© 2012 Taco Electronic Solutions, Inc. 1
Application Guide
505-012
PSU1 Pump Sequencing Unit
Self-Contained Interoperable Controller Model UCP-1
SUPERSEDES: New
EFFECTIVE: August 10, 2012
Plant ID: 001-4090
Table of Contents
PSU1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Purpose of This Guide . . . . . . . . . . . . . . . . . . . . . . . . . 3
Representations and Warranties . . . . . . . . . . . . . . . . . 3
Applicable Documentation . . . . . . . . . . . . . . . . . . . . . . 4
Installation Instructions . . . . . . . . . . . . . . . . . . . . . . . . . 4
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Static Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
FCC Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Before Installing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
About this Document . . . . . . . . . . . . . . . . . . . . . . . . 5
Inspecting the Equipment . . . . . . . . . . . . . . . . . . . . 5
What is Not Included with this Equipment . . . . . . . . 5
Equipment Location . . . . . . . . . . . . . . . . . . . . . . . . . 5
Selecting a Power Source . . . . . . . . . . . . . . . . . . . . 6
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Mounting the Device . . . . . . . . . . . . . . . . . . . . . . . . 6
Routing Cabling to the Device . . . . . . . . . . . . . . . . . 7
Grounding the Device . . . . . . . . . . . . . . . . . . . . . . . 8
Wiring Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Connecting Input Devices . . . . . . . . . . . . . . . . . . . 11
Connecting Output Devices . . . . . . . . . . . . . . . . . . 12
Other Connections . . . . . . . . . . . . . . . . . . . . . . . . . 12
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Mechanical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Application Description. . . . . . . . . . . . . . . . . . . . . . . . 14
Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . 15
Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . 15
Auto Flow Recovery Mode. . . . . . . . . . . . . . . . . . . 16
Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Lead Pump Select . . . . . . . . . . . . . . . . . . . . . . . . . 19
Constant Circulation . . . . . . . . . . . . . . . . . . . . . . . 19
Low Supply Temperature Circulation. . . . . . . . . . . 19
Pump Exercising . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Controller Identification . . . . . . . . . . . . . . . . . . . . . . . 20
Network Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Diagnostic LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Troubleshooting Tips . . . . . . . . . . . . . . . . . . . . . . . 26
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iWorx® PSU1
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PSU1
The PSU1 pump sequencing unit is a stand-alone microprocessor-based controller for radiant heating or cooling appli-
cations.
Overview
The PSU1 is a compact, microcontroller-based controller for support of radiant applications with pump sequencing
needs. It controls the pump sequences, rotates and stages the pumps according to the programmed mode, maintains
desired differential temperature (Delta T), and generates flow alarms if no flow is detected.
The controller is based on LONWORKS
®
networking technology. The controller can be networked to a higher-level control
system for monitoring and control applications.
Features
• Control of two primary pumps with four control modes
• Standby pump operation with manually selectable lead pump
• Equal runtime operation with adjustable run time
• Two-stage digital control or single-stage modulated control (with digital enable) based on an adjustable primary
loop temperature differential
• Automatic configuration with a Local Control Interface (LCI) touchscreen
• Alarm/Event reporting
• LONWORKS® interface to building automation systems
PURPOSE OF THIS GUIDE
The iWorx® PSU1 Application Guide provides application information for the PSU1 Controller.
The reader should understand basic HVAC concepts, intelligent environmental control automation, and basic LON-
WORKS networking and communications. This application manual is written for:
• Users who engineer control logic
• Users who set up hardware configuration
• Users who change hardware or control logic
• Technicians and field engineers
REPRESENTATIONS AND WARRANTIES
This Document is subject to change from time to time at the sole discretion of Taco Electronic Solutions, Inc. All
updates to the Document are available at www.taco-hvac.com. When installing this product, it is the reader’s responsi-
bility to ensure that the latest version of the Document is being used.
iWorx® products shall only be used for the applications identified in the product specifications and for no other pur-
poses. For example, iWorx® products are not intended for use to support fire suppression systems, life support sys-
tems, critical care applications, commercial aviation, nuclear facilities or any other applications where product failure
could lead to injury to person, loss of life, or catastrophic property damage and should not be used for such purposes.
