Miura EXW Series User manual

Revised August 19, 2014 Control Number: MA-MN-007-01

TABLE OF CONTENTS
SECTION 1 Introduction 1
1.1 Definitions and Symbols 1
1.2 Guarantee 1
1.3 Introduction 1
1.4 Features 2
1.5 Specifications 5
SECTION 2 Acts & Regulations 5
2.1 Acts & Regulations 5
2.2 National Regulatory Organizations 5
SECTION 3 Installation 5
3.1 Unloading 5
3.2 Assembling 5
3.3 Recommended Piping 5
3.4 Water Piping 5
3.5 Fuel Piping 5
3.6 Clearances and Ventilation 5
3.7 Stack & Breeching Installation (CGA Canada Only) 5
3.8 Electrical Installation 5
SECTION 4 Operation & Maintenance 5
4.1 Preparation before Start-up 5
4.2 Start-up 5
4.3 Shut-down 5
4.4 Cautions During Operation 5
4.5 Safety Attachments 5
4.6 Water Treatment 5
SECTION 5 Maintenance 5
5.1 Maintenance & Cleaning Schedule 5
5.2 Troubleshooting 5
5.3 Flow Chart of EXW Sequence Operation 5
i

1
SECTION 1 INTRODUCTION
1.1 DEFINITIONS AND SYMBOLS
Note, Caution and Danger are used throughout this manual with the following definitions and
symbols.
1.2 GUARANTEE
Refer to warranty documents for specific details.
SIX-MONTH labor warranty from boiler start up may be available, contact Local Sales and
Service representatives for details. This labor warranty covers routine inspection and repairs at
the job site. Travel and lodging expenses are not covered except within local representative
service area.
ONE YEAR Standard warranty for parts from boiler commissioning date or 18 months from
shipping date whichever occurs first. Express shipping cost for overnight or next day delivery
of parts is not included. Damage to the boiler or parts of the boiler occurring after leaving the
factory are not covered. Parts replaced under this warranty must be returned to MIURA. If the
failed part is not returned, the customer will be charged for the new item.
SEVEN-YEAR limited factory warranty on pressure vessel against material or workmanship
defects.
1.3 INTRODUCTION
Miura Boiler Co., Ltd. began North American activities in 1988, when the manufacturing plant in
Brantford, Ontario, was established. Their engineering department developed procedures to meet
ASME codes and listing approval from UL, CSA. The United States corporate sales office,
Miura Boiler, Inc., was established and has developed relationships with national, state and city
inspectors and agencies.
The North American network consists of branches in Chicago, Los Angeles, New York, Atlanta
and Ontario. The parent Company, Miura Boiler Ltd. in Japan, is the leading manufacturer of
boilers and other thermal equipment in the Pacific Rim holding more than 55% of the market.
With factories in five countries, production now exceeds 14,000 units per year.
NOTE: Indicates an area or subject of special merit, emphasizing either the product
capabilities or common errors in installation, operation or maintenance.
C
AUTION
: Indicates possible damage to equipment. It also indicates any condition or
practice, which if not observed or remedied could result in damage or destruction of
equipment.
DANGER: Indicates any condition or practice, which if not observed, could result in
personal injury or possible death.

