Watts AERCO MLX EXT 450 2S 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
OMM-0158_A •6/28/2022
Modulex EXT - Ufly Controller
Light Commercial Series
Modulating and Condensing Boilers
Applies To Modulex Models:
•MLX EXT 450 2S
•MLX EXT 600 2S
•MLX EXT 800 2S
•MLX EXT 1100 2S
Installation, Operation & Maintenance Manual
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 Light Commercial Series
TABLE OF CONTENTS
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TABLE OF CONTENTS
TABLE OF CONTENTS __________________________________________________________________________2
CHAPTER 1: SAFETY PRECAUTIONS ______________________________________________________________5
CHAPTER 2: GENERAL INFORMATION ____________________________________________________________7
2.1 Correct Use Of The Appliance_______________________________________________________________7
2.2 Water Treatment ________________________________________________________________________7
2.3 Information To Be Made Available To The User_________________________________________________7
2.4 Safety Warnings _________________________________________________________________________8
2.5 Modifications To Parts Connected To The Appliance_____________________________________________8
2.6 For Appliances Operating With Propane Gas ___________________________________________________8
2.7 Data Plate ______________________________________________________________________________9
2.8 Operational Requirements ________________________________________________________________10
General Requirements________________________________________________________________10
Regulatory Requirements _____________________________________________________________10
Water Quality Requirements___________________________________________________________10
2.9 Tools, Materials, And Additional Equipment __________________________________________________11
2.10 Disposal______________________________________________________________________________11
2.11 General Warnings______________________________________________________________________11
Using the Operation and Maintenance Manual ___________________________________________11
Installation and Servicing Personnel ____________________________________________________12
Installation Materials________________________________________________________________12
Preparing Boiler for Servicing _________________________________________________________12
Returning a Boiler to Service __________________________________________________________12
Change in Ownership________________________________________________________________12
2.12 Operational Limits Of The Boiler __________________________________________________________12
CHAPTER 3: TECHNICAL FEATURES & DIMENSIONS_________________________________________________13
3.1 Modulex Ext Technical Features____________________________________________________________13
Temperature Control Devices:__________________________________________________________13
Control Panel (Ufly) Includes: __________________________________________________________13
Other Features Include:_______________________________________________________________13
3.2 General Boiler Operation _________________________________________________________________14
3.3 Boiler Freeze Protection __________________________________________________________________14
3.4 Dimensional Drawings ___________________________________________________________________15
3.5 Performance Data_______________________________________________________________________19
CHAPTER 4: INSTALLATION INSTRUCTIONS _______________________________________________________21
4.1 General Warnings_______________________________________________________________________21
Appropriate Use of the Boiler __________________________________________________________21
Prerequisite System Flushing___________________________________________________________21
Installation Personnel Qualifications_____________________________________________________21
Carbon Monoxide Detector Installation __________________________________________________21
4.2 Code And Standards Approvals ____________________________________________________________22
4.3 Packaging _____________________________________________________________________________22
4.4 Transporting And Securing The Boiler Safely __________________________________________________25
4.5 Removal From Boiler Bed And Installation Of Boiler Feet ________________________________________25
4.6 Boiler Location Inside A Boiler Room ________________________________________________________27
Boiler Room Safety Concerns___________________________________________________________27
Products to Avoid in the Boiler Room ____________________________________________________28
4.7 Recommended Clearances For Servicing _____________________________________________________28
4.8 Boiler Connections ______________________________________________________________________29
Changing Exhaust Outlet Location_______________________________________________________29
Reversing Gas Manifold Connections ____________________________________________________30
Reversing Cold/Hot Water Flow & Return Connections ______________________________________31
4.9 Gas Connection General Information________________________________________________________33
4.10 Natural Gas Connections ________________________________________________________________34

