iWorx® PSU1
16
505-012, Effective: August 10, 2012
© 2012 Taco Electronic Solutions, Inc.
Standby Mode
In Standby Mode, whenever the lead primary pump is turned on by the controller and the Enable Alarm setting is not
“Disabled”, the Pump Flow Proof is monitored. If the Pump Flow Proof switch remains open after a configurable delay,
the lead pump is turned off and disabled, the lag pump is turned on, and an alarm for the lead pump is communicated
to the LCI. If the Pump Flow Proof switch remains off after another duration of the configurable delay, the lag pump is
turned off and disabled, the
In Alarm?
indicator displays “Yes” and an alarm for the lag pump is communicated to the
LCI. When either pump is on, the Pump Flow Proof switch continues to be monitored for an open state, and switches
pumps after the configurable delay, if necessary. Unless Flow Recovery Mode is enabled, the controller is locked out
whenever both pumps are disabled. The controller must be reset to enable pumps that have failed.
Equal Runtime Mode
The lead pump is started first and remains on as long as there is a call for it. The first pump runs for the number of
hours specified in the pump settings
Max Runtime
field. Once the number of hours specified has passed, the sequence
to swap the pumps is started.
NOTE:
The lead pump may be changed manually at any time by changing the
Lead Pump Sel
setting.
When changed, the timers used by Equal Runtime mode are reset and the new lead is run for
Max Run-
time
.
When a swap is needed, the lead pump is placed into a Post Purge state.
NOTE:
If modulated pump control is being used, the lead pump decelerates during the post purge period
until it is operating at its minimum speed or the post purge period has expired. The pump ramps down at a
rate defined by
Pump Mod Set: Ramp Down
.
After the time period specified by
Pump Settings: Post Purge Time
has elapsed, the lead pump turns off and the lag
pump is turned on.
If Enable Alarm setting is not “Disabled,” the Pump Flow Proof switch continues to be monitored for an open state, and
switches pumps after the configurable delay, if necessary. The pumps are not rotated if one of the pumps has failed.
This mode also includes all of the capabilities of Standby Mode.
Two Stage Mode
The lag pump may be set to operate as a second stage pump to meet increased demand. When the lead pump is oper-
ating and
Delta T
exceeds the amount specified in
Temperature Differential
for at least two minutes, the lag pump is
started. When
Delta T
is reduced to less than 5°F below the
Temperature Differential
for at least two minutes, the lag
pump is turned off.
NOTE:
Delta T
is always converted to an absolute value before comparing against the
Temperature Differ-
ential
setting.
Two stage operation may be disabled by changing the
Operational Mode
from “2 Stage” to another operating mode.
This mode is also disabled whenever one of the pumps has failed.
When
Operational Mode
is set to “2 Stage,”
Operational Type
is automatically set to “Switching.” Modulation is not
available in this mode.
This mode also includes all of the capabilities of Standby Mode.
Auto Flow Recovery Mode
Auto Flow Recovery Mode augments all modes that include Standby Mode capabilities. It is intended to prevent con-
troller lockout in the event of a faulty Pump Flow Proof switch or in the event that pump motors temporarily do not
respond to the PSU1 control signals.
The Auto Flow Recovery sequence begins after Standby Mode has disabled the lag pump. When Auto Flow Recovery
is active, the controller operates both pumps simultaneously. The controller is able to restart itself and resume normal
operation once flow is detected.
