Munchkin Gas-Fired Hot Water Circulating Heater User manual

WARNING
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.
• Installation
• Startup
• Maintenance
• Parts
Installation
Manual
MH18082

1
GAS-FIRED HEATER Installation Manual
WARNING
If the information in this manual is not followed exactly, a fire or explo-
sion may result causing property damage, personal injury or loss of life.
Do not store or use 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 performed by a qualified
installer, service agency or the gas supplier.
• Installation and service must performed by a qualified
installer, service agency or the gas supplier.

2
GAS-FIRED HEATER Installation Manual
CONTENTS
Part 1 – Product and Safety Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4,5
Part 2 – How The Heater Operates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
Part 3 – Prepare Heater Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11
A. Installations Must Comply With:
B. Before Locating Heater
C. Clearances for Service Access
D. Residential Garage Installation
E. Air Intake and Exhaust Vent
F. Prevent Combustion Air Contamination
G. When Removing an Appliance from an Existing Common Vent System
Part 4 – Prepare Munchkin Contender Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12
A. Remove Munchkin Contender Heater from Box
B. Placing Wall-Mounted Munchkin Contender
C. Munchkin Contender Wall Mounting Instruction
D. Installation Steps
Part 5 – Munchkin Contender Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-24
– Contender Piping Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-24
A. Relief Valve
B. General Piping Information
C. Separate Low Water Cutoff
D. Backflow Preventer
E. System Water Piping Methods
F. Circulators
G. Hydronic Piping with Circulators, Zone Valves and Multiple Heaters
H. Circulator Sizing
I. Fill and Purge Heating System
J. Zoning with Zone Valves
K. Zoning with Circulators
L. Multiple Heaters
M. Contender Piping Details
Part 6 – Contender Piping with Optional Vision 1 System . . . . . . . . . . . . . . . . . . . . . 25-35
– Contender Piping Details With Vision I System . . . . . . . . . . . . . . . . . . . . . . . . . . 26-35
A. Vision 1 System Piping
B. Zoning with Zone Valves Using Vision I
C. Zoning with Circulators Using Vision I
D. Contender Piping Details with the Vision I System
Part 7 – Venting Combustion Air And Condensate Removal. . . . . . . . . . . . . . . . . . . . 36-44
– Venting Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43,44
A. Installing Exhaust Vent and Intake Air Vent
B. General
C. Approved Materials for Exhaust Vent and Intake Air Vent
D. Exhaust Vent and Intake Air Vent Pipe Location.
E. Exhaust Vent and Intake Air Vent Sizing

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GAS-FIRED HEATER Installation Manual
CONTENTS
(CONT’D)
F. Exhaust Vent and Intake Air Pipe Installation.
G. Heater Removal from a Common Vent System
H. Condensate Removal System
I. Diagrams for Side Wall Venting
Part 8 – Gas Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45,46
A. Gas Connection
B. Gas Piping
C. Gas Table
D. Dungs Gas Valve
Part 9 – Field Wiring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47-49
A. Installation Must Comply With
B. Field Wiring
C. Line Voltage Wiring
D. Thermostat
Part 10 – Field Wiring – Vision 1 Option. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Part 11 – Start Up Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51-53
A. Check/Control Water Chemistry
B. Freeze Protection (when used)
C. Fill and Test Water System
D. Purge Air from Water System
E. Check for Gas Leaks
F. Check Thermostat Circuit(s)
G. Condensate Removal
H. Final Checks Before Starting The Munchkin Contender
Part 12 – Start-Up Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53-55
A. Operating Instructions
B. Adjusting the Set Point
C. Status Menu
D. Test Mode
Part 13 – Start-Up Procedures With The Vision 1 Option . . . . . . . . . . . . . . . . . . . . . . 55-56
A. Programming the Vision I Option
B. Vision I Program Access
C. Vision I Program Navigation
Part 14 – Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59-61
A. Munchkin Error Code
B. Heater Error
C. Heater Fault
Part 15 – Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61-65
A. Maintenance Procedures
B. Combustion Chamber Coil Cleaning Instructions
Part 16 – Heater Inspection and Maintenance Start-Up Charts . . . . . . . . . . . . . . . . . 66-68

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GAS-FIRED HEATER Installation Manual
PART 1: PRODUCT AND SAFETY INFORMATION
SPECIAL ATTENTION BOXES
The following defined terms are used throughout this manual to bring attention to the presence of
hazards of various risk levels or to important information concerning the product.
DANGER
DANGER indicates an imminently hazardous
situation which, if not avoided, will result in
death or serious injury.
WARNING
WARNING indicates a potentially hazardous
situation which, if not avoided, could result in
death or serious injury.
CAUTION
CAUTION Indicates a potentially hazardous
situation which, if not avoided, may result in
minor or moderate injury.
CAUTION
CAUTION used without the safety alert symbol
indicates a potentially hazardous situation which,
if not avoided, may result in property damage.
DEFINITIONS
NOTICE
Heat Transfer Products, Inc., reserves the right to make product changes or updates without notice
and will not be held liable for typographical errors in literature.

