Watts AERCO EXT Instruction manual

Heating and Hot Water Solutions
AERCO International, Inc. • 100 Oritani Drive • Blauvelt, NY 10913
USA: T: [phone] • Toll Free: [phone] • AERCO.com
Technical Support • [phone] • Mon-Fri, 8 am - 5 pm EST
© 2022 AERCO
Installation, Operation & Maintenance Manual
Modulex EXT –Ufly Controller
Commercial Series
Modulating and Condensing Boilers
Applies To Modulex Models:
•MLX EXT 1500 2S
•MLX EXT 2300 2S
•MLX EXT 2600 2S
•MLX EXT 3000 2S
OMM-0160_A •6/28/2022
Disclaimer
The information contained in this manual is subject to change without notice
from AERCO International, Inc. AERCO makes no warranty of any kind with
respect to this material, including, but not limited to, implied warranties of
merchantability and fitness for a particular application. AERCO International is
not liable for errors appearing in this manual, not for incidental or
consequential damages occurring in connection with the furnishing,
performance, or use of these materials.

Modulex EXT Commercial Series
CONTENTS
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Table of Contents
CHAPTER 1: SAFETY PRECAUTIONS.................................................................................................6
CHAPTER 2: GENERAL INFORMATION ............................................................................................10
2.1 Correct Use of The Appliance...................................................................................................................... 10
2.2 Water Treatment........................................................................................................................................ 10
2.3 Information To Be Made Available to The User............................................................................................10
2.4 Safety Warnings..........................................................................................................................................11
2.5 Modifications To Parts Connected to The Appliance....................................................................................11
2.6 For Appliances Operating with Propane Gas................................................................................................ 11
2.7 Data Plate................................................................................................................................................... 12
2.8 Operational Requirements..........................................................................................................................13
2.8.1 General Requirements......................................................................................................................13
2.8.2 Regulatory Requirements................................................................................................................. 13
2.8.3 Water Quality Requirements ............................................................................................................ 14
2.9 Tools, Materials, and Additional Equipment ................................................................................................ 14
2.10 Disposal Of Packaging and Parts................................................................................................................ 15
2.11 General Warnings ..................................................................................................................................... 15
2.11.1 Using the Operation and Maintenance Manual............................................................................... 15
2.11.2 Installation and Servicing Personnel................................................................................................ 15
2.11.3 Installation Materials...................................................................................................................... 15
2.11.4 Preparing Boiler for Servicing.......................................................................................................... 15
2.11.5 Returning a Boiler to Service........................................................................................................... 15
2.11.6 Change in Ownership...................................................................................................................... 15
2.12 Operational Limits of The Boiler ................................................................................................................15
CHAPTER 3: TECHNICAL FEATURES & DIMENSIONS.....................................................................16
3.1 MODULEX EXT Commercial Technical Features............................................................................................16
3.1.1 Temperature Control Devices: ..........................................................................................................16
3.1.2 Control Panel (Ufly) Includes:............................................................................................................ 16
3.1.3 Other Features Include:.................................................................................................................... 16
3.2 General Boiler Operation ............................................................................................................................ 17
3.3 Boiler Freeze Protection.............................................................................................................................. 17
3.4 Dimensional Drawings................................................................................................................................. 18
3.5 Performance Data....................................................................................................................................... 21
CHAPTER 4: INSTALLATION INSTRUCTIONS ..................................................................................22
4.1 Installation Warnings and Requirements.....................................................................................................22
4.1.1 Appropriate Use of the Boiler ........................................................................................................... 22
4.1.2 Prerequisite System Flushing............................................................................................................22
4.1.3 Installation Personnel Qualifications................................................................................................. 22
4.1.4 Carbon Monoxide Detector Installation ............................................................................................22
4.1.5 Installation Conformity Requirements .............................................................................................. 22
4.2 Code And Standards Approvals ................................................................................................................... 23
4.3 Packaging ................................................................................................................................................... 23
4.4 Transporting And Securing the Boiler Safely ................................................................................................ 24
4.5 Unpacking The Boiler .................................................................................................................................. 24
4.6 Boiler Package Contents.............................................................................................................................. 25
4.7 Location in Boiler Room .............................................................................................................................. 26
4.7.1 Boiler Room Safety Concerns............................................................................................................26
4.7.2 Products to Avoid in the Boiler Room................................................................................................ 27
4.8 Recommended Clearances for Servicing......................................................................................................27
4.9 Gas Connection General Information ..........................................................................................................28
4.9.1 Natural Gas Connections .................................................................................................................. 29
Natural Gas Piping Sizes................................................................................................................. 29
Natural Gas Piping Connections .....................................................................................................29
Natural Gas Supply Pressure Requirements.................................................................................... 29
4.9.2 Propane Gas Connections................................................................................................................. 29

