Siebring 7500S, Instructions Manual

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Adjustable Pressure Regulating Unloader
The following Unloader models are used on Siebring Pressure Washer applications: Cat
Pump model 7500, 7534, 7600 & 7672. J.E. Adams Golden Eagle model 7100.
Operation – The unloader holds established system pressure in the discharge line when
the trigger gun is closed, solenoid valve is closed (gate) valve is closed or the nozzle is
clogged, bypassing the unrequired flow between the pump and the unloader. It returns
to established system pressure without delay upon squeezing the trigger gun or opening
the solenoid (gate) valve.
When properly set the unloader protects the pump from pressure extremes associated
with obstructions in the discharge line, while maintaining the established system
pressure. When no flow is required by the system, the unloader by-passes all the
system flow and relieves the load on the pump. Pressure is held in the discharge line
(between the unloader and the gun) ready for a quick return to high pressure operation.
Note: A minimum bypass of 5-10% is necessary for the unloader to operate properly.
CAUTION – If the entire output is directed through the unloader (zero by-pass) the
“cushioning” feature of the by-pass liquid is eliminated and the unloader can malfunction
or wear prematurely.
Do not leave the unit running in by-pass mode for extended periods of time.
Overheating of the pump manifold could result.
Problem Solution
Unloader Cycles Check for leak downstream of unloader
Worn o-ring or check valve
Air in system, poor connection
O-ring in gun worn
Liquid leaking from bottom fitting O-ring for fitting cut or worn
O-ring for seat cut or worn
Liquid leaking form middle O-ring for piston cut or worn
O-rings for piston stem cut or worn
Unloader will not come up to pressure Not properly sized for system pressure
Foreign material in unloader. Clean filter.
Piston stem o-rings worn
Nozzle worn
Insufficient flow to pump
Extreme pressure spikes Adjusting nut turn completely into unloader
Restricted by-pass or no by-pass
System flow exceeds unloader rating
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