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GAS-FIRED HEATER Installation Manual
PART 1: PRODUCT AND SAFETY INFORMATION (CONT’D)
Before Installing
WHEN SERVICING THE MUNCHKIN CONTENDER
• To avoid electric shock, disconnect electrical
supply before performing maintenance.
• To avoid severe burns, allow heater to cool
before performing maintenance.
MUNCHKIN CONTENDER OPERATION
• Do not block flow of combustion or
ventilation air to heater.
• Should overheating occur 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.
• Do not use this heater if any part has been
under water. Immediately call a qualified
service technician to inspect the heater and
to replace any part of the control system and
any gas control that has been under water.
HEATER WATER
The piping and components connected to the
Munchkin Contender for space the heating
application shall be suitable for use with potable
water. Toxic chemicals, such a used for boiler
treatment, shall not be introduced into the
potable water when the Munckin Contender is
used for space heating.
When the Munchkin Contender is used to sup-
ply potable water, it shall not be connected to
any heating system or component(s) previously
used with a non-potable water heating appli-
ance.
• 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.
• Do not use petroleum-based cleaning or sealing
compounds in heater system. Gaskets and seals
in the system may be damaged. This can result
in substantial property damage.
• Do not use “homemade cures” or “boiler patent
medicines.” Substantial property damage,
damage to heater, and/or serious personal injury
may result.
• Continual fresh make-up water will reduce the
heater life. Mineral buildup in heat exchanger
reduces heat transfer, overheats the stainless
steel heat exchanger, and causes failure.
Addition of oxygen carried in by make-up water
WARNING
Installer — Read all instructions in this manual,
and Munchkin Contender Venting section,
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.
User — Have this heater serviced/inspected by
a qualified service technician annually.
Failure to comply with the above could result in
severe personal injury, death or substantial
property damage.
WARNING
Failure to adhere to the guidelines on this page
can result in severe personal injury, death or
substantial property damage.
WARNING
NEVER use any toxic chemical, including
automotive or standard glycol antifreeze or
ethylene glycol made for hydronic (non-potable)
systems. These chemicals are poisonous if
consumed and can cause injury or death. These
chemicals can also attack gaskets and seals in
water heaters.
WARNING
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electric switch; do not use
any phone in your building.
• Immediately call your gas supplier from a
neighbor's phone. Follow the gas suppliers'
instructions.
• If you cannot reach your gas supplier, call the
fire department.

6
GAS-FIRED HEATER Installation Manual
can cause internal corrosion in system
components. Leaks in heater or piping must be
repaired at once to prevent make-up water.
WINTERIZING THE MUNCHKIN CONTENDER
To winterize the Munchkin Contender, 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 all of the water that is
possible, you will then need to pump in the non
toxic propylene glycol food grade NSF® listed
antifreeze (SAFE-T-THERM www.houghton.com
or PARATHERM www.paratherm.com). Try to
calculate the entire volume of the piping system
to insure the entire system will be adequately
protected. Consult the glycol manufacturer for
mixture % recommendations to adequately pro-
tect the system for the local climate of the instal-
lation.
With a pump, fill the system with the non-toxic
propylene glycol food grade NSF® listed
antifreeze, allowing the air and remaining water
to escape from the purge valve. Once the
stream coming out of the purge valve matches
the color of the non toxic propylene glycol food
grade NSF® listed antifreeze, the system should
be adequately filled. It is rcommended at this
point to start any circulation pump and allow the
system to circulate for at least 30 minutes to
completely blend any trapped water that might
be in the system with the NSF® listed solution.
At this point it is suggested that you check the
concentration of NSF® antifreeze to be sure that
protection is adequate. Consult the glycol man-
ufacturer for specific instructions on the con-
centration % as well as the freeze and burst pro-
tection methods.
FREEZE PROTECTION FLUIDS
PART 1: PRODUCT AND SAFETY INFORMATION (CONT’D
CAUTION
Consider piping and installation when
determining heater location. Any claims for
damage or shortage in shipment must be filed
immediately against the transportation
company by the consignee.
CAUTION
NEVER use automotive or standard glycol
antifreeze, even ethylene glycol made for
hydronic systems. Use only inhibited propylene
glycol solutions, which are specifically
formulated for hydronic systems. Ethylene
glycol is toxic and can attack gaskets and seals
used in hydronic systems.
PART 2: HOW THE MUNCKIN CONTENDER OPERATES
Munchkin Contender Condensing Technology is
an intelligent system that delivers highly efficient
hydronic heating, while maximizing efficiency by
measuring the Data Parameters of your heating
system.
1. Stainless Steel Heat Exchanger
The highly efficient durable Munchkin
Contender Stainless Steel Heat Exchanger is
designed to take the colder return water from
the system and extract the last bit of energy
before it is exhausted. The heat exchanger
design is separated by an internal baffle which
diverts the exhaust gas through the primary
heat exchanger into the secondary heat
exchanger where the colder return water
extracts the last residual heat.
2. Modulating Combustion System
Modulation during the central heating
operation is based on the supply temperature.
The set point used for the control depends
upon the programmed central heating curve.
The slope of the heating curve can be changed
by the installer of the Munchkin Contender in
the sense that both turning points of the curve
can be moved. The control monitors the
system to regulate the output of the burner
during operation to match the system
demand. This increase in efficiency allows for
substantial fuel savings.
3. Gas Valve
The gas valve senses suction from the blower,
allowing gas to flow only if the gas valve is

