4. Type of Operation/Air Flow

Two important considerations in the selection and location of the unit cooler are uniform air distribution and air velocities which are compatible with the particular application.

The direction of the air and air throw should be such that there is movement of air where there is a heat gain; this applies to the room walls and ceiling as well as the product. The unit cooler(s) should be arranged to direct its discharge air at any doors or openings, if it all possible. Avoid placing the unit cooler in a position close to a door where it may induce additional infiltration in to the room; this can cause fan icing and a condition known as hoar-frost. Also, avoid placing a unit in the air stream of another unit, because defrosting difficulties can result.

For general storage coolers and holding freezers, there are not criteria for air velocities within the room. The total supply of air is such that approximately 40 to 80 air changes occur each hour. This is an air conditioning term which is calculated as follows:

Air Changes = (total cfm*) x 60 internal room volume

* includes all unit coolers and auxiliary fans

This equation disregards the air motion which is induced by the discharge air from the unit cooler. For simplicity, the gross volume of the room is used unless the product and equipment occupy more than 10% of the volume. Specific applications such as cutting rooms and banana ripening rooms have desired limits. The table below indicates the minimum and maximum quantities of air for particular applications.

Recommended Air Changes/Hour

 

Recommended Number

 

 

of Air Changes

 

Type of Application

 

Minimum

 

Maximum

 

 

 

 

 

Holding freezer

40

 

80

Packaged Holding center

40

 

80

 

 

 

 

 

Cutting Room

20

 

30

Meat Chill Room

80

 

120

 

 

 

 

 

Boxed Banana Ripening

120

 

200

Vegetables and Fruit Storage

30

 

60

Blast Freezer

150

 

300

Work Areas

20

 

30

 

 

 

 

 

Unpackaged Meat Storage

30

 

60

 

 

 

 

 

Derating Factors

A.Ambient

B.Altitude

C.Saturated Suction Temperature (S.S.T.)

D.50 Cycle Power

In the selection of refrigeration equipment it should be noted that the manufacturer’s equipment has ratings based on certain criteria. Care should be taken to determine actual job conditions and the proper derating factors should be applied. These factors may vary by manufacturer but can be used here as rule of thumb approximation.

A. Ambient

Condensing unit ambient is of concern as most equipment is generally cataloged as 90º to 95ºF. ambient.

Decrease condensing unit capacity 6% for each 10ºF. increase in operating ambient.

Increase condensing unit capacity 6% for each 10ºF. decrease in operating ambient.

B. Altitude

Most manufacturers rate their equipment at sea level conditions. An increase in altitude results in a decrease in air density. While the fans on direct drive equipment will deliver a constant cubic feet per minute of air regardless of density, the thinness of the air will affect capacity performance. Belt drive equipment can be speeded up to compensate for the decrease in air density.

Effects of Altitude on Air Cooled Equipment

Altitude

Absolute

Pressure

Standard

 

Capacity

Feet

 

 

Air

 

Multipliers

Above

 

 

Density

Air

Direct Drive Fans

Sea

 

 

At 70ºF.

Dens.

Refrig.

Air Cooled

Level

In. Hg.

PSIA

lbs./Cu.Ft.

Ratio

Evap.

Cond. Unit

-1,000

31.02

15.27

.0778

1.04

1.03

1.005

 

 

 

 

 

 

 

-500

30.47

14.97

.0763

1.02

1.02

1.002

0

29.92

14.70

.0749

1.00

1.00

1.00

 

 

 

 

 

 

 

500

29.38

14.43

.0735

0.98

0.98

0.995

1,000

28.86

14.28

.0719

0.96

0.96

0.998

2,000

27.82

13.67

.0697

0.93

0.93

0.985

3,000

26.81

13.27

.0671

0.90

0.90

0.98

 

 

 

 

 

 

 

4,000

25.84

12.70

.0647

0.86

0.875

0.975

5,000

24.89

12.23

.0623

0.83

0.85

0.969

 

 

 

 

 

 

 

6,000

23.98

11.78

.0600

0.80

0.82

0.960

7,000

23.09

11.34

.0578

0.77

0.79

0.955

 

