When installing models manufactured after July 7, 2008, you will notice additional selections on the
control installer menu that will not apply to this unit. DO NOT CHANGE THESE FACTORY SETTINGS.
Refer to the Control Program Reference Chart within this manual for selections that apply to this model.
This manual must be used by a qualified installer/service technician. Read all instructions in this manual
before installing. Perform steps in the given order. Failure to comply could result in substantial property
damage, severe personal injury, or death.
NOTE TO CONSUMER: PLEASE KEEP ALL INSTRUCTIONS FOR FUTURE REFERENCE.
Circulating Heater
INSTALLATION
START-UP
MAINTENANCE
PARTS
Models
MC50 / MC80
MC99 / MC120
NOTICE: HTP reserves the right to make product changes or updates without notice and will not be held
liable for typographical errors in literature.
120 Braley Rd. P.O. Box 429 East Freetown, MA 02717-0429 www.htproducts.com
LP-171 Rev. 6.2.11
2
IF THE INFORMATION IN THIS MANUAL IS NOT FOLLOWED EXACTLY, A FIRE OR EXPLOSION
MAY RESULT, CAUSING PROPERTY DAMAGE, PERSONAL INJURY, OR LOSS OF LIFE. DO NOT
STORE GASOLINE OR OTHER FLAMMABLE VAPORS AND LIQUIDS IN THE VICINITY OF THIS OR
ANY OTHER APPLIANCE.
WHAT TO DO IF YOU SMELL GAS
Do not try to light any appliance.
Do not touch any electrical switch.
Do not use any phone in your building.
Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s
instructions.
If you cannot reach your gas supplier, call the fire department. Installation and service must be
provided by a qualified installer, service agency, or the gas supplier.
3
The following defined terms are used throughout this manual to bring attention to the presence of
hazards of various risk levels, or to important product information.
DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or serious
injury.
WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or
serious injury.
CAUTION indicates a potentially hazardous situation which, if not avoided, may result in minor or
moderate injury.
CAUTION used without the safety alert symbol indicates a potentially hazardous situation which, if not
avoided, may result in property damage.
This manual must only be used by a qualified heating installer/service technician. Read all instructions in
this manual before installing. Perform steps in the order given. Failure to comply could result in severe
personal injury, death or substantial property damage.
FOREWORD
This manual is intended to be used in conjunction with other literature provided with the MC Series GasFired Heater. This includes all related control information. It is important that this manual, all other
documents included with this system, and additional publications including the National Fuel Gas Code,
ANSI Z223.1-2002, be reviewed in their entirety before beginning any work.
Installation should be made in accordance with the regulations of the local code authorities and utility
companies which pertain to this type of water heating equipment.
FOR THE INSTALLER
This appliance must be installed by qualified and licensed personnel. The installer should be guided by
the instructions furnished with the heater, and with local codes and utility company requirements. In the
absence of local codes, preference should be given to the National Fuel Gas Code, ANSI Z223.1-2002.
INSTALLATIONS MUST COMPLY WITH:
Local, state, provincial, and national codes, laws, regulations and ordinances.
The latest version of the National Fuel Gas Code, ANSI Z223.1, from American Gas Association
Laboratories, 8501 East Pleasant Valley Road, Cleveland, OH 44131.
In Canada – CGA No. B149 (latest version), from Canadian Gas Association Laboratories, 55 Scarsdale
Road, Don Mills, Ontario, Canada M3B 2R3. Also, Canadian Electrical Code C 22.1, from Canadian
Standards Association, 5060 Spectrum Way, Suite 100, Mississauga, Ontario, Canada L4W 5N6.
Code for the installation of Heat Producing Appliances (latest version), from American Insurance
Association, 85 John Street, New York, NY 11038.
The latest version of the National Electrical Code, NFPA No. 70.
NOTE: The gas manifold and controls met safe lighting and other performance criteria when undergoing
tests specified in ANSI Z21.10.3 – latest edition.
