Raypak 399B-2339B Hydronic Heating, Temperature & Pressure Gauge, Pump Selection

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.

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	10°F ΔT		20°F ΔT		30°F ΔT			Min. Flow			Max. Flow
No.	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

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.

Table G: Heater Rates of Flow and Pressure Drops

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