iWorx® PSU1
505-012, Effective: August 10, 2012 19
© 2012 Taco Electronic Solutions, Inc.
Modulation
Pump modulation is available in Single, Standby and Equal Runtime modes.
To enable the modulated outputs, set Pump Settings: Operational Type to “Modulating.” Under Pump Mod Set, config-
ure the modulation settings according to the specific pump in use.
NOTE: Out Min and Out Max must be specified. These values configure the voltage range of the modu-
lated output. The min and max default to zero volts and must be set properly before the physical output will
be able to modulate pump speed.
When modulation is enabled, the pump's Pump Enable Output and Pump Modulated Output are both active whenever
a pump is on. The Pump Modulated Output adjusts the pump's speed to maintain the desired Delta T.
NOTE: Delta T is always converted to an absolute value before comparing against the Temperature Differ-
ential setting.
A larger Delta T value than the Temperature Differential setting acts to accelerate the pump; a smaller value than the
setting acts to decelerate the pump.
Lead Pump Select
The lead pump may be changed manually at any time by changing the Lead Pump Sel setting.
NOTE: When Lead Pump Sel setting is changed, the timers used by Equal Runtime mode are reset.
The lead pump may be set to a specific pump, the pump with lowest hours, or alternating.
The specific pump choices are “Pump 1" or “Pump 2."
The “Lowest Hours” setting automatically chooses the pump with lowest runtime hours when there is a call to run. If
both pumps have equal runtimes, then preference is given to Pump 1.
If the “Alternating” setting is chosen, then the lead pump alternates on each call to run.
Constant Circulation
If the Const Pump Circ setting is “On,” a primary pump remains on continuously, regardless of demand.
2 Stage Mode: When Constant Circulation is “On” and the controller is in 2 Stage Mode, pump staging occurs accord-
ing to the water temperature differential and user settings.
Pump Modulation and Other Modes: When Constant Circulation is set to “On” and the controller Operating Type is set
to “Modulating,” pump speed is modulated according to the water temperature differential and user settings.
Low Supply Temperature Circulation
If the Low Temp Setting is greater than 0.01°F, the Low Supply Temperature circulation feature is enabled. When the
Supply Temperature falls below the setpoint, the lead pump is turned on.
2 Stage Mode: No staging occurs when Low Supply Temp Circulation is active.
Pump Modulation and Other Modes: Pump speed is fixed at the minimum speed when Low Supply Temp Circulation is
active.
Pump Exercising
If Pump Settings: Pump Exercise is “On,” the pumps run sequentially for 15 seconds every week during periods of inac-
tivity. There is a 1-second delay between pumps.
Pump Modulation: Pump speed is fixed at the minimum speed when pumps are exercising.
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