Munchkin HeatTransfer 399M Wiring diagram

HEAT TRANSFER PRODUCTS, INC.
120 BRALEY RD., E. FREETOWN, MA 02717
Installing, Operating & Maintaining
MUNCHKIN™ HIGH EFFICIENCY
399M COMMERCIAL BOILER
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.
WARNING
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.
WARNING
This manual must only be used by a qualified heating installer / service
technician. Failure to comply could result in severe personal injury, death or
substantial property damage. It is also important to keep these Instructions
with the appliance.
MH27745
CONTROLS

USING THIS MANUAL
2
SPECIAL ATTENTION BOXES
Throughout this manual you will see these
special attention boxes similar to this one,
which are intended to supplement the
instructions and make special notice of
potential hazards. These categories mean, in
the judgement of Heat Transfer Products, Inc.:
WARNINGS
• THIS UNIT IS FOR CATEGORY IV VENTING - 2 PIPE ONLY. THIS IS A SEALED
COMBUSTION APPLIANCE.
• THIS HEATER INSTALLATION MUST CONFORM TO THE LATEST EDITION OF THE
“NATIONAL FUEL GAS CODE” ANSI Z223.1 NFPA 54 AND OR CAN/CGA B149
INSTALLATION CODES. STATE AND LOCAL CODES MIGHT ALSO APPLY TO
INSTALLATION.
• WHERE REQUIRED BY THE AUTHORITY HAVING JURISDICTION, THE
INSTALLATION MUST CONFORM TO THE STANDARDS FOR CONTROLS AND
SAFETY DEVICES FOR AUTOMATICALLY FIRED HEATERS, ANSI/ASME HEATER
AND PRESSURE VESSEL CODE, Section IV, ALONG WITH CSD1.
• THE HEATER, GAS PIPING, WATER PIPING, VENTING AND ELECTRICAL MUST BE
INSTALLED BY TRAINED & QUALIFIED PERSONNEL FAMILIAR WITH
INSTALLATION PRACTICES, LOCAL CODE, LICENSING REQUIREMENTS.
• IF THE INFORMATION IN THESE INSTRUCTIONS ARE NOT FOLLOWED EXACTLY,
A FIRE OR EXPLOSION MAY RESULT; CAUSING PROPERTY DAMAGE, PERSONAL
INJURY, OR DEATH.
• DO NOT STORE OR USE GASOLINE OR OTHER FLAMMABLE VAPORS AND
LIQUIDS IN THE VICINITY OF THIS OR ANY OTHER APPLIANCE;
• THE USE OF A LOW WATER CUT-OFF DEVICE MAY BE REQUIRED BY STATE OR
LOCAL CODES IF THE MUNCHKIN IS INSTALLED ABOVE RADIATION LEVELS.
USING THIS MANUAL
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
situtation 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.