2
As a result of design necessities in Japan, such as limited space and total dependence on foreign
energy, the MIURA BOILER has been engineered as a highly efficient, vertical water tube, once-
through, forced-flow design. The MIURA Boiler features a compact unit with a low-water
content and is designed to run with a minimum amount of maintenance with simple push-button
controls. Operation is quiet and radiant heat losses are minimal. Miura Boilers are often
installed in a multiple boiler network. MIURA Boilers, along with the patented MIURA
Multiple Installation panel, allows appropriate horsepower to be brought on and off line quickly
to meet sophisticated production needs with maximum fuel economy. The 40-year, field proven
‘Miura Advantage’ is the ability to reach full output from cold start in less than 5 minutes using
the least amount of energy and having the lowest environmental impact. The high efficiency
Miura Boiler has won numerous awards from Engineering Societies and Gas Associations
because it is a compact, safe, cost-effective boiler.
1.4 FEATURES
The MIURA BOILER is a low water content, water tube design, which provides full output within
5 minutes. In addition, it is a compact, safe, cost saving boiler. Miura Boiler is designed to run
with a minimum amount of maintenance with simple, push-button controls. With the patented
Miura XJ1 computer controller, Miura can monitor detail boiler operation from our offices and
provide fast, accurate data. Radiant heat losses are minimal. Miura Boilers are often installed in
multiple boiler networks. Miura Boilers, along with the patented Miura Multiple Installation panel,
allows appropriate horsepower to be brought on and off line quickly to meet sophisticated
production needs with maximum economy. Such features contribute to the success of the boiler
obtaining more than 50% of the market share in Japan, Korea and Taiwan.
The completely packaged EXW has the following items as standard equipments:
High-Low Gas pressure switch
Low Air pressure switch
Control water temperature by thermocouple with water temperature switch backup
Water flow switch
ASME safety relief valve
Main gas line & Pilot line regulators
Dual pilot gas solenoid valves
Dual main gas fluid actuator valves and plugged leak test port (vent valve available)
Forced draft blower and motor
Completely enclosed, heavy gauge casing
ASME stamped Pressure Vessel with internal Inspection ports
Two independent high temperature limit controls
Low-water fuel cutoff with manual reset
Digital display water temperature with back up thermometer gauge
Pressure gauge
Friendly digital display
Communication interface capability
Display of hours of operation and record of five most recent faults
Remote monitoring of boiler performance and trouble shooting by modem link with Miura

3
factory is available.
Oil pump with motor and oil solenoid valves for oil fired boilers
Please note that all flanges used on all EXW boilers are class 150# (EXH used class 300#) and
comply with ASME/ANSI standard B16.5. The 150# stamping refers to a standard classification
not Maximum Allowable Working Pressure (MAWP). As specified in Table A-361 of ASME
codes, Section I, 1998 edition, the MAWP for 150# flanges is 205 PSIG for saturated steam
service and 170 PSIG for Boiler Feed and Blow-off line service
D
ANGER: Change from standard boiler to FGR boiler must be properly set up by a Miura
representative.

4
EXW BOILER SECTION VIEW

5
1.5 SPECIFICATIONS
1.5.1 SPECIFICATION FOR EXW-100
ITEM
UNITS
EXW-100
Boiler type
Multiple water tubes
Boiler Horsepower Rating
BHP
100
Maximum working pressure
PSIG (Kg/cm²)
160 (11.25)
Max. working temperature
F (C)
250 (121)
Heat input
Gas
Btu/Hr
(Kcal/Hr)
4,185,000 (1,054,000)
Oil
4,083,000 (1,029,000)
Heat output
3,348,000 (843,600)
Efficiency
%
80% Gas fired (82% Oil fired)
Heating surface area
Ft² (m²)
193 (17.9)
Full water content
Gal (L)
85.5 (325)
Operational Weight
Lb (Kg)
5,400 (2,450)
Shipping Weight
4,700 (2,150)
Combustion control
Step modulation: Hi-Low-Off
Combustion system
Proprietary Forced draft
Ignition system
Electric spark ignited, interrupted gas pilot
Spark system (15,000V)
High voltage electrical spark
Power Supply
575, 460, or 230V, 3 phases, 60 Hz
Max. Electric Consumption
KVA
11
Blower Motor Output
HP (KW)
10 (7.5)
Fuel Type
Natural Gas or Propane
Fuel Gas Supply Pressure
PSIG
3 –5 (Natural Gas or Propane)
Fuel consumption
Natural Gas
SCFH (Nm3/Hr)
4,170 (121) *
No. 2 Oil
US Gal/Hr (L/Hr.)
29.2 (110)
Flue Gas Volume (Wet)
SCFH (Nm3/Hr)
55,900 (1,500) *
Flue Gas Volume (Dry)
47,700 (1,279) *
Flue Gas Velocity
Ft/s (m/s)
26.0 (7.9) *
Flue Gas Temperature
F (C)
470 (240)
Main Water Inlet
Inches
4
Main Water Outlet
4
Safety Valve Outlet
2
Fuel Inlet
2” Gas - 3/4" Oil
Drain
1
Chimney Diameter
14
Flame Detector
Ultraviolet Flame eye
Overheating Protection
Low water cutoff & Flow switch
NOTE:
i. Fuel consumption is based on Natural Gas with a High heating value of 1,004 Btu/SCF.
ii. Efficiency is based on high heating values of fuels.
iii. Flue gas temperature and velocitycalculated for natural gas with 100°F (40°C) feed water.
iv. Safety valve Outlet size may increase if set below 160 PSIG.