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4.11 Propane Gas Connections________________________________________________________________34
4.12 Flow And Return Pipe Connections ________________________________________________________35
4.13 Pressure Relief Valve (Supplied)___________________________________________________________35
4.14 Csd-1 Manifold Assembly (Supplied) _______________________________________________________35
Installing the Flow Switch and CSD-1 Components_________________________________________36
4.15 Determination Of Primary Boiler Pump Or Boiler System Pump __________________________________37
4.16 Condensate Piping And Drain_____________________________________________________________38
4.17 Water Treatment ______________________________________________________________________39
4.18 Important Installation Warnings___________________________________________________________40
Oxygen Levels in the System Water Warning _____________________________________________40
Antifreeze Compatibility Warning ______________________________________________________40
Lime Scale and Corrosive Water Damage Warning _________________________________________40
Connection to Refrigeration System Warning_____________________________________________40
4.19 Air Intake Connection___________________________________________________________________40
4.20 Flue Manifold Connection _______________________________________________________________41
4.21 Flue Exhaust Piping To Vent ______________________________________________________________42
4.22 Vent Starter Pieces _____________________________________________________________________43
4.23 Combustion Air And Ventilation Openings___________________________________________________44
Insufficient Ventilations and Combustion Air _____________________________________________44
Room Air Combustion _______________________________________________________________45
Sealed Combustion _________________________________________________________________45
4.24 Installation Of The Exhaust And Air Intake System_____________________________________________45
Important Factors for Terminal Orientation and Location ___________________________________46
Minimum and Maximum Wall Thickness_________________________________________________46
4.25 Vent Pipe Sizing _______________________________________________________________________47
4.26 Electrical Connections___________________________________________________________________49
Regulations in Force_________________________________________________________________49
Mains Electrical Supply Connection (120 V –60 Hz) ________________________________________49
Service Relay Requirement ___________________________________________________________50
Electrical Requirements______________________________________________________________50
4.27 FUNCTIONAL WIRING DIAGRAM Page 1_____________________________________________________52
4.28 FUNCTIONAL WIRING DIAGRAM Page 2_____________________________________________________53
4.29 Ladder Diagrams_______________________________________________________________________54
4.30 General Ladder Diagram_________________________________________________________________55
4.31 Input/Output Box Terminal Assignments____________________________________________________56
4.32 Starting Up: Filling And De-Aerating The Boiler _______________________________________________57
Necessary Precautions for Safety ______________________________________________________57
Supply Voltage, Gas Pressure, and Water pressure_________________________________________57
4.33 Filling The System ______________________________________________________________________58
Necessary Precautions While Filling the System ___________________________________________58
Filling Locations and Preparation_______________________________________________________58
4.34 Testing The Ignition Safety Shut Off Device __________________________________________________60
4.35 Burner Calibration _____________________________________________________________________61
Installing the Gas Analyzer Probe ______________________________________________________61
Maximum Output Calibration _________________________________________________________62
Minimum Output Calibration _________________________________________________________63
Final Check and Ignition Failure Adjustment Procedure _____________________________________63
4.36 Sweeper Mode (Manual Control)__________________________________________________________65
4.37 High Altitude Adjustment________________________________________________________________67
4.38 High Altitude Conversion Label ___________________________________________________________68
4.39 Conversion From Natural Gas To Propane Gas________________________________________________68
4.40 Controls And Emergency Functions ________________________________________________________69
4.41 Initial Boiler Ignition ____________________________________________________________________70
Preliminary Checks__________________________________________________________________70
CHAPTER 5: UFLY CONTROLLER & BCM MODULES _________________________________________________71
5.1 Ufly Controller _________________________________________________________________________71

