Hydronic Heating - Raypak 399B-2339B Installation & Operating Instructions Manual

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.
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.
10°F ΔT
Model
No.
gpm ΔP (ft)
399B 67 5.5
499B 84 9.1
649B
749B
899B
989B
1259B
1529B
1799B
1999B
2069B
2339B
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.
20°F ΔT 30°F ΔT
gpm ΔP (ft) gpm
34 1.4 22
42 2.3 28
55 4.1 36
63 5.7 42
76 8.3 50
83 5.2 55
106 9.6 71
129 15.7 86
101
112
116
132
Table G: Heater Rates of Flow and Pressure Drops
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.
Min. Flow
ΔP (ft) gpm ΔP (ft)
0.6 20 0.5
1.1 21 0.6
1.8 27 1.1
2.6 32 1.5
3.8 38 2.2
2.3 42 1.3
4.3 53 2.4
7.1 64 4.0
10.7 76 6.0
13.8 84 7.9
14.8 87 8.5
21.4 98 12.1
16
Max. Flow
ΔT gpm ΔP (ft)
34 90 10.0
40 90 10.4
40 90 10.8
40 90 11.3
40 90 11.7
40 132 13.1
40 132 14.8
40 132 16.5
40 132 18.3
40 132 19.0
40 132 19.0
40 132 21.4
ΔT
7
9
12
14
17
13
16
19
23
25
26
30