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Hi-E Model EPH Pool and Spa Heater
3. A minimum of 5 inches (127 mm) W.C. for
natural gas and 11 inches (279 mm) W.C. for
propane gas, when the burner is firing, is required.
4. If the supply gas pressure is less than the mini-
mum, check for under-sized pipe between the
meter and the heater, a restrictive fitting, an under-
sized gas meter.
IMPORTANT: Any gas supply problem must be
corrected. The source of the incorrect supply pressure
must be found and corrected. If you cannot clear up
the supply pressure problem, contact a qualified
service technician or your local gas company.
3A-3. Checking the Metering Orifice
Gas flow is controlled by the orifice in the fitting
between the gas valve and the venturi throat. The
orifice must be the correct size for the fuel being used
(see Table 2).
To inspect the gas orifice:
1. Disconnect the venturi pressure tube (see Fig. 6).
2. Carefully remove the fitting between the gas valve
and the venturi throat.
3. Remove the orifice and inspect it.
4. Reassemble all parts properly after making sure the
orifice size is correct.
3A-4. Checking the Venturi Pressure Switch
The venturi pressure switch is calibrated to open
when the pressure falls below the minimum values,
shutting off the heater. If a dull blue lazy flame is
detected or it takes a long time for the heater to heat
up, the cause may be:
1. A restriction in the combustion system flow by a
partially blocked combustion air inlet or vent
terminal.
2. Excessive vent pipe length or too many 90 degree
elbows (see Document 3090B, Installation and
Operation Manual).
3. Worn or dirty combustion air filter.
4. Internal blockage in the condensate trap or drain
system.
To check the venturi pressure difference perform
the following stack test:
1. Remove upper inlet pressure tap from the top of
the venturi (see Fig. 6).
2. Attach the hose from the manometer to the upper
tap on the venturi.
NOTE: The manometer must be able to read a
negative pressure.
3. Start the heater and let the unit fire.
4. Take a reading. Readings should be:
a.
-2.2 to -3.2 inches (-56 to -81 mm) W.C. for
outdoor units with standard stack extensions.
b. - 1.4 to -3.2 inches (-36 to -81 mm) W.C. for
indoor units with proper venting.
3A-5. Checking the Air Flow (Filter)
The amount of gas that flows to the burner is
regulated by the amount of air through the venturi.
Testing pressure readings at the gas valve pressure tap
can determine if there is an air flow problem.
If the heater is heating slowly or cycling on and
off, perform the following filter test:
1. Attach a manometer or a negative pressure gauge
to the press tap opening on the gas valve.
2. Turn on the heater.
NOTE: The fan will come on and the heater will fire
about 20 to 30 seconds later.
3. Take a reading. Reading should be -0.3 to -0.5
inches (-7.6 to -12.7 mm) W.C.
4. If the reading is less than -0.3 inches (-7.6 mm)
W.C., check the tubing between the gas valve
regulator and the venturi port for blockage.
5. If the reading is greater than -0.5 inches (-12.7
mm) W.C., there is a restriction of air through the
heater. This will not harm the heater, only reduce
its output British Thermal Unit (BTU) rating.
To correct the reduced air flow check the following:
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