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Ufly Controller Features and Functions___________________________________________________71
Reading the Icons on Home Page _______________________________________________________72
Display Modes ______________________________________________________________________73
5.2 Bcm (Boiler Communication Module) _______________________________________________________73
CHAPTER 6: OPERATION, MENU & PARAMETERS __________________________________________________75
6.1 Setup Menu ___________________________________________________________________________76
Setting Time and Date ________________________________________________________________76
Setting Comfort and Eco Building Reference Temperatures___________________________________76
Setting Comfort and Eco Domestic Hot Water Setpoints _____________________________________77
Display Settings _____________________________________________________________________77
Language and Unit Settings ____________________________________________________________77
Password __________________________________________________________________________78
6.2 Heating Menu__________________________________________________________________________78
6.3 Domestic Hot Water Menu________________________________________________________________79
6.4 Devices Menu __________________________________________________________________________80
6.5 Burner Menu___________________________________________________________________________82
Service Mode/Manual Firing Rate Function _______________________________________________82
Manual Setpoint Function _____________________________________________________________83
Reset Burner Working Hours and Ignition Count ___________________________________________84
6.6 Bcm Parameters ________________________________________________________________________85
6.7 Bmm Parameters _______________________________________________________________________89
CHAPTER 7: TROUBLESHOOTING _______________________________________________________________92
7.1 Ufly Controller Error Codes________________________________________________________________92
BCM (Boiler Communications Module) Fault Codes _________________________________________93
BMM (Burner Management Module) Fault Codes __________________________________________95
CHAPTER 8: MAINTENANCE SCHEDULE __________________________________________________________97
8.1 Instructions For Inspection And Maintenance _________________________________________________97
8.2 Periodic Examination Of Venting System _____________________________________________________98
8.3 Proper Procedure For Cleaning Exhaust Flue __________________________________________________98
Cleaning the Condensate Drain Line _____________________________________________________98
8.4 Checking Csd-1 Manifold Flow Switch _______________________________________________________99
8.5 Visual Inspection Of The Flame ____________________________________________________________99
8.6 Reassembly And Resealing Of 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 _________________________________109
8.12 Cleaning The Heat Exchanger ____________________________________________________________111
Mechanical Cleaning of the Heat Exchanger _____________________________________________111
Cleaning the Heat Exchanger with Cleaning Solution ______________________________________113
Repeat Cleaning___________________________________________________________________113
8.13 Reassembly Of The Burner Modules ______________________________________________________114
8.14 Final Procedures After Maintenance ______________________________________________________114
8.15 Maintenance Kit Part Numbers __________________________________________________________114
CHAPTER 9: SPARE PARTS DRAWING AND LISTS __________________________________________________115

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SAFETY PRECAUTIONS
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CHAPTER 1: SAFETY PRECAUTIONS
Observe all CAUTIONS and WARNINGS in this manual to avoid injury, death, and damage to
the equipment. Failure to heed safety warnings and cautions may void 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 may be dangerous for people, animals and property.
NOTE: Carefully read all conditions and clauses on 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 usedas anti-freezeprotection, abackflow preventermust be installed upstream
of 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 ownerto securethe servicesof qualified licensed professionals forthe installation
of hard wired carbon monoxide detectors

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SAFETY PRECAUTIONS
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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.
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" in the
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)]

Modulex Light Commercial Series
CHAPTER 2: General Information
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CHAPTER 2: GENERAL INFORMATION
2.1 Correct Use Of The Appliance
The MODULEX EXT boiler has been designed utilizing the latest heating technologies and in
compliance with the 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 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 fordamagesor 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 to maintain the pH of boiler water between 6.5 and 8 to avoid damage to the boiler.
•The hardness of the main water supply affects how often the heat exchanger must be cleaned.
•Inhard waterareas wherethe main watercanexceed 9 grainspergallon totalhardness,a scale
reducing device is recommended, taking into consideration the characteristics of the water.
•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 water heat
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 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 absolutely forbidden to make any alterations to the boiler not 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 to appliance must be carried out by AERCO authorized 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 following parts:
•The boiler
•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 tightening or loosening the screw pipe connections, use only properly sized wrenches.
The improper 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 hasbeen 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 gasoline or any flammable vapors or liquids near this appliance.
I F Y O U S M E L L G A S :
•Do not try to light any appliance.
•Do not touch any electrical switch.
•Do not use any phone in the building.
•Immediately call your gas supplier from a neighbor’s phone. Follow their 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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CHAPTER 2: General Information
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2.7 Data Plate
Each unit is fitted with a data plate indicating gas type, power source and venting classification.
A sample Data Plate for a MODULEX EXT 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 Data Plate (Left) and Data Packing Label (Right)