6
1.5.2 SPECIFICATION FOR EXW-200
ITEM
UNITS
EXW-200
Boiler type
Multiple water tubes
Boiler Horsepower Rating
BHP
200
Maximum working pressure
PSIG (Kg/cm²)
160 (11.25)
Max. working temperature
F (C)
250 (121)
Heat input
Gas
Btu/Hr
(Kcal/Hr)
8,369,000 (2,109,000)
Oil
8,165,000 (2,057,000)
Heat output
6,695,000 (1,687,000)
Efficiency
%
80% Gas fired (82% Oil fired)
Heating surface area
Ft² (m²)
323 (30.0)
Full water content
Gal (L)
140 (530)
Operational Weight
Lb (Kg)
9,600 (4,350)
Shipping Weight
8,400 (3,810)
Combustion control
Step modulation: Hi-Low-Off
Combustion system
Proprietary Forced draft
Ignition system
Electric spark ignited, interrupted gas pilot
Spark system (15,000V)
High voltage electrical spark
Power Supply
575, 460, or 230V, 3 phases, 60 Hz
Max. Electric Consumption
KVA
21
Blower Motor Output
HP (KW)
20 (15)
Fuel Type
Natural Gas or Propane
Fuel Gas Supply Pressure
PSIG
3 –5 (Natural Gas or Propane)
Fuel consumption
Natural Gas
SCFH (Nm3/Hr)
8,340 (224) *
No. 2 Oil
US Gal/Hr (L/Hr.)
58.3 (220)
Flue Gas Volume (Wet)
SCFH (Nm3/Hr)
111,700 (3,000) *
Flue Gas Volume (Dry)
95,500 (2,700) *
Flue Gas Velocity
Ft/s (m/s)
25.4 (7.8) *
Flue Gas Temperature
F (C)
470 (240)
Main Water Inlet
Inches
6
Main Water Outlet
6
Safety Valve Outlet
2
Fuel Inlet
2” Gas - 3/4" Oil
Drain
1
Chimney Diameter
20
Flame Detector
Ultraviolet Flame eye
Overheating Protection
Low water cutoff & Flow switch
NOTE:
i. Fuel consumption is based on Natural Gas with a High heating value of 1,004 Btu/SCF.
ii. Efficiency is based on high heating values of fuels.
iii. Flue gas temperature and velocitycalculated for natural gas with 100°F (40°C) feed water.
iv. Safety valve Outlet size may increase if set below 160 PSIG.

7
1.5.3 SPECIFICATION FOR EXW-250
ITEM
UNITS
EXW-250
Boiler type
Multiple water tubes
Boiler Horsepower Rating
BHP
250
Maximum working pressure
PSIG (Kg/cm²)
160 (11.25)
Max. working temperature
F (C)
250 (121)
Heat input
Gas
Btu/Hr
(Kcal/Hr)
10,461,000 (2,636,000)
Oil
10,206,000 (2,572,000)
Heat output
8,369,000 (2,109,000)
Efficiency
%
80% Gas fired (82% Oil fired)
Heating surface area
Ft² (m²)
390 (36.2)
Full water content
Gal (L)
148 (560)
Operational Weight
Lb (Kg)
14,200 (6,440)
Shipping Weight
12,900 (5,850)
Combustion control
Step modulation: Hi-Low-Off
Combustion system
Proprietary Forced draft
Ignition system
Electric spark ignited, interrupted gas pilot
Spark system (15,000V)
High voltage electrical spark
Power Supply
575, 460, or 230V, 3 phases, 60 Hz
Max. Electric Consumption
KVA
27
Blower Motor Output
HP (KW)
25 (18.6)
Fuel Type
Natural Gas or Propane
Fuel Gas Supply Pressure
PSIG
3 –5 (Natural Gas or Propane)
Fuel consumption
Natural Gas
SCFH (Nm3/Hr)
10,420 (279) *
No. 2 Oil
US Gal/Hr (L/Hr.)
72.9 (276)
Flue Gas Volume (Wet)
SCFH (Nm3/Hr)
139,600 (3,740) *
Flue Gas Volume (Dry)
119,300 (3,200) *
Flue Gas Velocity
Ft/s (m/s)
18.7 (5.7) *
Flue Gas Temperature
F (C)
470 (240)
Main Water Inlet
Inches
8
Main Water Outlet
8
Safety Valve Outlet
2½
Fuel Inlet
2½” Gas - 3/4" Oil
Drain
1
Chimney Diameter
26
Flame Detector
Ultraviolet Flame eye
Overheating Protection
Low water cutoff & Flow switch
NOTE:
i. Fuel consumption is based on Natural Gas with a High heating value of 1,004 Btu/SCF.
ii. Efficiency is based on high heating values of fuels.
iii. Flue gas temperature and velocitycalculated for natural gas with 100°F (40°C) feed water.
iv. Safety valve Outlet size may increase if set below 160 PSIG.

