Installation
Mounting
The GL-235 is designed for outdoor use. Mount the box vertically with the knockouts
facing downward. For safety, the GL-235 must be a minimum of 5 feet (horizontally) from
the pool or spa.
Power input
Turn off power at circuit breaker before wiring. Remove the internal panel to expose
the wiring connections. Either 115VAC or 240VAC can be used. Refer to the input wiring
diagram (Figure 1) on next page.
WARNING: Applying 240VAC to the 120VAC input
terminals will cause permanent damage to the control.
Grounding
Refer to NEC and local codes for specific grounding requirements. In general, a separate
ground conductor must be run to the ground terminal on the pool service panel.
Low Voltage (LV) output: Solar Valve
The GL-235 controls a single valve. In most applications this is the solar valve, which
diverts water through the collector panels or through the normal pool loop depending
on conditions.
All controls are shipped with the output voltage set to the industry standard 24VAC.
To use the GL-235 with older 12VAC valves, move jumper J4, located on the right side
of the circuit board.
Description
The GL-235 is a differential temperature control for solar heating of pools, spas, and hot
tubs. It provides differential temperature control with an adjustable, calibrated water
temperature high limit. Automatic nocturnal cooling (for pools that overheat in hot
climates) and recirculate freeze protection functions can be enabled/disabled via
internal jumpers.
Input power can be either 115 or 240 VAC. The output controls a 24VAC automatic valve
actuator. For older systems with 12VAC valves, an internal jumper can be moved to
select 12VAC output operation. The GL-235 also has a high voltage output for
controlling a filter pump or booster pump.
Specifications
Temperature/Resistance/Voltage
All Hayward controls use 10K thermistor sensors. When disconnected from the control
the sensor will read 10K ohms at 25ºC/77ºF. Refer to the chart below for the resistance
at other temperatures. For a given temperature, the resistance reading should be
accurate to ±1%. For a given resistance reading, the temperature reading should be
accurate to ±0.5ºF. Voltage measurements should be accurate to ± 2%. Ohm
measurements made with sensor disconnected from unit. Voltage measurements made
with sensor connected to unit and power applied. Sensor voltages are DC volts.
2
11
°F
Ohm s
V olts °F
Ohm s
V olts
°F
Ohm s
V olts
°F
Ohm s
V olts
1
82,719
4.46
41
25,391
3.59
81
9,076
2.38
121
3,679
1.34
2
80,142
4.45
42
24,704
3.56
82
8,861
2.35
122
3,602
1.32
3
77,656
4.43
43
24,037
3.53
83
8,651
2.32
123
3,527
1.30
4
75,255
4.41
44
23,391
3.50
84
8,447
2.29
124
3,454
1.28
5
72,937
4.40
45
22,764
3.47
85
8,249
2.26
125
3,382
1.26
6
70,698
4.38
46
22,156
3.45
86
8,056
2.23
126
3,312
1.24
7
68,535
4.36
47
21,566
3.42
87
7,867
2.20
127
3,244
1.22
8
66,447
4.35
48
20,993
3.39
88
7,684
2.17
128
3,177
1.21
9
64,428
4.33
49
20,438
3.36
89
7,506
2.14
129
3,112
1.19
10
62,479
4.31
50
19,900
3.33
90
7,333
2.12
130
3,049
1.17
11
60,595
4.29
51
19,377
3.30
91
7,164
2.09
131
2,987
1.15
12
58,774
4.27
52
18,870
