12-8. (B) Pump control ON/OFF conditions: BTU requirements
A. Calculating the ON/OFF conditions of the pump
【Condition needed to turn the pump ON】
( T
set
– T
in
) × GPM × 500 > 18,600
【Condition needed to turn the pump OFF】
4 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 < 14,800 or T
in
= T
set
Where: T
set
= Set temperature and T
in
= Inlet temperature
B. Calculation example
Set temperature: T
set
= 122 ˚F Flow rate = 2.5 GPM
【Condition needed to turn the pump ON】
( 122 – T
in
) × 2.5 × 500 > 18,600 T
in
< 107.1˚F
【Condition needed to turn the pump OFF】
( 122 – T
in
) × 2.5 × 500 < 14,800 T
in
> 107.1˚F
C. ON/OFF table
Set temperature
(˚F)
Flow rate (GPM)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
113
ON 38.6 75.8 88.2 94.4 98.1 100.6 102.4 103.7
OFF 53.8 83.4 93.3 98.2 101.2 103.1 104.5 105.6
122
ON 47.6 84.8 97.2 103.4 107.1 109.6 111.4 112.7
OFF 62.8 92.4 102.3 107.2 110.2 112.1 113.5 114.6
131
ON 56.6 93.8 106.2 112.4 116.1 118.6 120.4 121.7
OFF 71.8 101.4 111.3 116.2 119.2 121.1 122.5 123.6
140
ON 65.6 102.8 115.2 121.4 125.1 127.6 129.4 130.7
OFF 80.8 110.4 120.3 125.2 128.2 130.1 131.5 132.6
158
ON 83.6 120.8 133.2 139.4 143.1 145.6 147.4 148.7
OFF 98.8 128.4 138.3 143.2 146.2 148.1 149.5 150.6
167
ON 92.6 129.8 142.2 148.4 152.1 154.6 156.4 157.7
OFF 107.8 137.4 147.3 152.2 155.2 157.1 158.5 159.6
185
ON 110.6 147.8 160.2 166.4 170.1 172.6 174.4 175.7
OFF 125.8 155.4 165.3 170.2 173.2 175.1 176.5 177.6
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