FlexCore CK-Series Gas-Fired Direct Vent Stainless Steel Boilers
Models CK0850-CK3000
CK0850 FlexCore CK Series Gas Boiler HeatNet Control
Control Manual Virtuoso2 10:1 Supplement
This instruction manual applies only to RBI firmware version 4.x on version 3.x control boards equipped with the high turndown option.
Also read and follow: FlexCore CK-Series Control Manual FlexCore CK-Series Gas Boiler Installation and Operating Instructions
WARNING This manual is intended only for use by a qualiied heating installer/technician. Read and follow this manual, all supplements and related instructional information provided with the boiler. Install, start and service the boiler only in the sequence and methods given in these instructions. Failure to do so can result in severe personal injury, death or substantial property damage.
WARNING Do not use the boiler during construction. Construction dust and particulate, particularly drywall dust, will cause contamination of the burner, resulting in possible severe personal injury, death or substantial property damage. he boiler can only be operated with a dust-free air supply. Follow the instruction manual procedures to duct air to the boiler air intake. If the boiler has been contaminated by operation with contaminated air, follow the instruction manual guidelines to clean, repair or replace the boiler if necessary.
CAUTION Aix these instructions near to the boiler. Instruct the building owner to retain the instructions for future use by a qualiied service technician, and to follow all guidelines in the User’s Information Manual.
Introduction
FlexCore CK-Series boilers equipped with the High Turndown feature include the Virtuoso2 High Turndown Control and the air shutter module to allow up to 10:1 Turndown. The shutter provides
protection from intake and flue pressure fluctuations by keeping the blower RPMs high for increased stability. The combustion is also monitored using an oxygen sensor to provide feedback on the
combustion efficiency. This system provides robust operation at lower inputs, improves the air-fuel mixture to the burner and maximizes overall operational efficiency.
This manual covers the new settings, adjustments, and fault messages for the high turndown feature.
Specifications
| Control | Microprocessor based stepper motor and O2 sensor control (NOT a safety limit) |
| Environment | -40 °F to 140 °F, <90% RH non-condensing |
| Input Power | 12VDC, 60W |
| Relays | Alarm, 5A 250 VAC resistive |
| Dimensions | 3.5” wide; 2” high; 3” deep |
| Communications | HeatNet Minibus |
Components & Accessories
Part Number
| 40-0080-001 | Virtuoso2 High Turndown Control |
| 40-0092 | HeatNet V3.0, Full, SATA |
| 16-0341 | Oxygen Sensor |
| 15-0353-001 | 12V DC Power Supply |
| 48-0708-001 | Minibus SATA Cable 2M |
| 48-0708-002 | Minibus SATA Cable 4M |
| 82-0962-001 | Installation & Operation Manual |
Operation & Setup
At power-up the air shutter will find its home position by hitting the end switch, and then go to the appropriate starting position for the boiler model selected. The air shutter stays in the starting position throughout the ignition cycle. Once the boiler is running it will vary its position depending on the boiler modulation. During the post purge period at the end of the boiler cycle, the air shutter will find its home position and then return to the appropriate starting position.
The blower speed is varied according to the boiler modulation the same as typical 5:1 boilers. However, when operating in 10:1 turndown, the blower speed is not reduced all the way down to the minimum input. Lower inputs are obtained by keeping the blower running at the Blower Clamp value and adjusting the air shutter position.
An oxygen sensor is used to monitor the combustion values and provide feedback on the combustion efficiency of the boiler. The accuracy of the O2 sensor is checked during the post purge period.
High Turndown Status
A new High Turndown tab has been added to the boiler information screen. 
The High Turndown screen shows the details of the high turndown features. The screen shows the modulation input of the boiler, the O2% and CO2% readings, and the position of the air shutter. he leaf icon to the right of the combustion values indicates the combustion efficiency of the boiler. A 
green leaf indicates good combustion, and a 
yellow leaf indicates that the combustion values may need to be adjusted. Please refer to the Boiler Manual, Installation and Operation Instructions for more information.
This screen will also indicate if a Warning or Fault is present and display the orresponding message.
High Turndown Messages and Log Entries
| Message | Description/Resolution |
| Air Stepper Fault | The Air stepper a was unable to find the end switch. Verify stepper and end switch wiring, and check the air shutter is not bound. A power cycle is required to clear. |
| O2 Sensor Warning | There is a problem with the O2 sensor, or its wiring. Verify wiring or replace the O2 sensor. |
| O2 Circuit Warning | There is a problem with the O2 sensor circuitry. If a power cycle does not clear the warning, replace the Virtuoso2 High Turndown Control. |
| O2 Sensor Near End of Life | The O2 sensor is near the end of its life and should be replaced soon. |
| Replace O2 Sensor | The O2 sensor has reached the end of its life and should be replaced. |
| Minibus Packet Error | Minibus packet errors are being generated. Verify the minibus wiring and termination |
| Lost Minibus Heartbeat | The Virtuoso2 High Turndown Control is not responding to minibus heartbeat requests. Verify the minibus wiring and termination. |
| Lost Minibus | The Virtuoso2 High Turndown Control is not responding to any minibus communications. Verify the minibus wiring, termination and power to the Virtuoso2 High Turndown Control. |
| High Turndown Control Interlock (J11A-5,6) | The High Turndown Control Interlock is open on the HeatNetV3 control. Verify wiring to J11A-5 and 6, and make sure the Virtuoso2 High Turndown Control is operational and Is not faulted. |
| High Turndown Control is Offline | The Virtuoso2 High Turndown Control is not responding to any minibus communications. Verify the minibus wiring, termination and power to the Virtuoso2 High Turndown Control. |
High Turndown Settings
The HeatNet V3 control board must be configured correctly for proper 10:1 operation. Only boilers equipped with an Ametek blower can be used with the Virtuoso2 High urndown Control to achieve 10:1 turndown. The O2 Sensor and the Primary Fuel type must be set correctly to accurately display combustion values.
High Turndown System Wiring
10:1 Calibration
NOTICE The calibration of the FlexCore CK-Series boiler should only be performed by a licensed/Certified technician.
All calibration settings should be adjusted based on the boiler’s parameters. See the Boiler Installation, Operation, and Maintenance manual – (10:1) Startup Procedure.
To enter the calibration menus, place the S2 switch on the main control board to the CAL position. A reloading message will appear and then the calibrate screen will be displayed. The calibration screen allows the Ignition% and Maximum% to be adjusted.
Pressing the Start Calibrate 
Button will allow the Min Air Shutter and Blower Clamp values to be set.
Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications.
RBI MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Page 2 http://www.rbiwaterheaters.com
The RBI name and logo, Mestek name and logo, FlexCore CKSeries, HeatNet, and H-Net name and logo areregistered trademarks of Mestek, Incorporated in the U.S.A. and other countries.
BACnet is a registered trademark of ASHRAE. LonWorks is a registered trademark of Echelon Corporation. All trademarks mentioned herein are property of their respective companies.
2020, Mestek Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
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