Hydronic heating – Raypak 399B-2339B User Manual
Page 16
Cold Water Run
Cold water run differs from cold water start in that the
system water entering the heater remains below 105ºF
(41ºC) continuously. Typically, this is the case in swim-
ming pool heating and water source heat pump
applications as well as some others. If the system
water is kept in a narrow temperature range, a perma-
nent manual bypass can be employed and manually
adjusted to achieve an inlet temperature of 105ºF
(41ºC) or higher. An injector pump arrangement may
also be utilized to keep the heater loop at or above
105ºF (41ºC). 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.
Table G: Heater Rates of Flow and Pressure Drops
Notes:
1. Basis for minimum flow: Models 399–899, 20 gpm or 40°F ΔT. Models 989–2339, 30 gpm or 40°F ΔT.
Basis for maximum flow: Models 399–899, 90 gpm. Models 989–2339, 132 gpm.
2. Flow switch will not operate if flow is less than 20 gpm.
as the system heats up, the outlet temperature may
continue to climb and actuate the high limit, thereby
shutting down the heater. Thus an automatic valve
system, such as a three-way proportional valve or a
modulating two-way valve to control the bypass,
should be utilized.
Temperature & Pressure Gauge
The temperature and pressure gauge is factory-
mounted in the in/out header.
Hydronic Heating
Pump Selection
In order to ensure proper performance of your heater
system, you must install a correctly sized pump. Ray-
pak recommends using a 20°F ΔT as design ΔT. (ΔT is
the temperature difference between the inlet and out-
let water when the heater is firing at full rate). If a ΔT
of larger than 20°F is necessary, see Table G and
Table H for flow rate requirements.
Model
No.
10°F ΔT
20°F ΔT
30°F ΔT
Min. Flow
Max. Flow
gpm
ΔP (ft)
gpm
ΔP (ft)
gpm
ΔP (ft)
gpm
ΔP (ft)
ΔT
gpm
ΔP (ft)
ΔT
399B
67
5.5
34
1.4
22
0.6
20
0.5
34
90
10.0
7
499B
84
9.1
42
2.3
28
1.1
21
0.6
40
90
10.4
9
649B
55
4.1
36
1.8
27
1.1
40
90
10.8
12
749B
63
5.7
42
2.6
32
1.5
40
90
11.3
14
899B
76
8.3
50
3.8
38
2.2
40
90
11.7
17
989B
83
5.2
55
2.3
42
1.3
40
132
13.1
13
1259B
106
9.6
71
4.3
53
2.4
40
132
14.8
16
1529B
129
15.7
86
7.1
64
4.0
40
132
16.5
19
1799B
101
10.7
76
6.0
40
132
18.3
23
1999B
112
13.8
84
7.9
40
132
19.0
25
2069B
116
14.8
87
8.5
40
132
19.0
26
2339B
132
21.4
98
12.1
40
132
21.4
30
16