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CONTENTS
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Propane Gas Piping Sizes ............................................................................................................... 29
Propane Gas Piping Connections....................................................................................................29
Propane Gas Supply Pressure Requirements.................................................................................. 29
4.10 Flow And Return Pipe Connections............................................................................................................ 29
4.11 Pressure Relief Valve................................................................................................................................. 30
4.12 CSD-1 Manifold Assembly (Supplied)......................................................................................................... 30
4.13 Determination Of Primary Boiler Pump or Boiler System Pump.................................................................. 32
4.14 Condensate Piping And Drain.................................................................................................................... 33
4.15 Water Treatment......................................................................................................................................35
4.16 Important Installation Warnings................................................................................................................ 35
4.16.1 Oxygen Levels in the System Water Warning ..................................................................................35
4.16.2 Antifreeze Compatibility Warning................................................................................................... 35
4.16.3 Lime Scale and Corrosive Water Damage Warning .......................................................................... 35
4.16.4 Connection to Refrigeration System Warning..................................................................................36
4.17 Optional Air Intake Connection .................................................................................................................36
4.18 Flue Manifold Installation..........................................................................................................................36
4.19 Flue Exhaust Piping To Vent ......................................................................................................................38
4.20 Vent Starter Pieces.................................................................................................................................... 39
4.21 Combustion Air and Ventilation Openings ................................................................................................. 40
4.21.1 Insufficient Ventilation and Combustion Air....................................................................................40
4.21.2 Room Air Combustion..................................................................................................................... 41
4.21.3 Sealed Combustion......................................................................................................................... 41
4.22 Installing the Exhaust and Air Intake System.............................................................................................. 42
4.22.1 Important Factors for Terminal Orientation and Location................................................................ 42
4.22.2 Minimum and Maximum Wall Thickness......................................................................................... 43
4.23 Vent Pipe Sizing ........................................................................................................................................43
4.24 Electrical Connections............................................................................................................................... 45
4.24.1 Regulations in Force .......................................................................................................................45
4.24.2 Mains Electrical Supply Connection (120 V –60 Hz).........................................................................45
4.24.3 Service Relay Requirement ............................................................................................................. 46
4.24.4 Electrical Requirements.................................................................................................................. 46
4.25 Functional Wiring Diagram page 1............................................................................................................. 48
4.26 Functional Wiring Diagram, page 2............................................................................................................ 49
4.27 Module Ladder Diagram............................................................................................................................ 50
4.28 General Ladder Diagram ........................................................................................................................... 51
4.29 Input/Output Box Terminal Assignments................................................................................................... 52
4.30 Starting Up: Filling and De-Aerating The Boiler ..........................................................................................53
4.30.1 Necessary Precautions for Safety.................................................................................................... 53
4.30.2 Supply Voltage, Gas Pressure, and Water pressure..........................................................................53
4.31 Filling The System .....................................................................................................................................53
4.31.1 Necessary Precautions While Filling the System ..............................................................................53
4.31.2 Filling Locations and Preparation ....................................................................................................54
4.32 Testing The Ignition Safety Shut-Off Device ............................................................................................... 56
4.33 Burner Calibration..................................................................................................................................... 57
4.33.1 Installing Gas Analyzer Probe into Flue Outlet................................................................................. 57
4.33.2 Maximum Output Calibration .........................................................................................................58
4.33.3 Minimum Output Calibration.......................................................................................................... 59
4.33.4 Final Check and Ignition Failure Adjustment Procedure...................................................................59
4.34 Sweeper Mode (Manual Control) ..............................................................................................................61
4.35 High Altitude Adjustment..........................................................................................................................63
4.36 High Altitude Conversion Label..................................................................................................................64
4.37 Conversion From Natural Gas to Propane Gas ........................................................................................... 64
4.38 Controls And Emergency Functions ........................................................................................................... 65
4.39 Initial Boiler Ignition.................................................................................................................................. 65
4.39.1 Preliminary Checks ......................................................................................................................... 65
CHAPTER 5: UFLY CONTROLLER & BCM MODULES......................................................................67

