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18
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 pressure relief valve. A 3/4" pressure relief
valve having a capacity equal to BTU/HR output of the
model to be installed is recommended for this heater. The
maximum acceptable pressure relief valve setting is 125
psi.
A 3/4" NPT connection is provided in the plastic
header for installation of a pressure relief valve. The valve
shall be installed in a vertical position. Do not over
tighten. Install pressure relief valve hand tight plus 1/2
turn.
PLASTIC HEADER
Pressure Relief Valve
PRV Discharge
Connection
Inlet/Outlet Header
Fig. #2004
A 3/4" NPT connection is provided in the header for
installation of a pressure relief valve. The valve shall be
installed in a vertical position.
CAST IRON HEADER
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 connection
throughout its entire length and must pitch downward
from the valve. No shutoff valve shall be 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.
UNITHERM GOVERNOR OPERATION
CAUTION:
The patented Unitherm Governor is a thermostatic mixing
valve specifically designed to maintain constant heater
internal temperature between 105° to 115°F despite
continually changing flow rates from the filter and chang-
ing pool temperatures. This narrow range is needed to
prevent damaging condensation on the burners which will
occur if the heater runs for any length of time below 100°F.
It is also needed to inhibit scale formation in the tubes
by maintaining temperatures well below accelerated
scaling temperatures.
INTERNAL AUTOMATIC BY-PASS VALVE
In addition to the Unitherm Governor, a built-in
automatic by-pass valve is provided in the in/out
header. While the Unitherm Governor responds to the
changes in water temperature in the heater, the internal
by-pass valve automatically responds to changes in
water pressure in the piping system. Proper amount of
water flow is maintained through the heater under
varying pressures dictated by the conditions of the
pump and filter.
Fig.#2003
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 down 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.
From Heater To Heater
To Pool From Pool
AUXILLARY BYPASS VALVE
(DO NOT USE GATE VALVE)
Fig. # 8150.0ss
PRV Discharge
Connection
Inlet/Outlet Header
Pressure Relief
Valve
Fig. # 8095.0