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ENGLISH
Jandy
®
Pro Series, Hi-E2
®
and Hi-E2R Gas-Fired Heater
|
Installation & Operation Manual
Figure 33. Venturi flow system components.
VENTURI
THROAT
SERVICE
PORT
VENTURI
INLET
SERVICE
PORT
GAS VALVE
SERVICE
PORT
4.6.1 Pressure Measurement Ports
Figure 33 shows venturi and gas control components
and service port locations. Air flow enters the venturi
from below through the filter box. It is pulled through
a converging section to the throat, where pressure is
reduced substantially. Gas flow is pulled into the throat
through an orifice inside the pipe between the throat and
the elbow. Air and gas are combined in the throat and mix
thoroughly as they proceed through the venturi tailpipe to
the burner.
Service ports are provided at three (3) places. On the right
side of the venturi an inlet service port is provided just
above the air filter box. Also on the right side, a throat
service port is provided - at the narrowest section of the
venturi casting. A gas valve service port is provided on the
outlet face (right side) of the gas valve.
To evaluate system operation requires accurate
measurement at these ports. A digital manometer, known
to be accurately calibrated, is ideal. Other instruments
may be used, but the “positive/negative” nature of the
readings must be very clear. Also, gas pressure offset
measurements are at very low levels (0.2” WC) and
the instrumentation must be capable of determining it
accurately.
4.6.2 Venturi System Checkout
WARNING
When servicing is complete be sure to replace
pressure service port plugs and assure that pressure
switch and equalizer tube connections are unaltered
and firmly in place.
4.6.2.1 Gas Orifice Differential
This measurement indicates how much “pull” is available
to move gas through the orifice. Turn off the heater
and connect the manometer tubes with the
positive
side
connected to the gas valve service port and the
negative
side to the venturi throat service port as shown in Figure
34. Turn on heater. The manometer will read zero until
the gas valve opens, and then it will indicate the gas
orifice differential. The
gas orifice differential
should
be 4.0” ± 0.3” WC for a unit at sea level. See section on
High Elevation Operation for other elevations.
Note the reading and turn off the heater at the control.
Then go on to the next measurement - gas pressure offset.
4.6.2.2 Gas Pressure Offset
Note that an equalizer tube is connected from a port on
the front of the venturi inlet to the vent of the gas valve
regulator. This is a very important component which
allows the regulator to track air pressure even when
abnormal things occur, such as blockage of the combustion
air. Before firing, confirm that this tube and the venturi
pressure switch tubes are in place and firmly connected.
Connect the positive side of the manometer to the venturi
inlet service port, which is at the bottom on the right
side. Connect the negative side of the manometer to the
gas valve service port, see Figure 35. Turn the heater on.
Until the heater fires, the manometer will indicate several
inches of water pressure, but after the gas valve opens, it
will indicate the gas
pressure offset
, which should be 0.2”
± 0.1” WC - i.e. the gas pressure should be 0.2” WC less
than the pressure at the venturi inlet service port.
If the offset is incorrect, adjust the gas pressure regulator
to the correct pressure. This can usually be done while
the heater is firing, but the burner may go off when the
regulator seal cap is removed. In any case, the offset
pressure measurement must be read
when the heater is
operating and the seal cap is firmly in place
. Note that a
special tool is required to remove the regulator cap.
Figure 36 shows the gas pressure offset reading when a
U-Tube manometer is used.
WARNING
In order to discourage incorrect adjustment by
unqualified persons, the gas valve regulator cap
requires a special tool for removal. Contact your
representative about a special tool for this cap.
WARNING
When servicing is complete be sure to replace
pressure service port plugs and assure that pressure
switch and equalizer tube connections are unaltered
and firmly in place.
Summary of Contents for HI-E2
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