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Efficiency Factors for Condensing Units - For years compressors inside the condensing unit were sized to meet the highest load demand for whatever application they were serving. Even today, many compressors, located inside the condensing unit are sized in accordance with their highest load demand even though it is unlikely they will only be needed to run for full load conditions approximately 30-35% of the time.
While many systems have worked just fine this way for many years they have not been very energy efficient. So even on a mild day, these compressors run full blast even though the system may only require the compressor to run at 50% capacity to satisfy the demand. That creates problems with short cycling which causes premature wear, higher maintenance costs, and reduces total compressor lifespan.
Efficiency Factors for Condensing Units
Compressor Staging
HVAC Compressor manufacturers realize this and have developed new technologies to solve this problem. The first type of new HVAC compressor technology covered in this article is the two-stage scroll compressor. Inside this compressor is a plate with two precision holes drilled in it. One hole represents 80% capacity and the other hole represents 100% capacity. When the compressor is operating normally it is running at 80% capacity. With an increased demand this plate shifts allowing the compressor to handle the increased load.
This process increases efficiency and decreases energy usage. The two-stage scroll compressor is a variation of what some manufacturers have been trying to do but never had the technology to do it. Some manufacturers use reciprocating compressors that have two-speed windings in them along with several controls to engage the higher speed compressor winding when the demand calls for it.
Other HVAC manufacturers put two compressors, one small and one big, in their units. These HVAC systems work just fine but are usually more expensive to manufacture. The new two-stage scroll offers you efficiency and energy savings without the added cost of these older HVAC systems. Remember there are more ways than one to calculate efficiency but there is only one way many of us calculate our energy savings and that is when we get the bill.
Variable Speed Compressors in Condensing Units – Efficiency Factors for Condensing Units
The next HVACR development in new technology for compressors is the variable speed compressor. These compressors will only be available in the commercial market but it’s a good guess that it won’t be long before the compressor technology crosses over into residential systems. A variable-speed compressor adds a whole new dimension to the efficiency factors for compressors. It also raises the bar on the type of controls used to control the drive that determines the speed of the compressor.
Just to name a few of the factors needed to be taken into account to control this compressor are the suction and discharge temperatures of the compressor along with the pressures, superheat and sub-cooling, and inside and outside ambient temperatures. Variable speed compressor systems will require a control algorithm that will process the inputs and send the desired output speed to the compressor based on the factors mentioned above. Variable speed compressor systems are complex and will require the attention of a properly trained HVAC technician to troubleshoot any problems that may arise with the system.
Commercial Systems | Efficiency Factors for Condensing Units
Currently, commercial refrigeration and air conditioning systems used loaders or unloaders and/or multi-compressor staging systems to meet demand. By and large, these systems dominate the market now but when this new variable speed compressor technology takes off, these systems will most likely wither away being slowly replaced with the more efficient variable speed compressor systems.
Other Efficiency Factors for Condensing Units
One other note to consider in this age of new technology and higher HVAC energy-efficient equipment being developed and manufactured, you can have the most energy-efficient engine but if it’s in an old 60 or 70’s model car your efficiency is going to suffer.
The same is true with HVAC systems. You have the most energy-efficient compressor available on the market but if your ductwork is leaky or your house or business is not properly insulated that compressor is wasted money. Yes, bad ductwork WILL affect the performance of the refrigeration system absolutely.
It is also important that when these systems are installed that they receive proper commissioning and start-up to ensure they are working as designed. This typically involves checking out the whole HVAC system to make sure everything is working as efficiently as possible by a qualified HVAC technician. Just remember, as the cost of energy rises it becomes more and more critical to make sure the whole system works together as designed. Follow that little nugget of advice and you will see your energy bills decrease.
HVAC Air Conditioner or Heat Pump Condenser Coils
From time to time in commercial and residential HVAC, there are HVAC units where it is more cost-effective to change a major HVAC component than it is to replace the entire HVAC unit. Before this is done an evaluation should be performed on the potential financial risk of changing the major HVAC component versus changing the HVAC equipment.
Consideration should be given to the age of the unit and the chances of another major component failure in the near future. Age will also factor into the issue of actually finding a replacement part. Does the manufacturer even make the major component any longer or will you have to have one custom-made? It becomes necessary to look at other major HVAC components in the HVAC system and check their condition.
HVAC Professional Attention for Proper Air Conditioner Function and Performance
This often requires the attention of the owners of the equipment and someone trained (HVAC Professional) to make a fair evaluation and assessment of the other major components in the HVAC system. It is always a risk changing a major component because of the potential of another component failing in the near future and costing more than the cost of total HVAC unit replacement.
Other considerations are the efficiency of the old HVAC unit versus the efficiency of a new HVAC unit. What are the years to pay back versus paying a higher utility bill for repairing and maintaining the old HVAC equipment?
What is the maintenance and repair history of the old HVAC equipment in need of repair? Has the HVAC equipment in question been a headache with constant repair issues? After all these things are assessed one can make the best decision and that is to replace the major HVAC component or replace the entire HVAC unit.
Dirty condenser coils will definitely affect the efficiency of the condenser and lead to issues that will shorten the operating life of the equipment. Problems like high head pressure and lower cooling factors because of increased temperatures. This causes problems in compressors because of the excessive heat.
Condenser Coils | Efficiency Factors for Condensing Units
This brings up the issue and title of this article. Condenser coils. The above paragraph could apply to evaporator coils, compressors, or even replacing motors or variable frequency drives in the system. Sometimes coils can be repaired but other times they cannot. When you get a refrigerant leak in a condenser coil problems occur when applying heat to the condenser or evaporator coils.
Evaporator and condenser coils are designed to transfer heat. When an HVAC technician has to repair an evaporator or condenser coil they generally have to use a lot of heat to solder the hole in the evaporator or condenser coil. This heat is then transferred to other parts of the evaporator or condenser coil and that likely will cause factory-made solder joints to loosen up. Before you know it another leak appears in another part of the condenser or evaporator coil and it’s like a dog chasing his tail.
The evaporator or condenser coil needs to be replaced or an evaluation for HVAC unit replacement needs to do for possible replacement versus major component retrofit. And don’t forget maintenance. Keep that condenser clean for optimal performance.
Efficiency Factors for Condensing Units
Technical Resource: Refrigeration and Air Conditioning Technology