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5.1 Ufly Controller ............................................................................................................................................ 67
5.1.1 Ufly Controller Features and Functions ............................................................................................. 67
5.1.2 Reading the Icons on Home Page...................................................................................................... 68
5.1.3 Display Modes.................................................................................................................................. 69
5.2 BCM (BOILER COMMUNICATION MODULE)................................................................................................. 69
CHAPTER 6: OPERATION, MENU & PARAMETERS .........................................................................73
6.1 SETUP MENU .............................................................................................................................................. 74
6.1.1 Setting Time and Date ......................................................................................................................74
6.1.2 Setting Comfort and Eco Building Reference Temperatures............................................................... 74
6.1.3 Setting Comfort and Eco Domestic Hot Water Setpoints ................................................................... 74
6.1.4 Display Settings................................................................................................................................ 75
6.1.5 Language and Unit Settings............................................................................................................... 75
6.1.6 Password.......................................................................................................................................... 76
6.2 Heating Menu.............................................................................................................................................77
6.3 Domestic Hot Water Menu ......................................................................................................................... 78
6.4 Devices Menu.............................................................................................................................................79
6.5 Burner Menu ..............................................................................................................................................81
6.5.1 Service Mode/Manual Firing Rate Function....................................................................................... 81
6.5.2 Manual Setpoint Function.................................................................................................................82
6.5.3 Reset Burner Working Hours and Ignition Count............................................................................... 83
6.6 BCM Parameters......................................................................................................................................... 84
6.7 BMM Parameters........................................................................................................................................ 88
CHAPTER 7: TROUBLESHOOTING ...................................................................................................91
7.1 Ufly Controller Error Codes .........................................................................................................................91
7.1.1 BCM (Boiler Communications Module) Fault Codes........................................................................... 92
7.1.2 BMM (Burner Management Module) Fault Codes.............................................................................94
CHAPTER 8: MAINTENANCE SCHEDULE.........................................................................................96
8.1 Instructions For Inspection and Maintenance.............................................................................................. 96
8.2 Periodic Examination Of Venting System ..................................................................................................... 97
8.3 Proper Procedure For Cleaning Exhaust Flue ............................................................................................... 97
8.3.1 Cleaning the Condensate Drain Line.................................................................................................. 98
8.4 Checking CSD-1 Manifold Flow Switch......................................................................................................... 98
8.5 Visual Inspection Of The Flame ...................................................................................................................99
8.5.1 Flame Color......................................................................................................................................99
8.6 Proper Reassembly And Resealing Of The Vent-Air Intake System ............................................................... 99
8.7 Pressure Switch Hoses and Connections.................................................................................................... 100
8.8 Burner / Heat Exchanger Cleaning Procedure ............................................................................................ 101
8.9 Heat and Return Sensor Resistance Values................................................................................................ 101
8.10 Unit Disassembly..................................................................................................................................... 102
8.11 Cleaning The Burner Module and Combustion Chamber.......................................................................... 108
8.12 Cleaning The Heat Exchanger .................................................................................................................. 109
8.12.1 Mechanical Cleaning of the Heat Exchanger.................................................................................. 109
8.12.2 Cleaning the Heat Exchanger with Cleaning Solution..................................................................... 110
8.12.3 Repeat Cleaning ........................................................................................................................... 111
8.13 Reassembly Of the Burner Modules ........................................................................................................ 111
8.14 Final Procedures After Maintenance ....................................................................................................... 112
8.15 Maintenance Kit Part Number................................................................................................................. 112
CHAPTER 9: SPARE PARTS DRAWING AND LISTS.......................................................................113

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CHAPTER 1: SAFETY PRECAUTIONS
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CHAPTER 1: SAFETY PRECAUTIONS
The following defined symbols are used throughout this manual to notify the reader of potential
hazards of varying risk levels.
D A N G ER !
Indicates an imminent hazard which if not avoided WILL result in death or serious injury.
W A R N I N G !
Indicates a potentially hazard which if not avoided MAY result in death or serious injury.
C A U T I O N !
Indicates a potential hazardous situation which if not avoided COULD result in minor or moderate
injury. Also may caution against unsafe practices.
Note that all hazard notifications and notes are presented enclosed in a rectangle as shown below,
in order to differentiate them from the main text.
It is of utmost importance to observe all hazard notifications presented in this manual to avoid
injury, death, and damage to the equipment. Failure to properly heed safety hazard notifications
may result in the voiding of applicable warranties.
W A R N I N G !
Never use flames to detect gas leaks!
What to do if you smell gas:
•Do NOT try to light or turn on any appliance.
•Do NOT touch any electric switch or open switched doors.
•Do NOT use any phone or intercom device in your building.
•Do NOT touch metal doorknobs or any grounded device or surface without using insulated
gloves or other insulated material if you suspect static charge buildup.
•Immediately call your gas supplier from a neighbor’s phone or, if you are outside, your cell
phone. Follow the gas supplier’s instructions.
•If you cannot reach your gas supplier, call the fire department.
W A R N I N G !
This boiler has been built for installation in the country indicated on the technical data plate.
Installation in any other country be dangerous to people, animals and property.
NOTE: Carefully read the information on the warranty certificate attached to the boiler.
Important –For Massachusetts Installations
Boiler Installations within the Commonwealth of Massachusetts must conform to the following requirements:
•Boiler must be installed by a plumber or a gas fitter who is licensed within the Commonwealth of
Massachusetts.
•Prior to unit operation, the complete gas train and all connections must be leak tested using a non-
corrosive soap.
•If a glycol solution is used as anti-freeze protection, a backflow preventer must be installed upstream of