TABLE OF CONTENTS
PART 1: GENERAL SAFETY INFORMATION ............................................................................................ 7
A. PRECAUTIONS .................................................................................................................................... 7
B. IMPROPER COMBUSTION.................................................................................................................. 7
C. GAS ....................................................................................................................................................... 7
D. WHEN SERVICING THE HEATER ...................................................................................................... 8
4
E. HEATER WATER .................................................................................................................................. 8
F. WINTERIZING ....................................................................................................................................... 8
PART 2: BEFORE YOU START .................................................................................................................. 8
A. WHAT’S IN THE BOX ........................................................................................................................... 8
B. HOW THE HEATER OPERATES ......................................................................................................... 9
C. OPTIONAL EQUIPMENT ................................................................................................................... 10
PART 3: PREPARE LOCATION ................................................................................................................ 11
A. BEFORE LOCATING THE HEATER .................................................................................................. 11
B. CLEARANCES FOR SERVICE ACCESS .......................................................................................... 12
C. RESIDENTIAL GARAGE INSTALLATION ......................................................................................... 12
D. EXHAUST AND INTAKE AIR VENTS ................................................................................................ 13
E. PREVENT COMBUSTION AIR CONTAMINATION ........................................................................... 13
F. REMOVING AN EXISTING HEATER FROM AN EXISTING COMMON VENT SYSTEM ................. 14
PART 4: PREPARE HEATER .................................................................................................................... 15
A. REMOVE HEATER FROM BOX ......................................................................................................... 15
B. WALL MOUNTING CONSIDERATIONS ............................................................................................ 15
C. WALL MOUNTING INSTRUCTIONS ................................................................................................. 15
D. INSTALLATION STEPS...................................................................................................................... 16
PART 5: HEATER PIPING ......................................................................................................................... 16
A. GENERAL PIPING INFORMATION ................................................................................................... 16
B. RELIEF VALVE ................................................................................................................................... 16
C. SEPARATE LOW WATER CUTOFF .................................................................................................. 18
D. BACKFLOW PREVENTER ................................................................................................................. 18
E. SYSTEM WATER PIPING METHODS ............................................................................................... 18
F. CIRCULATORS ................................................................................................................................... 19
G. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE HEATERS ............ 19
H. CIRCULATOR SIZING ........................................................................................................................ 20
I. FILL AND PURGE HEATING SYSTEM ............................................................................................... 21
J. ZONING WITH ZONE VALVES .......................................................................................................... 22
K. ZONING WITH CIRCULATORS ......................................................................................................... 22
L. MULTIPLE HEATERS ......................................................................................................................... 22
M. PIPING DETAILS ............................................................................................................................... 23
PART 6: PIPING WITH OPTIONAL VISION 1 SYSTEM ........................................................................... 30
A. VISION 1 SYSTEM PIPING ................................................................................................................ 30
B. ZONING WITH ZONE VALVES USING VISION 1 ............................................................................. 30
5
C. ZONING WITH CIRCULATORS USING VISION 1 ............................................................................ 30
D. PIPING DETAILS WITH THE VISION 1 SYSTEM ............................................................................. 31
PART 7: VENTING, COMBUSTION AIR, AND CONDENSATE REMOVAL ............................................ 41
A. GENERAL ........................................................................................................................................... 41
B. APPROVED MATERIALS FOR EXHAUST AND INTAKE AIR VENTS ............................................. 41
C. EXHAUST AND INTAKE AIR VENT PIPE LOCATION ...................................................................... 42
2. DETERMINE AIR INTAKE VENT LOCATION ................................................................................ 42
D. ROTATING THE FLUE ADAPTER ..................................................................................................... 45
E. EXHAUST AND INTAKE AIR VENT SIZING ...................................................................................... 45
F. EXHAUST VENT AND INTAKE AIR PIPE INSTALLATION ............................................................... 46
G. CONDENSATE REMOVAL SYSTEM ................................................................................................ 47
H. DIAGRAMS FOR SIDEWALL VENTING ............................................................................................ 48
PART 8: GAS PIPING ................................................................................................................................ 49
A. GAS TABLE ........................................................................................................................................ 50
B. GAS VALVE ........................................................................................................................................ 51
PART 9: FIELD WIRING ............................................................................................................................ 52
A. INSTALLATION MUST COMPLY WITH: ............................................................................................ 52
B. FIELD WIRING .................................................................................................................................... 52
C. LINE VOLTAGE WIRING.................................................................................................................... 52
D. THERMOSTAT ................................................................................................................................... 52
PART 10: FIELD WIRING – VISION 1 OPTION ........................................................................................ 54
PART 11: START-UP PREPARATION ...................................................................................................... 56
A. CHECK/CONTROL WATER CHEMISTRY......................................................................................... 56
B. FREEZE PROTECTION (WHEN USED) ............................................................................................ 56
C. FILL AND TEST WATER SYSTEM .................................................................................................... 57
D. AIR PURGING PROCEDURE FOR HEAT EXCHANGER ................................................................. 57
E. PURGE AIR FROM WATER SYSTEM ............................................................................................... 59
F. CHECK FOR GAS LEAKS .................................................................................................................. 59
G. CHECK THERMOSTAT CIRCUIT(S) ................................................................................................. 59
H. CONDENSATE REMOVAL ................................................................................................................ 60
I. FINAL CHECKS BEFORE STARTING HEATER................................................................................. 60
PART 12: START-UP PROCEDURE ......................................................................................................... 60
A. OPERATING INSTRUCTIONS ........................................................................................................... 61
B. ADJUSTING THE SET POINT ........................................................................................................... 61
6
C. STATUS MENU .................................................................................................................................. 62
D. TEST MODE ....................................................................................................................................... 62
PART 13: START-UP PROCEDURES WITH VISION 1 OPTION ............................................................. 63
A. PROGRAMMING THE VISION I OPTION .......................................................................................... 63
B. VISION 1 PROGRAM ACCESS ......................................................................................................... 63
C. VISION 1 PROGRAM NAVIGATION .................................................................................................. 63
PART 14: TROUBLESHOOTING .............................................................................................................. 66
A. ERROR CODE .................................................................................................................................... 66
B. HEATER ERROR ................................................................................................................................ 66
C. HEATER FAULT ................................................................................................................................. 66
PART 15: MAINTENANCE ......................................................................................................................... 69
A. MAINTENANCE PROCEDURES ....................................................................................................... 69
B. MAINTENANCE SCHEDULE FOR THE SERVICE TECHNICIAN .................................................... 70
C. COMBUSTION CHAMBER COIL CLEANING INSTRUCTIONS ....................................................... 70
D. MAINTENANCE SCHEDULE FOR THE OWNER ............................................................................. 71
HTP CUSTOMER INSTALLATION RECORD FORM ........................................................................ 82
INSTALLER – Read all instructions in this manual before installing. Perform steps in the order given.