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GAS-FIRED HEATER Installation Manual
PART 2: HOW THE MUNCHKIN CONTENDER OPERATES
(CONT’D)
powered and combustion air is flowing.
4. Swirl Plate System
The Swirl Plate on the gas valve controls the
air and gas flow into the burner, which will
assure better mixing for improved
combustion.
5. Supply water temperature sensor
This sensor monitors heater output water
temperature (system supply). The control
module adjusts the heater firing rate so the
outlet temperature is correct.
6. Return water temperature sensor
This sensor monitors the return water
temperature (system return). The control
module reduces or increases heater input,
depending on how close the return water
temperature is to the outlet water
temperature.
7. Temperature and pressure gauge
Allows the user to monitor the systems
temperature and pressure.
8. Control
The integrated control system monitors the
return and supply water and regulates the fan
speed to regulate the unit’s BTU output. This
allows the unit to only deliver the amount of
heated energy required and nothing more!
9. 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 even in the most challenging
applications.
10. Burner
Made with metal fiber and stainless steel
construction, the burner uses pre-mixed air
and gas and provides a wide range of firing
rates.
11. Electrical field connections with terminal strips
The electrical cover plate allows access the
line voltage terminal strip and the low voltage
terminal strip. Attach line voltage conduits to
the three holes at the right of the line voltage
terminal strip for power, CH pump and DHW
pump. Route low voltage wires through the
opening to the left of the low voltage terminal
strip. (See Field Wiring Instructions Part 9.)
12. Condensate drain connection
This is a condensing high efficiency appliance,
therefore this unit has a condensate removal
system. Condensate is nothing more than
water vapor, derived from the combustion
products, similar to an automobile when it is
initially started. It is very important that the
condensate line is sloped away from the
heater and down to a suitable inside drain, if
the condensate outlet on the Munchkin
Contender is lower than the drain, you must
use a condensate removal pump (kit p/n
554200 available from Heat Transfer Products,
Inc.) A condensate filter, if required by local
authorities can be made up of lime crystals,
marble or phosphate chips and will neutralize
the condensate. This can be done in the field
by the installer or you may purchase one from
Heat Transfer Products, Inc. (P/N N1100). It is
also very important that the condensate line is
not exposed to freezing temperatures or any
other type of blockage. Plastic tubing should
be the only material used for the condensate
line. Steel, brass, copper or others will be
subject to corrosion or deterioration. A second
vent may be necessary to prevent condensate
line vacuum lock if a long horizontal run is
used. Also, an increase in pipe size may be
necessary to drain properly. Support of the
condensation line may be necessary to avoid
blockage of the condensate flow.
13. 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.
14. The Vision 1 Optional System
The Vision I System will allow the installing
contractor to take the highly efficient
modulating Munchkin Contender and make it
even more efficient by controlling the
temperature delivered to the central heating
circuits based on the outside temperature. The
Vision I system is also a two temperature
system, one temperature for central heating
and the other temperature to the Super Stor
Ultra Indirect water heater. This allows the user
to increase the temperature supplied to the

