Here is a general listing of possible causes of oil failure trips:
To learn more, download Oil Pressure Problems in Refrigeration Systems
Superheat generally does not affect actual oil return to the compressor crankcase unless the superheat is set so high that it caused a starved condition resulting in low return gas velocity or evaporator icing. Low superheat at the compressor results in liquid refrigerant being present in the oil sump. The violent action of liquid refrigerant boiling in the crankcase will cause oil to be blown out into the system resulting in low oil levels. Liquid refrigerant in the compressor’s pressurized lubrication system will result in a loss of net oil pressure resulting in an oil failure trip, bearing damage due to the loss of lubrication to bearing surfaces and possible valve damage to due liquid slugging caused by the returning oil.
To learn more, download Principles of Refrigeration Superheat.
The 3-way valve you are referring to is called a headmaster. The headmaster maintains a minimum liquid pressure at the receiver by injecting hot gas on the liquid surface and by stacking liquid refrigerant in the condenser thereby reducing the condenser capacity during low ambient conditions.
To learn more, download Flooded Condenser Using a Headmaster.
The 3-way valve has horsepower limitations. Larger units produce mass flows much high than the capacity of the largest 3-way valve. In these situations a Dual valve System is used to maintain a minimum discharge pressure. The Dual Valve System uses an Open on Rise of Inlet Pressure Valve (ORI) and an Open on Rise of Differential Pressure Valve (ORD)
To learn more, download The Dual Valve System ORI/ORD.
Head pressure control and the use of a heated Insulated receiver are two separate subjects. Climatic Conditions dictate the use of mechanical head pressure controls. Application and calculated run times (based on expected winter load) dictate whether to use the heated insulated receiver option.
If extended winter off cycle periods are expected even in mild climates then a heated Insulated Receiver may be an option to consider. For example an outdoor walk in cooler in northern Kentucky may require a heated insulated receiver due to extended off cycle periods in the winter months due to low product loads rather than winter design temperatures for that area. On the other hand, a walk in freezer in the same area sized for an 18 hour run time and heavy winter product loads may not require a heated insulated receiver since it will not be subjected to extended off cycle periods.
To learn more, download Requirements for Extreme Low Ambient Conditions.
Condenser fan cycling does have limitations. Most compressors require airflow from the condenser for compressor cooling. A condensing unit having only one condenser fan motor would not be a good candidate for pressure fan cycling since the condenser fan could be off for extended periods of time.
Another consideration is the affects of wide pressure swings on the TEV since liquid pressure is an opening force of the valve.
To learn more, download Pressure Fan Cycling.
When fans cycle too rapidly, the condenser does not have sufficient time to stabilize and often, the controls overshoot the set points. Large swings in temperature can shorten the life of any condenser. Typically a 20 psig minimum differential is a good starting base line. You may have to adjust up from this point considering that fan cycling in excess of three minutes is considered excessive.
To learn more, download Condenser Fan Cycling Control Points.
There are several options to consider depending on horsepower, type of compressor and the severity of the load variations. The simplest for minor variations is to increase the dead band of the room thermostat. Other options include sizing the equipment to that they come on line in stages to maintain the desired box temperature. Wider load variations can be best controlled through capacity control. This includes hot gas bypass and or mechanical unloaders to balance the system capacity to the load.
To learn more, download Capacity Control Tech Topics.
Maybe you missed air throw and air distribution. Evaporators are intended to be Non-ducted but airflow and throw is an important factor to consider. Usually unstable product temperatures are directly related to Evaporator coil selection, airflow restrictions and air throw.
To learn more, download Nonducted Air Flow Condensers.
These are typical symptoms of an improperly selected nozzle. Liquid temperature at the expansion valve not only affects nozzle selection but also affects the TEV selection since colder liquid has more capacity. Typically nozzles and expansion valves are selected based on the BTU capacity of the condensing unit divided by the number of evaporators, 95°F. ambient and 105°F. condensing with a 90°F. to 95°F. degree liquid temperature. If the liquid temperature or the design condition change the selection may not be correct for the application. Consult an Application Engineer.
