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12-8. (B) Pump control ON/OFF conditions: BTU requirements
A. Calculating the ON/OFF conditions of the 520 Indoor or 520 Outdoor
Condition needed to turn the pump ON
( T
– T
) × GPM × 500 > 14,880
set
in
Condition needed to turn the pump OFF
5 minutes after activation, if the computer detects a BTU requirement of less than 18,600 BTU/h, the
computer will stop the pump 90 seconds.
( T
– T
) × GPM × 500 < 14,880 or T
set
in
Where: T
= Set temperature and T
set
B. Calculation example
Set temperature: T
set
Condition needed to turn the pump ON
( 120 – T
) × 2.5 × 500 > 14,880
in
Condition needed to turn the pump OFF
( 120 – T
) × 2.5 × 500 < 14,880
in
C. ON/OFF table (ON values are the same as OFF values)
Set temperature
(˚F)
100
115
120
135
145
155
165
105.5
185
125.5
in
= Inlet temperature
in
= 120 ˚F
Flow rate = 2.5 GPM
T
< 108.1˚F
in
T
> 108.1˚F
in
0.5
1.0
40.5
70.2
55.5
85.2
60.5
90.2
100.2
75.5
105.2
115.2
85.5
115.2
125.2
95.5
125.2
135.2
135.2
145.2
155.2
165.2
520 Indoor / 520 Outdoor Service Manual
= T
set
Flow rate (GPM)
1.5
2.0
80.2
85.1
95.2
100.1
105.1
120.1
130.1
140.1
150.1
170.1
71
CONFIDENTIAL
2.5
3.0
88.1
90.1
103.1
105.1
108.1
110.1
123.1
125.1
133.1
135.1
143.1
145.1
153.1
155.1
173.1
175.1
Ver. 1.00
3.5
4.0
91.5
92.6
106.5
107.6
111.5
112.6
126.5
127.6
136.5
137.6
146.5
147.6
156.5
157.6
176.5
177.6
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