Fulton Hopkins (HPN) Horizontal Coil Thermal Fluid (hot oil) Heater - Manual (Page 75)

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SECTION 4
HPN-IOM-2014-0416
MAINTENANCE
4-15
TABLE 10-K - HIGH GAS PRESSURE SWITCH TROUBLESHOOTING
Problem Potential Remedy
Gas pressure setting on the
main regulator is too high With unit running at high fi re, make sure that the modulated gas valve is at full open.
Since unit lights at low fi re, it may be necessary to increase high gas pressure setting or jumper contacts to allow unit to modulate to
where modulation gas valve back pressure is lessened.
Check net last elbow gas pressure and compare to factory test fi re sheet. Net gas pressure is running gas pressure minus p urge
pressure. Make sure net pressure reading is within .2” w.c. of factory reading. If there is a diff erence, adjust main regulator. Adjust for
proper combustion throughout range.
Low fi re gas valve setting is
too low Because the sensing point of the High Gas Pressure Switch is upstream of the modulating gas valve, the highest pressure read will
occur during low fi re.
Check net last elbow gas pressure and compare to factory test fi re sheet. Net gas pressure is running gas pressure minus purge
pressure. Make sure net pressure reading is within .1” w.c. of factory reading. If there is a diff erence, adjust modulating gas valve
linkage. Adjust for proper combustion throughout range.
Gas pressure switch setting is
improper If above two items are proper, check the pressure that the high gas pressure switch is sensing by way of a tee installed in the line.
Hold unit at low fi re and check pressure. Setting on switch should be 10% over pressure read. Call Fulton if you have any questions.
Gas regulator has failed open This is highly unlikely. Regulators will usually fail safe in the closed position. The gas regulator can be checked by checking upstream
pressure and comparing to downstream pressure. Make sure that the upstream pressure is not above the rating of the regulator.
Make sure that the downstream pressure does not exceed the range of the spring. If regulator has failed, replace, reset input and
adjust input throughout the range.
TABLE 10-L- LOW GAS PRESSURE SWITCH TROUBLESHOOTING
Problem Potential Remedy
Gas pressure setting on the
main regulator is too low At high fi re, the modulating gas valve is full open resulting in the least amount of back pressure in the gas train. With unit running
at high fi re, check net last elbow gas pressure and compare to factory test fi re sheet. Net gas pressure is running gas pressure minus
purge pressure. Make sure net pressure reading is within .2” w.c. of factory reading. If there is a diff erence, adjust main regulator.
Adjust for proper combustion throughout range.
Gas orifi ce plate is damaged If the orifi ce plate is damaged, it may be holding back less gas creating a lower pressure on the sensing switch. Pull burner and
inspect gas orifi ce plate. Plate should in no way be warped or degraded. If it is, replace. After reinstallation, recheck input and adjust
combustion throughout range.
Gas regulator has failed closed Regulators will usually fail safe in the closed position. The gas regulator can be checked by checking upstream pressure and
comparing to downstream pressure. Make sure that the upstream pressure is not above the rating of the regulator. If regulator has
failed, replace, reset input and adjust input throughout the range.
TABLE 10-M - LOW OIL PRESSURE SWITCH TROUBLESHOOTING
Problem Potential Remedy
Oil pressure setting on the
back pressure valve is too low At low fi re, the modulating oil valve is at its most open position resulting in the least amount of back pressure in the fuel train. With
unit running at low fi re, check oil pressure and compare to factory test fi re sheet. Make sure oil pressure reading is within 10 psi of
factory reading. If there is a diff erence, adjust back pressure regulator. Adjust for proper combustion throughout range.
Fuel oil pump may have lost
its prime An air bubble in the pump will result in a momentary loss of prime that will be enough to cause the Low Oil Pressure Switch to trip.
Ensure that oil pump is primed properly and all connections are tight. Check the pump seal. A blown seal will allow air in the pump
housing.
Fuel oil pump motor may have
failed Check the pump motor for proper voltage. If voltage is proper but motor does not turn, replace or rebuild motor. If there is no
voltage, check motor starter for input signal and incoming 3-phase power.
Fuel oil pump coupling may
have failed A failed coupling will result in the pump not turning. Check coupling. Replace if necessary..