To learn more, download Refrigerant Distribution.
Chances are there was nothing wrong with the original valve. All indications point to a wet system. The expansion valve will feed until the saturated suction temperature reaches 32F the freezing point of water. The wet refrigerant and oil will block the TXV until the internal temperature reaches the melting point and the blockage clears. The remedy is good service and installation practices to ensure a clean dry system. Recover the refrigerant, replace the driers and oil if its POE, evacuate to 500 microns or less and recharge. This problem should go away provided the system is clean and dry.
To learn more, download Evacuation of a Refrigeration System.
All units sold by Heatcraft Refrigeration Products are covered under the standard catalog warranty. The basic terms of the standard catalog warranty is as follows:
Products warranted for one year from date of original installation, or eighteen (18) months from date of original shipment, from Heatcraft Refrigeration Products, whichever occurs first.
Replacement parts used on equipment past warranty terms are warranted for 1 year from date of installation.
Whenever possible, replacement parts are to be obtained from a local authorized Heatcraft Refrigeration Products wholesaler. Replacement parts which are covered under the terms of our warranty statement will be reimbursed for total cost of the part only plus applicable taxes. The original invoice from the wholesale parts suppler must accompany all warranty claims for replacement parts reimbursement. Processing or handling fees assessed by parts wholesalers are not reimbursable under Heatcraft's warranty terms.
Contact Heatcraft Refrigeration Product's warranty department at (800) 537-7775 with the model and serial number of the equipment that was serviced along with the equipment's original installation date.
Warranty claims should be submitted to the original purchaser of your Heatcraft Refrigeration Products equipment. If assistance is needed to identify the equipment's original purchaser you can contact Heatcraft Refrigeration Product's warranty department at (800) 537-7775 with the model and serial number of the equipment that was serviced.
Heatcraft Refrigeration Product currently does not have a warranty claim form. Instead, all warranty claims for Heatcraft equipment are processed through the original purchaser of the equipment serviced.
The original purchaser must receive written permission from Heatcraft Refrigeration Products to return the product. Contact your Heatcraft Sales Representative or a Heatcraft Refrigeration Product's warranty representative at (800) 537-7775.
Heatcraft Refrigeration Products does not have authorized service contractors. A qualified refrigeration service contractor of your choice is permitted to service Heatcraft equipment as needed. All service contractors should contact Heatcraft Refrigeration Products warranty department to confirm warranty status prior to beginning any service related work.
If you are a Heatcraft Refrigeration Products customer, you can use the WebWarranty claims process on Access2Answers to order the replacement part.
To locate an authorized Heatcraft Refrigeration wholesaler, use our wholesaler locator. You can also contact a Heatcraft Refrigeration Products Customer Service Representative at (800) 537-7775 between the hours of 8:00 AM to 5:30 PM Eastern Time or by clicking one of the various wholesaler links found on Heatcraft Refrigeration Products Warranty Webpage.
You can contact Heatcraft Refrigeration Product's warranty department at (800) 537-7775. Make sure to have your Heatcraft equipment serial number handy for reference purposes.
WebWarranty is an online claims filing process available to Heatcraft Refrigeration Products customers through Access2Answers.
WebWarranty guides users through a simple online claims process through a series of tabs and information prompts. With this tool, users can submit claims for replacement parts directly and receive instant claim credit. Claims status can also be viewed online once a claim is filed. Documentation to substantiate the claim may still be required.
To access WebWarranty, you must be a member of Access2Answers with a valid username and password.
Contact your Heatcraft Refrigeration Sales Representative. If you need a contact, use our Find a Sales Rep.
If you need technical assistance, email firstname.lastname@example.org. Please include your name, address and daytime phone numbers.