Emerson 3000/ITR manual 7.4Refrigeration System, 7.3.3Air Distribution, 7.4.1Suction Pressure

Component Operation and Maintenance

7.3.3Air Distribution

All unit models are designed for constant volume air delivery. Therefore any unusual restrictions within the air circuit must be avoided. For downflow models operating on a raised floor, refer to the following table for recommended free area for proper air flow.

Table 5 Recommended free area ft2 (m2) for grilles or perforated panels at output velocities of 550 and 600 fpm (2.8 and 3.1 m/s)

	550 FPM	600 FPM
Model	(2.8 m/s)	(3.1 m/s)
60 Hz Units
3 Ton	3.3 (0.31)	3.0 (0.28)
5 Ton	5.1 (0.41)	4.7 (0.44)
50 Hz Units
3 Ton	3.3 (0.31)	3.0 (0.28)
5 Ton	4.7 (0.44)	4.3 (0.40)

Grilles used in raised floors vary in size, the largest being 18" x 6" (46 cm x 15 cm). This type of grille has approximately 56 in2 (361 cm2) of free area. Perforated Panels are usually 2' x 2' (61 cm x 61 cm) and have a nominal free area of approximately 108 to 144 in2 (697 to 929 cm2).

NOTICE

Risk of airflow restriction. Can cause inefficient operation and equipment overheating.

In raised-floor use, all under-floor restrictions, such as clusters of cables or piping, must be avoided because they may form barriers to airflow. Whenever possible, cables and pipes should be run parallel to the airflow. Never stack cables or piping.

7.4Refrigeration System

Each month, the components of the refrigeration system should be inspected for proper function and signs of wear. Since, in most cases, evidence of malfunction is present prior to component failure, peri- odic inspections can be a major factor in the prevention of most system failures.

Refrigerant lines must be properly supported and not allowed to vibrate against ceilings, floors or the unit frame. Inspect all refrigerant lines every six months for signs of wear and proper support. Also inspect capillary and equalizer lines from the expansion valve and support as necessary.

Each liquid line has a sight glass that indicates liquid refrigerant flow and the presence of moisture. Bubbles in the sight glass indicate a shortage of refrigerant or a restriction in the liquid line. The moisture indicator changes from green to yellow when moisture is present in the system.

7.4.1Suction Pressure

Suction pressure will vary with load conditions. The low pressure switch will shut the compressor down if suction pressure falls below the cut-out setting. High suction pressure reduces the ability of the refrigerant to cool compressor components and can result in compressor damage. Minimum (pres- sure switch cut-out setting) and maximum (design operating) suction pressures are in Table 6.

Table 6 Suction pressures - R407c

	Minimum	Maximum
System	PSIG (kPa)	PSIG (kPa)
Air w/FSC	15 (103)	95 (654)
(Fan Speed Control)
Air w/Lee-Temp Control
(Floodback head	20 (137)	95 (654)
pressure control)
Water Cooled	20 (137)	95 (654)
Glycol Cooled	20 (137)	95 (654)

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