Diagnosing a refrigerant flow problem could save your HVAC system.
If there is a low-temperature difference across the evaporator coil in your air conditioning system, you might have a refrigerant flow problem. The heat-handling capabilities of your system may also be failing as well, as the low-temperature difference also indicates a capacity drop. It can be difficult to diagnose issues with such a complex system as your facilities central cooling and heating applications. However, if you take the time to notice the specific signs that certain parts of your HVAC unit are malfunctioning, it’s easier to fix them. Refrigerant problems are quite common. This week, we’ll walk you through how to diagnose refrigerant flow problems so you can efficiently rectify the problem with the help of an informed HVAC maintenance team.
Subcooling In The Condenser
Subcooling is the difference between your system’s measured liquid temperature and the saturation level at a given pressure. To get the amount of liquid subcooling in the condenser, simply subtract the condenser outlet temperature from the saturation temperature. If charged properly, a forced-air condenser will have 6-10 degrees of liquid subcooler. Condenser subcooling can be an indicator of your system’s refrigerant charge. The less the refrigerant charge, the less the subcooling. Making sure you actively check the amount of subcooling taking place in your condenser will help you diagnose whether or not you have a refrigerant flow problem within your HVAC system.
Watch Out For Liquid Line Restriction
A restricted liquid line will starve your evaporator of refrigerant. A notable sign that you have a liquid line restriction is low pressure in your evaporator. Liquid line restrictions can be caused by a restricted filter-drier, a restricted thermostatic expansion valve screen, a kinked liquid line, a bent lower condenser coil, or an oil-logged capillary tube. An evaporator that is starved of refrigerant will house a starved compressor and condenser as well. Liquid subcooling will also increase because of most of the refrigerant charge is housed in the condenser. A blocked line will drastically affect refrigerant flow. The worse the restriction, the harder your system will need to work in order to adequately heat and cool your facility. This is extremely wasteful! Save energy and money by knowing how to diagnose your refrigerant flow problems.
Undercharge and Overcharge
With no refrigerant to subcool, undercharged systems have a lowered mass flow rate, low suction and discharge pressures, and high superheat in the evaporator coil. With decreased refrigerant flow, the compressor’s draw will be very low. Symptoms for an undercharge problem are quite similar to a line restriction issue, except the latter usually shows signs of subcooling in the condenser, whereas an undercharged diagnosis does not. On the opposite side of the spectrum, if your refrigerant flow problem is the direct result of an overcharged HVAC system, it will have high condensing temperatures, increased amp draw, and higher head pressures. If your system is more than 10% overcharged, the liquid may enter the suction line. This could result in compressor damage which leads to system failure. It’s extremely important to routinely diagnose refrigerant flow problems to keep that HVAC system up and running!
Let Us Evaluate Your Refrigerant Issues For You
Crockett Facilities Services, Inc. (CFSI) is committed to helping building owners, property managers, engineers, and facility professionals lower their operating expenses through HVAC preventive maintenance. We can develop a cost-effective, customized preventive maintenance plan for your commercial building that will provide you with peace of mind, improved comfort, and energy savings.
To learn more about the importance of HVAC Preventive Maintenance, please contact us at 202.600.2787 or sales@crockett-facilities.com. Our PM contract customers receive priority service with 24/7 emergency service in Maryland, Virginia and Washington, DC.