USER – This manual is for use only by a qualified heating installer/service technician. Refer to user’s
information manual for your reference. Have this heater serviced/inspected by a qualified service
technician annually.
FAILURE TO ADHERE TO THE GUIDELINES ON THIS PAGE CAN RESULT IN SUBSTANTIAL
PROPERTY DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
NOTE: If the heater is exposed to the following, do not operate until all corrective steps have been made
by a qualified serviceman:
1. FIRE
2. DAMAGE
3. WATER
Any claims for damage or shortage in shipment must be filed immediately against the transportation
company by the consignee.
Do not obstruct combustion and ventilating air flow. Adequate air must be provided for safe operation.
WHAT TO DO IF YOU SMELL GAS
Do not try to light any appliance.
Do not touch any electrical switch.
Do not use any phone in your building.
Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s
instructions.
If you cannot reach your gas supplier, call the fire department. Installation and service must be
provided by a qualified installer, service agency, or the gas supplier.
PART 1: GENERAL SAFETY INFORMATION
A. PRECAUTIONS
This appliance is for indoor installations only. Clearance to combustible materials: 0‖ top, bottom, sides
and back. Front must have room for service, 24‖ recommended. (A combustible door or removable panel
is acceptable front clearance.) This appliance has been approved for closet installation. Do not install this
appliance directly on carpeting. For installation on combustible flooring. Category IV vent systems only.
7
DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN UNDERWATER. Immediately call a qualified
service technician. Replace any part of the control unit that has been under water.
B. IMPROPER COMBUSTION
C. GAS
Should overheating or gas supply fail to shut off, do not turn off or disconnect electrical supply to
circulator. Instead, shut off the gas supply at a location external to the appliance.
NEVER use any toxic chemical, including automotive, standard glycol antifreeze, or ethylene glycol made
for hydronic (non-potable) systems. These chemicals can attack gaskets and seals in heaters, are
poisonous if consumed, and can cause injury or death.
D. WHEN SERVICING THE HEATER
To avoid electric shock, disconnect electrical supply before performing maintenance.
To avoid severe burns, allow heater to cool.
E. HEATER WATER
Do not use petroleum-based cleaning or sealing compounds in a heater system. Gaskets and
seals in the system may be damaged. This can result in substantial property damage.
Do not use ―homemade cures‖ or ―patent medicines‖. Substantial property damage, damage to
heater, and/or serious personal injury may result.
Continual fresh make-up water will reduce heater life. Mineral buildup reduces heat transfer,
overheats the stainless steel heat exchanger, and causes failure. Addition of oxygen by make-up
water can cause internal corrosion in system components. Leaks in the heater or piping must be
repaired at once.
If you have an old system with cast iron radiators, thoroughly flush the system (without heater
connected) to remove sediment. The high-efficiency heat exchanger can be damaged by build-up
or corrosion due to sediment.
When the heater is used to supply potable water, do not connect it to any heating system or
component(s) previously used with a non-potable water-heating appliance.
8
F. WINTERIZING
NOTE: Consider piping and installation when determining heater location.
To winterize the heater, drain the entire system. Then apply air pressure to the drain valve and allow air
and water to escape from the purge valve (see piping instructions).
Once you have evacuated as much water as possible, pump non-toxic, NSF food grade propylene glycol,
FDA rated as GRAS (Generally Recognized As Safe), into the system. Consult the glycol manufacturer
for specific instructions on concentration percentage as well as freeze and burst protection methods.
Check the volume and concentration of antifreeze to assure protection is adequate to protect the entire
system from freezing. When pumping, allow air and remaining water to escape from purge valve. When
the stream coming out of the purge valve matches the color of the non-toxic glycol, the system is
adequately filled.
Finally, it is recommended to start the circulation pump and allow the system to circulate for at 30 minutes
to completely blend any trapped water that might be in the system with the glycol.
PART 2: BEFORE YOU START
A. WHAT’S IN THE BOX
Also included with the heater:
Temperature and Pressure Relief Valve
Pressure and Temperature Gauge
Intake PVC Tee with Screens
Exhaust PVC Coupling with Screens
Plastic hose and Instructions for Purging Heat Exchanger
Installation Manual
Warranty
B. HOW THE HEATER OPERATES
Modulation Condensing Technology is an intelligent system that delivers highly efficient water heating,
while maximizing efficiency by measuring the data parameters of your system.
Stainless Steel Heat Exchanger
The highly efficient and durable stainless steel heat exchanger is designed to extract the last bit of energy
from flue gas before it is exhausted.
Modulating Combustion System
Modulation during operation is based on supply temperature and desired temperature set point. The set
point used for the control depends upon the programmed central heating curve. The heating curve slope
can be changed by the installer to better fit system needs. The control monitors the system to regulate
burner output during operation to match system demand. This increase in efficiency allows for substantial
fuel savings.
Gas Valve
The gas valve senses suction from the blower, allowing gas to flow only if the gas valve is energized and
combustion air is flowing.
Swirl Plate System
The gas valve swirl plate controls air and gas flow into the burner, assuring better mixing for improved
combustion.
Supply Water Temperature Sensor
This sensor monitors heater output water temperature (system outlet/supply). The control module adjusts
the heater firing rate so the outlet/supply temperature is correct.