8
GAS-FIRED HEATER Installation Manual
located in the Vision One section of this
manual. Optional kit consists of the following
• Outdoor sensor – 7250P-319
• Indirect tank sensor – 7250P-325
Super Stor Ultra Indirect Water Heater to get a
fast recovery by prioritizing the flow at a higher
temperature than may be needed for the
central heating circuits (this will require two
separate circulators). You must follow the
piping, wiring and programming instructions
PART 2: HOW THE MUNCHKIN CONTENDER OPERATES
(CONT’D)
F
D
E
C
P
M
S
K
H
L
1
2
3
B
A
BACK VIEW
FRONT VIEW RIGHT SIDE
VIEW VIEW
LEFT SIDE
7
Q
N
O
R
8
G
J
EXHAUST VENT CONNECTION
SYSTEM RETURN 4
CONDENSATE CUP/DRAIN ASSEMBLY
5
7
8
SYSTEM RELIEF
GAS LINE CONNECTION
6
COMBUSTION AIR INLET CONNECTION
SYSTEM SUPPLY
1
2
3
ELECTRICAL BOX/CONTROL PANEL
MUNCHKIN CONTENDER HEATER DIMENSIONS AND SPECIFICATIONS
MODEL
NUMBER
BTU/HR
INPUT
LOW
FIRE
BUT/HR
INPUT
HIGH
FIRE
ABCDEFGHJKLMNOPQRS
COMBUSTION AIR
INLET/EXHAUST
VENT
CONNECTION
SIZE
SYSTEM
RELIEF
PIPE SIZE
SYSTEM SUPPLY/
SYSTEM RETURN/
PIPE SIZE
GAS
LINE
CONN.
HEATER
WATER
VOLUME
ENERGY
FACTOR
EF 3
DOE
EFF.
AFUE
1
LOW
WATER
EFF.
LTAAE
2
APPROX.
SHIPPING
WEIGHT
MC50 18,000 50,000 12.50 27.50 7.00 2.75 5.25 9.00 17.25 7.75 5.50 2.75 5.25 5.00 9.00 2.75 4.00 6.50 10.25 4.00 2.00 .75 1.25 .75 .58 .91 92% 98% 71 LBS
MC80 19,000 80,000 12.50 27.50 7.00 2.75 5.25 9.00 17.25 7.75 5.50 2.75 5.25 5.00 9.00 2.75 5.25 6.50 10.25 4.00 2.00 .75 1.25 .75 .67 .93 92% 98% 74 LBS
MC99 44,000 99,000 13.50 27.50 7.00 2.75 6.50 10.25 17.25 7.75 5.50 2.75 5.25 6.00 9.00 2.75 7.75 6.50 11.25 4.00 2.00 .75 1.25 .75 .96 .95 93% 98% 84 LBS
MC120 44,000 120,000 13.50 27.50 7.00 2.75 6.50 10.25 17.25 7.75 5.50 2.75 5.25 6.00 9.00 2.75 7.75 6.50 11.25 4.00 2.00 .75 1.25 .75 .96 .95 92% 98% 84 LBS
1. Tested by Heat Transfer Products to the ANSI/ASHRAE 103
2. Tested by Heat Transfer Products to the ANSI/ASHRAE Standard 103 with 90° return and 110° supply water
3. Tested by Heat Transfer Products to the 10 CFR 430.23 2005
PART 3: PREPARE MUNCHKIN CONTENDER LOCATION
A. INSTALLATIONS MUST COMPLY WITH:
• Local, state, provincial, and national codes,
laws, regulations and ordinances.
• National Fuel Gas Code, ANSI Z223.1 – latest
edition.
• National Electrical Code.
• For Canada only: B149.1 or B149.2
Installation Code, CSA C22.1 Canadian
Electrical Code Part 1 and any local codes.