Taco Electronic Solutions, Inc. will not be responsible for any product or part not installed or operated in conformity with
the Document and instructions or which has been subject to accident, disaster, neglect, misuse, misapplication, inade-
quate operating environment, repair, attempted repair, modification or alteration, or other abuse. For further informa-
tion, please refer to the last page of this Document for the company’s Limited Warranty Statement, which is also issued
with the product or available at www.taco-hvac.com.
iWorx® PSU1
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APPLICABLE DOCUMENTATION
See the table below for additional documentation that may be applicable to this controller.
INSTALLATION INSTRUCTIONS
Precautions
General
CAUTION: This symbol is intended to alert the user to the presence of important installation and mainte-
nance (servicing) instructions in the literature accompanying the equipment.
CAUTION: Risk of explosion if battery is replaced by an incorrect type. Contains lithium type battery; dis-
pose of properly.
WARNING: Electrical shock hazard. Disconnect ALL power sources when installing or servicing this
equipment to prevent electrical shock or equipment damage.
Make all wiring connections in accordance with these instructions and in accordance with pertinent national and local
electrical codes. Use only copper conductors that are suitable for 167 °F (75 °C).
Static Electricity
Static charges produce voltages that can damage this equipment. Follow these static electricity precautions when han-
dling this equipment.
• Work in a static free area.
• Touch a known, securely grounded object to discharge any charge you may have accumulated.
• Use a wrist strap when handling printed circuit boards. The strap must be secured to earth ground.
Description Audience Purpose
iWorx® network interface description
document, file name:
iWorx_IDS_117.doc
– Application Engineers
– Installers
– Service Personnel
– Start-up Technicians
Provides information concerning the iWorx®
network interface.
iWorx® LCI2 Application Guide, Doc-
ument No. 505-002
– Application Engineers
– Installers
– Service Personnel
– Start-up Technicians
– End user
Provides instructions for setting up and using
the iWorx® Local Control Interface.
http://iWorxWizard.taco-hvac.com – Application Engineers
– Wholesalers
– Contractors
An on-line configuration and submittal package
generator based on user input. Automatically
generates bill of materials, sequence of opera-
tions, flow diagrams, wiring diagrams, points
and specifications.
Additional
Documentation
LonWorks FTT-10A Free Topology Transceiver User’s Guide, published by Echelon Corpo-
ration. It provides specifications and user instructions for the FTT-10A Free Topology Trans-
ceiver. See also: www.echelon.com/support/documentation/manuals/transceivers.
iWorx® PSU1
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Location
Avoid locations where corrosive fumes, excessive moisture, vibration or explosive vapors are present.
Avoid electrical noise interference. Do not install near large contactors, electrical machinery, or welding equipment.
This equipment is suitable for indoor use only. Preferably, or as required by National Electrical Code, the unit is
intended to be installed within an electrical control enclosure. Operate where ambient temperatures do not exceed
140 °F (60 °C) or fall below 32 °F (0 °C) and relative humidity does not exceed 90%, non-condensing.
FCC Compliance
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of
the FCC rules. These limits are designed to provide reasonable protection against harmful interference. This equip-
ment can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause
harmful interference to radio communications. However, there is no guarantee that interference will not occur in a par-
ticular installation. If this equipment does cause harmful interference to radio or television reception, which can be
determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or
more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and the receiver.
• Connect the equipment to a power source different from that to which the receiver is connected.
• Consult the equipment supplier or an experienced radio/TV technician for help.
You are cautioned that any changes or modifications to this equipment not expressly approved in these instructions
could void your authority to operate this equipment in the United States.
BEFORE INSTALLING
About this Document
The instructions in this manual are for the PSU1 module which supports a liquid source heat pump.
Inspecting the Equipment
Inspect the shipping carton for damage. If damaged, notify the carrier immediately. Inspect the equipment for damage.
Return damaged equipment to the supplier.
What is Not Included with this Equipment
• A power source for the equipment electronics and peripheral devices.
• Tools necessary to install, troubleshoot and service the equipment.
• The screws or DIN rail needed to mount the device.