8
1.5.4 SPECIFICATION FOR EXW-300
ITEM
UNITS
EXW-300
Boiler type
Multiple water tubes
Boiler Horsepower Rating
BHP
300
Maximum working pressure
PSIG (Kg/cm²)
160 (11.25)
Max. working temperature
F (C)
250 (121)
Heat input
Gas
Btu/Hr
(Kcal/Hr)
12,563,000 (3,163,000)
Oil
12,256,000 (3,086,000)
Heat output
10,050,000 (2,531,000)
Efficiency
%
80% Gas fired (82% Oil fired)
Heating surface area
Ft² (m²)
390 (36.2)
Full water content
Gal (L)
148 (560)
Operational Weight
Lb (Kg)
14,200 (6,440)
Shipping Weight
12,900 (5,850)
Combustion control
Step modulation: Hi-Low-Off
Combustion system
Proprietary Forced draft
Ignition system
Electric spark ignited, interrupted gas pilot
Spark system (15,000V)
High voltage electrical spark
Power Supply
575, 460, or 230V, 3 phases, 60 Hz
Max. Electric Consumption
KVA
27
Blower Motor Output
HP (KW)
25 (18.6)
Fuel Type
Natural Gas or Propane
Fuel Gas Supply Pressure
PSIG
3 –5 (Natural Gas or Propane)
Fuel consumption
Natural Gas
SCFH (Nm3/Hr)
12,500 (336) *
No. 2 Oil
US Gal/Hr (L/Hr.)
87.5 (331)
Flue Gas Volume (Wet)
SCFH (Nm3/Hr)
167,500 (4,500) *
Flue Gas Volume (Dry)
143,000 (3,840) *
Flue Gas Velocity
Ft/s (m/s)
22.6 (7.0) *
Flue Gas Temperature
F (C)
470 (240)
Main Water Inlet
Inches
8
Main Water Outlet
8
Safety Valve Outlet
2½
Fuel Inlet
2½” Gas - 3/4" Oil
Drain
1
Chimney Diameter
26
Flame Detector
Ultraviolet Flame eye
Overheating Protection
Low water cutoff & Flow switch
NOTE:
i. Fuel consumption is based on Natural Gas with a High heating value of 1,004 Btu/SCF.
ii. Efficiency is based on high heating values of fuels.
iii. Flue gas temperature and velocitycalculated for natural gas with 100°F (40°C) feed water.
iv. Safety valve Outlet size may increase if set below 160 PSIG