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GAS-FIRED HEATER Installation Manual
PART 3: PREPARE MUNCHKIN CONTENDER LOCATION (CONTINUED)
BEFORE LOCATING THE MUNCHKIN
CONTENDER
1. Check for nearby connection to:
• System water piping
• Venting connections
• Gas supply piping
• Electrical power
2. Check area around heater. Remove any
combustible materials, gasoline and other
flammable liquids.
3. The Munchkin Contender must be installed
so that gas control system components are
protected from dripping or spraying water or
rain during operation or service.
4. If the new Munchkin Contender is to replace
an existing heater, check for and correct any
existing system problems such as:
• System leaks.
• Incorrectly-sized expansion tank.
• Lack of freeze protection in heating water
causing system and heater to freeze and
leak.
• Excessive glycol which will affect the
heater system operation.
C. CLEARANCES FOR SERVICE ACCESS
1. See Figure 3-1 for recommended service
clearances. If you do not provide minimum
clearances shown, it might not be possible to
service the heater without removing it from
the space.
WARNING
Failure to keep heater area clear and free of
combustible materials, gasoline and other
flammable liquids and vapors can result in
severe personal injury, death or substantial
property damage.
24"
FRONT CLEARANCE
24"
Figure 3-1: Clearances required
6" 6"
SIDE
CLEARANCE SIDE
CLEARANCE
NOTICE
The Munchkin Contender Heater gas manifold
and controls met safe lighting and other
performance criteria when heater underwent
tests specified in ANSI Z21.10.3 — latest edition.

10
GAS-FIRED HEATER Installation Manual
PART 3: PREPARE MUNCHKIN CONTENDER LOCATION (CONTINUED)
D. RESIDENTIAL GARAGE INSTALLATION
Precautions
Take the following special precautions when
installing the Munchkin Contender in a residen-
tial garage. If the heater is located in a residen-
tial garage, per ANSI Z223.1, paragraph 5.1.9:
• Mount the heater with a minimum of 18
inches above the floor of the garage to the
bottom of the heater to ensure the burner
and ignition devices will be no less than 18
inches above the floor.
• Locate or protect the heater so it cannot be
damaged by a moving vehicle.
E. EXHAUST VENT AND INTAKE AIR VENT
The Munchkin Contender requires a special vent
system, designed for pressurized venting.
Munchkin Contenders are rated ANSI Z21.10.3
Category IV (pressurized vent, likely to con-
dense in the vent).
You must also install air intake piping from outside
to the heater flue adaptor. The resultant installa-
tion is categorized as direct vent (sealed combus-
tion). Note: To prevent combustion air con-
tamination see Table 3-2 in this section
when considering exhaust vent and intake
air vent termination.
Intake and exhaust must terminate near each
other and may be vented vertically through the
roof or out a side wall. The intake and exhuast
venting methods are detailed in the Venting
Section. Do not attempt to install the Munchkin
Contender 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.
F. PREVENT COMBUSTION AIR CONTAMINATION
Install intake air piping for the Munchkin
Contender as described in the Venting section.
Do not terminate exhaust in locations that can
allow contamination of intake air.
WARNING
The space must be provided with combus-
tion/ventilation air openings correctly sized for
all other appliances located in the same space as
the Munchkin Contender heater. The heater
cover must be securely fastened to the heater to
prevent heater from drawing air from inside the
heater room. This is particularly important if the
heater is located in the same room as other ap-
pliances. Failure to comply with the above warn-
ings could result in severe personal injury, death
or substantial property damage. WARNING
You must pipe outside air to the heater air
intake. Ensure that the intake air will not
contain any of the contaminants below.
Contaminated air will damage the heater,
resulting in possible severe personal injury,
death or substantial property damage. For
example, do not pipe intake air vent near a
swimming pool. Also avoid areas subject to
exhaust fumes from laundry facilities. These
areas will always contain contaminants.
Products to avoid
Spray cans containing fluorocarbons
Permanent wave solutions
Chlorinated waxes/cleaners
Chlorine-based swimming pool chemicals
Calcium chloride used for thawing
Sodium chloride used for water softening
Refrigerant leaks
Paint or varnish removers
Hydrochloric acid/muriatic acid
Cements and glues
Antistatic fabric softeners used in clothes dryers
Chlorine-type bleaches, detergents, and cleaning
solvents found in household laundry rooms
Adhesives used to fasten building products and
other similar products
Areas likely to have contaminants
Dry cleaning/laundry areas and establishments
Swimming pools
Metal fabrication plants
Beauty shops
Refrigeration repair shops
Photo processing plants
Auto body shops
Plastic manufacturing plants
Furniture refinishing areas and establishments
New building construction
Remodeling areas
Garages and workshops
Table 3-2: Corrosive contaminants and sources