TABLE OF CONTENTS
3
TABLE OF CONTENTS
PART 1 . . . . . . . . . . . . . . . . . . . . . .4 thru 6
GENERAL INFORMATION
AHow It Operates . . . . . . . . . . . . . . . . . .4
BMunchkin Ratings and Dimensions .4–5
CPre-installation Requirements . . . . . . .5
DPressure Relief Valve . . . . . . . . . . . . . .6
PART 2 . . . . . . . . . . . . . . . . . . . . . .6 thru 8
ELECTRICAL
AElectrical Connection . . . . . . . . . . . . . .6
PART 3 . . . . . . . . . . . . . . . . . . . . .8 thru 10
GAS CONNECTION
AGas Connection . . . . . . . . . . . . . . . . . . .9
BGas Piping . . . . . . . . . . . . . . . . . . . . . . .9
CGas Table . . . . . . . . . . . . . . . . . . . . . . . .9
PART 4 . . . . . . . . . . . . . . . . . . . .11 thru 17
VENTING
AApproved Venting Materials . . . . . . . .11
BVenting the Munchkin in
4” or 6” Plastic Pipe . . . . . . . . . . . . . .11
CLonger Vent Runs Using a
Combination of 4” to 6” Pipe . . . . . . .14
DHeater Removal from a
Common Vent System . . . . . . . . . . . .15
ECondensate Requirements . . . . . . . . .17
PART 5 . . . . . . . . . . . . . . . . . . . .17 thru 28
PIPING
AHydronic piping with
Circulators or Zone Valves . . . . . . . . .17
BCirculator Sizing . . . . . . . . . . . . . . . . .18
CFill and Purge Heating System . . . . . .19
DPiping Illustrations . . . . . . . . . . . . .20–28
PART 6 . . . . . . . . . . . . . . . . . . . .29 thru 32
START UP PROCEDURES
AItems to be checked before
lighting the Munchkin . . . . . . . . . . . . .29
BLighting Instructions . . . . . . . . . . . . . .29
COperating Instructions . . . . . . . . . . . .30
DAdjusting the Temperature
on the Munchkin Display . . . . . . . . . .30
EStatus Menu . . . . . . . . . . . . . . . . . . . .31
FTest Mode . . . . . . . . . . . . . . . . . . . . . .31
GTo Turn Off Gas to Appliance . . . . . . .31
PART 7 . . . . . . . . . . . . . . . . . . . .32 thru 36
SERVICING
ASequence of operation . . . . . . . . . . . .32
BMunchkin Temporary
Fault Condition . . . . . . . . . . . . . . . . . .32
CMunchkin Fault Requiring
Manual Reset . . . . . . . . . . . . . . . . . . .34
PART 8 . . . . . . . . . . . . . . . . . . . .37 thru 41
MAINTENANCE
AMaintenance Procedures . . . . . . . . . .37
BBefore Each Heating Season . . . . . . .37
CCondensate Cleaning Instructions . . .37
DCombustion Chamber
Coil Cleaning Instructions . . . . . . . . . .38
EMunchkin Controller . . . . . . . . . . . . . .39

GENERAL INFORMATION
4
B. MUNCHKIN RATINGS AND DIMENSIONS
PERFORMANCE RATING
CONNECTION SIZES
RECOMMENDED SERVICE CLEARANCES
ledoMnoitaludoMtupnIgnitaeHEODycneiciffEnoitsubmoCycneiciffElamrehT*EUFAthgieWgnippihS
M993000,993ot000,001000,972ot000,39%59%53.39%39.sbl252
PART 1. GENERAL INFORMATION
A. HOW IT OPERATES
When the room thermostat calls for heat, the Munchkin control board will start the circulator and start
to monitor the return temperature of the system before the heater will begin to heat the water. Once
the controller has sensed a drop in the return water temperature below the temperature set point
minus the differential set point, the heater will start to heat the water. This eliminates the Munchkin
starting every time the thermostat calls for heat. This feature keeps the system from short cycling.
Once the system has sensed the temperature difference, the Munchkin will activate the blower motor
for 5 seconds to pre-purge the system before starting the Munchkin. The Munchkin controller will now
start to modulate the pre-mix burner based on analyzing the return temperature, supply water
temperature and the set point temperature. By compiling this information, the controller utilizes an
algorithm to fully adjust the firing rate while maintaining the desired output temperature. The pre-mix
burner fan has a direct drive current low-voltage motor with a pulse relay counting. This system allows
precise control over the fan speed and combustion air volumes. Coupled with the Honeywell gas valve
and the Venturi system which are set to provide a one-to-one ratio of precisely measured volumes of
fuel to air, an accurate and instant burner output is achieved. This keeps the Munchkin running at the
highest efficiency.
When the thermostat is satisfied, the Munchkin will then go through a 4 second post-purge cycle before
shutting off. Every Munchkin heater is equipped with a display which will read the outlet temperature of
the heater and then will illuminate a green light showing flame on. If a problem occurs, the front indicator
light will turn red and the display will read a fault code; see Part 7, Section B/C, pages 33 and 34.
ledoM
nruteR/ylppuS
noitcennoC
noitcennoCsaG
eziS.aiDtneV
M993TPN"2"4/1-1"4
Figure 1-1
(NOTE: The Munchkin
is rated at zero
clearance to
combustibles.)
24"
12"
24"
FRONT
12"
15"

5
GENERAL INFORMATION
DIMENSIONS
C. PRE-INSTALLATION REQUIREMENTS
The Munchkin is designed for installation on non-rated flooring, in alcoves, basements, utility rooms,
and closet but never a bedroom closet. Choose a location for your Munchkin, centralized to the piping
system, along with consideration for Electrical (Part 2, Page 6), Gas Connection (Part 3, Page 8) and
Venting (Part 4, Page 11).
Figure 1-2