• Peripheral devices, such as sensors, actuators, etc.
• Cabling, cabling raceway, and fittings necessary to connect this equipment to the power source, FTT-10A network
and peripheral devices.
Equipment Location
Abide by all warnings regarding equipment location provided earlier in this document.
Optimally, the equipment should be installed within a secure enclosure.
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If the equipment is to be installed outdoors, it must be contained within a protective enclosure. The enclosure must
maintain internal temperature and humidity within the ranges specified for this equipment.
The equipment must be installed within 500 feet of all input peripherals (smoke detectors, sensors, etc.) that are con-
nected to the equipment.
Selecting a Power Source
This equipment requires a UL recognized Class 2 external power source (not supplied) to operate. The controller
power input requires a voltage of 24 Volts AC.
To calculate power source current requirements, add the power consumption of all peripheral devices to that of the
controller.
The controller and sensor power supplies can use the same power source. If both are using the same power source,
the loads must have EMF protection. This protection can be integral to the load, or installed in the 24 VAC wiring across
the load’s coil.
To provide necessary RFI and transient protection, the controller’s ground (GND) pin (T40) must be connected to earth
ground or the earth ground of the packaged unit’s enclosure ground. Failure to properly ground the controller may
cause it to exceed FCC limits. Excessive noise could also produce inaccurate sensor data. The power source must be
capable of operating with this connection to ground.
INSTALLATION
Warning: Electrical shock hazard. To prevent electrical shock or equipment damage, disconnect ALL
power sources to controllers and loads before installing or servicing this equipment or modifying any wir-
ing.
Mounting the Device
1.Select a mounting location. Enclosure mounting is recommended.
2.Hold the controller on the panel you wish to mount it on. With a marker or pencil mark the mounting locations on
the panel.
3.Using a small drill bit pre-drill the mounting holes.
4.Using two #6 pan head screws, mount the controller to the panel.
5.Wire the controller (See Routing Cabling to the Device).
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Figure 1: Mounting Dimensions
Routing Cabling to the Device
Cabling used to connect the power source and cabling used to connect the FTT-10A network must remain
separated within the control enclosure and wiring conduit.
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Grounding the Device
The ground terminal (T40) must be securely connected to earth ground. Failure to properly ground this
equipment will result in improper operation. Improper grounding may also increase the risk of electrical
shock and may increase the possibility of interference with radio/TV reception.
For best performance, connect the power supply common terminal (T38) to the same external point as the
ground terminal (T40).
WIRING INFORMATION
WARNING: Terminals 4, 6, 9, 12, 15, 18, and 38 are connected internally on all PSU1 controllers. Discon-
nect ALL power sources when installing or servicing this equipment to prevent electrical shock or equip-
ment damage.
Figure 2: PSU1 Wiring Example - Power Sourcing
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Figure 3: PSU1 Wiring Example - Power Sinking
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Figure 4: PSU1 Wiring Example - Power Isolated
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Connecting Input Devices
The figure below demonstrates typical sensor wiring:
Figure 5:
Precon II or III Wiring
Precon II or III sensors are wired as a standard thermistor. One terminal is connected to a common pin, the other to the
SWT/RWT input. Dip switches for SWT/RWT inputs using Precon II or III sensors must be configured for VTH input.
Supply Temp (SWT)
To connect the Supply Temp sensor to the unit, attach one wire from the sensor to SWT (T19) and the other wire to the
adjacent common (T18). Please refer to the Wiring Information for the sensor types and the corresponding DIP switch
settings.
This sensor is required for pump staging or modulation.
Return Temp (RWT)
To connect the Return Temp sensor to the unit, attach one wire from the sensor to RWT (T17) and the other wire to the
adjacent common (T18). Please refer to the Wiring Information for the sensor types and the corresponding DIP switch
settings.
This sensor is required for pump staging or modulation.
Pump Flow Proof (PFP)
To connect the Pump Flow Proof sensor to the unit, attach one wire from the sensor to PFP (T16) and the other wire to
the adjacent common (T15). This must be a dry contact normally open or closed switch.
