710 / 710 ASME Service Manual
Ver. 1.00
59
CONFIDENTIAL
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
set
– T
in
) × GPM × 500 > 14,880
【
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
set
– T
in
) × GPM × 500 < 14,880 or
T
in
= T
set
Where: T
set
= Set temperature and T
in
= Inlet temperature
B. Calculation example
Set temperature: T
set
= 120 ˚F
Flow rate = 2.5 GPM
【
Condition needed to turn the pump ON
】
( 120 – T
in
) × 2.5 × 500 > 14,880 T
in
< 108.1˚F
【
Condition needed to turn the pump OFF
】
( 120 – T
in
) × 2.5 × 500 < 14,880 T
in
> 108.1˚F
C.
ON/OFF table (ON values are the same as OFF values)
Flow rate (GPM)
Set temperature
(˚F)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
100
40.5
70.2
80.2
85.1
88.1
90.1
91.5
92.6
115
55.5
85.2
95.2
100.1
103.1
105.1
106.5
107.6
120
60.5
90.2
100.2
105.1
108.1
110.1
111.5
112.6
135
75.5
105.2
115.2
120.1
123.1
125.1
126.5
127.6
145
85.5
115.2
125.2
130.1
133.1
135.1
136.5
137.6
155
95.5
125.2
135.2
140.1
143.1
145.1
146.5
147.6
165
105.5
135.2
145.2
150.1
153.1
155.1
156.5
157.6
185
125.5
155.2
165.2
170.1
173.1
175.1
176.5
177.6
