High- And Low-Pressure Switches; Capacity Control - Carrier 30HS Series Installation, Start-Up And Service Instructions Manual
Reciprocating liquid chillers
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Also See for 30HS Series:
- Wiring diagrams (8 pages) ,
- Product data (36 pages) ,
- Installation instructions (4 pages)
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To Recalibrate
-
Break painted seal at dial screw.
With a screwdriver in the adjusting slot,
hold the
angular position of the dial assembly while com-
pleting the following steps:
1. Loosen the 2 dial screws.
2. Rotate
dial only
until number under the fixed
indicator is observed temperature of mixture.
3. Retighten dial screws.
Turn dial assembly until desired compressor
cutoff temperature is directly under fixed indi-
cator. Recalibration is now complete.
HIGH- AND LOW-PRESSURE SWITCHES
High-Pressure Switch -
Slowly close discharge
shutoff valve until compressor shuts down (should
be at cutout pressure shown in Table 4).
Re-energize compressor contactor and control
relay for circuit by pressing START-STOP button
to STOP then to START.
Reopen discharge shutoff valve; compressor
should start when pressure drops to cut-in pressure
shown.
Table 4 - Pressure Switch Settings (psig)
UNIT
30
HIGH PRESSURE*
LOW PRESSURE
( ±7 psig)
( ±4 psig)
Cutout
Cut-in
Cutout
Cut-in
HR
HS
265
340
185
250
24
24
74
74
*Fixed range; 80 ±14 psig differential.
Low
-
Pressure Switch --
Range is adjustable from
5 psig minimum cutout to 100 psig maximum cut-
in. Differential is adjustable from 8 to 50 psig. To
check: slowly close suction shutoff valve and allow
compressor to pump down. Compressor should cut
out when suction pressure falls to 24 psig and auto-
matically restart when pressure builds up to 74 psig.
WINTER START (30HS units with remote air-
cooled condenser(s) - Proper condenser head
pressure control should eliminate the need for
winter-start modifications. However, if nuisance
cutouts on low pressure occur during cold weather
start-up, adjust the low-pressure switch (LPS) cut-
out point to 15 psig. If cutouts still occur (and the
condenser fan regulation is functioning properly),
disconnect LPS capillaries from crankcases of com-
pressors no. 1 and no. 3 and readjust LPS back to
30 psig. Reconnect each capillary to the 1/ 4-in. flare
port on respective charging valve for each circuit
(located at the filter-drier).
Be sure charging valve
is back-seated when installing the capillary and mid-
seated after capillary is installed.
NOTE: Add 1/4-in. tubing to the short LPS
capillaries.
The 1/ 4-in. flare connections will make all addi-
-.1
tional connections mechanical (no sweat
connections).
Check both switches at start-up and at least once
each year.
Table 5 - Capacity Control Steps
UNIT
30HR
3OHS
CONTR
STEPS
'
TRANS SW POS 1*
TRANS SW POS 2*
Oper Cylinders
Oper Cylinders
%
Cap.
Tot.
Ckt 1 Ckt 2
%
Carl.
Tot.
Ckt 11 Ck 2
Compr
Comp
1
2 3 4
1
2
3
4
1
28.6
4
- - 4 -
14.3
2
2 -
--
2
42.9
6
2- 4-
42.9
6
2- 4-
3
57.2
8
2- 6-
57.2
8
2- 6-
070
4
71.2
10
4 - 6 -
71.2
10
4 - 6 -
5
85.7
12
4
4 4-
85.7
12
4 4
4 -
6
100.0
14
4
4 6- 100.0
14
4 4
6 -
1
25.0
4
-
4 -
25.0
4
4 - - -
2
50.0
8
4- 4-
50.0
8
4
4-
3
62.5
10
4 - 6 -
62.5
10
4 - 6 -
080
4
75.0
12
6 - .6
7
-
75.0
12
6 - 6 -
5
_,
87.5
14
6
4 4-
$47.5
14
6 4
4 -
6
'
100.0
16
6
4 6- 100.0
16
6 4
6 -
1
22.2
4
- - 4 -
22.2
4
4.-
-
2
44.4
8
4- 4 -
44.4
8
4- 4-
3
55.5
10
4
6 -
55.5
10
4 - 6 -
090
4
66.7
12
6 - 6 -
66.7
12
6 - 6 -
5
88.8
16
6
6 4-
88.8
16
6
6
4 -
6
100.0
18
6
6 6- 100.0
18
6
6
6 -
1
20.0
4
-
4 -
20.0
4
4 - - -
2
40.0
8
4- 4-
40.0
8
4'
4 -
3
50.0
10
4 - 6 -
50.0
10
4 - 6 -
100
4
5
60.0
70.0
12
14
6
6
-
4
6
4-
-
60.0
70.0
12
14
6
6
-
4
6
4
-
-
6
80.0
16
6
4 6-
80.0
16
6 4
6 -
7
90.0
18
6
4 4 4
90.0
18
6 4
4
4
8
100.0
20
6
4 6 4
,
100.0
20
6 4
6
4
1
18.2
4
- - 4 -
18.2
4
4 - - -
2
36.3
8
4
4 -
36.3
8
4- 4 -
3
45.4
10
4 - 6 -
45.4
10
4 - 6 -
110
4
5
54.5
72.7
12
16
6
6
-
6
6
4-
-
54.5
72.7
12
16
6
6
6
6
4
-
-
6
81.8
18
6
6 6-
81.8
18
6
6
6 -
7
90.9
20
6
6 4 4
90.9
20
6
6
4
4
8
100.0
22
6
6 6 4 100.0
22
6
6
6
4
1
16.6
4
- - 4 -
16.6
4
4 - - -
2
33.3
8
4- 4-
33.3
8
4- 4 -
3
41.0
10
4 - 6 -
41.0
10
4 - 6 -
120,
4
50.0
12
6
- 6 -
50.0
12
6 - 6 -
160
5
66.7
16
6
6 4
66.7
16
6 6
4 -
6
75.0
18
6
6
6-
75.0
18
6
6
6 -
7
91.6
22
6
6 4 6
91.6
22
6
6
4
6
8
100.0
24
6
6 6
6
100.0
24
6
6
6
6
1
19.0
4
- - 4 -
19.0
4
-
2
38.0
8
4- 4-
38.0
8
- 4 -
3
47.6
10
4 - 6 -
47.6
10
- 6 -
140
4
5
57.0
69.0
12
16
6
6
-
6
6
4-
-
57.0
69.0
12
16
-
6
6
4
-
-
6
78.6
18
6
6
6-
78.6
18
6
6 -
7
90.4
22
6
6 4
6
90.4
22
6
4
8
100.0
24
6
6
6
6
100.0
24
6
6
*Transfer Switch, manually operated.
NOTE:
Circuits and compressors numbered from left to right when viewed
from front of unit.
CAPACITY CONTROL
Controls cycle compressors and alternately load
and unload cylinders to give capacity control steps
as shown in Table 5. Controls for each unit include
a step controller, a chilled water temperature con-
troller and 2 solenoid-operated cylinder unloaders.
Step Controller
-
A 24-volt transformer in the
step controller provides power to a low voltage
motor with windings for rotating a camshaft
clockwise and counterclockwise. Factory-set cams
operate load switches which start or stop com-
pressors and load or unload cylinders. Motor
windings of camshaft drive motor are energized by a
balancing relay which contains windings in the tem-
perature bridge circuit between chilled water
9
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