Return Water Temperature Sensor
This sensor monitors the return water temperature (system inlet/return). The control module reduces or
increases heater input, depending on how close the inlet/return water temperature is to the outlet water
temperature.
Temperature and Pressure Gauge
Allows the user to monitor system temperature and pressure.
Control
The integrated control system monitors inlet/return and outlet/supply water temperature and regulates fan
speed to regulate the unit’s BTU output. This allows the unit to deliver the required amount of heated
energy and nothing more.
Flue Pipe Adapter
The flue pipe adapter may be positioned so that the installer is able to find a position that will best
facilitate the exhaust and combustion air pipe connections with the least number of elbows in even the
most challenging of situations.
Burner
Constructed of metal fiber and high grade stainless steel, the burner uses pre-mixed air and gas and
provides a wide range of firing rates.
Electrical Field Connections with Terminal Strips
The electrical cover plate allows access to the line voltage and low voltage terminal strips. Attach line
voltage conduits to the three holes at the right of the line voltage terminal strip for power, CH pump and
9
10
DHW pump. Route low voltage wires through the opening to the left of the low voltage terminal strip (see
Field Wiring Instructions, Part 9).
Condensate Drain Connection
As this is a condensing high efficiency appliance, the unit has a condensate removal system. Condensate
is nothing more than water vapor, derived from combustion products and similar to an automobile when it
is initially started. It is very important that the condensate line slopes away from the heater and down to a
suitable inside drain.
If the condensate outlet on the heater is lower than the drain, you must use a condensate removal pump
(kit p/n 554200 available from HTP.) In addition, local authorities may require a condensate neutralizer to
neutralize the condensate. Condensate neutralizers are made up of lime crystals, marble or phosphate
chips. Neutralizers can be installed in the field by the installer and purchased from HTP (p/n N1100).
It is also very important not to expose the condensate line to freezing temperatures or any type of
blockage. Plastic tubing must be the only material used for the condensate line. Steel, brass, copper or
other materials will be subject to corrosion or deterioration. A second vent may be necessary to prevent
condensate line vacuum lock on a long horizontal run. Also, an increase in pipe size may be necessary to
allow condensate to drain properly. Support of the condensation line may be necessary to avoid blockage
of the condensate flow.
Spark Ignition
The burner flame is ignited by applying a high voltage to the system spark electrode. This causes a spark
from electrode to ground.
The Vision 1 Optional System
By controlling the temperature delivered to the central heating circuits based on outside temperature, the
Vision 1 System allows the installer to take this highly efficient heater and make it even more efficient.
The Vision 1 System is also a two temperature system, using one temperature for central heating and the
other for use with an indirect water heater. This allows the user to increase the temperature supplied to
the indirect water heater to get a faster recovery by prioritizing the flow at a higher temperature than may
be needed for the central heating circuits (this requires two separate circulators). You must follow the
piping, wiring, and programming instructions located in the Vision One section of this manual.
C. OPTIONAL EQUIPMENT
Below is a list of optional equipment available from HTP:
These additional options may be purchased through your HTP distributor.
Failure to keep heater area clear and free of combustible materials, liquids, and vapors can result in
substantial property damage, severe personal injury, or death.
PART 3: PREPARE LOCATION
11
Figure 1 –Specifications – LP-171-B
Before considering location, many factors need to be addressed. Piping, Venting, and Condensation
Removal are just a few of the issues that need attention prior to the installation of the heater. Please read
the entire manual, as it could save time and money.
A. BEFORE LOCATING THE HEATER
Check for nearby connections to:
System water piping
Venting connections
Gas supply piping
Electrical power
Condensate drain
Check area around heater. Remove any combustible materials, gasoline, and other flammable liquids.
12
The space must be provided with combustion/ventilation air openings correctly sized for all other
appliances located in the same space as the heater. The heater cover must be securely fastened to
prevent the heater from drawing air form the heater room. This is particularly important if the heater is in a
room with other appliances. Failure to comply with the above warnings could result in substantial property
damage, severe personal injury, or death.
The heater gas control system components must be protected from dripping water during operation and
service.
If replacing an existing heater, check for and correct any existing system problems, such as:
System leaks
Heater is located in a condition that could cause the system to freeze and leak.
Incorrectly-sized expansion tank
Excessive glycol which will affect the heater system operation
Clean and flush system when reinstalling a heater.
B. CLEARANCES FOR SERVICE ACCESS
See Figure 2 for recommended service clearances. If you do not provide the minimum clearances shown,
it may not be possible to service the heater without removing it from the space.
Figure 2 – Required Clearances
C. RESIDENTIAL GARAGE INSTALLATION
PRECAUTIONS
If the heater is located in a residential garage, per ANSI Z223.1:
Mount the bottom of the heater a minimum of 18‖ above the floor of the garage, to ensure the
burner and ignition devices are well off the floor.
Locate or protect the heater so it cannot be damaged by a moving vehicle.
13
Vents must be properly supported. Heater intake and exhaust connections are not designed to carry
heavy weight. Vent support brackets must be within 1’ of the heater and the balance at 4’ intervals.
Heater must be readily accessible for visual inspection for the first 3’ from the heater.
