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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