Demand (DMD)
To connect the Demand sensor to the unit, attach one wire from the sensor to DMD (T14) and the other wire to the
adjacent common (T15). This must be a dry contact switch.
Setting DIP Switches
Each input has a corresponding pair of DIP switches. The DIP switches are in three black cases with white switches
located near the inputs. While holding the board with the inputs facing down, the pair of dip switches furthest to the right
correspond to the right-most input (SWT), the next pair of dip switches correspond to the next input (RWT) and so on.
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Dip switch pairs must be set properly for each input to operate correctly as shown below:
Figure 6: DIP Switch Settings
NOTE: The dip switches are black boxes with white switches; this drawing is a negative image; the switch
position is shown as black.
Connecting Output Devices
Pump Enable Output (PMP1, PMP2)
The outputs for the Pump Enable must be connected to 24 VAC pilot relays.
• Connect PMP1 (T31) to load. Use TC12 (T30) as common.
• Connect PMP2 (T29) to load. Use TC12 (T30) as common.
Pump Modulated Outputs (MOD1, MOD2)
The modulated outputs can be set to 0-10 V through the control logic. The control signal input of the pump connects to
the 0-10V outputs of the PSU1.
• Connect MOD1 (T37) to load. Use COM (T36) as common.
• Connect MOD2 (T35) to load. Use COM (T36) as common.
Other Connections
Network (LON)
Network wiring must be twisted pair. One network wire must be connected to terminal NETA (T1) and the other network
wire must be connected to terminal NETB (T2). Polarity is not an issue since an FTT-10A network is used for commu-
nications.
Power (PWR)
Connect one output wire from a 24 VAC power supply to PWR (T39) and the other output wire from the power supply to
the adjacent common terminal (T38).
Ground (GND)
Terminal GND (T40) must be connected to earth ground. Failure to properly ground this equipment will
result in improper operation. Improper grounding may also increase the risk of electrical shock, and may
increase the possibility of interference with radio and TV reception.
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SPECIFICATIONS
Electrical
Inputs
• Cabling: twisted shielded pair, 18 AWG recommended—500 feet max. (152 meters)
• Resolution: 10 bit
Demand
• Dry Contact
• Normally Open
Flow
• Dry Contact
• Normally Open, Normally Closed
Supply Water Temperature, Return Water Temperature
• Precon Type II or III 10K Thermistor
Outputs
Pump Enable
• 24 Volts AC
• 1 Amp at 50 °C, 0.5 Amps at 60 °C, limited by Class 2 supply
Pump Modulation
• 0 - 10 Volts DC
• 2K Ohm minimum load
Power
Power Requirements
• 24VAC (20VAC to 28VAC), requires an external Class 2 supply
Power Consumption
• 7.2W with no external loads, maximum limited by the Class 2 supply rating
Recommended Sensor Wire
FTT-10A Network
• Speed: 78KBPS
• 42.4 Volts DC max
• Cabling: Maximum node-to-node distance: 1312 feet (400 meters)
• Maximum total distance: 1640 feet (500 meters)
For detailed specifications, refer to the FTT-10A Free-Topology Transceiver User’s Guide published by Echelon Corpo-
ration (www.echelon.com/support/documentation/manuals/transceivers).
Cable Type Pairs Details Taco Catalog No.
18AWG 1 Stranded Twisted Shielded Pair, Plenum WIR-018
Cable Type Pairs Details Taco Catalog No.
Level 4 22AWG (0.65mm) 1 Unshielded, Plenum, U.L. Type CMP WIR-022
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Mechanical
Housing
• Dimensions: 5.55” (141mm) high, 6.54” (166 mm) wide, 1.75” deep (44 mm)
• ABS
Weight
• Controller Weight: 0.70 pounds (0.32 kilograms)
• Shipping Weight: 1.0 pounds (0.46 kilograms)
Electronics
• Processor: 3150 Neuron 10 MHz
• Flash: 48 Kilobytes
• SRAM: 8 Kilobytes
• Termination: 0.197” (5.0 mm) Pluggable Terminal Blocks, 14-22 AWG
Environmental
• Temperature: 32 °F to 140 °F (0 °C to 60 °C)
• Humidity: 0 to 90%, non-condensing
Agency Listings
• UL Listed for US and Canada, Energy Management Equipment PAZX and PAZX7.
