Electro Industries Mini-Boiler EMB-R1-01-120-1 Manual

12/28/2023 BI312
Electric
Mini-Boiler™
Installation&OperatingInstructions
Application: This Electro Mini-Boiler is factory equipped
with outlet temperature sensing control designed to deliver
the exact water temperature for your application. This model
is equipped with pump/valve outputs, backup gas boiler
output, auto and manual high limit safety interlocks, power
company load management, and up to three temperature
sensors depending on the model.
Primary application is any hydronic water heating system (high or low temperature systems).
This series is equipped for power company load management interrupt and can apply to standard baseboard
radiation, dual heat combinations, under floor radiant, wood boiler supplement, etc.
Accessories: Attached BL001 lists various accessory or option items which are not part of basic Electro-Boiler.
Note: This product meets the requirements of the ASME Boiler and Pressure Vessel Code.
Conforms to: UL STD.UL834
Certified to: CSA STD.C22.2#165
DO NOT DESTROY THIS MANUAL. PLEASE READ CAREFULLY AND KEEP IN A SAFE
PLACE FOR FUTURE REFERENCE BY A SERVICE TECHNICIAN.

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TABLE OF CONTENTS
Description Page
System Components 1
Mini-Boiler Selection Guide 1
Electrical Specifications 2
Water Flow Requirements 2
Multiple Zones & Radiant Temperatures 3
Safety Temperature Control 3
Room Thermostat Placement 4
Water Flow Calculation 4
Installation Requirements 4
Electric Supply 5
Clearances 5
Mechanical Installation 6
Electrical Hookup 7
Water Fill Procedure 10
WarmFlo Hi Temperature Mode & Emergency Heat 11
Operational Tips 12
Troubleshooting Helps 13
Drawings: BX306
BH311
UAW431
BL001
XX017

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INTRODUCTION
The Mini-Boiler has been designed in a compact package with up to 9 kW of heating capabilities for radiant
heat applications. When properly sized, the Mini-Boiler will provide the needed hot water to properly heat a
space in a single zone application. The EMB-R Series models provide industry leading hydronic control for
precise temperature management and ease of use. Proper design of the radiant system is required to assure
minimum required water flow (GPM) through the boiler.
GENERAL
The basic components for an electric energy heating system typically include:
1. Electric Mini-Boiler itself – covered by this manual.
2. Thermostat hookup control – covered by this manual.
3. Outdoor Thermistor – if outdoor reset option is ordered as a kit, reference catalog number EMB-ODR.
4. Plumbing kit or piping material at the boiler itself – can be ordered as a kit, reference catalog number
EMB-PK.
a. These items are shown on plumbing installation drawing BX306.
5. Circulating pump – typically sized for head pressure and system flow requirement, typical catalog
number EMB-P2.
6. Radiant heat devices/components.
MINI-BOILER SELECTION GUIDE
Mini‐BoilerSelectionGuide1‐9kW
Element
ControlPhaseZonesVoltagePowerRating(kW)
13579
Staging11
120VACEMB‐R1‐
01‐120‐1
EMB‐R1‐
03‐120‐1‐ ‐ ‐
240VAC‐ ‐EMB‐R1‐
05‐240‐1
EMB‐R1‐
07‐240‐1
EMB‐R1‐
09‐240‐1