6
GENERAL INFORMATION / ELECTRICAL
NOTE: Service clearance of the Munchkin
1. The front of the appliance needs 24" of clearance for service minimum. It may have
a non-rated or combustible door or access panel and must have a minimum of 24"
clearance.
2. The left side of the heater is 12" clearance
3. The right side of the heater is 12" clearance
4. The top of the heater is 15" clearance.
If the Munchkin is set up for liquefied petroleum (LP) gas, some geographic areas follow the Uniform
Mechanical Code, section 304.6, “Liquefied petroleum gas burning appliances shall not be installed in
a pit, basement or similar location where heavier-than-air gas might collect. Appliances so fueled, shall
not be installed in a below grade under-floor space or basement unless such location is provided with
an approved means for removal of unburned gas.”
PART 2. ELECTRICAL
A. ELECTRICAL CONNECTION
The electrical connection for the Munchkin is on the left hand side of the unit. There is a ½” knockout
location for an electrical connection for both the incoming power and the central heating circulator
connection. All electrical wiring must be performed by a qualified licensed electrician in accordance
with National Electrical Code ANSI Z223.1/NFPA 54 to and/or the Canadian Electrical Code, Part 1 CSA
C22.1, or to the applicable codes and standards. For your convenience, we have labeled all the wires
that need to be connected to operate the Munchkin.
CAUTION
Condensation removal: This is a condensing, high efficiency appliance, therefore
condensation removal must be addressed to avoid damage to surrounding area or
appliance. See Part (4) Section E for Condensate Requirements.
WARNING
D. PRESSURE RELIEF VALVE
A pressure relief valve is installed into the front right side manifold. We recommend a WATTS ¾"
M 335 MI valve or equivalent and meets the requirements of ANSI/ASME Heater and Pressure
Vessel Code, Section IV or CSA B51; Heater, Pressure Vessel and Piping Code as applicable for
heating heaters. A ¾" pipe must be directed to a floor drain or suitable location within 6" of a drain
or floor. Protect from freezing, do not plug or cap pressure relief valve. Serious explosion causing
property damage and or loss of life could result. Under no circumstances should the relief valve
be eliminated, capped or plugged.
CAUTION
The Munchkin is certified as an indoor appliance. Do not install the Munchkin
outdoors or locate where it will be exposed to freezing temperature. This includes all
related piping and components. If the Munchkin is subjected to flood water or
submersed in water, the Munchkin must be replaced.

7
ELECTRICAL
The electrical requirements are for standard 120 volts, 60 Hz 15 Amp service. This unit is wired with
#18 awg and fused for no more than 15 Amps.
There are two ground points in the electrical compartment that must be connected to the building
ground system. Connect the building ground to the green ground screw and the green ground wire
inside electrical box provided.
The Incoming Power Supply is connected to the Black (Hot) and the White (Neutral).The Munchkin
Control board is polarity sensitive. If the polarity is reversed, the Munchkin control will not sense a
flame and lock out the system. The Orange and Brown wire are provided to the supply of 120 volts to
the Central Heating Circulator. Connect the Orange (Hot) and the Brown (Neutral) directly to the Central
Heating Circulator.
Connect the gray wires to your heating thermostat (TT) connection. Your thermostat heat anticipator
setting is .056 amp.
It is important that the electrical power is not turned on at this time. Double check all connections and then
turn the power on. The display that is provided with the Munchkin should now be reading the outlet
temperature. Note: see Part 6/Startup Procedure section in the manual to change the temperature setting
or run the heater.
DANGER
IT IS VERY IMPORTANT THAT THE BUILDING GROUND IS INSPECTED BY A
QUALIFIED ELECTRICIAN PRIOR TO MAKING THIS CONNECTION!
DANGER
The Orange wire for the Central Heating Circulator is Switched Hot and must have a
wire nut if not connected to the Central Heating Circulator. Failure to follow this
instruction will result in a short, and the Control Board will have to be replaced.
CAUTION
Electrical wiring on the Incoming Power and Central Heating Circulator shall be
connected directly to the intended connection source and not be connected together
inside the electric box provided. An Electrical Short will result and the Control board
will have to be replaced! If Electrical Requirements of the Central Heating Circulator
exceeds 4 amps (or 3 amps on HA models only) please follow the wiring diagrams on
Page 8, Figures 2-1, 2-2 and 2-3.
DANGER
IT IS EXTREMELY IMPORTANT THAT THIS UNIT BE PROPERLY GROUNDED!
CAUTION
Do not power zone valves directly from the heater transformer. Doing so will greatly
reduce the life of the transformer. Use a separate transformer sized to handle the total
electric load of all zone valves.