Agency Compliances
• FCC Part 15 Class A
APPLICATION DESCRIPTION
The PSU1 is intended for control of two primary pumps and can either extend the features of an iWorx® Series boiler
controller, or can operate as a stand-alone controller.
Figure 7: Typical Application
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Four possible operational modes are provided. The first is Single mode where a lead pump is manually selected via the
LCI. If the lead pump does not provide the required flow as determined by the flow/pressure switch input, then an alarm
is generated. Depending on the Lead Pump Sel setting and pump runtimes, the lag pump may also be turned on. The
second mode, Standby mode, is similar to Single mode with the exception that the lag pump is always started when the
lead pump fails to provide the required flow. The third mode, Equal Runtime Mode, allows for standby operation plus
equal runtime rotation of the two pumps based on a runtime setting on the LCI.
These three modes (Single, Standby and Equal Runtime) also allow the option for Delta T temperature modulation via
digital pump enable and modulated pump output signals. The fourth mode -- 2 Stage mode -- allows for standby opera-
tion, plus provides two-stage operation (digital pump control only) of the pumps based on the Delta T of the primary
loop.
NOTE: The Delta T displayed and used for sequencing algorithms is always the absolute value of the Sup-
ply - Return Temperature. The controller is indifferent to the sign of the equation result. This behavior pro-
motes automatic changeover between heating and cooling systems at the point where Delta T is 0 °F.
SEQUENCE OF OPERATION
This section describes the detailed sequence of operation for the PSU1 control strategy.
Operational Modes
The four primary modes of operation for sequencing primary pumps are described below.
Table 1: Operational Mode Features
Single Mode
If only one pump is used, or if one pump is unavailable due to servicing, then this mode may be used to disable standby
failover. 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 In Alarm? indicator displays “Yes” and an alarm for the lead pump is communi-
cated to the LCI. If the Lead Pump Sel setting is set to “Lowest Hours” and the lag pump has a lower runtime, or if the
Lead Pump Sel setting is set to “Alternating,” then the lag pump is started. If purely single pump operation is desired,
then Operation Mode must be set to “Single” and the Lead Pump Sel setting must be set to either “Pump1” or “Pump2”.
Operational
Mode Setting
Lead Pump Sel
Setting
Standby Failover?
Pump Alternation
During Operation?
Delta T Pump
Staging?
Delta T Modulated
Outputs?
Single Pump1, Pump2 No No No Yes (Optional)
Lowest Hours Yes, if lag hours >=
lead
Alternating Yes
Standby Any Yes No No Yes (Optional)
Equal Runtime Any Yes Yes No Yes (Optional)
2 Stage Any Yes No Yes No
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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.
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All operating modes that support standby failover normally switch off pumps that fail to satisfy the flow proof input. If
Flow Recovery is enabled both pump outputs will be energized after a 30 second delay. If modulated outputs are con-
figured, modulation levels are fixed to the minimum "On" level specified under the Pump Mod Set: On settings. Pump
runtime is not accumulated at any point in time while Flow Recovery is active.
Flow is monitored while the controller is operating in Flow Recovery mode. An automatic restart occurs during Flow
Recovery mode if automatic restarts are remaining and the controller detects flow for the amount of time specified by
the Flow Delay setting. The Restarts Left output value indicates the number of automatic restarts remaining. The num-
ber of automatic restarts is configurable under the Auto Recovery: Number Restarts setting. To prevent the controller
from restarting in Flow Recovery Mode, set Auto Recovery: Number Restarts setting to "0."
An automatic restart succeeds when a single pump is able to satisfy the flow proof sensor. Once an automatic restart
succeeds, a timer is started. The Restarts Left output value is restored to the Auto Recovery: Number Restarts setting
after one day of successful operation. Each automatic restart resets this timer to zero and another day of successful
operation must occur before the Restarts Left output value is restored.
While in Flow Recovery Mode, the Flow Recovery Mode output on the LCI displays "Yes".
