Flow Rates; Internal Automatic Bypass Valve; External Auxiliary Bypass Valve; Auxiliary Bypass Valve Adjustment - Raypak 259B Installation & Operating Instructions Manual

FLOW RATES

MODEL PIPE SIZE
259B 1-1/4"–1-1/2" - 2"
409B 1-1/4"–1-1/2" - 2"
*When flow rates exceed maximum GPM, an external auxil-
iary bypass valve is required. See external bypass valve
section for details.
Table J: Flow Rates

INTERNAL AUTOMATIC BYPASS VALVE

A built-in automatic bypass valve is provided in the
in/out header. The internal bypass valve automatically
responds to changes in water flow in the piping sys-
tem. Proper amount of water is maintained through
the heater under varying flows dictated by the condi-
tions of the pump and filter.
BYPASS
VALVE
BYPASS
SPRING
UNITHERM
GOVERNOR (UG)
Fig. 15: Internal Bypass Valve

EXTERNAL AUXILIARY BYPASS VALVE

(Where Required)
An auxiliary bypass valve should be used when flow
rates exceed 125 GPM. Usually a high-performance
pump size larger than two horsepower will exceed this
flow rate. This valve is required to complement the
function of the automatic bypass valve, particularly
when starting the heater in winter or early spring when
the spa or pool temperature is below 50°F. It also
serves to eliminate needless pressure drop through
the heater and accompanying reduction in the flow
rate to the spa jets, etc.
MIN. GPM MAX. GPM*
25 125
40 125
Fig. 16: Auxiliary Bypass Valve
(DO NOT USE GATE VALVE)

AUXILIARY BYPASS VALVE ADJUSTMENT

To set bypass: With clean filter, adjustment is made by
feeling the inlet and outlet pipes at the heater. Outlet
pipes should be slightly warmer than inlet and comfort-
able to the touch. If pipe is hot, close bypass; if cold,
open bypass.

PRESSURE RELIEF VALVE INSTALLATION

To conform to local building codes, it may be neces-
sary to install a 3/4" pressure relief valve, having a
capacity at least equal to the BTUH output of the
model. The maximum acceptable pressure relief valve
setting is 125 psi.
Fig. 17: Pressure Relief Valve
NOTE: To avoid water damage or scalding due to
valve operation, drain pipe must be connected to valve
outlet and run to a safe place of discharge. Drain pipe
must be the same size as the valve discharge connec-
tion throughout its entire length and must pitch down-
ward from the valve.
installed between the relief valve and the drain line.
Valve lever should be tripped at least once a year to
ensure that waterways are clear.
25
No shut-off valve shall be