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ELECTRICAL SPECIFICATIONS
Model Power Input, Operation Circuit Breakers Power Rating Amps Btu/h
EMB-R1-01-120-1 120-volt, 1-Staging – 1.4 kW 11.7A 4,777
EMB- R1-03-120-1 120-volt, 1- Staging – 3.0 kW 25.0A 10,236
EMB- R1-05-240-1 240/208-volt, 1- Staging 30A CB 5.0/3.8 kW 20.8A / 18.0A 17,060/12,796
EMB- R1-07-240-1 240/208-volt, 1- Staging 45A CB 7.0/5.3 kW 29.2A / 25.2A 23,885/17,913
EMB- R1-09-240-1 240/208-volt, 1- Staging 60A CB 9.0/6.8 kW 37.5A / 32.5A 30,709/23,032
APPROVED TUBING/PIPING
When plumbing this boiler and its peripheral parts to the radiant floor loop system, all plumbing parts and/or
tubing must be sealed to prevent entrance of oxygen.
Use only tubing or polyethylene tubing with oxygen Diffusion Barrier (ie. PEX).
WATER FLOW REQUIREMENTS
In order to prevent rapid stage cycling and long term deterioration of components and elements, it is important
the water flow be greater than the specified 0.3 GPM per kW.
(MINIMUM 0.3 GPM PER KW WATER FLOW THROUGH BOILER)
Model
Water Temperature Rise
Flow – 10° F/6° C Head Loss Flow – 20° F/11° C Head Loss
gpm lpm ft m gpm lpm ft m
EMB-R1-01-120-1 0.96 3.62 0.012 0.004 0.48 1.81 0.003 0.001
EMB-R1-03-120-1 2.05 7.75 0.051 0.016 1.02 3.87 0.014 0.004
EMB-R1-05-240-1 3.41 12.92 0.132 0.040 1.71 6.46 0.037 0.011
EMB-R1-07-240-1 4.78 18.08 0.246 0.075 2.39 9.04 0.068 0.021
EMB-R1-09-240-1 6.14 23.25 0.392 0.119 3.07 11.62 0.109 0.033
Note: Head Loss based on 110° F return temperature, approximately 3 feet of Mini-Boiler ¾” pipe, and a Hazen-Williams
Coefficient of 140.

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MULTIPLE ZONES AND RADIANT TEMPERATURES
Same water temperature all zones – this model series has a built-in supply control algorithm for staging the
elements in single or multi zone applications. If more than one zone is required, a zone controller may be used.
If using zone valves, the end switches of all the zone valves are paralleled and directly control the respective R
and W zone inputs to turn on the boiler. Since zone valves have a slow reaction time, to ensure proper
temperature regulation output from the boiler when using zone valves always connect the end switches of the
zone valves to the respective R and W zone inputs.
Two zones with different water temperatures – for applications that require two different temperatures,
consider using the EMB-M2 Series Mini-Boiler. For two temperature applications using the EMB-R1 series, it
is best to run the boiler at the higher desired water temperature and use a return water mixing valve to lower the
water temperature for the lower water temp zone.
CAUTION
ELECTROCUTION IS A RISK INSIDE THE ENCLOSURE OF THE BOILER. ALWAYS TURN POWER OFF
TO THE BOILER PRIOR TO MODIFYING THE ZONE 2 TEMPERATURE SETPOINT OR ACTIVATION
LOCATED INSIDE THE BOILER. HAZARDS OR UNSAFE PRACTICES COULD RESULT IN PROPERTY
DAMAGE, PRODUCT DAMAGE, SEVERE PERSONAL INJURY AND/OR DEATH.
Various water temperature requirements – if this is the case, a primary loop with mixing valve for the
various zone temperature requirements is necessary. Injection pump techniques can also be used. However,
usually injection pump techniques come with a controller which is designed to protect a gas boiler from cool
water return. This is simply not needed and a duplication with the temp sensing controller within this Mini-
Boiler and the injection pump controller will be of no benefit within the operating system. The zone valve/zone
pump control strategy must be wired to provide the boiler “R and W” contact closure and the primary pump is
connected to the boiler pump contacts. This assures the primary pump is active and running whenever the boiler
is turned on via contact closure on “R and W”. At least one zone must be open before turning on the primary
pump/Mini-Boiler. Do not design a system where the Mini-Boiler is supposed to operate as a “hot boiler” based
upon its outlet sensor without the primary pump circulating water, minimum .3 GPM is required.
SAFETY TEMPERATURE CONTROL
The hi-limits within this unit are for safety purposes only. The system installation must have a proper responding
slab or air sensing thermostat or zone controlling device to properly turn the boiler on and off. If the water flow is
greater than the nominal GPM specified and the heat load large enough, this boiler should not reach hi-limit and the
hydronic loop should continue to flow in the normal heating pattern until the operating slab stat is satisfied. If hi-
limiting is experienced prior to satisfying the operating stat, there is likely a water flow issue.
In addition to the built-in supply temperature sensor and temperature control algorithm, there is a 190° F automatic
reset hi-limit and a 205° F top vessel manual reset hi-limit.