3.27
92
6,999
2.06
132
2,926
1.13
13
57,014
4.25
53
18,377
3.24
93
6,839
2.03
133
2,867
1.11
14
55,313
4.23
54
17,899
3.21
94
6,683
2.00
134
2,809
1.10
15
53,669
4.21
55
17,435
3.18
95
6,530
1.98
135
2,752
1.08
16
52,078
4.19
56
16,985
3.15
96
6,382
1.95
136
2,697
1.06
17
50,541
4.17
57
16,548
3.12
97
6,238
1.92
137
2,643
1.05
18
49,054
4.15
58
16,123
3.09
98
6,097
1.89
138
2,591
1.03
19
47,616
4.13
59
15,711
3.06
99
5,960
1.87
139
2,539
1.01
20
46,225
4.11
60
15,310
3.02
100
5,827
1.84
140
2,489
1.00
21
44,879
4.09
61
14,921
2.99
101
5,697
1.81
141
2,440
0.98
22
43,577
4.07
62
14,543
2.96
102
5,570
1.79
142
2,392
0.97
23
42,318
4.04
63
14,176
2.93
103
5,446
1.76
143
2,345
0.95
24
41,099
4.02
64
13,820
2.90
104
5,326
1.74
144
2,299
0.93
25
39,919
4.00
65
13,473
2.87
105
5,208
1.71
145
2,254
0.92
26
38,777
3.97
66
13,136
2.84
106
5,094
1.69
146
2,210
0.90
27
37,671
3.95
67
12,809
2.81
107
4,982
1.66
147
2,167
0.89
28
36,601
3.93
68
12,491
2.78
108
4,873
1.64
148
2,125
0.88
29
35,565
3.90
69
12,182
2.75
109
4,767
1.61
149
2,084
0.86
30
34,561
3.88
70
11,882
2.72
110
4,664
1.59
150
2,044
0.85
31
33,590
3.85
71
11,589
2.68
111
4,563
1.57
151
2,005
0.84
32
32,648
3.83
72
11,305
2.65
112
4,464
1.54
152
1,966
0.82
33
31,737
3.80
73
11,029
2.62
113
4,368
1.52
153
1,929
0.81
34
30,853
3.78
74
10,761
2.59
114
4,274
1.50
154
1,892
0.80
35
29,998
3.75
75
10,500
2.56
115
4,183
1.47
155
1,856
0.78
36
29,169
3.72
76
10,246
2.53
116
4,094
1.45
156
1,821
0.77
37
28,365
3.70
77
9,999
2.50
117
4,007
1.43
157
1,787
0.76
38
27,587
3.67
78
9,758
2.47
118
3,922
1.41
158
1,753
0.75
39
26,832
3.64
79
9,525
2.44
119
3,839
1.39
159
1,720
0.73
40
26,100
3.61
80
9,297
2.41
120
3,758
1.37
160
1,688
0.72
Power
:
105-130VAC, .5A 50/60Hz.
or
195-250VAC, .3A 50/60Hz
Output:
Selectable low voltage
24VAC, 20VA, .85A
or
12VAC, 20VA,1.7A
SPST-NO isolated contact
115VAC 1HP
240VAC 2HP
Sensors:
2 required (thermistor,
10Kohm @ 25C/77ºF).
Differential
: on at 4ºF, off at 1.5ºF
Desired
Pool
Temp.:
70-104ºF calibrated scale
or Solar Off, 75 (24ºC) -
104ºF (40ºC) on some
models
Recirculate
freeze
:
On at <40ºF (4.5ºC), off at
> 42ºF
(5.5ºC),
Enabled via jumper
Nocturnal
cooling:
On when collector 8ºF
less than pool and pool
hotter than limit, off when
collector 3ºF less than
pool or pool cooler than
high limit. Enabled via
jumper
With the sensor disconnected from the unit, measure the resistance of the sensor using
an ohmmeter. At room temperature (25ºC/77ºF) the sensor should measure approxi-
mately 10K ohms (10,000 ohms ± 1%). For other resistance measurements at different
temperatures, consult the table at back of manual. If the sensor is not returning the
correct value, it is defective and will need to be replaced. If the sensor is returning
approximately the correct value, reconnect it to the terminals marked “SOLAR SEN-
SOR”. If the “CHECK SENSOR” indicator remains on, the unit is defective and needs
to be replaced.
If FREEZE PROTECTION is enabled:
When a sensor is disconnected from the unit and freeze protection has been enabled,
the GL-235 will recognize this as a freeze condition and activate freeze protection.
