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Vapor Power International LLC
551 S County Line Road, Franklin Park, Il 60115
Phone: 630-694-5500 Fax: 630-694-2230
set pressure. Proper system operation can be checked via the pressure
gauge mounted on the boiler’s sensing manifold.
B.
Response/Range Adjustment - For boilers supplied with solid state step
controls. A “span” adjustment on the control adjusts the response/
differential of the control.
C.
Interstage Time Delay – Most solid state step controls now include
adjustable interstage time delays. Some even include different delays for
steps-on and steps-off which can be adjusted to minimize contactor cycles
while still maintaining the required responsiveness of the control. Check
the vendor-supplied literature provided at the rear of this manual.
4.2.2
Pressure Control (Boilers supplied with one or more non-proportioning
pressure controls)
Smaller STR boilers are provided with one or more independent pressure
controls which switch on or off heating elements in accordance with their
temperature setting. The differential between the pressure settings should
be set in accordance with system requirements.
4.2.3
Pressure Limit Cutouts
Check that the Honeywell “Limitrol” pressure limit switches are plumb using
external leveling indicator, which must swing freely and point to the index
mark on the case, and is set approximately 10% greater than the pressure
control but not to exceed 94% of the safety valve set pressure.
4.2.4
Auxiliary Controls
Other controls supplied with the boiler (eg, KW limit controls, cycle or delay
timers, etc) should be set per the Engineer’s specifications.