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2.8 Operational Requirements
General Requirements
The following instructions MUST be followed:
•Boiler must only be used for its designated purpose as described.
•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 must only be used if specifically designed for
the intended application and do not affect the system performance or the 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.
•Operation of a condensing gas boiler must use a vent system that has been specifically
designed 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.
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 will not result in damage to the area
adjacent to the boiler orto lowerfloorsof the structure. When such locationscannotbe 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.
•Inform owner, in writing, of any defects found and the associated hazard.
W A R N I N G !
Should overheating occur or gas supply fail to shut off, do not turn off or disconnect the electrical
supply to the pump; shut off the gas supply at a location external to the boiler.
Water Quality Requirements
NOTE: For additionalinformation concerning waterqualityandtreatment, refer to 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.
•You must follow 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, or distilled.
•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.

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•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 Multi-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
2.10 Disposal
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
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.

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Installation and Servicing Personnel
Installation and servicing mustbe carried out inaccordance 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 and using only original spare
parts. Non-observance of the above requirement may jeopardize the safety of the appliance and
void any warranties.
In the eventof failure and/or faulty functioning of the appliance, switchoff 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.
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.
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.
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 flowan appropriate amount of time in order
to circulate throughout the entire system.
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
•Max Allowable Working Temperature ASME: 200 °F
•Max. Allowable Working Pressure ASME: 92 psi

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CHAPTER 3: TECHNICAL FEATURES & DIMENSIONS
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CHAPTER 3: TECHNICAL FEATURES & DIMENSIONS
3.1 Modulex Ext 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 in either an inside or outside location.
•Low internal water volume.
•Fast response to load variations.
•Flue exhaust outlet positionable on three sides.
•Manifold delivery and return (reversible).
•Made up of two or more heating elements (2 to 7), 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 (reversible).
•Individual modules capable of between 46 and 160.5 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.
Temperature Control Devices:
•Local NTC sensor (each heating element)
•Limit thermostat room (each heating
element)
•Flow NTC sensor (General)
•Return NTC sensor (General)
•Safety thermostat approved (manual reset)
•Flow sensor BCM
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)
Other Features Include:
•NTC heat sensors for global temperature control on the flow and return.
•0-10V 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: instantaneous power microprocessor control with preset parameters for comparison
between temperature (or calculated from external regulation) and global temperature flow.
•Operation modes:
oControl power to individual heating elements for calibration with or without code access.
oACS control by boiler feed pump or by three-way diverter valve controller.

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•Ufly electronic controller included.
•BCM (Boiler Communication Manager) 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 and 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 provides 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 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 condensatedrain 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. Such a 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 Dimensional Drawings (Side Views)
On Modulex EXT models 321,
642 and 962 the flue terminal
ends inside the casing