PRODUCTS TO AVOID
AREAS LIKELY TO HAVE CONTAMINANTS
Spray cans containing fluorocarbons
Dry cleaning/laundry areas and establishments
Permanent wave solutions
Swimming pools
Chlorinated waxes/cleaners
Metal fabrication plants
Chlorine-based swimming pool chemicals
Beauty shops
Calcium chloride used for thawing
Refrigeration repair shops
Sodium chloride used for water softening
Photo processing plants
Refrigerant leaks
Auto body shops
Paint or varnish removers
Plastic manufacturing plants
Hydrochloric or Muriatic acid
Furniture refinishing areas and establishments
Cements and glues
New building construction
Antistatic fabric softeners used in clothes dryers
Remodeling areas
Chlorine-type bleaches, laundry detergents, and
cleaning solvents
Garages and workshops
Adhesives used to fasten building products
You must pipe outside air to the heater air intake. Ensure that the intake air will not contain any of the
contaminants above. For example, do not pipe intake air vent near a swimming pool. Also, avoid areas
subject to exhaust fumes from laundry facilities. These areas always contain contaminants. Contaminated
air will damage the heater, resulting in possible substantial property damage, severe personal injury, or
death.
NOTE: DAMAGE TO THE HEATER CAUSED BY EXPOSURE TO CORROSIVE VAPORS IS NOT
COVERED BY WARRANTY. (Refer to the limited warranty for complete terms and conditions).
D. EXHAUST AND INTAKE AIR VENTS
The heater is rated Category IV (pressurized vent, likely to form condensate in the vent) and requires a
special vent system designed for pressurized venting.
You must also install air intake piping from outdoors to the heater flue adaptor. The resultant installation is
categorized as direct vent (sealed combustion). NOTE: To prevent combustion air contamination, see
Table 1.
Intake and exhaust must terminate near each other and may be vented vertically through the roof or out a
side wall. Intake and exhaust venting methods are detailed in the Venting Section. Do not attempt to
install the heater using any other means. Be sure to locate the heater such that the air intake and exhaust
vent piping can be routed through the building and properly terminated. The air intake and exhaust vent
piping lengths, routing and termination method must all comply with the methods and limits given in the
venting section.
E. PREVENT COMBUSTION AIR CONTAMINATION
Install intake air piping for the heater as described in the Venting section. Do not terminate exhaust in
locations that can allow contamination of intake air.
Table 1 - Contaminant Table
14
Do not install the heater into a common vent with any other appliance. This will cause flue gas spillage or
appliance malfunction, resulting in possible substantial property damage, severe personal injury, or death.
Failure to follow all instructions can result in flue gas spillage and carbon monoxide emissions, causing
severe personal injury or death.
Figure 3
F. REMOVING AN EXISTING HEATER FROM AN EXISTING COMMON VENT SYSTEM
When removing an existing heater, follow the
steps below with each appliance remaining
connected to the common venting system in
operation, while other appliances remaining
connected to common venting system are not
operating.
1. Seal any unused openings in the common
venting system.
2. Visually inspect the venting system for
proper size and horizontal pitch to determine if
there is blockage, leakage, corrosion or other
deficiencies that could cause an unsafe
condition.
3. If practical, close all building doors,
windows and all doors between the space in
which the appliance remains connected to the
common venting system located and other
spaces in the building. Turn on clothes dryers and any appliances not connected to the common venting
system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, at maximum speed. Do
not operate a summer exhaust fan. Close all fireplace dampers.
4. Place in operation the appliance being inspected. Follow the lighting instructions. Adjust the thermostat
so the appliance will operate continuously.
5. Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the
flame of a match or candle or smoke from a cigarette.
6. After it has been determined that each appliance remaining connected to common venting system
properly vents when tested as outlined, return doors, windows, exhaust fans, fireplace dampers and any
other gas burning appliance to their previous condition of use.
7. Any improper operation of the common venting system should be corrected to conform to the National
Fuel Gas Code, ANSI Z223.1. When resizing any portion of the common venting system, the system
should approach the minimum size as determined using the appropriate tables in Appendix G in the
National Fuel Gas Code, ANSI Z 223.1.
UNCRATING HEATER – Any claims for damage or shortage in shipment must be filed immediately
against the transportation company by the consignee.
COLD WEATHER HANDLING – If the heater has been stored in a very cold location (BELOW 0oF)
before installation, handle with care until the plastic components come to room temperature.
The wall must be capable of carrying the weight of the heater and its related components. The weights of
the heaters are approximately:
MC-50 – 71 lbs.
MC-80 – 74 lbs.
MC-99 – 84 lbs.
MC-120 – 84 lbs.
Failure to comply with above could result in substantial property damage, severe personal injury, or
death.
This heater is heavy and awkward to lift. It is recommended and safer to install the heater with two
people. Use caution as to not drop the heater, which could damage the heater and cause property
damage and/or personal injury. Verify that the heater is securely mounted before leaving unsupervised.
If the heater is not vertically plumb, improper and unsatisfactory operation may occur, causing excessive
condensation build-up, nuisance fault codes, and unnecessary maintenance.
PART 4: PREPARE HEATER
A. REMOVE HEATER FROM BOX
The heater is easy to handle. Care must be taken to place it in a safe location prior to installation to
prevent damage to the bottom mechanical connections.
B. WALL MOUNTING CONSIDERATIONS
These heaters are wall mounted. Use only the wall mounting instructions included in installation
envelope.