9
SECTION 2 ACTS & REGULATIONS
2.1 ACTS & REGULATIONS
There are a number of codes, standards, laws and regulations for boilers and related equipment that
should be considered. Regulatory requirements are dictated by a variety of sources and are focused
primarily on safety. The equipment shall be installed in accordance with the current regulations,
codes and specifications of the applicable City, Country, Provincial/State and Federal agencies.
Authorities having jurisdiction should be consulted before installations are made. For more
information on how the various rules affect boiler selection and operation, you may want to contact
your local MIURA authorized representative or the engineering firm designing the boiler
installation. Here are some essential rules to consider:
a) The boiler industry is tightly regulated by the American Society of Mechanical Engineers
(ASME) and ASME Codes, which controls boiler design, inspection, and quality assurance.
All boilers’ pressure vessels including economizers, deaerator, blowdown tank and other
pressure vessels should have an ASME stamp.
b) All pressure vessels should be inspected and registered with the National Board.
c) In Canada, the design of all boilers, pressure vessels, fittings, and piping must be registered with
local province as required in CSA B51.
d) The insurance company insuring the facility or boiler may dictate additional requirements.
Boiler manufacturers can provide special boiler trim according to the requirements of major
insurance companies such as IRI, FM. Special boiler trim items usually pertain to added safety
controls. Some industries, such as food processing, brewing, or pharmaceuticals may also have
additional regulations that have an impact on the boiler and boiler room.
e) CSA/CGA, c-UL, UL approval may be required to verify boiler safety performance.
f) A full time boiler operator may be required. Operator requirements depend on the boiler’s size,
pressure, heating surface area and volume of water. Boilers can be selected to minimize the
requirements; either by choosing boiler that is exempt from the rules or by installing special
equipment that gives the operator more freedom in the facility. Contact the local boiler
inspector for details.
g) Most state/province or local authorities require a permit to install and operate a boiler.
Additional restrictions may apply in non-attainment areas where air quality does not meet the
national ambient air quality standards and emission regulations are more stringent.
h) Most states or provinces require an annual boiler inspection. There may be other requirements
on piping as well.
i) Most areas have established a maximum temperature at which water can be discharged to the
sewer. In this case, a blowdown separator or blowdown tank is required.
j) For all new boilers with inputs over 10 million Btu/Hr, U.S. Federal emission standards apply
including permitting and reporting procedures.
2.2 NATIONAL REGULATORY ORGANIZATIONS
MIURA Boiler recommends contacting your actual insurance provider as well as the utility
companies for assistance in identifying and complying with codes and regulations.

10
A partial list of agencies having jurisdiction over boiler installation and operation is given below.
This list is comprehensive but by no means all-inclusive.
UNDERWRITERS LABORATORIES
333 Pfingsten Rd.
Northbrook, IL
60062
[phone]
NATIONAL BOARD
1055 Crupper Ave.
Columbus, OH
43229
[phone]
A.S.M.E.
345 East 47th St.
New York, NY
10017
[phone]
INDUSTRIAL RISK INSURERS
85 Woodland Street,
Hartford, CT 06105-1226
AMERICAN GAS ASSOCIATION
1515 Wilson Boulevard
Arlington, VA 22209
OCCUPATIONAL SAFETY & HEALTH ADM.
LOCAL FIRE MARSHALL
LOCAL BOILER INSPECTION
CSA INTERNATIONAL
178 Rexdale Blvd.
Etobicoke, Ontario
M9W 1R3
[phone]
T.S.S.A.
3300 Bloor St., West
4th Floor, West Tower
Etobicoke, Ontario M8X 2X4
[phone]
N.F.P.A.
1 Batterymarch Park
P.O. Box 9101
Quincy, MA 02269-9101
[phone]
FACTORY MUTUAL RESEARCH CORPORATION
1151 Boston-Providence Turnpike,
Norwood, MA 02062
[phone]
AMERICAN NATIONAL STANDARD INSTITUTE
11 West 42nd Street,
New York, NY 10036
ENVIRONMENT PROTECTION AGENCY
LOCAL BUILDING & CONSTRUCTION INSP.
FOOD & DRUG ADMINISTRATION

11
SECTION 3 INSTALLATION
3.1 UNLOADING
For transportation, the EXW boiler may be disassembled and shipped in separate components as
follows:
Boiler vessel with burner and control box (blower assembly may be shipped separated if
required by customer)
Optional parts such as silencer, filter box, valves etc.
The EXW series boiler may be unloaded from the transport truck using a forklift. However, if a
forklift is used, precautions should be taken to ensure that the boiler does not tip over. The boiler
is top heavy and the weight is not centered. Because of the many variables involved such as
model, size of forklift and size of the loading dock, MIURA is not able to recommend a specific
method of unloading the boiler. As a general starting point, the boiler center of gravity will be
the midpoint of the two lifting lugs. Securing the top of the boiler to the forklift with a chain or
similar methods is strongly recommended.
3.2 ASSEMBLING
NOTE: The installation of the equipment shall be in accordance with the regulations of the
authorities having jurisdiction.
CAUTION: All boiler prices are F.O.B. the factory at Brantford, Ontario. This means
that MIURA Boiler is not responsible for damage to the boiler occurring during shipping.
We strongly recommend a complete inspection of all boiler shipments at place and time of
delivery. This inspection should include photographs of the boiler and ancillary equipment
packing crates. If any damage is found, do not release the driver or unload the equipment
until a satisfactory arrangement is made with shipping company to cover the damage.
MIURA Boiler makes reasonable effort to ensure that no vibration or shock damage will
occur. However, if such damage occurs and is not discovered and noted at the time of
delivery, MIURA Boiler is not responsible to pay for the cost of repairs and any damaged
parts will not be under warranty.
NOTE: It is customer’s responsibility to confirm utility availability before ordering the
boiler and follow all local regulations.
NOTE: Some small parts, such as bolts and nuts etc. will be shipped inside associated
control box for the boiler.
C
AUTION
: This is a completely shop tested, assembled and fully packaged boiler. Each unit
and assembly has been well adjusted in the factory. It is very important not to make any
adjustments without first consulting your nearest authorized MIURA dealer. Field
reassembly is customer’s responsibility.

