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Condensing Unit Accessories
Suction Filters, Driers, Sight Glasses
There are two types of suction and liquid filter/driers used on Heatcraft Refrigeration Products units. Replaceable core and/or sealed units are used, dependent upon the option package ordered.
Suction filters, regardless of type, are always installed upstream of the compressor suction service valve, and any accumulators or other options that may be installed.
Suction filters are equipped with “Schrader” type access valves to allow field measurement of pressure drop across the device. This allows plugged filters and elements to be identified very quickly and easily so they can be replaced when the pressure drop is excessive. Refer to the specific manufacturersʼ recommendation on servicing these units by make and model.
Liquid filter/driers, regardless of type, are always installed downstream of the receiver outlet service valve, and upstream of the liquid line solenoid valve (if supplied). Liquid line driers may or may not have an access valve, dependent on the size and application. The basic servicing of these units is similar to suction filters. Liquid line driers should be replaced whenever there is evidence of excessive pressure drop across the filter, or the system becomes contaminated due to system leaks, compressor burnouts, acid formation, or moisture accumulation as indicated by the liquid line sight glass.
The sight glass is installed in the main liquid line assembly, downstream from the receiver outlet service valve, and immediately after the liquid line drier. The sight glass is designed to give a visual indication of moisture content in the system. Generally, it requires no field service. However, in cases of extreme acid formation in a system after a compressor burnout, the acid may damage the sensing element or etch the glass. This would require that the sight glass be replaced, along with the liquid line drier after any compressor motor burnout.
Table 1. Recommended Low Pressure Control Settings for Outdoor Air Cooled Condensing Units
*Minimum
Temp. ˚F
50
40
30
10
0
-10
-20
-30
Cut-In
PSI
70
55
40
30
15
15
10
6
R-22
Cut-Out
PSI
20
20
20
10
0
0
0
0
R-404A/R-507
Cut-In Cut-Out
PSI
90
70
55
45
25
20
12
8
PSI
35
35
35
25
7
1
1
1"Hg.
Cut-In
PSI
45
35
25
13
8
---
---
---
R-134a
Cut-Out
PSI
15
10
10
0
0
---
---
---
* Minimum ambient or box temperature anticipated, Hi pressure control setting: R-22, 360 PSI; R-404A, R-507, 400 PSI; R-134a, 225 PSI.
Table 2. Thermostat Settings
Models
2-fan units:
4-fan units:
3-fan units:
6-fan units:
8-fan units:
Design
T.D.
30
25
20
15
30
25
20
15
30
25
20
15
NOTE: Cycle pairs of fans on double wide units.
75
60
65
70
T1
60
65
70
75
60
65
70
75
Thermostat Settings
T2
50
55
65
70
40
55
60
65
T3
30
40
50
60
CAUTION: Fans closest to the headers should not be cycled on standard temperature or pressure controls. Dramatic temperature and pressure changes at the headers as a result of fan action can result in possible tube failure. Fan motors are designed for continuous duty operation.
Fan cycling controls should be adjusted to maintain a minimum of (5) minutes on and (5) minutes off. Short cycling of fans may result in a premature failure of motor and/or fan blade.
Compressors operating below +10°F SST must have air flowing over the compressor at all times when the compressor is running.
5
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