value at the outlet of the evaporator and adjust the thermostatic expansion valve (TXV), if required. Be sure to check this value when the case temperature is within 5°F of its set point and not when the case temperature is extremely high, such as during its initial pulldown. During pulldown, the high load placed on the evaporator will temporarily drive the superheat value higher than normal. Attempting to adjust the TXV during this time may result in too low a value when the case is at set point;
• Check the refrigerant’s superheat value at the inlet of the compressor to make sure it is within the manufacturer’s specifications. Too low of a superheat value may result in liquid returning to the compressor during low-load conditions;
• Check the condenser’s subcooling value to verify the system is charged properly;
• Measure the refrigerant’s discharge line temperature 6 inches from where it exits the compressor. Generally speaking, temperatures warmer than 225° should be investigated, and a system with temperatures exceeding 275° should not be left in operation;
• If the compressor has an oil sight glass, check its level. Systems with long line sets may require additional oil be added to the system to compensate for the oil in circulation. Check the oil level after the system has been in operation for a period of time. It may seem fine at the initial start of the system but can drop as the oil begins leaving the compressor and circulates with the refrigerant;
• Measure the voltage applied to the condensing unit/compressor both before the system is energized and again after it is operating. Verify the applied voltage is within plus or minus 10 percent of the data plate rating and there is not a severe voltage drop at startup. Normally, the voltage should not drop by more than 3 percent from a de-energized state to an energized state;
• Check the compressor amperage draw;
• When installing a freezer, make sure to manually initiate a defrost and make sure the defrost cycle terminates normally;
• Allow the system to cycle on and off on its temperature control and verify the controls are adjusted properly; and
• Visually inspect the complete system, making sure everything is plum, level, secured, and mounted properly and piping is appropriately sloped.
Some systems may require additional checks. Many equipment manufacturers will have a form to reference and complete for a detailed startup. It’s a good idea to use the forms so you do not overlook checking an important parameter. These forms also serve as a great reference for future work and maintenance. It gives you a baseline for the system when it was first installed and operating normally.
Completing these checks will allow you to catch potential system problems before they become critical. It does take extra time to complete, but it’s definitely a valuable investment. It will help keep warranty costs down and keep your customer satisfied with you and your company.
Publication date: 2/1/2016