Refrigeration / Condensing Units

Hybrid Condenser Takes a Test

January 17, 2011
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A condenser retrofit at a Massachusetts supermarket included running the existing piping from the existing condenser to the inlet of a new hybrid condenser, running a water line to the new condenser and bringing over the power and control wiring.

The 3C Hybrid Condenser was developed by Muller Industries to help mitigate the impact of increasingly hot ambient conditions that are causing air-cooled refrigeration and air conditioning systems to lose cooling capacity while consuming more energy. Particularly well suited for supermarkets with their continuous need for refrigeration, the condenser can reverse capacity losses and lower energy usage, the manufacturer said.

Hoping to test the authenticity of such assertions, Big Y Foods of Springfield, Mass., recently installed the condenser in its Southwick store. This article provides the details of this installation and describes the benefits that were actually achieved.
 

THE CONDENSER

At its heart, the condenser is air-cooled and rejects its heat to ambient air drawn by fans across condenser coils (heat exchangers). It, however, is different from traditional air-cooled systems in a number of significant ways:

• The standard horizontal condenser coils have been replaced with vertically mounted aluminum micro channel heat exchangers that allow for increased heat rejection and lower refrigerant charge.

• Evaporative cooling pads have been mounted to the outside of the heat exchangers. Under high ambient conditions, water flowing across the pads evaporates into the condenser air thereby lowering its temperature and increasing heat rejection. To minimize water use, water that is not evaporated is re-circulated over the pads and then flushed to drain at the end of each day. With no standing water, chemical treatment is not required.

• The condenser runs in the dry mode the majority of the time, only using water when the ambient temperature rises above a predetermined set point. That allows for a reduction in water use of up to 90 percent.

• The low-efficiency fans typically found in air-cooled condensers have been replaced with high-efficiency, ultra quiet EC fans with integral variable-speed drives. This can reduce fan energy use by up to 75 percent depending on the ambient conditions. Additional energy savings can be achieved as the cooling systems are now able to run at lower, far steadier head pressures.

• The condenser’s all-aluminum construction makes it extremely durable, lightweight, easy to support, and 100 percent recyclable.
 

BACKGROUND

When Big Y Foods purchased the condenser to replace an existing air-cooled condenser in its Southwick store, energy conservation was its primary objective. The old condensers struggled to keep up with the load, especially during record high ambient temperatures. That made the new hybrid condenser’s evaporative cooling feature extremely attractive to Big Y due to its promised ability to increase peak ambient cooling capacity.
 

REFRIGERATION EQUIPMENT

Big Y Southwick is served by three air-cooled rack systems that run on HFC-404A refrigerant. Rack A, where the retrofit took place, is low temperature. Racks B and C are medium temperature.

The installation took three days in the summer. The first two were mainly spent on preparation work: placing the new condenser on structural steel, running the refrigerant piping from the existing condenser to the inlet of the new condenser, running a water line to the new condenser, and bringing over the power and control wiring. The actual changeover took place two days after the project started. To implement the changeover, the refrigeration system was shut down for approximately two hours.
 

EC fans with integral variable speed drives reduce condenser energy use while providing consistent head pressures.

OBSERVATIONS

At 2 p.m. on the third day, with the roof temperature approximately 89°F, Big Y senior technical specialist Ken Soto witnessed the following conditions:

• The low temperature Rack A with the new hybrid condenser had a head pressure of 185 pounds and a condensing temperature of 85°.

• The medium temperature Rack B, with a standard air-cooled condenser, had 256 pounds head pressure and 105° condensing temperature.

• The medium temperature Rack C, with a standard air-cooled condenser, had 253 pounds of head pressure and 104° condensing temperature.

Based on this, Soto made the following observations:

1. The 185 pound head pressure measured at Rack A was within 2° of ambient, while racks B and C could do no better than 22° above ambient. Compressor manufacturer data suggests that this 20° differential will reduce compressor energy use by about 20 percent while substantially increasing cooling capacity.

2. The previous day, under similar ambient conditions but with the old air-cooled condenser still running, the head pressure on Rack A had been roughly 250 pounds and all five 7.5 HP compressors were running to satisfy the load. With the new condenser in place, at least two compressors were cycled off and the case temperatures were being easily maintained.

3. Additional energy savings were being achieved at the Rack A condenser where two high-efficiency EC fans were running instead of the four standard-efficiency fans on the air-cooled condenser. As the EC fans have integral VFDs, their speed is reduced as the ambient temperature falls and additional savings are realized.

4. With the new condenser in place, the Rack A receiver had roughly 50 percent less refrigerant than with the old condenser. That is because the 3C heat exchangers require far less refrigerant than the old condenser coils.
 

A hybrid condenser is mounted on structural steel at a supermarket in Massachusetts.

INCENTIVES

Western Massachusetts Electric (WMECO), which provides electricity to the Southwick store, is evaluating the installation for the purpose of granting an energy conservation incentive. Should the new condenser pass their evaluation, the utility will pay a portion of the installed cost; thereby lowering Big Y’s out of pocket costs.

Big Y director of facilities Tony Coppola points to the environmental benefits Big Y hopes to realize through the hybrid condenser. “In this age of heightened environmental awareness, Big Y is continuously striving to positively impact the planet. We were attracted to the 3C because of the promised energy savings and capacity increases. The Southwick installation validated those expectations. It is also of great importance, however, that the new condenser allows us to reduce the amount of refrigerant in the system, and that the new condenser can be recycled at the end of its useful life. Benefits like this can only help us to make a more positive impact in the communities we serve.”

Muller North America VP of Sales Paul Noreen said, “While in recent years there have been significant efficiency advancements in devices like lighting, motors, fans, and individual components within refrigeration and air conditioning systems, air-cooled condensers have remained relatively unchanged. The 3C changes all of that. It is exactly what is needed as we face the unprecedented environmental challenges ahead.”

For more information, visit www.mullerna.com.

Publication date: 01/17/2011

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