Presentation on theme: "July 2014 Tuesday’s Tech Talk or “3T Meeting”. A fallen tree knocked over a homeowner’s Trane condenser in Kansas. The condenser looks like a goner. It’s."— Presentation transcript:
July 2014 Tuesday’s Tech Talk or “3T Meeting”
A fallen tree knocked over a homeowner’s Trane condenser in Kansas. The condenser looks like a goner. It’s completely split open and had been lying in the grass like this for a week. But the dealer wasn’t surprised when he righted the unit and turned it on. Of course it still works, it’s a Trane!
Feel Good Story of the Month
Fall Training Schedule
TruComfort Update Unit Operation without Demand Request We have had a one field call regarding system operation without demand request from the comfort control. Engineering has extracted 950 field data and has duplicated the runaway condition. We are implementing a software fix in the OD unit & 950 control. The 950 software fix will be the first to launch – date TBD. Should anyone see this condition please contact Dustin or Dave, we will be able to help you with a thermostat software version that will cure this.
Obituary of a Compressor Will focus on compressor failures and proper clean up procedures in the following categories: Four Part Series --Electrical Issues(June) --Refrigerant Starvation(July) --Refrigerant Flooding(August) --Refrigerant Contaminants(September)
While my engineers designed me for 25 years of life, I only lasted for 5. Low refrigerant charge with high superheat caused my lock rotor conditions and premature death. Excessive temperatures reduced my oils viscosity and caused it to break down. I’ve generated acids, alcohol, water and carbonaceous sludge that I distributed throughout the system. The sludge started to plug the liquid line filter drier and the acids are corroding the copper in the refrigerant lines. I felt the increase of friction as the copper plated my bearings and I displayed this issue with higher amp draws... but no one noticed.
My suction pressure continued to drop with the restricting drier and I began pumping oil out of my shell. This loss of oil sent me over the edge and my bearings finally seized. The service technician removed me from the system, but did not pay much attention to my condition—thinking “it’s just another locked rotor compressor”. He replaced the capacitor, left the original filter drier & did not consider any system clean up. He pulled a vacuum, weighed in the refrigerant charge and started the system. Because of the high indoor load condition, the pressures looked “good enough” and he walked away with a perfect 20° temperature split. This technician will be back to replace another compressor and wonder why. He has no idea of the contaminants he has left behind and what they will continue to do to the system.
Do not let the thought of “just another locked compressor” trick you into taking shortcuts. You can have an acidic & contaminated system without a compressor shorting to ground
Because of the continual circulation of contaminates, this system will be increasingly more difficult to clean up. The following problems may exist: *The cap tubes on the reversing valve are plugged with sludge—the valve will not shift. *The screens at the TXV & check valves are plugged—every screen will have to be removed and replaced. *The system is acidic and may require multiple suction & liquid drier replacements to achieve safe conditions. And to think, the replacement of the liquid drier & addition of acid away may have been enough to prevent this.
Refrigeration Starvation comes from four general areas: Lack of Refrigerant Charge Refrigerant Restriction or Improper Line Set Application High Evaporator Load Conditions Leaking Reversing Valve
Proper refrigerant charge is one of the most important items to check when you work on a system. A low refrigerant charge will not only decrease system efficiency & capacity; it will destroy a compressor as well. A compressor is designed to pump refrigerant and will pump excessive amounts of oil when it runs with low pressure. A hot running compressor with a low oil condition will not run for long. The technique of “gas & go” as an alternative to repairing a refrigerant leak will often lead to refrigerant contamination & premature compressor failures. Lack of Refrigerant Charge
Restricted Refrigerant Circuits Refrigerant restrictions will also cause starving conditions for the compressor. Restrictions can come from: --undersized or kinked refrigerant lines --excessively long refrigerant lines --restricted metering device --restricted driers or screens The temperature drop across a drier should never exceed 2 degrees. A filter drier does not have to “frost” to be considered restricted.
Be cautious with long suction lines Especially when they run through hot attics. It is not uncommon to see line sets pick up 10 degrees in the peak of summer. This turns your 16 degrees of superheat at the evap coil into 26 degrees at the condenser--many expansion valves have been improperly diagnosed because of this. When running refrigerant line sets, position the systems to minimize line set lengths and use a thicker wall insulation when running through unconditioned spaces. Remember, a cool running compressor will thank you with years of reliable service.
High Load Conditions A hot house can exceed the ability of the refrigerant circuit. This is typical with new system start ups in the summer. Indoor temperatures exceeding 80 degrees may overload the coil & the ability of the metering device to move enough refrigerant to keep the compressor cool. High indoor temperatures also make it impossible to accurately charge a system. While this is a temporary condition with a new start up, it is a continual stress for homes who only “Cool” when it becomes “HOT”. This continual high load will cause high superheat conditions; the end result may be another compressor obituary.
Leaking Reversing Valves Most of us take our superheat readings before the reversing valve. This reading may confirm the proper working of the expansion valve, but we may have reversing valve issues. A temperature rise across the suction side of the reversing valve is typically less than 3 degrees. A valve with a 7 degree rise is leaking; it is time to recommend the replacement of the valve. A valve with 13 degrees is considered failed and must be replaced.
System Evaluation & Clean up processes: *Acid tests are quick, easy & economical ways to determine acidic system conditions. *Suction line swab test—use a rag to swab the inside of the suction line once the compressor is removed. Whatever you find on the rag has been distributed throughout the entire system (this test is also useful on line sets with system replacements). A dirty rag suggests a more aggressive clean up process. *Replace the liquid line filter drier & use Acid Away with every compressor replacement. Install a suction line filter drier if the system is acidic or the swab test shows contamination.
Thermal Expansion Valves
Installation Practices Brazing to Evaporator Section – Important Do Not unseal refrigerant tubing until ready to cut and fit Refrigerant Lines
TXV Bulb TXV Bulb MUST be protected (Wrapped with wet rag) or removed, while brazing the tubing. Overheating of the sensing bulb will affect the functional characteristics and performance of the coil.
Evacuation Braze and Evacuate according to Indoor and Outdoor installation Instructions Flow a small amount of Nitrogen through the tubing while brazing Evacuate system to a minimum 350 microns
TXV Troubleshooting Airflow is essential to a systems survival. If you don’t have the air you don’t have anything. You will need the proper tools for diagnosing a system. Pressures, Superheat, and subcooling are vital in determining what is going on in the system.
TXV- Placement Always verify the bulb is properly attached to the suction line. It should be attached by the metal clamp provided by the factory for proper heat transfer and proper attachment. The bulb should also be insulated. It should be at the 10 o’clock or 2 o’clock position and should never be mounted in the 6 o’clock position.
Hand Test If you have: Low Suction Pressure High Discharge High Superheat High Subcooling With no Restrictions in the Liquid Line The hand test is always a good method of seeing if you can get the valve to open with a rise in pressure and a decrease in superheat.
Know Your System Don’t forget about your indoor check valve, outdoor check valve and reversing valve when diagnosing a system. Use both gauge connections when diagnosing heat pumps Outdoor Check Valve Restriction If only used service valves: Subcooling- 60 Superheat- 77 Suction- 51 Discharge- 170 If you looked at common suction and discharge: Common Discharge- 546 What is wrong with this system??
Is it the compressor?? Suction- 225 Discharge- 266 Superheat- 0 Subcooling- 0 Could it be the check valve?? Is it the TVX? What steps could we take next?? Stuck Open Check Valve