 

 

 

 

 

 

8,000

22.22

10.92

.0556

0.74

0.76

0.946

9,000

21.38

10.50

.0535

0.71

0.73

0.939

 

 

 

 

 

 

 

10,000

20.58

10.11

.0515

0.69

0.71

0.93

12,000

19.03

9.35

.0477

0.64

0.66

0.91

 

 

 

 

 

 

 

14,000

17.57

8.63

.0439

0.59

0.61

0.88

 

 

 

 

 

 

 

C. Suction Temperature

Care should be taken in the selection of unit coolers, especially freezer models. There is no set rating standard adopted by the industry for the ratings criteria. The model number of a low temperature unit cooler can be rated at -30º SST, -20º SST, -10º SST, 0º SST, or even +10º SST. The capacity difference between the -30º SST and the +10º SST can be as much as 15% higher for the lower rated unit cooler. Most manufacturers provide a suction temperature correction factor for their unit coolers and this should be noted in equipment selections.

D. 50 Cycle Power

Since we live in a “global village,” the opportunity to quote refrigeration equipment for export markets is one not to be ignored. Motors that are sized for 60 cycle operation run at 83% (50/60) speed on 50 cycles operation. Compressors produce only 5/6 of their capacity. However, while fans are only running 83% speed, there is also a decrease in static pressure through the condenser or unit cooler coil and performance does not suffer the full 17% penalty. If it has been verified by the manufacturer that their equipment can be run on 50 cycle power then the following derating factors can be applied:

A.Unit coolers and air-cooled condensers (Capacity x 0.92)

B.Air-cooled condensing units (capacity x .85)

System capacity (unit cooler and air-cooled condensing unit) can be derated by 0.88

To select refrigeration equipment after the load has been determined, divide the BTUH required by (0.88):

=Conversion to select 60 cycle

0.88equipment for 50 cycle loadBTUH

This provides for larger equipment necessary to compensate for 50 cycle derating factor.

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Heatcraft Refrigeration Products H-ENGM0806 Derating Factors, Type of Operation/Air Flow, Recommended Air Changes/Hour

H-ENGM0408, H-ENGM0806 specifications

Heatcraft Refrigeration Products offers a diverse range of commercial refrigeration solutions designed to meet various operational needs. Among their notable offerings are the H-ENGM0806 and H-ENGM0408 models, which stand out for their efficiency and innovative features.

The H-ENGM0806 model boasts a robust construction and high-performance capabilities, making it ideal for large-scale refrigeration requirements. This model is engineered with an advanced compressor that provides powerful cooling while maintaining energy efficiency. The unit operates at low sound levels, making it suitable for environments where noise reduction is essential, such as restaurants and grocery stores. Additionally, the H-ENGM0806 incorporates a reliable fan system designed to ensure optimal air circulation, promoting even cooling throughout the refrigerated space.

Meanwhile, the H-ENGM0408 model is designed for medium-sized applications that require flexibility without compromising on performance. This unit features a compact design, making it an excellent choice for businesses with limited space. Its energy-efficient compressor reduces operational costs, and its user-friendly digital controls allow for easy temperature adjustments and monitoring. The H-ENGM0408 is engineered to operate in various ambient conditions, ensuring reliability and consistent performance regardless of the environment.

Both models feature a state-of-the-art microprocessor control system that allows for precise temperature management. These systems not only optimize performance but also enhance the longevity of the refrigeration units. The H-ENGM0806 and H-ENGM0408 come with a robust evaporator coil design, facilitating rapid cooling and reducing the downtime associated with equipment maintenance.

In terms of durability, both products are constructed with high-quality materials resistant to corrosion and wear, making them suitable for demanding commercial environments. Additionally, they comply with industry standards and regulations, ensuring safety and reliability in operation.

In conclusion, Heatcraft's H-ENGM0806 and H-ENGM0408 models combine efficiency, flexibility, and advanced technology to provide reliable refrigeration solutions. Their thoughtful design and robust features make them ideal choices for businesses looking to maintain optimal temperature control while minimizing energy consumption and operational costs.