15
C. WALL MOUNTING INSTRUCTIONS
The wall must be vertically plumb and capable of carrying the weight of the heater and its related
components.
The building frame (studs) must be 16" on center. If not, you must use 1/2" minimum plywood 24" x 48",
fastened with at least (14) #12 x 3" (3/16" x 3") round head tapping screws to the frame of the building to
provide proper support for the heater. Alternate methods of mounting must not be used. (ex. toggle bolts,
hollow wall anchors) or any other fastener other than #12 x 3" (3/16" x 3") round head tapping screws.
16
Use two wrenches when tightening water piping at heater. Use one wrench to prevent the heater return or
supply line from turning. Failure to prevent piping connections from turning could cause damage to heater
components.
The heater control module uses temperature sensors to provide both high limit protection and modulating
temperature control. The control module also provides low water protection by sensing the water
pressure. Some codes/jurisdictions may require additional external controls.
Never use dielectric unions or galvanized steel fittings when connecting to a stainless steel storage tank
or heater. Use only copper or brass fittings. Teflon thread sealant must be used on all connections. All
piping and components connected to the heater must be approved for potable water systems.
D. INSTALLATION STEPS
1. Prior to lifting the heater onto the wall, use the enclosed template to level and locate the 2 primary (#12
x 3" [3/16" x 3"]) round head tapping screws, leaving about 1/4" between the screw head and the wall
surface to allow for access to the keyway slot located in the back of the heater panel. It is extremely
important that the line on the template is level when locating the first 2 screws. Failure to do so will result
in an uneven or out of level installation.
2. Remove the heater cover. Locate the 2 keyway slots over the screws. Then lower the heater onto the
smallest part of the keyway slot.
3. Once the heater is mounted on the first 2 screws, finish tightening the screws to the back panel. Then
install the 6 additional screws of the same size to the back panel holes. This will provide additional
strength and support to the heater.
PART 5: HEATER PIPING
A. GENERAL PIPING INFORMATION
1. The water supply should be shut off while connecting the heater. A manual control valve must be
placed on the inlet connection to the heater. Unions can be used on both the hot and cold water lines for
future servicing and disconnection of the unit.
2. Purge the water line to remove all debris and air. Debris will damage the water heater.
3. If the heater is to be used as a potable water source, it must not be connected to a system that was
previously used for non-potable purposes.
4. Ensure that the water filter on the heater is clean and installed.
5. New plumbing typically has contamination in the lines. Please flush the system before connection.
B. RELIEF VALVE
The relief valve must comply with the standard for Relief Valves and Automatic Gas Shutoff Devices for
Hot Water Supply Systems (ANSI Z21.22) and/or the standard Temperature, Pressure, Temperature and
To avoid water damage or scalding due to relief valve operation:
Discharge line must be connected to relief valve outlet and run to a safe place of disposal.
Terminate the discharge line in a manner that will prevent possibility of severe burns or property
damage should the relief valve discharge.
Discharge line must be as short as possible and the same size as the valve discharge connection
throughout its entire length.
Discharge line must pitch downward from the valve and terminate at least 6‖ above the floor
drain, making discharge clearly visible.
The discharge line shall terminate plain, not threaded, with a material serviceable for
temperatures of 375oF or greater.
Do not pipe discharge to any location where freezing could occur.
No shutoff valve may be installed between the relief valve and heater or in the discharge line. Do
not plug or place any obstruction in the discharge line.
Test the operation of the relief valve after filling and pressurizing the system by lifting the lever.
Make sure the valve discharges freely. If the valve fails to operate correctly, immediately replace
with a new properly rated relief valve.
Test relief valve at least once annually to ensure the waterway is clear. If valve does not operate,
turn the heater ―off‖ and call a plumber immediately.
Take care whenever operating relief valve to avoid scalding injury or property damage.
For heaters installed with only a pressure relief valve, the separate storage vessel must have a
temperature and pressure relief valve installed. This relief valve shall comply with Relief Valves
for Hot Water Supply Systems, ANSI Z21.22 / CSA4.4.
FAILURE TO COMPLY WITH THE ABOVE GUIDELINES COULD RESULT IN FAILURE OF RELIEF
VALVE OPERATION, RESULTING IN POSSIBILITY OF SUBSTANTIAL PROPERTY DAMAGE,
SEVERE PERSONAL INJURY, OR DEATH.
Hot water outlet pipes can be hot to touch. Insulation must be used for hot water pipes below 36‖ to
protect children against injuries due to scalds.
APPROXIMATE TIME / TEMPERATURE
RELATIONSHIPS IN SCALDS
120oF
More than 5 minutes
125oF
1 ½ to 2 minutes
130oF
About 30 seconds
135oF
About 10 seconds
140oF
Less than 5 seconds
145oF
Less than 3 seconds
150oF
About 1 ½ seconds
155oF
About 1 second
Table 2
Pressure Relief Valves and Vacuum Relief Valves, CAN1-4.4, as well as all local codes. In addition, the
relief valve must be rated to the maximum BTU/hr rating of the heater.
The American National Standard (ANSI Z21.10.3) / Canadian Standard (CSA 4.3) do not require a
combination temperature and pressure relief valve for this heater. However, a combination temperature
and pressure relief valve may be required by local codes.
Connect discharge piping to safe disposal location following guidelines in the WARNING below.