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Figure 3-2: MODULEX EXT and Vent Adaptor Dimensional Drawings (Top View)
TABLE 3-1: MODULEX EXT Dimensions and Sizes
Model
450 2S
600 2S
800 2S
1100 2S
Dimensions
No. of Modules
3
4
5
7
Height (Open) -
inches/mm
52.1‘‘
1323
52.1‘‘
1323
52.1‘‘
1323
52.1‘‘
1323
Height (Closed) -
inches/mm
45.3‘‘
1150
45.3‘‘
1150
45.3‘‘
1150
45.3‘‘
1150
Width ‘’A’’ -
inches/mm
30.0‘‘
764
40.6‘‘
1032
40.6‘‘
1032
51.2‘‘
1300
Width ‘’B’’ -
inches/mm
27.8‘‘
707
38.4‘‘
975
38.4‘‘
975
48.9‘‘
1243
Depth ‘’D’’ -
inches/mm
30.3‘‘
770
30.3‘‘
770
30.3‘‘
770
30.3‘‘
770
Depth ‘’E’’ - inches/mm
27.7‘‘
704
27.7‘‘
704
27.7‘‘
704
27.7‘‘
704
Connections
Gas - inches/mm
2‘‘
60.3
2‘‘
60.3
2‘‘
60.3
2‘‘
60.3
M C/H System Flow
-inches/mm
2½‘‘
76.1
2½‘‘
76.1
2½‘‘
76.1
2½‘‘
76.1
R C/H System Return
-inches/mm
2½‘‘
76.1
2½‘‘
76.1
2½‘‘
76.1
2½‘‘
76.1
Vent Connection ‘’C’’
-inches/mm
5.9‘‘
150
5.9‘‘
150
5.9‘‘
150
7.8‘‘
200
Condensate drain
diameter -inches/mm
1.57‘‘
40
1.57‘‘
40
1.57‘‘
40
1.57‘‘
40
C

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Figure 3-3: MODULEX EXT Main Components (Left Side View)
CONTROL
PANEL

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Figure 3-4: MODULEX EXT Main Components (Right Side View)
•Exhaust and condensate evacuation connections are on the RIGHT-HAND
side (supply condition), but may be moved to the REAR position.
•Air intake connection: located on the LEFT HAND side.
•Cold/Hot flow connection: on the RIGHT HAND side (supply condition) but
may be moved to the LEFT HAND position.
•Cold/Hot return connection: on the RIGHT HAND side (supply condition) but
may be moved to the LEFT HAND position.
•Gas connection: on the RIGHT HAND side (supply condition) but may be
moved to the LEFT HAND position.

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3.5 Performance Data
TABLE 3-2: MODULEX EXT Performance Data
EXT 450 2S
EXT 600 2S
EXT 800 2S
EXT 1100 2S
Min Input
46,000
46,000
46,000
46,000
Max Input
481,500
642,000
802,500
1,123,500
Max Output*
422,000-
457,000
564,000-
609,000
707,000-
762,000
993,000-
1,067,000
Efficiency Range
87%-99%
87%-99%
87%-99%
87%-99%
Boiler Category
IV
IV
IV
IV
Gas Connections (NPT)
2”
2”
2”
2”
Max. Gas Pressure
10.5”
10.5”
10.5”
10.5”
Min. Gas Pressure
3.5”
3.5”
3.5”
3.5”
Max. Allowed Working Pressure
92 psi
92 psi
92 psi
92 psi
Electrical Req: 120V
2.7 FLA
3.6 FLA
4.5 FLA
6.3 FLA
Water Connections (NPT)
2 1/2”
2 1/2”
2 1/2”
2 1/2”
Min. Water Flow @ Min. Fire
(GPM)
7
9
11
16
Min. Water Flow @ Full Fire (GPM)
18
24
30
42
Max. Water Flow (GPM)
42
56
71
99
Water Pressure Drop @ Max. Flow
(Ft. of Hd)
9.5
4.9
5.9
8.0
Water Volume: Gallons
3.8
4.9
5.9
8.0
Thermal Modules
3
4
5
7
Turndown or Operating Range
10.5:1
14:1
17.5:1
24.5:1
Vent & Air Inlet Size
4”
4” air intake
6” exhaust
6”
6”
Vent Materials (as per local code)
Can support PVC, cPVC , Polypropylene or AL29-4C venting
materials
Type of Gas
Natural Gas or Propane
Temperature Control Range
Units deliver 68°-180°F supply; Min. 35°F inlet water required
Maximum Noise Level
<50 dBa when operating at or below full fire
Standard Listings and Approvals
UL, ASME, CSD-1, Mass. Approval, SCAQMD
Water Quality
PH operating range 6.5 to 8.0 and Glycol (if used) MUST be
compatible Cast Aluminum heat exchangers.
NOTE: The Technical data plate is placed under the casing.

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