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CHAPTER 1: SAFETY PRECAUTIONS
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the Fill/Makeup Valve.
•The vent termination must be located a minimum of 4 feet above grade level.
•If side-wall venting is used, the installation must conform to the following requirements extracted from
248 CMR 5.08 (2):
A. For all side wall horizontally vented gas fueled equipment installed in every dwelling, building or
structure used in whole or in part for residential purposes, including those owned or operated by the
Commonwealth and where the side wall exhaust vent termination is less than seven (7) feet above
finished grade in the area of the venting, including but not limited to decks and porches, the following
requirements shall be satisfied:
1. INSTALLATION OF CARBON MONOXIDE DETECTORS. At the time of installation of the side
wall horizontal vented gas fueled equipment, the installing plumber or gasfitter shall observe that
a hard-wired carbon monoxide detector with an alarm and battery back-up is installed on the floor
level where the gas equipment is to be installed. In addition, the installing plumber or gasfitter shall
observe that a battery operated or hard-wired carbon monoxide detector with an alarm is installed
on each additional level of the dwelling, building or structure served by the side wall horizontal
vented gas fueled equipment. It shall be the responsibility of the property owner to secure the
services of qualified licensed professionals for the installation of hard-wired carbon monoxide
detectors
a) In the event that the side wall horizontally vented gas fueled equipment is installed in a crawl
space or an attic, the hard-wired carbon monoxide detector with alarm and battery back-up may
be installed on the next adjacent floor level.
b) In the event that the requirements of this subdivision cannot be met at the time of completion
of installation, the owner shall have a period of thirty (30) days to comply with the above
requirements; provided, however, that during said thirty (30) day period, a battery-operated
carbon monoxide detector with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE DETECTORS. Each carbon monoxide detector as required
in accordance with the above provisions shall comply with NFPA 720 and be ANSI/UL 2034 listed
and IAS certified.
3. SIGNAGE. A metal or plastic identification plate shall be permanently mounted to the exterior of
the building at a minimum height of eight (8) feet above grade directly in line with the exhaust vent
terminal for the horizontally vented gas fueled heating appliance or equipment. The sign shall read,
in print size no less than one-half (1/2) inch in size, "GAS VENT DIRECTLY BELOW. KEEP
CLEAR OF ALL OBSTRUCTIONS".
4. INSPECTION. The state or local gas inspector of the side wall horizontally vented gas fueled
equipment shall not approve the installation unless, upon inspection, the inspector observes
carbon monoxide detectors and signage installed in accordance with the provisions of 248 CMR
5.08(2)(a)1 through 4.
(Continued on Next Page)

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Important - For Massachusetts Installations
(Continued from Previous Page)
B. EXEMPTIONS: The following equipment is exempt from 248 CMR 5.08(2)(a)1 to 4:
1. The equipment listed in Chapter 10 entitled "Equipment Not Required To Be Vented" inthe most
current edition of NFPA 54 as adopted by the Board; and
2. Product Approved side wall horizontally vented gas fueled equipment installed in a room or
structure separate from the dwelling, building or structure used in whole or in part for residential
purposes.
C. MANUFACTURER REQUIREMENTS - GAS EQUIPMENT VENTING SYSTEM PROVIDED: When
the manufacturer of Product Approved side wall horizontally vented gas equipment provides a venting
system design or venting system components with the equipment, the instructions provided by the
manufacturer for installation of the equipment and the venting system shall include:
1. Detailed instructions for the installation of the venting system design or the venting system
components; and
2. A complete parts list for the venting system design or venting system.
D. MANUFACTURER REQUIREMENTS - GAS EQUIPMENT VENTING SYSTEM NOT PROVIDED:
When the manufacturer of a Product Approved side wall horizontally vented gas fueled equipment
does not provide the parts for venting the flue gases, but identifies "special venting systems", the
following requirements shall be satisfied by the manufacturer:
1. The identification of each "special venting system" shall include the listing of either the website,
phone number or manufacturer’s address where the venting system installation instructions can be
obtained; and
2. The "special venting systems" shall be Product Approved by the Board, and the instructions
provided with the system shall include a parts list and detailed installation instructions.
E. A copy of all installation instructions for the Product Approved side wall horizontally vented gas fueled
equipment, all venting instructions, all parts lists for venting instructions, and/or all venting design
instructions shall remain with the appliance or equipment at the completion of the installation.
[End of Extracted Information From 248 CMR 5.08 (2)]