11
GAS-FIRED HEATER Installation Manual
G. WHEN REMOVING AN EXISTING HEATER
FROM AN EXISTING COMMON VENT SYSTEM
At the time of removal of an existing heater, the fol-
lowing steps shall be followed with each appliance
remaining connected to the common venting sys-
tem placed in operation, while the other appli-
ances remaining connected to the common vent-
ing system are not in operation.
a. Seal any unused openings in the common
venting system.
b. Visually inspect the venting system for
proper size and horizontal pitch and
determine there is non blockage or
restriction, leakage, corrosion and other
deficiencies which could cause an unsafe
condition.
c. Insofar as is practical, close all building doors
and windows and all doors between the space
in which the appliances remaining connected
to the common venting system are located
and other spaces of the building. Turn on
clothes dryers and any appliance not
connected to the common venting system.
Turn on any exhaust fans, such as range
hoods and bathroom exhausts, so they will
operate at maximum speed. Do not operate a
summer exhaust fan. Close fireplace dampers.
d. Place in operation the appliance being
inspected. Follow the lighting instructions.
Adjust thermostat so appliance will operate
continuously.
e. Test for spillage at draft hood opening after 5
minutes of main burner operation. Use the
flame of a match or candle, or smoke from a
cigarette, cigar, or pipe.
f. After it has been determined that each
appliance remaining connected to the
common venting system properly vents
when tested as outlined herein, return doors,
windows, exhaust fans, fireplace dampers,
and any other gas-burning appliance to their
previous conditions of use.
g. Any improper operation of the common
venting system should be corrected so the
installation conforms with the National Fuel
Gas Code, ANSI Z223.1 — latest edition.
Correct by resizing to approach the minimum
size as determined using the appropriate
tables in Table 13 of NFPA54 ANSI Z223.1
2006 of that code. Canadian installations
must comply with B149.1 or B149.2
Installation Code.
PART 3: PREPARE MUNCHKIN CONTENDER LOCATION (CONTINUED)
DANGER
Do not install the Munchkin Contender heater
into a common vent with any other appliance.
This will cause flue gas spillage or appliance
malfunction, resulting in possible severe
personal injury, death or substantial property
damage.
WARNING
Failure to follow all instructions can result in flue
gas spillage and carbon monoxide emissions,
causing severe personal injury or death.
PART 4: PREPARE MUNCHKIN CONTENDER HEATER
A. REMOVE MUNCHKIN CONTENDER
HEATER FROM BOX
1. The Munchkin Contender is easy to handle.
Care must be taken to place it in a safe location
prior to installation on the wall to prevent dam-
age to the bottom mechanical connections.
B. PLACING THE WALL-MOUNTED
MUNCHKIN CONTENDER HEATER
Munchkin Contender Heaters are wall mounted.
Use only the Munchkin Contender Heater wall
mounting instructions included in installation
envelope.
CAUTION
Cold weather handling — If heater has been
stored in a very cold location (below 0°F) before
installation, handle with care until the plastic
components come to room temperature.

12
GAS-FIRED HEATER Installation Manual
PART 4: PREPARE MUNCHKIN CONTENDER (CONTINUED)
D. INSTALLATION STEPS
1) Prior to lifting the Munchkin Contender
Heater onto the wall, use the enclosed
template to level and locate the 2 primary
screws (#12 x 3" [3/16" x 3"]) round head
tapping screw leaving about 1/4" under the
screw head to the wall surface to allow for
access to the keyway slot which is 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 Munchkin Contender cover and
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 first two 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 Munchkin Contender Heater.
C. MUNCHKIN CONTENDER
WALL MOUNTING INSTRUCTIONS
The wall must be vertically plumb and capable of
carrying the weight of the Munchkin Contender and
its related components.
The building frame (studs) must be 16" on cen-
ter. 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.
WARNING
The wall must be capable of carrying the weight
of the heater and its related components. The
weights of the heater are approximately:
MC-50- 71 lbs.
MC-80- 74 lbs.
MC-99-
MC-120-
]]
84 lbs.
Failure to comply with above could result in
severe personal injury, death or substantial
property damage.
WARNING
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 cause personal injury. Verify
that the heater is securely mounted before
leaving the heater unsupervised.
CAUTION
If the Munchkin Contender is not vertically
plumb, improper and unsatisfactory operation
may occur. This will cause excessive
condensation build-up causing unnecessary
maintenance and nuisance fault codes.

