How we save energy

With our Air-Cooled V3 Concept

In the face of constantly increasing energy costs, Annexair is responding by creating smart, energy-conscious designs. The traditional multi-stage compressor approach tries to improve comfort and generate savings, but without modulation, the opposite occurs. After analyzing many different cooling control techniques, the Annexair design team concluded that variable speed compressors are the best choice for our new Air-Cooled Condensing Units. Each one of them uses minimum amounts of energy without compromising on comfort.


Engineered to Minimize Energy Costs

It’s no secret that refrigeration systems are costly to operate. Continuous setpoint satisfaction is the reason why these systems require greater amounts of energy. We designed our V3 technology to radically reduce energy requirements and even eliminate all peak loads at unit start-up, helped by our soft-start compressors and their 30 to 90Hz modulating capability. For example, a 22-ton unit will modulate from 7 to 22 tons, a 30-ton unit will modulate from 5 to 30 tons and a 70-ton unit will modulate from 7 to 70 tons.

Figure 1 demonstrates the modulating capacities of several ACCU sizes available, from the minimum to maximum capacities including EER value for 30, 60, and 90 Hz operation.

Figure 1

Designed for Maximum Comfort

Designing an affordable refrigeration system that delivers increased comfort and savings is a challenge. By using only variable speed compressors and variable speed condenser fans in unison, we have created the perfect sequence to maintain comfort levels and avoid wasting energy.

Figure 2


Figure 2 shows how conventional AC units continuously cycle on and off, wasting energy and affecting comfort levels.

Figure 3


Figure 3 illustrates how our V3 Concept requires less power to maintain comfort levels and how it eliminates ON/OFF cycling. Supply temperature can be held at ± 0.2°F of desired setpoints. As a result, annual unit operating costs can be 15 to 30% less

Full Load vs. Part Load

Even though units are designed for Full Load operation, the reality is that they will run most of the time in Part Load operation. Units that cannot match design requirements with a certain accuracy result in wasted energy when working at Part Load. Figure 4 below demonstrates the actual Full Load vs. Part Load requirement for 5 major cities in the United States. The graph represents an analysis of 25 years of bin data for each city collected from ASHRAE weather data and compiled to demonstrate the percentages of Full Load and Part Load operation. Full Load operation is maintained for a maximum of 2% during the year while the remainder is considered Part Load operation. Part Load capacity ranges have been divided into 3 zones represented by different colors. Considerable energy savings are obtained due to the impressive quantity of hours at Part Load.

Figure 4 Digits in columns (%) represent the outdoor air temperature annual frequency of operation that exceeds

Figure 4

50°F dew point. Take note that full load zone (dark gray) has been defined for systems operating between 96 to 100% of ASHRAE city design condition, 96% and below are defined as part load zones. Data is based on ASHRAE 2009 Weather Viewer Dew Point Bin Data.


New Compressor Technology That Saves Energy

Figure 5

All ACCU models come with a smart head pressure control logic which modulates condenser fan speeds, therefore keeping the compressor motors at their perfect operational pressure level. These critical components nick-named, “the Combo”, by Annexair’s engineering team, perform smoothly together through synchronicity. This unique concept consumes the least amount of energy and delivers maximum comfort by always running in the optimal range.

Figure 5 represents the power consumption for the refrigeration system while in operation (orange line). The optimal range is the ideal zone where the addition in kW from the compressors and fans are at their lowest.


Smart Head Pressure Control Delivers Optimal Performance

Traditional systems address part load conditions with unloading techniques (for example with hot gas bypass), multiple compressors, or by using digital compressor technology. These solutions are inefficient either because high compressor efficiency cannot be maintained at part load or because the load matching ability is limited. Hot gas bypass is an alternative solution, but it also wastes a significant amount of energy.

The VSH compressor made by Danfoss, which is designed to maintain high isentropic efficiency and has the inherent benefit of matching the load precisely and continuously by operating from 30 Hz to 90 Hz. With no excess evaporator and condenser capacity under part load, the compressor COP is higher and delivers significant energy savings. Also, because it is in continuous operation, this means less cycling and system stress, higher reliability and a longer lifespan. Helped by the Annexair unit PLC, the supply desired setpoint can be exceptionally precise with an accuracy of 0.1°F.

Each compressor come equipped with a factory programmed VFD keypad which graphically displays multiple parameters: hertz, amps, load capacity %, etc. It’s a great tool for monitoring, troubleshooting and maintenance. These values are also displayed on the unit PLC and accessible to the BMS via BACnet or LonWorks.

Additional savings are also achieved because the power factor remains above 0.90 regardless of the load; drive controller logic ensures soft starts that reduce inrush current. Depending on project location, V3 Technology energy savings can be 15 to 30% greater than conventional systems.


Micro-channel coils for improved performance

Since 2008, Annexair has been manufacturing units with micro-channel coils. As of today, they are available for almost all projects. Entirely made of aluminum, these coils require less amounts of refrigerant as compared to conventional coils. Also, the air pressure drop of the coil is less and includes an integrated receiver. With a significantly enhanced performance, this product fits perfectly with variable speed compressors.


Protective Nylon Screens

Micro-channel’s increased thermal efficiency is in part due to the close spacing between its fins. Since air pollution and aggressive particles can collect on the coils surface and reduce condensing performance, protecting the coil is crucial. To ensure a performing system, Annexair’s standard is to include a protective nylon screen for all condenser coils. In addition, this screen protects the unit from hail and helps prevent vandalism. Rain will automatically cleanse the screen but, should intensive washing be required, tool-free nylon “quick latches” make removing the screen fast and easy.


Variable Speed Condenser Fans

Variable speed condensing fans are a major component of the V3 Concept. Variable voltage controllers provide 100% fan speed control. The unit’s PLC controller will vary the fan speed to maintain the compressor’s safety pressure in relation to outdoor air temperature. All banks of fans run together at the same speed to ensure a perfect airflow balance across the entire surface of the coils. Meanwhile, lower noise levels are achieved because the condensing fans will rarely operate at full speed.


Unmatched acoustics and efficiency

Annexair uses German-made condenser fans named Zielh-Abegg. The superior quality assembly of these fans easily surpasses all other axial fans in the industry. These fans have 7 blades and are housed in a safety guard. The profiled die-cast aluminum blades and motor are mounted inside a high profile bell mouth, which lowers the acoustical noise levels.

Annexair uses 2 types of blades, the FC design (left) which is commonly used and just recently, we offer the FE2Owlet design (middle and right) for project requiring lower acoustical needs. FC blades are 80dB maximum, while FE2Owlet are 77dB at maximum condensing unit capacity.

As shown in the pictures, parts that are painted are epoxy coated as a standard.

FC Fan Blade

Owlet Fan Blade

Owlet Fan Blade