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Modulex EXT Commercial Series
CHAPTER 2: General Information
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CHAPTER 2: GENERAL INFORMATION
2.1 Correct Use of the Appliance
The MODULEX EXT Commercial boiler has been designed utilizing the latest heating technologies
and in compliance with current safety regulations. However, if not used or operated properly, the
unit may cause injury or death to persons, or serious damage to the equipment or surrounding
objects.
The MODULEX EXT Commercial boiler is designed to be used in pumped hot water central heating
systems. Any other use of this appliance shall be considered improper, and AERCO declines any
responsibility for damages or injuries caused by the improper use of this equipment. In order to use
the equipment appropriately and safely according to its design, it is essential to carefully follow the
instructions in this manual.
2.2 Water Treatment
•It is vital tomaintain the pHof boiler waterbetween 6.5 and8. Failure to do so could result in severe
damage to the boiler.
•The hardness of the main water supply influences the frequency with which the heat exchanger
must be cleaned.
•In hard water areas where the main water can exceed 9 grains per gallon (gpg) total hardness, a
scale reducing device is recommended.
•In order to improve the resistance to lime scale it is recommended that the domestic hot water
temperature be as near as possible to the temperature required for end use.
•AERCO recommends inspecting the state of cleanliness of the domestic hot waterheat exchanger
at the end of the first year and subsequently, on the basis of the lime scale found, this period can
be extended to two years after the initial inspection.
2.3 Information To Be Made Available to The User
Go through the information in this manual with the owner/operator and make sure that he or she is
familiar with all necessary operating instructions, in particular:
•These instructions shall be made available to the end user, together with any other literature
regarding this appliance. It is highly recommended that the user keeps these documents in a safe
and convenient place in order to always have them at hand for future reference.
•It is imperative that a proper venting and exhaust system be implemented with this unit. Refer to
the AERCO Venting Application Guide (TAG-0098).
•It is absolutelyforbidden tomake anyalterationsto the boilernot in keeping with the manufacturer’s
recommendations and instructions.
•It is critical to check the system’s water pressure and ensure it is at the correct pressure.
•For optimal operation of time and temperature controls, thermostats, heating controls, and
radiators, refer to separate Ufly Controller User Manual (OMM-0159).
•It is obligatory to carry out comprehensive maintenance services annually with a combustion
analysis every two years (in compliance with national and local laws).
•If the appliance is sold or transferred to another owner, or if the present user moves from the
installation site and leaves the appliance installed, ensure that the manual stays with the boiler so
that it can be consulted by the new owner and/or installer.
Failure to follow these instructions can cause injury to persons or animals or damage to property. The
manufacturer shall not be held liable for any such injury and/or damage.

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2.4 Safety Warnings
W A R N I N G !
Children must be supervised so they do not play on, around, or with the appliance.
The installation, adjustment, and servicing of this appliance must be carried out by a competent
person and installed in accordance with the current standards and regulations. Failure to correctly
install this appliance could cause injury to persons, animals or damage to property. The
manufacturer shall not be held liable for any injury and/or damage.
Servicing or repairs of the appliance must be carried out by AERCO authorized service technicians;
AERCO recommends drawing up a service contract. Incomplete, inappropriate, or irregular
servicing could compromise the safe operation of the appliance, and could cause injury to persons,
animals or damage to property for which AERCO shall not be held liable.
2.5 Modifications To Parts Connected to The Appliance
Do NOT carry out any modifications to the boiler or any of the following parts:
•To the gas, air, water supply pipes and electrical power
•To the flue pipe, safety relief valve and its drainage pipe
•To the constructive components which influence the appliance’s safe operation
W A R N I N G !
When adjusting the screw pipe connections use only properly sized wrenches. The use of
inadequate equipment can cause damage (for example, water or gas leakages) to the equipment.
2.6 For Appliances Operating with Propane Gas
Before installing the appliance, ensure that the gas tank has been purged. For correct instructions
on purging the tank, contact the liquid gas supplier or a competent person who is legally authorized
to provide such information. If the tank has not been correctly purged, problems may occur during
ignition. If this happens contact the liquid gas tank’s supplier.
W A R N I N G !
Do not store or use gas or other flammable vapors orliquids in the vicinity of this or any appliance.
W A R N I N G !
What to do if you smell gas:
• Donot try to light any appliance.
• Do not touch any electrical switch.
• Do not use any phone in the building.
• Immediately call gas supplier from a neighbor’s phone. Follow supplier’s instructions.
• If you cannot contact your gas supplier, call the fire department.
W A R N I N G !
The boiler must be protected against environmental variations with:
• The insulation of the hydraulic pipelines and the condensate drain.
• The adoption of specific antifreeze products in the Cold/Hot water installation.