13
GAS-FIRED HEATER Installation Manual
A. RELIEF VALVE
Connect discharge piping to safe disposal loca-
tion, following guidelines in the WARNING below.
B. GENERAL PIPING INFORMATION
C. SEPARATE LOW WATER CUTOFF
A low water cutoff may be required by state
local code or some insurance companies. Check
code requirements before installation of the
Munchkin Contender Heater. It is also required
that a low water cutoff be used if the heater is
installed above the piping level.
If required:
• Use a low water cutoff designed for
hydronic installations that is an electrode
probe type
• 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.)
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.
CAUTION
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 Heat Transfer Products
representative or refer to separate Munchkin
Contender piping details in this manual (Part 5).
CAUTION
Use two wrenches when tightening water
piping at heater, using one wrench to prevent
the heater return line or supply line from
turning. Failure to support the heater piping
connections to prevent them from turning could
cause damage to heater components.
NOTICE
The Munchkin Contender 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
of the heat exchanger. Some codes/jurisdictions
may require additional external controls for high
limit and/or low water cutoff protection.
PART 5: MUNCHKIN CONTENDER PIPING
WARNING
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 valve discharge.
• Discharge line must be as short as possible and be
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
where any discharge will be clearly visible.
• The discharge line shall terminate plain, not thread-
ed, with a material serviceable for temperatures of
375 °F or greater.
• Do not pipe the discharge to any place where freez-
ing could occur.
• No shutoff valve shall be installed between the re-
lief valve and heater, or in the discharge line. Do not
plug or place any obstruction in the discharge line.
• Test the operation of the valve after filling and pres-
surizing system by lifting the lever. Make sure the
valve discharges freely. If the valve fails to operate
correctly, replace it with a new relief valve.
• For heaters installed with only a pressure relief
valve, the separate storage vessel must have a tem-
perature and pressure relief valve installed. This re-
lief valve shall comply with the standard for Relief
Valves for Hot Water Supply Systems, ANSI
Z21.22 CSA4.4.
• Failure to comply with the above guidelines could
result in failure of the relief valve to operate, re-
sulting in possibility of severe personal injury, death
or substantial property damage.

14
GAS-FIRED HEATER Installation Manual
PART 5: MUNCHKIN CONTENDER PIPING (CONTINUED)
2. Expansion tank must be located as shown in
Piping Part 5, 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
1. Always install an automatic air vent on top of
the air separator to remove residual air from
the system.
F. CIRCULATORS
Sizing space heat system piping
1. See Piping Details in this manual Part 5. 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
The Munchkin Contender is designed to function
in a closed loop 15 PSI System. A factory installed
water pressure switch will ensure that you have
adequate pressure in the system. The Munchkin
Contender will not operate without a minimum of
10 PSI water pressure. This assures you that if the
system does have leak, the Munchkin Contender
will lock out (PRO on the display) before it
damages the Stainless Steel Heat Exchanger. We
have also included a Temperature and Pressure
gauge which allows the user to monitor the
system pressure and outlet temperature from the
Munchkin Contender. It is important to note that
the Munchkin Contender has a minimal amount
of pressure drop and must be calculated when
sizing the circulators. Each Munchkin Contender
installation must have an Air Elimination device
that will remove air from the system. Install the
Munchkin Contender so the gas ignition system
components are protected from water (dripping,
spraying, etc.) allowing clearance for basic
service of circulator replacement, valves and
other. Observe minimum 1” clearance around all
un-insulated hot water pipes when openings
around pipes are not protected by non-
combustible materials. On a Munchkin Contender
installed above radiation level, some states and
local codes require a low water cut off device at
the time of installation (See Part C this section). If
the Munchkin Contender 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.
Freeze Protection for new or existing systems
must use glycol that is specifically formulated for
this purpose. It will include inhibitors that will
prevent the glycol from attacking the metallic
system components. Make certain that the
system fluid is checked for the correct glycol
CAUTION
Undersized expansion tanks cause system
water to be lost from relief valve and makeup
water to be added through fill valve. Eventual
failure can result due to excessive make-up
water addition.
CAUTION
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 system, resulting in water-
logging the expansion tank.
CAUTION
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 Munchkin Contender. Failure
to comply could result in unreliable
performance and nuisance shut downs from
insufficient flow.

15
GAS-FIRED HEATER Installation Manual
PART 5: MUNCHKIN CONTENDER PIPING (CONTINUED)
concentration and inhibitor level. The system
should be tested at least once a year and as
recommend by the producer of the glycol
solution. Allowance should be made for the
expansion of the glycol solution in the system
piping. Example 50% by volume solution
expands 4.8% in volume for the temperature
increase from 32 F to 180 F, while water expands
3% with the same temperature rise.
Basic steps are listed below, with Illustration,
which will guide you through the installation of
the Munchkin.
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 preventor 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.
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 Munchkin Contender can
not 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 Munchkin Contender Heat Exchanger does
have pressure drop which must be considered
in your system design. Refer to the graph in Fig.
5-1 below for pressure drop through the
Munchkin Contender Heat Exchanger for rec-
ommended pump selection at a 20∆t design.
CAUTION
The Munchkin Contender should not be
operated as a potable Hot Water Heater.
Figure 5-1
* NOTE: The recommended circulators are based on 1 gpm per 10,000 btu/hr with 20°∆t.

