SAMUEL JACKSON HG-1-1501, Руководство по эксплуатации и обслуживанию

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PAGE 25 of 46 HG-1-1501 GAS-FIRED HEATER
© SAMUEL JACKSON, INCORPORATED 2011 ALL RIGHTS RESERVED
GAS LOW PRESSURE -- The blower is on for this step. The +/- switch is now used to
test for presence of gas, adjust its pressure, test for valve leakage and adjust the gas low
pressure switch, if necessary. The “+” position opens the first Safety Shutoff Valve
SSOV, admitting gas pressure to the cavity. The display will show that the gas cavity is
“CHARGED” when the pressure is above 1.5 PSI in the gas train registered by the Gas
Low Pressure Switch GLPS. “NOT CHARGED” will be shown if pressure is less than
1.5 PSI. The final pressure should be between 2.5 and 3 PSI when the heater is operating.
With the gas cavity charged, leave the valves closed several minutes to see that the
pressure does not leak off. This tells us that the downstream valves, Pilot Valve PV and
second SSOV, are not leaking. Turn the +/- selector to “-” to energize PV. This will
evacuate the gas cavity. Leave the valves closed several minutes to see that the pressure
does not build up. This tells us that the upstream valve, first SSOV, is not leaking. The
operating program will perform similar tests every time the heater is shut down. This is
one reason electrical power must be supplied to the heater continuously, or at least for 10
minutes after each shutdown.
In rare cases, the screen on the inlet to the SSOV block may become clogged with debris
from the gas supply. Evidence of this will be gas low pressure errors and a loss of heat
output while the pressure shown on Gas Pressure Gage 1 (GPG1) is normal of about 3
PSI. The GPG1 pressure tap is upstream of the screen. To clean the screen, it is necessary
to remove the valve block from the flanged inlet and outlet pipe fittings. The pilot valve
(PV) line behind the SSOV block will have to be disconnected to remove the SSOV
block. Contact the factory for technical assistance.
Screen on inlet to SSOV block
GPG1
SSOV block