17
NOTE: If a relief valve discharges periodically,
this may be due to thermal expansion in a closed
water supply system. DO NOT PLUG THE RELIEF VALVE. An expansion tank may be
required.
All piping methods shown in this manual use primary/secondary connection to the heater loop. This is to
avoid the possibility of noise or actuator problems in zone valves because of the high-head heater
circulator. For other piping methods, consult your local HTP representative or refer to separate piping
details in this manual.
Undersized expansion tanks cause system water to be lost from relief valve and make-up water to be
added through fill valve. Eventual failure can result due to excessive make-up water addition. SUCH FAILURE IS NOT COVERED BY WARRANTY.
C. SEPARATE LOW WATER CUTOFF
A low water cutoff may be required by state and local codes, or by some insurance companies. A low
water cutoff is also required if the heater is installed above the piping level. Check code requirements
before installing the heater.
If required:
Use an electrode probe type low water cutoff designed for hydronic installations.
Install in a tee on the supply piping above the heater.
Follow low water cutoff manufacturer’s instructions.
D. BACKFLOW PREVENTER
Use a backflow preventer specifically designed for hydronic heater installations. This valve should be
installed on the cold water fill supply line per local codes. (See piping details at the end of this section.)
18
E. SYSTEM WATER PIPING METHODS
EXPANSION TANK AND MAKE-UP WATER
1. Ensure expansion tank size will handle heater and system water volume and temperature. Allow 3
gallons for the heater and its piping.
2. Expansion tank must be located as shown in Piping diagrams, or following recognized design methods.
See tank manufacturer’s instructions for details.
3. Connect the expansion tank to the air separator only if the separator is on the suction side of the
circulator. Always install the system fill connection at the same point as the expansion tank connection to
the system.
4. Most chilled water systems are piped using a closed type expansion tank.
DIAPHRAGM (OR BLADDER) EXPANSION TANK
Always install an automatic air vent on top of the air separator to remove residual air from the system.
19
DO NOT install automatic air vents on closed-type expansion tank systems. Air must remain in the
system and return to the tank to provide its air cushion. An automatic air vent would cause air to leave the
system, resulting in water-logging the expansion tank.
DO NOT use the heater circulator in any location other than the ones shown in this manual. The heater
circulator is selected to ensure adequate flow through the heater. Failure to comply could result in
unreliable performance and nuisance shut downs from insufficient flow.
The heater should not be operated as a potable hot water heater. Operating this heater as a potable
water heater will VOID warranty.
F. CIRCULATORS
SIZING SPACE HEAT SYSTEM PIPING
1. See Piping Details in this section. In all diagrams, the space heating system is isolated from the
heating loop by the primary/secondary connection.
2. Size the piping and components in the space heating system using recognized design methods.
G. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE HEATERS
This heater may function in a closed loop 15 psi system. An optional water pressure switch ensures
adequate pressure in the system. The heater will not operate without a minimum of 10 psi water pressure.
This assures you that if the system does have a leak, the heater will lock out (PRO on the display) before
it damages the heat exchanger.
The included temperature and pressure gauge allows the user to monitor the system pressure and outlet
temperature from the heater. It is important to note that the heater has a minimal amount of pressure drop
that must be calculated when sizing the circulators. Each installation must also have an air elimination
device that will remove air from the system.
Observe minimum 1‖ clearance around all un-insulated hot water pipes when openings around pipes are
not protected by noncombustible materials. On a heater installed above radiation level, some states and
local codes require a low water cut off device (See Part C this section). If the heater supplies hot water to
heating coils in air handler units, flow control valves or other devices must be installed to prevent gravity
circulation of heater water in the coils during the cooling cycle. Chilled water medium must be piped in
parallel with the heater.
1. Connect the system return marked ―Heater In‖.
2. Connect the system supply marked ―Heater Out‖.
3. Install purge and balance valve or shut off valve and drain on system return to purge air out of each
zone.
4. Install a back flow preventer on the cold feed make-up water line.
5. Install a pressure reducing valve on the cold feed make-up water line, (15 psi nominal on the system
return). Check temperature and pressure gauge, which should read minimum pressure of 12 psi.
20
6. Install a circulator as shown in piping details (this section). Make sure the circulator is properly sized for
the system and friction loss.
7. Install an expansion tank on the system supply. Consult the tank manufacturer’s instruction for specific
information relating to expansion tank installation. Size the expansion tank for the required system
volume and capacity.
8. Install an air elimination device on the system supply.
9. Install a drain valve at the lowest point of the system. NOTE: The heater cannot be drained completely
of water without purging the unit with an air pressure 15 psi.
10. The safety relief valve is installed at the factory. Pipe the discharge of the safety relief valve to prevent
injury in the event of pressure relief. Pipe the discharge 6‖ above the drain to a drain. Provide piping that
is the same size as the safety relief valve outlet. Never block the outlet of safety relief valve.
H. CIRCULATOR SIZING
The heat exchanger has pressure drop which must be considered in your system design. Refer to the
graph in Figure 4 for pressure drop through the heat exchanger for recommended pump selection at a
20∆t design.
The chart below represents various system temperatures and their respective flows and friction loss
through the heater, which will aid circulator selection.
Figure 4 – Pressure Drop Graph and Temperature Rise Chart – LP-171-FNOTE: The recommended
circulators are based on 1 gpm per 10,000 btu/hr with 20∆t.