16
GAS-FIRED HEATER Installation Manual
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 opera-
tion.
1. Glycol in hydronic applications which is
specially formulated for this purpose includes
inhibitors that prevent the glycol 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 a BTU
output loss of 15% with a 5% increase in
head against system circulator.
5. A 50% mixture of glycol will result in a BTU
output loss of 30% with a 50% increase in
head against system circulator.
PART 5: MUNCHKIN CONTENDER PIPING (CONTINUED)
CAUTION
For installation that incorporates standing Iron
Radiation and systems with manual vents at the
high points. Follow above section and starting
with the nearest manual air vent, open vent
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.
WARNING
Use only inhibited propylene glycol solutions
which are 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%.
SYSTEM TEMPERATURE RISE CHART
Model
Friction
Feet
Flow
GPM
Friction
Feet
Flow
GPM
Friction
Feet
Flow
GPM
Friction
Feet
Flow
GPM
Friction
Feet
Flow
GPM
Friction
Feet
Flow
GPM
MC-50 6.5' 5 4.5' 4 3' 3.3 2' 2.5 N/RN/RN/RN/R
MC-80 7.8' 8 4.7' 6.4 2.9' 5.3 2' 4.6 1.5' 4 1' 3.5
MC-99 9' 10 6' 9 5' 7.8 4' 6.3 3.5' 5.6 2' 4.8
MC-120 10' 12 7' 9.6 5' 8 4' 6.8 3.5' 6 2' 5.3
40˚ǻt45˚ǻt20˚ǻt25˚ǻt30˚ǻt35˚ǻt
The chart below represents the various system temperatures and their respective flows and friction loss
through the Munchkin Contender which will aid circulator selection.
N/R = Not recommended

17
GAS-FIRED HEATER Installation Manual
MUNCHKIN CONTENDER PIPING (CONTINUED)
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.
2. Install a separate circulator for each zone.
3. 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.
CAUTION
It is highly recommended that you carefully
follow the glycol manufacturer’s recommended
concentrations, expansion requirements and
maintenance recommendations (pH additive
breakdown, inhibitor reduction, etc.). You must
carefully figure the additional friction loss in the
system as well as the reduction in heat transfer
co-efficients.

18
GAS-FIRED HEATER Installation Manual
circulator
(w/ isolation flanges)
gate valve
globe valve
ball valve
swing-check valve
flow-check valve
spring-loaded check valve
hose bib / heater drain
TRV (straight)
TRV angle
circuit setter
manual 3-way valve
zone valve
air separator
backflow preventer
diaphragm-type
expansion tank
pressure reducing valve
diff. pressure bypass
anti-scald mixing valve
temperature /pressure
gauge
pressure relief valve
float-type
air vent
heat exchanger
union
4-way motorized
mixing valve
3-way motorized
mixing valve
Munchkin Contender Heater
radiant manifold
with valve actuators
Super Stor Ultra
Indirect DHW Tank
Piping symbol legend
radiant manifold
purging valve
circulator
(w/ integral check valve)
aquastat
DHW temperature sensor
Outdoor temperature
sensor
T/P
M. CONTENDER PIPING DETAILS

19
GAS-FIRED HEATER Installation Manual
Standard Munchkin Contender Heater!
(zoning with valves)
Space heating mode
Super Stor Ultra
indirect DHW Tank
Drawing 1A
make-up water
see note 6
OFF
differential
pressure
bypass
valve
anti-scald
mixing valve
purging
valves
closely
spaced
tees
P2
Munchkin
Contender
Heater
T/P
purge
NOTES:
1. This drawing is meant to show system piping concept only.
Installer is responsible for all equipment & 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 & downstream of all closely spaced tees.
4. The minimum pipe size for connecting a Super Stor Ultra Indirect Water Heater is 1-inch.
5. The minimum pipe size for connecting the Munchkin Contender is 1.25-inch
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 119˚F.
8. Install a minimum of 12 diameters of straight pipe upstream of all circulators.
9. Winterization: When winterizing the Munchkin Contender, put a drain valve on both the supply and return between the union and the
shut-off connection.
!
zone valves