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2.7 Data Plate
A sample Data Plate for a MODULEX EXT Commercial boiler is shown in the left figure below. A
sample of the Data Packaging label is shown in the right image below.
Figure 2-1: MODULEX EXT Commercial Data Plate (L) and Data Packing Label (R)
Each unit is fitted with a data plate, which may be consulted for the details on gas type, power
source, and venting classification.

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2.8 Operational Requirements
2.8.1 General Requirements
The following instructions MUST be followed:
•The boiler must only be used for its designated purpose as described herein.
•Each unit is fitted with a data plate. Consult the details on this plate to verify whether the boiler
is compliant with its intended location, e.g.: gas type, power source, and venting classification.
•Only use the boiler with the accessories and spare parts listed.
•Other combinations of accessories and products may only be used if specifically designed for
the intended application and do not affect system performance or safety requirements.
•Maintenance and repairs must only be performed by trained professionals.
•Installation of a condensing gas boiler must be approved per all federal and local government
codes, regulations, and laws.
•Operationofacondensinggasboilermustuseaventsystemthathasbeenspecificallydesigned
and approved for this type of boiler.
•Note that local permission and approval for the vent system and condensate water connection
to a public sewage system may be required.
2.8.2 Regulatory Requirements
You must also conform to any rules, regulations, or laws concerning the following:
•Local building codes regarding the installation.
•Local building codes concerning the air intake and outlet systems and the vent connection.
•Regulations for the power supply connection.
•Technical rules laid down by the gas utility company concerning the connection of the gas
connection to the local gas mains.
•Instructions and standards concerning safety equipment for the water/space heating system.
•Installation instructions for building heating systems.
•The boiler must be located in an area where leakage of the boiler or connections will not result
in damage to the area adjacent to the boiler or to lower floors of the structure. When such
locations cannot be avoided, it is recommended that a suitable drain pan be installed under the
boiler.
•Do not restrict or seal any air intake or outlet openings.
•If you find any defects, you must inform the owner, in writing, of the system defect and the
associated hazard.
W A R N I N G !
Should overheating occur,or the gas supply fail toshut off, donot turn off or disconnect the electrical
supply to the pump. Instead, shut off gas supply at a location external to the boiler.

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2.8.3 Water Quality Requirements
NOTE: For additional information concerning water quality and treatment, referto AERCO technical
documents Glycol Directive and AERCO Piping Application Guide (GF-136-P).
Unsuitable heating system water can cause the formation of scale or sludge, which affects system
efficiency. It can also cause corrosion and reduce life of the heat exchanger.
•Follow all guidelines for boiler water quality.
•Thoroughly flush the system prior to filling.
•Follow the cleaning instructions.
•Never use water that has been treated by reverse osmosis, deionization, mineralization or
distillation to fill the heating system
•Do not use inhibitors or other additives unless approved by AERCO for that purpose.
•When frost protection of the heating system is desired, only use AERCO-approved antifreezes.
The allowed maximum concentration is 50%.
•When using oxygen-permeable pipes, e. g. for under floor heating systems, you must separate
the system from the boiler using plate heat exchangers.
•Close the valves of the boiler while flushing the system, do not introduce any system cleaner into
the boiler loop. Flush system thoroughly to remove all system cleaner before filling boiler.
Approved antifreeze (maximum concentration of 50%):
•Sentinel X500 (available from AERCO)
•Rhomar RhoGard Mutli-Metal (AL safe)
•Noble Noburst AL
Approved system cleaners:
•Sentinel X300 (available from AERCO)
•Noble Noburst Hydronic System Cleaner
•Fernox F3 Cleaner
•Rhomar Hydro-Solv 9100
The system cleaners from NoBurst, Rhomar, and Fernox are NOT to be used in the boiler itself.
The boiler must be closed off (valves closed) from the rest of the system or not connected while the
cleaners are in the system. The system should then be drained and then thoroughly flushed with
clean water to remove all the system cleaner.
Approved inhibitors:
•Sentinel X100 (available from AERCO)
•Rhomar Pro-tek 922
•Noble Noburst AL inhibitor
•Intercool NFP-AA
•Cryo-tek 100/Al
2.9 Tools, Materials, and Additional Equipment
For the installation and maintenance of the boiler you will need:
•Standard tools for space heating, gas, and water fitting
•Manometer that is capable of reading both positive and negative pressures
•Combustion analyzer
•Digital multimeter
•pH digital meter
•Metric Allen wrenches
•Metric socket wrenches