12
3.2.1 BLOWER ASSEMBLY
Place the blower on the foundation
so that the blower outlet is directly
under the windbox inlet. Tighten
the foundation bolts. Install air
hose between blower outlet and
windbox inlet as straight as
possible to reduce the pressure
drop in this duct. Ensure that the
hose is placed as far as possible
over the air duct to minimize
leakage, the chance that it will
blow off, as well as eliminate any
bend in the hose (trim any excess
length if required). Tighten hose clamps.
3.3 RECOMMENDED PIPING
3.3.1 CLOSED SYSTEM
A closed system should operate with little or no make-up. Consequently, very little water needs to
be added over the years of servicing. Liming or scale build-up should be negligible unless the
make-up is too great. The most common cause of problems due to excessive make-up is leaks in
the system, automatic vent not valved off after start-up, improper air elimination and faulty pressure
reducing valve. It is important to realize that air elimination is a continuous process in a
properly designed system.
Simply venting off excessive air during start-up will not satisfy this requirement. The expansion
tank provides the air cushion to accommodate the expansion and contraction of the system water.
This tank should be sized to approximately ¾ full when the system is at maximum operating
temperature and ¼ full when at ambient temperature. Therefore, ½ of the tank capacity must
accommodate the expansion of the entire system. This would include the water content of the
heater system piping and all heat users or loops.
When the expansion tank has little or no air in it, it is referred to as being "water logged" which
means that air has either escaped or migrated to some other part of the system instead of being
properly returned to the expansion tank. Greater amounts of air occurring in the tank, in spite of
attempts to bleed down, indicates that air is being drawn into the system at some point where there
is a leak and the system pressure is below that of the atmosphere. This condition cannot occur if the
circulation pump intake is located at the outlet of the boiler (i.e., water is being pulled from the
boiler rather than being pumped into the boiler). The cause for a water logged expansion tank must
be quickly found and corrective action taken, otherwise there will be a constant loss of water from
(2)-Hose Clamps
(4) 1/2'' dia Holes
for Anchor Bolt

13
the relief valve, constant make-up of water which will result in the liming of a system that was
intended to be closed.
3.4 WATER PIPING
EXW-100
EXW-200
EXW-250/300
Minimum flow (Gal/mim)
100
200
300
Water Inlet (150# Flange)
4"
6"
8”
Water Outlet (150# Flange)
4"
6"
8”
Drain Outlet
1” NPT
Safety Valve Outlet
2” NPT
Safety valve Outlet size may increase if set below 160 PSIG.
Please Contact your nearest MIURA representative or Distributor about accessories.
Before the boiler is fired for the first time after installation is completed, flush all piping.
MIURA is not responsible for damage as a result of debris in piping such as stuck open check
valve.
Practical experience has proven that even though hot water boilers generally operate on closed
NOTE:
Dirt and scale from the entire system will tend to collect in the boiler and should be
washed out until the system is clean.
Periodic water analysis should be performed to see if additional treatment is needed.
NOTE: Installer must identify emergency shut-off device, which includes power switch,
main fuel, and water cock.