When Flow Recovery Mode displays "Yes" and Restarts Left displays "0" the controller is in Flow Recovery mode, but
no longer able to attempt an automatic reset. Flow is not monitored. Since a successful automatic restart is required
before Restarts Left is restored, the controller operates in this state indefinitely until flow issues are resolved and a
manual controller reset is performed. Both outputs will be energized in accordance with demand inputs regardless of
the flow reading.
The controller will leave Flow Recovery Mode when an automatic restart occurs, the controller is manually reset, or
commissioning mode is used. While in Flow Recovery Mode, pump outputs are energized corresponding to the
demand input. Cycling demand causes controller outputs to turn on or off, but does not cause the controller to leave
Flow Recovery Mode.
The Pump Settings: Post Purge Time is enforced when demand input changes from active to inactive in Flow Recovery
mode. Both pump outputs are energized until the post purge time is complete.
In order to enable the Flow Recovery sequence, the following conditions must be met:
• Pump Settings: Operational Mode must be set to a mode other than "Single".
• Enable Alarm must be set to "Switch (Open)" for monitoring of a normally open flow switch or "Switch (Closed)" for
monitoring of a normally closed flow switch.
• Auto Recovery: Enable must be set to "On."
iWorx® PSU1
18 505-012, Effective: August 10, 2012
© 2012 Taco Electronic Solutions, Inc.
Figure 8: Example Auto Flow Recovery Sequence
NOTE: This flow chart depicts Auto Flow Recovery behavior in Standby Mode with an active demand
input. Unrelated operational behavior has been intentionally omitted.
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.
iWorx® PSU1
20 505-012, Effective: August 10, 2012
© 2012 Taco Electronic Solutions, Inc.
Commissioning
Either pump may be commissioned at any time by means of the Commissioning: Pump 1 Comm or Commissioning:
Pump 2 Comm setting. To turn the pump on, set the switch to “Enable.” To turn the pump off, set the switch to “Disable.”
To resume automatic operation, set the switch to “Auto.”
When pump 1 or pump 2 is enabled in this manner, the pump's modulated output is also set to the speed setting spec-
ified in the Commissioning: Pump 1 Mod or Commissioning: Pump 2 Mod setting.
NOTE: Care should be taken to ensure that the Pump 1 Mod or Pump 2 Mod setting is acceptable before
changing the Pump 1 Comm or Pump 2 Comm field to “Enable.”
Alarms
Circulation Pump Failed Alarm
The Pump Flow Proof is monitored whenever the lead primary pump is turned on by the controller. If the Pump Flow
Proof switch remains open after a configurable delay and Enable Alarm is not set to “Disabled,” a Circulation Pump
Failed Alarm is communicated to the LCI.
Dual Pump Failure
When both pumps have failed, a Dual Pump Failure alarm is communicated to the LCI. A dual pump failure alarm
occurs when:
• Two pumps have failed and Auto Flow Recovery Mode is not configured.
• Two pumps have failed, Flow Recovery is active and flow has not been detected for twice the duration configured
under Flow Delay.
Circulation Water Temp alarms
A temperature alarm is communicated to the LCI under the following conditions:
• Circulation Supply Water Temp High
• Circulation Supply Water Temp Low
• Circulation Return Water Temp High
• Circulation Return Water Temp Low
A “Temp High” alarm is generated when measured water temperature exceeds the limit defined in Water Temp Alm:
High Limit. A Temp High alarm returns to normal when the water temperature falls below the High Limit minus 1°F.
A “Temp Low” alarm is generated when measured water temperature is below the limit defined in Water Temp Alm:
Low Limit. A Temp Low alarm returns to normal when the water temperature rises above the Low Limit plus 1°F.
Circulation alarms are disabled when both Water Temp Alm: High Limit and Water Temp Alm: Low Limit are set to 32
°F.
CONTROLLER IDENTIFICATION
To register the controller with the LCI, press the service pin on the controller once it is properly installed and the LCI is
active on the network.
Once the PSU1 is properly installed and recognized by the LCI, the LCI can be used to configure the settings of the
controller. This section describes the commands available on the LCI for configuration of the PSU1, and the meanings
and default values for controller parameters. For more information on using the LCI, see the iWorx® LCI Application
Guide.
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