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2.10 Disposal Of Packaging and Parts
•Dispose of the boiler packaging in an environmentally sound manner.
•Dispose of components of the heating system (e.g. boiler or control device), that must be
replaced in an environmentally responsible manner.
2.11 General Warnings
2.11.1 Using the Operation and Maintenance Manual
This instruction manual is an integral and indispensable part of the product and must be retained by
the person in charge of the appliance. Please read the instructions contained in this manual
carefully as they provide important information regarding the safe installation, use and servicing of
this appliance. Keep this manual in a safe place for future reference.
2.11.2 Installation and Servicing Personnel
Installation and servicing must be carried out in accordance with the regulations in force according
to the manufacturer’s instructions and by legally competent authorized persons. By definition, a
competent person is a person who has a specific technical qualification in the field of components
for central heating systems for domestic use, domestic hot water production, and servicing. This
person must have the qualifications legitimized by the current laws and regulations in force.
Inappropriate, incomplete, or irregular servicing could compromise the safe operation of the
appliance, and could cause injury to persons, animals or damage to property. The manufacturer
shall not be held liable for any such injury and/or damage.
Any repairs must be carried out by AERCO authorized technicians using original spare parts. Non-
observance of the above requirement may jeopardize the appliance and void any warranties.
In the event of failure and/or faulty functioning of the appliance, switch off the boiler. Do not attempt to
make any repairs, but instead contact qualified technicians.
To guarantee the efficiency and correct functioning of the appliance it is required that the boiler be
serviced annually by a qualified person.
2.11.3 Installation Materials
The installations for the domestic hot water production MUST be built, in their entirety, with
materials (taps, pipes, fittings, etc.) approved for drinkable water.
2.11.4 Preparing Boiler for Servicing
Before carrying out any cleaning or servicing turn off the electrical supply to the boiler by means of
the ON/OFF switch and/or by means of the appropriate shutdown devices.
2.11.5 Returning a Boiler to Service
Before putting a boiler, which has been unused for a length of time, back into service, rinse the
entire domestic hot water system, allowing the water to flow an appropriate amount of time in order
to circulate throughout the entire system.
2.11.6 Change in Ownership
If the appliance is sold or transferred to another owner, or if the present user moves from the
installation site and leaves the appliance installed, ensure that the manual stays with the appliance
so that it can be consulted by the new owner and/or installer.
2.12 Operational Limits of The Boiler
•Max. boiler temperature: 180° F (82° C)
•Max Allowable Working Temperature ASME: 200 °F
•Max. Allowable Working Pressure ASME: 92 psi