14
systems, water losses and entrance of air may lead to pitting, corrosion and formation of sludge
or scale. It is therefore essential to obtain suitable water treatment recommendations from
specialists and to apply them rigidly. A water meter is recommended to know the amount of
make-up water used.
To avoid condensation in the boiler and the chimney, do not operate boiler for extended
periods of time at boiler outlet temperatures lower than 180F (minimum heating return
temperature should be above 130°F). If the boiler is maintained at lower temperatures, the
moisture in the flue gases will condense in the boiler tubes or chimney and form water. The net
result is that corrosion occurs on the combustion side of the flues and in the vent stub and
chimney. If lower water temperatures are required, mixing valves should be used.
The GPM circulating rate in relation to full boiler output and system temperature drop may be
determined from the Performance Curve or from the following formula:
GPM BoilerOutput(Btu / Hr)
500SystemTemperatureDrop(F)
Main hot water piping should slope upward. If the slope is downward, it must be properly
vented to remove air.
Relief valve discharge outlet must be piped toward the drain, leaving the pipe open so as to
enable observation of water flow, when active.
3.5 FUEL PIPING
3.5.1 GAS PIPING
FUEL TYPE: Natural & Propane Gas
SUPPLY PRESSURE: 3 - 5 PSIG *
NOTE: In multiple installations of hot water boilers, the equalization of water flow to the
boilers is an important consideration. This can be accomplished by using individual
circulating pumps for the boilers with symmetrical piping to the boilers, or by using
balancing valves or orifice plates and gauges in the piping to the individual boilers. If
balancing valves or orifice plates are used, there must be a significant pressure drop across
the balancing devices. If care is not taken to ensure equal flow, the unequal flow will cause
an unequal-firing rate. The net result would be that the common header outlet water
temperature would not be up to the desired temperature.
NOTE: 3 –5 PSIG is the setting range, NOT the allowable fluctuation range. Maintain
steady, set gas supply pressure within 0.2 PSIG but NEVER below 3 PSIG during operation.
This pressure must be at the regulator supplied with MIURA Boiler gas piping. If necessary,
use larger pipe for long piping runs. Failure to maintain required gas flow rate pressure will
result in frequent boiler misfire!
NOTE: Do not use any gas piping with a diameter smaller than the gas inlet piping to
boiler. All main gas train piping to the burner is included, (except for individual regulator
and pressure switch vents).

15
EXW-100
EXW-200
EXW-250/300
Gas Inlet
2" NPT
2 ½” NPT
Main Gas Regulator Vent
1” NPT
Pilot Gas Regulator Vent
1/8”NPT
Pressure Switches Vent
1/8”NPT
Automatic Vent (option)
¾” NPT
1” NPT
1¼” NPT
Supply pressure of 3 to 5 PSIG
required at boiler regulator inlet at
full firing rate and when boiler
combustion is stopped. Installation
of a pressure gauge to monitor gas
supply pressure is recommended. If
the boiler is operated with propane
as the fuel, MIURA Boiler
STRONGLY recommends the use
of a vaporizer. Collecting the
propane gas from the top of the tank
is possible, but not recommended
due to variations in vapor space
pressure depending on ambient air
temperature. Also, ensure the vaporizer is sized for full boiler capacity even if the normal load is
less than the maximum capacity of the boiler. This recommendation is based on the boiler
operating at full rated fuel flow during the start up period.
If the supply gas pressure is above 5 PSIG, use only one approved reducing station per boiler
room to meet the required specifications. Do not use a separate reducing valve to supply each
boiler. This would result in pressure oscillations that could result in boiler flame failures or
momentary over firing conditions. Consult pressure regulator application engineers for correct
sizing and regulator model selection.. Use an approved booster pump, if necessary, to meet the
required minimum pressure specifications of 3 PSIG. To ensure an adequate volume of fuel is
available to support combustion during firing rate changes, a 3 PSIG minimum is required at the
inlet to the main regulator supplied with the boiler. Specifically, a change from burner Off to
Low Fire, which is approximately 40% of rated fuel usage, occurs over a 10-15 second period.
The fuel usage then goes from 40% to 100% rated consumption when the boiler goes to high fire.
This change occurs in less than one second. Fuel consumption then changes from 100% to zero
in less than one second when the boiler turns off. The utility gas regulator must maintain at least
3 PSIG and not exceed 5 PSIG under these conditions.
Install dirt pocket on Main gas inlet piping immediately up stream of boiler.
C
AUTION
: Do not attempt to change any part of this gas train without first consulting the
nearest authorized MIURA representative.

