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12-8. (B) Pump control ON/OFF conditions: BTU requirements for Re-circulation
mode
A. Calculating the ON/OFF conditions of the pump
【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
= 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
59
CONFIDENTIAL
710 / 710 ASME Service Manual
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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