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CHAPTER 3: TECHNICAL FEATURES & DIMENSIONS
3.1 MODULEX EXT Commercial Technical Features
•Compact, gas fired, Low NOx, condensing boiler.
•Comprised of one sectional boiler body, suitable as a single boiler or in a cascaded group.
•May be installed either an inside or outside location.
•Rated for ambient temperatures of 5 to 104°F (-15° to 40°C).
•Low internal water volume.
•Fast response to load variations.
•Flue exhaust outlet positionable on three sides.
•Manifold delivery and return.
•Made up of four or more heating elements (4 to 8), cast aluminum / silicon / magnesium.
•Full range of modulation by variable speed blowers and premix burners.
•Each heating element monitors its own water temperature, and will individually shutdown if flow
is interrupted, without affecting the other burner sections.
•One gas supply line.
•Individual modules capable of between 83 and 382.5 kBTU/hr.
These boilers are designed for use with category IV venting.
The boiler is supplied complete with all the safety and control devices in accordance with all current
regulations, and its technical and functional features comply with the regulations prescribed by:
ANSI Z21.13 / CSA 4.9 - Gas-fired low pressure steam and hot water boilers.
3.1.1 Temperature Control Devices:
•Local NTC sensor (each heating element)
•Limit thermostat (each heating element)
•Flow NTC sensor (General)
•Return NTC sensor (General)
•Safety thermostat approved (manual reset)
•Flow sensor BCM
3.1.2 Control Panel (Ufly) Includes:
•ON-OFF switch
•Temperature control / Boiler operation
•Fuses
•High limit sensors
•Air pressure fans
•Condensate level sensor
•Air pressure switch (anti-obstruction)
3.1.3 Other Features Include:
•NTC heat sensors for global temperature control on the flow and return.
•0-10 V output to control variable speed primary pump
•Integral insulation with hypoallergenic synthetic wool.
•Premix fiber mesh modulating burner (premixes into the fan with automatic diaphragm backflow
separation from the combustion chamber).
•Less than 49 dBA of noise at maximum power.
•Heating operation: instantaneous power microprocessor control, with preset parameters for
comparison between temperature (or calculated from the external temperature regulation) and
global temperature flow.

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•Operation modes:
oAbility to control power to the individual heating elements for any calibration with or without
confidential code access.
oProduction of A.C.S. (Active Cooling System) by NTC sensor of priorities for control by boiler
feed pump or by three-way diverter valve controller.
•Ufly electronic controller included.
•BCM (Boiler Communication Module) included.
•Ability to control power of the individual heating elements.
•Control of heat demand: constant or remote setpoint.
•Monitoring of operating status and temperature.
•Reporting of alarms.
•Setting of parameters.
•Emergency operation prevents the boiler from shutting down as a result of the interruption of
communication with a control system or any remote control unit.
•Alarm management.
•Alarm reset input.
•Warning alarm relay.
•Stainless steel condensate collector tank with siphon, drain trap, and smoke chamber.
•Easily removable stainless steel panels painted for outdoor installation.
•Built-in air vent
3.2 General Boiler Operation
The boiler is operated from the Ufly controller. The Boiler Control Manager (BCM) is used for
Modbus communication as well as backup operation. The boiler management logic automatically
fires the maximum number of simultaneously operating heating elements in order to maximize heat
production and overall efficiency. Burner efficiency and a high heat exchange between surfaces
contribute to the reliable and efficient output power. The various components are designed to work
together so that operating time is shared equally among the components, thus reducing
maintenance and labor costs.
The hot water moved by the pump is pushed to the return of the primary flow of the hydraulic
separator. From here a second pump will distribute the hot water to the various destinations. The
cooled return water is drawn by the pump through the hydraulic separator to resume the cycle via
the boiler.
W A R N I N G !
If installing to an outdoor location where freezing temperatures may occur, it is necessary to install
devices and/or materials to prevent any freezing in the condensate drain and the Flow and Return
manifolds. Failure to do so may cause serious damage to the equipment.
3.3 Boiler Freeze Protection
Should the boiler water outlet temperature decrease to less than 44.6°F (7°C), the system pump
will start, and all heat modules will start at minimum output until the minimum setpoint (BCM
Parameter 31) is reached. This protection device is exclusively for the boiler. For the protection of
the whole system, a second freeze protection thermostat is necessary to switch on the heating
system pump.
NOTE: If glycol is used as antifreeze in the boiler, a back-flow preventer must be installed in the
make-up/fill line.

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3.4 Dimensional Drawings
Figure 3-1: MODULEX EXT Commercial Dimensional Drawings

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TABLE 3-1: MODULEX EXT Commercial Dimensions and Sizes

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Figure 3-2: MODULEX EXT Commercial Main Components (Right Side View)
No.
S.E.
Description
No.
S.E.
Description
1
Condensate drain tap
13
E. RIL.
Detection electrode
2
Draining tap
15
TL
Limit Thermostat Probe
3
SRR
Global return temp. sensor
16
Burner
4
PF
Max air pressure switch
17
Aluminum silicon heat exchanger
5
SM
Global flow temp. sensor
18
SL
Condensate sensor level
6
Automatic air vent
19
Exhaust manifold
7
VM
Fan
20
Boiler frame
8
VG
Gas Valve
G
Gas inlet
9
PF min
Min air pressure switch
M
Heating system flow
10
Control panel
R
Heating system return
12
E. ACC
Ignition electrode
S.E.
= WIRING DIAGRAM KEY, see par. 4.25