16
Gas vent line to
outside boiler room.
Pilot Gas Regulator
Do not allow vent pipe
to be kinked. This will
result in pilot flame
failures
Pilot Gas Train
Main Gas Train High Gas Pressure
Switch if required
Solenoid Valve (For IRI)
Low Gas Pressure
Switch if required
Main Gas Regulator, local code
may required to be vent separately
Two pressure switches, HIGH and LOW gas pressure, may be required to be vented to the
atmosphere outside of the boiler room. Contact your local insurance provider and the Gas
Company for specific requirements. Note that some boiler models may have ANTUNES RLGP-
G 5~30’ switches on the gas train which do not require venting to the atmosphere.
To out doors
1/4'' Tube
To out doors
1'' N PT Use
drip leg
or rain
cap on
vent
Union
Fittin g
line
M ain G as R egulator
Pilot Gas Regulator

17
Typically, gas vent lines can be connected to a common
vent line. The vent line will have a cross-sectional area
not less than the area of the largest vent line plus 50
percent of the areas of all the additional vent lines.
An optional solenoid automatic vent valve located
between the main gas blocking valves may be required
for insurance purposes and is an additional cost option
to meet IRI specifications. Ensure IRI is specified on
the purchase order if necessary.
Follow all local regulations.
3.5.2 OIL PIPING
FUEL TYPE: No. 2 Oil
100
200
300
Oil Inlet
3/4" NPT
All oil piping to the burner is included.
Install a manual fuel oil shut off valve at the
boiler.
In order to comply with National Fire
Protection Code, the fuel pump suction
pressure should not exceed 3 PSIG.
Fuel pressure at pump suction must NOT be at
a vacuum. Do not use the MIURA supplied oil
pump to draw oil up from the tank, through the
overhead, and down to the boiler. This
arrangement almost always allows air to leak
into the pump suction connection and results in
very poor combustion.
Avoid high points in the pump suction piping
that would allow air to collect and result in loss
of pump priming. Do not pipe from oil tank to ceiling and down to boiler without an air vent
or air lock will occur. Piping along the floor is preferred.
To prevent loss of Oil Pump priming, it may be necessary to install a re-circulation pump.
NOTE: All EXW oil fired boilers (except EXW-100) require Natural or Propane gas for
pilot burner ignition.
C
AUTION
: Do not attempt to change any part of this oil train without first consulting
the nearest authorized MIURA representative.
To out doors
Gas Pressure Switch
1/4 " Tube
Oilpumpsuction
pipingconnection.
To burner
OilStrainer
OilPump

18
Vent all air from the piping to prevent damage to the oil pump seal before running the pump.
Follow all local regulations.
3.6 CLEARANCES AND VENTILATION
3.6.1 CLEARANCES
The EXW model was designed for non-combustible floors with minimum clearances from the unit
and flue connector to combustible materials of:
Boiler Top
40"
(1,020 mm)
Boiler Right Side
24"
(610 mm)
Boiler Left Side
24"
(610 mm)
Boiler Rear
24"
(610 mm)
Boiler Front
48"
(1,220 mm)
Follow all local regulations.
3.6.2 VENTILATION
The table below gives factory recommended minimums for ventilation of each boiler. The
recommendation is based on Canadian Gas Association standards. However, please confirm
with local building and safety codes as boiler room ventilation requirements vary by significant
amounts. For multiple boiler installations, multiply the below areas by the number of boilers
installed in the boiler room.
MODEL
SUPPLY AIR AREA
(Sq. in.)
VENTILATION AIR AREA
(Sq. in.)
CHIMNEY DIAMETER
(Inches)
EXW-100
139
14
14
EXW-200
286
29
20
EXW-300
415
41
26
Ventilation of the space occupied by the boiler should be provided by at least one opening directly
in contact with the outdoors. Such an opening is to be located at the highest practical point for the
purposes of generating natural convection processes of air circulation. The total cross-sectional
area of such openings should be at least equal to those values in the table above.
In addition to the required openings for required air ventilation, there should be a permanent air
supply via openings having a total cross-sectional area not less than what is required from the table
above. The location of these openings should not interfere with the openings intended for the
purposes of ventilation. These air supply openings should be either located at, or ducted to, a point
not more than 18 inches (450 mm), and nor less than 6 inches (150 mm), above the floor level.
Follow all local regulations.