For installations that incorporate standing iron radiation and systems with manual vents at the
highest points: Follow the above section and, starting with the nearest manual vent, open until water
flows out. Then close vent. Repeat procedure, working your way toward furthest air vent. It may be
necessary to install a basket strainer in an older system where larger amounts of sediment may be
present. Annual cleaning of the strainer may be necessary.
Use only inhibited propylene glycol solutions, specially formulated for hydronic systems. Ethylene glycol is
toxic and can attack gaskets and seals used in hydronic systems. Glycol mixtures should not exceed
50%.
It is highly recommended that you carefully follow the glycol manufacturer’s concentrations, expansion
requirements, and maintenance recommendations (pH additive breakdown, inhibitor reduction, etc.) You
must carefully figure the additional system friction loss, as well as the reduction in heat transfer
coefficients.
I. FILL AND PURGE HEATING SYSTEM
Attach the hose to balance and purge hose connector or drain valve and run hose to nearest
drain.
Close the other side of the balance and purge valve or the shut off valve after the drain.
Open first zone balance and purge or drain valve to let water flow out the hose. If zone valves are
used, open the valves one at a time manually. (NOTE: You should check valve manufacturer’s
instruction prior to opening valves manually, so as not to damage the valve.)
Manually operate fill valve regulator. When water runs out of the hose, while it’s connected to the
balance and purge valve or drain you will see a steady stream of water (without bubbles). Close
balance and purge valve or drain to stop the water from flowing. Disconnect the hose and
connect it to next zone to be purged.
Repeat this procedure for additional zones (one at time).
Upon completion, make sure that the fill valve is in automatic position and each zone balance and purge
or shut off is in an open position and zone valves are positioned for automatic operation.
21
1. Glycol for hydronic applications includes inhibitors that prevent it from attacking metallic system
components. Make certain that the system fluid is checked for the correct glycol concentration and
inhibitor level.
2. The glycol solution should be tested at least once a year and as recommended by the glycol
manufacturer.
3. Anti-freeze solutions expand more than water. For example a 50% by volume solution expands 4.8% in
volume for a temperature increase from 32° F to 180° F, while water expands 3% with the same
temperature rise. Allowances must be made for this expansion in the system design.
4. A 30% mixture of glycol will result in 15% BTU output loss and a 5% increase in head against system
circulator.
5. A 50% mixture of glycol will result in 30% BTU output loss and a 50% increase in head against system
circulator.
22
J. ZONING WITH ZONE VALVES
1. Connect heater to system as shown in 1A and 1B in Piping Details when zoning with zone valves. The
primary/secondary piping shown ensures the heater loop will have sufficient flow. It also avoids applying
the high head of the heater circulator to the zone valves.
2. Connect DHW (domestic hot water) piping to indirect storage water heater as shown.
K. ZONING WITH CIRCULATORS
1. Connect heater to system when circulator zoning as shown in 1C and 1D in Piping Details when zoning
with circulators. The heater circulator cannot be used for a zone. It must supply only the heater loop.
Install a separate circulator for each zone.
2. Connect DHW (domestic hot water) piping to indirect storage water heater as shown.
L. MULTIPLE HEATERS
1. Connect multiple heaters as shown in 1E and 1F in Piping Details.
2. All piping shown is reverse return to assure balanced flow through the connected heaters.
3. Each connected heater must have its own circulator pump to assure adequate flow.
4. Connect DHW (domestic hot water) piping to indirect storage water heater as shown.
M. PIPING DETAILS
23
Figure 5
24
Figure 6
NOTES:
1. This drawing is meant to demonstrate system piping concept only. Installer is responsible for all equipment and detailing required
by local codes.
2. All closely spaced tees shall be within 4 pipe diameters center to center spacing.
3. A minimum of 6 pipe diameters of straight pipe shall be installed upstream and downstream of all closely spaced tees.
4. The minimumpipe size for connecting an indirect water heater is 1‖.
5. The minimumpipe size for connecting the unit is 1.25‖.
6. Circulators are shown with isolation flanges. The alternative is standard flanges with full port ball valves. Purge valves can be
used with the circulator flanges as an alternative.
7. The anti-scald mixing valve is recommended if the DHW temperature is set above the factory setting of 119oF.
8. Install a minimum of 12 diameters of straight pipe upstream of all circulators.
9. Winterization: When winterizing the unit, put a drain valve on both the supply and return between the union and the shut-off
connection.
25
Figure 7
NOTES:
1. This drawing is meant to demonstrate system piping concept only. Installer is responsible for all equipment and detailing required
by local codes.
2. All closely spaced tees shall be within 4 pipe diameters center to center spacing.
3. A minimum of 6 pipe diameters of straight pipe shall be installed upstream and downstream of all closely spaced tees.
4. The minimumpipe size for connecting an indirect water heater is 1‖.
5. The minimumpipe size for connecting the unit is 1.25‖.
6. Circulators are shown with isolation flanges. The alternative is standard flanges with full port ball valves. Purge valves can be
used with the circulator flanges as an alternative.
7. The anti-scald mixing valve is recommended if the DHW temperature is set above the factory setting of 119oF.
8. Install a minimum of 12 diameters of straight pipe upstream of all circulators.
9. Winterization: When winterizing the unit, put a drain valve on both the supply and return between the union and the shut-off
connection.
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