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matic valve system, such as a three-way proportional
valve or a modulating two-way valve to control the
bypass, should be utilized.
Fig. 7: Cold Water Start
Cold Water Run
Cold water run differs from cold water start in that the
system water entering the heater remains below 120ºF
(49ºC) continuously. Typically, this is the case in
swimming pool heating and water source heat pump
applications as well as some others. If the system water
is kept in a narrow temperature range of no more than
10ºF, a permanent manual bypass can be employed and
manually adjusted to achieve an inlet temperature of
120ºF (49ºC) or higher as adjusted at the minimum
temperature in this narrow temperature range (i.e.
Range 75ºF – 85ºF – adjust bypass with temperature at
75ºF) so that when temperature is 85ºF, minimum inlet
∆
20°F
T
Model
No.
∆
gpm
P (ft)
503
44
2.8
753
65
6.4
1003
87
12.0
1252
109
20.9
1503
N/A
N/A
1753
N/A
N/A
2003
N/A
N/A
Notes: 1. Basis for minimum flow is ∆T . Basis for maximum flow is gpm.
∆
30°F
T
40°F
∆
gpm
gpm
P (ft)
29
1.4
N/A
44
3.1
33
58
6.0
43
73
10.2
54
87
16.0
65
102
22.5
76
116
31.9
87
Table F: Heater Rates of Flow and Pressure Drops
temperature would be 130ºF. An injector pump ar-
rangement may also be utilized to keep the heater loop
at or above 120ºF (49ºC). An injector pump approach
has the added value of being able to adjust to changes
in the system water coming back to the heater take-off.
Fig. 8: Cold Water Run
Temperature & Pressure Gauge
The temperature and pressure gauge is shipped loose
for field installation in the outlet piping.
∆
Min. Flow
T
∆
∆
gpm
P (ft)
P (ft)
N/A
25
1.1
1.9
33
1.9
3.7
43
3.7
6.2
54
6.2
9.5
65
9.5
13.4
76
13.4
18.9
87
18.9
13
SECTION C: Installation
Max Flow
∆
∆
∆
gpm
T
P (ft)
35
100
11.3
9
40
100
13.8
13
40
113
18.6
15
40
113
22.2
19
40
113
25.5
23
40
113
27.2
27
40
116
32.0
30
T
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