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20° T
MVB
(ft WC)
Model
GPM
504A
42
2.7
754A
63
6.0
1104A
92
13.3
1504A
N/A
N/A
2004A
N/A
N/A
Notes: Basis for minimum flow is ∆T . Basis for maximum flow is gpm.
NOTE: Opening the valve will increase the
temperature and closing the valve will decrease the
temperature.
3. With the heater operating at 100% firing rate, set
Valve A (the bypass) to
B to fully open position. See Fig. 16.
4. Adjust Valve A until the inlet water temperature is
105°F (40°C) or 120°F (49°C) depending upon
heater type.
5. If this process does not raise the inlet water tem-
perature to 105°F (40°C) for Pool Heater (P)
versions and 120°F (49°C) for Hydronic Heating
(H7) or Domestic Hot Water (WH7) versions and
Valve A is fully open, then slowly throttle Valve B
closed to increase the inlet water temperature to
the required temperature.
NOTE: For automatic temperature adjustment, a
Cold Water Run (CWR) system can be used instead
of a manual bypass. See Fig. 10.
Fig. 11: "H" Bypass Setting
30° T
P
P
(ft WC) GPM
GPM
28
1.4
42
2.9
62
6.7
84
13.3
112
26.9
Table F: Heater Rates of Flow and Pressure Drops
⁄
open position, and Valve
1
2
39° T
Min Flow
P
(ft WC) GPM
N/A
N/A
25
32
1.8
32
47
4.3
47
65
8.4
65
86
16.7
86
Hydronic Heating
Pump Selection
In order to ensure proper performance of your heater
system, you must install a correctly-sized pump. Ray-
pak requires designing for a ∆T within the range of
16°F to 39°F (9°C to 22°C). See Table F for accept-
able flow rates for each model (∆T is the temperature
difference between the inlet and outlet water when the
heater is firing at full rate).
Feedwater Regulator
Raypak recommends that a feedwater regulator be in-
stalled and set at 12 psi minimum pressure at the
highest point of the system. Install a check valve or
back flow device upstream of the regulator, with a
manual shut-off valve as required by local codes.
Piping
All high points should be vented. A heater installed
above radiation level must be provided with a low wa-
ter cut-off device (sales order option F-10). This
heater, when used in connection with a refrigeration
system, must be installed so that the chilled medium is
NOTE: Hot water heating systems all have unique
levels of operating diversity that must be accounted
for in the system design. The system should always
include adequate system flow in excess of the
connected boiler flow for proper operation. Where
the system flow may drop below the connected
boiler flow a buffer/decoupler may be needed.
Failure to design for adequate flow (i.e. bypasses, 3
way control valves, flow limiting balance devices,
buffer tanks, etc.) will result in boiler short cycling
and may reduce boiler life. Always contact your local
Raypak representative for system design assistance
to avoid these issues.
15
Max Flow
P
T
(ft WC)
(°F)
GPM
1.1
34
100
1.8
39
100
4.3
39
113
8.4
39
113
16.7
39
113
P
T
(ft WC)
(°F)
11.3
8
13.8
13
18.6
16
22.2
22
27.2
30
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