PART 3. GAS CONNECTION
8
WARNING
Failure to follow all precautions could result in fire, explosion or death!
ELECTRICAL / GAS CONNECTION
Figure 2-3: For circulator amp loads greater
than 4 amps (3 amps for “HA” models) use the
wiring diagram shown at left. The brown and
orange wires will not be used in this
application.
NORMALLY OPEN
T
T
GROUND
BUS
SWITCH JUNCTION BOX
120V 60 HZ
ELECTRICAL
SWITCH JUNCTION BOX
120V 60 HZ
ELECTRICAL
NORMALLY OPEN
THERMOSTAT
CONNECTION
WIRING DIAGRAM WITHOUT CONNECTION TO CIRCULATOR
GREEN
(GROUND)
GRAY
GRAY
CONNECTION
THERMOSTAT
(NEUTRAL)
WHITE
BLACK
(HOT)
GRAY
T
T
GRAY
WIRING DIAGRAM CONNECTING TO CIRCULATOR
BLACK
WHITE (NEUTRAL)
GREEN (GROUND)
DIAGRAM "A"
(HOT)
BLACK
GREEN
(GROUND)
(NEUTRAL)
WHITE
DIAGRAM "B"
BROWN (NEUTRAL) ORANGE (HOT) GREEN (GROUND)
ORANGE (HOT) BROWN (NEUTRAL) GREEN (GROUND)
IMPORTANT NOTE:
BE CERTAIN THAT THE ORANGE
WIRE IS SECURELY CAPED.
FAILURE TO DO SO COULD
RESULT IN INJURY OR FIRE
AND COULD DAMAGE THE CONTROL.
ORANGE
BROWN
GREEN
Figure 2-1: Connection Wiring Directly to
Central Heating Circulator
Figure 2-2: Connection Wiring without Wiring
Central Heating Circulator
Note to Electrical Contractor: The orange
wire is 120 Volt/4 Amp maximum for central
heating circulator only. Loads greater than 4
amps or 3 amps for HA models only will blow the
fuse on the board. The brown wire is the neu-
tral wire for the central heating pump only.
5
T
12
3
64
T
1K1 1K2
BOILER
"TT"
GRAY
ZONE
CIRCULATOR
120 VOLT
L1 HOT (BLACK)
GRAY
BOILER
"TT"
THERMOSTAT
ZONE
R845A
SWITCHING
RELAY ZONE
1K1
L2 NEUTRAL
(WHITE)

9
GAS CONNECTION
A. GAS CONNECTION
The gas supply shall have a maximum inlet
pressure of less than 14" water column (350
mm), ½ pound pressure (3.5 kPa), and a
minimum of 7" water column. The entire
piping system, gas meter and regulator must
be sized properly to prevent pressure drop
greater than 0.5" as stated in the National Fuel
Gas Code. This information is listed on the
rating plate. It is very important that you are
connected to the type of gas as noted on the
rating plate. "LP" for liquefied petroleum,
propane gas or, "Nat" natural or city gas. All
gas connections must be approved by the local gas supplier, or utility in addition to the governing
authority, prior to turning the gas supply on. The nipple provided is 1¼" and it is mandatory that a 1 x
1¼" reducing coupling (provided) is used, threaded into the branch of a 1¼" tee, and a drip leg
fabricated, as per the National Fuel Gas code. You must ensure that the entire gas line to the
connection at the Munchkin is no smaller than 1¼". Once all the inspections have been performed,
the piping must be leak tested. If the leak test requirement is a higher test pressure than the maximum
inlet pressure, you must isolate the Munchkin from the gas line. In order to do this, you must shut the
gas off using factory and field-installed gas cocks (following the lighting instructions in Part 6 Section
B.) This will prevent high pressure. Failure to do so may damage the gas valve. In the event the gas
valve is exposed to a pressure greater than ½ PSI, 14" water column, the gas valve must be replaced.
Never use an open flame (match, lighter, etc.) to check gas connections.
B. GAS PIPING
1. Run the gas supply line in accordance with all applicable codes.
2. Locate and install manual shutoff valves in accordance with state and local requirements.
C. GAS TABLE
Refer to Table (1) to size the supply piping to minimize pressure drop between meter or regulator
and unit.
Maximum Capacity of Pipe in Cubic Feet of Gas per Hour for Gas Pressures of 0.5 psi or Less and a
Pressure Drop of 0.3 Inch water Column
(TABLE 1) (Based on a 0.60 Specific Gravity Gas)
It is recommended that a soapy solution be used to detect leaks. Bubbles will appear on the pipe to
indicate a leak is present. The gas piping must be sized for the proper flow and length of pipe, to
avoid pressure drop. Both the gas meter and the gas regulator must be properly sized for the total
gas load. If you experience a pressure drop greater than 1" WC, the meter, regulator or gas line is
undersized or in need of service. You can attach a manometer to the incoming gas drip leg, by
Nominal
Iron Pipe Internal Length of Pipe (Feet)
Size Diameter
(inches) (inches) 10 20 30 40 50 60 70 80 90 100 125 150 175 200.
3/4 .824 278 190 152 130 115 105 96 90 84 79 72 64 59 55} BTU'S
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100} PER
1 1/4 1.380 1,050 730 590 500 440 400 370 350 320 305 275 250 225 210} HOUR
1 1/2 1.610 1,600 1,100 890 760 670 610 560 530 490 460 410 380 350 320} X 1,000

10
WARNING
Failure to follow all precautions could result in fire, explosion or death!
GAS CONNECTION
removing the cap and installing the manometer. The gas pressure must remain between 7" and 14"
during stand-by (static) mode and while in operating (dynamic) mode. If an in-line regulator is used,
it must be a minimum of 10 feet from the Munchkin. It is very important that the gas line is prop-
erly purged by the gas supplier or utility. Failure to properly purge the lines or improper line siz-
ing, will result in ignition failure. This problem is especially noticeable in NEW LP installations and
also in empty tank situations. This can also occur when a utility company shuts off service to an area
to provide maintenance to their lines. This gas valve must not be replaced with a conventional gas
valve under any circumstances. As an additional safety feature, this gas valve has a flanged con-
nection to the Venturi and blower.
MUNCHKIN BURNERTECH GAS VALVE
INLET PRESSURE TAP OUTLET PRESSURE TAP
THROTTLE ADJUSTER
VENTURI
110 VOLT AC ELECTRICAL CONNECTION
(NOTE: INLET GAS PRESSURE CAN
BE MEASURED TO ASSURE
PROPER GAS SUPPLY)
(NOTE: A NEGATIVE READING WILL BE
MEASURED WHILE THE FAN IS
IN OPERATION)
(NOTE: IF FOR ANY REASON THE THROTTLE
NEEDS TO BE ADJUSTED,
IT IS VERY IMPORTANT THAT A " COMBUSTION
ANALYZER " BE USED TO ENSURE SAFE AND PROPER OPERATION
TURN THE ADJUSTER TO THE (+) TO INCREASE GAS
OR TO THE (-) TO DECREASE THE GAS SUPPLY.
THIS ADJUSTMENT COULD AFFECT THE CO/CO % LEVELS.
MAKE SURE THE LEVELS CORRESPOND TO THE CHART IN
FIG. 3-2 COMBUSTION SETTINGS)
2
Fig. 3-1
Fig. 3-2
SGNITTESNOITSUBMOC
SLEDOMLLANOSETARGNIRIFWOLdnaSETARGNIRIFHGIH
saGlarutaNPLenaporP
wolhgihwolhgih
mppOCnobraC
edixonoM mpp02–0mpp531–mpp07mpp02–0mpp051–08
OCnobraC
%2
edixoiD %2/1-9–%2/1-8%2/1-9–%2/1-8%2/1-01–%2/1-9%2/1-01–%2/1-9