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ROOM THERMOSTAT PLACEMENT – RADIANT FLOOR
Comfort and proper space heating response is a direct relationship to the room thermostat type. For optimal system
performance, Electro recommends using a slab sensing thermostat. This type of thermostat uses a remote sensor
placed within the concrete slab via a piece of conduit or pex tube installed prior to pouring the slab.
If provisions were not made for a floor sensing thermostat, most any brand of air thermostat will work. We
suggest setting the cycles per hour adjustment to a value of 1-2.
INFORMATION/WATER FLOW CALCULATIONS
Water flow, GPM, can easily be calculated if the temperature rise across the electric boiler can be measured.
The following formula can only be used when the temperature rise is stable and the boiler is not hi-limiting. In
other words, verify constant current draw and stable outlet temperatures for at least 15 minutes.
GPM= Volts x Amps x 3.4 Example: 240 volts x 36 amps x 3.4 = 29376 = 5.8 gpm
500 x Temp. rise 500 x 10 de
g
ree rise 5000
INFORMATION/WATER FLOW CALCULATIONS – METRIC
L/min = Volts x Amps x 3.587 Example: 240 volts x 36 amps x 3.587 = 30991.68 = 20.57 L/min
251.04 x Temp. rise ° C 251.04 x 6° C rise 1506.24
INSTALLATION REQUIREMENTS
1. All installation work must be performed by trained, qualified contractors or technicians.
WARNING
ALL ELECTRICAL WIRING MUST BE IN ACCORDANCE WITH NATIONAL ELECTRIC CODE
AND LOCAL ELECTRIC CODES, ORDINANCES, AND REGULATIONS.
WARNING
OBSERVE ELECTRIC POLARITY AND WIRING COLORS. FAILURE TO OBSERVE COULD
CAUSE ELECTRIC SHOCK AND/OR DAMAGE TO THE EQUIPMENT.
CAUTION
This unit can only be used for its intended design as described in this manual. Any internal
wiring changes, modifications to the circuit board, modifications or bypass of any controls, or
installation practices not according to the details of this manual will void the product warranty,
the ETL/Intertek certification, and manufacturer product liability. Electro Industries, Inc.,
cannot be held responsible for field modifications, incorrect installations, and conditions which
may bypass or compromise the buil
t
-in safe
t
y features and controls.
2. This installation manual and Mini-Boiler products relate only to the addition of the Mini-Boiler to the
hydronic system. The owner/ installer assumes all responsibility and/or liability associated with any needed
installation of the gas/oil boiler, pump, plumbing, system design, hydronic systems or backup gas/oil boiler,
etc. Any instructions or comments made within this manual (or factory phone assistance) relating to the
gas/oil furnace are provided as comments of assistance and “helps” only.
CAUTION
Hazards or unsafe practices could result in property damage, product damage, severe personal
injury and/or death.
3. Remember, safety is the installer’s responsibility, and the installer must know this product well enough to
instruct the end user on its safe use. Safety is a matter of common sense - - a matter of thinking before
acting. Professional installers have training and experienced practices for handling electrical, sheet metal,
and material handling processes.

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ELECTRIC SUPPLY
Model Volts Phase kW Btu/h Amps CB Element
STG 1 STG 2
EMB- R1-01-120-1 120 1-60 Hz 1.4 4,777 11.67 – 1 –
EMB- R1-03-120-1 120 1-60 Hz 3.0 10,236 25 – 1 –
EMB-R1-05-240-1 240/208 1-60 Hz 5.0/3.8 17,060/12,795 20.8/18.0 30A 1 –
EMB-R1-07-240-1 240/208 1-60 Hz 7.0/5.3 23,885/17,913 29.2/25.2 45A 1 (1)
EMB-R1-09-240-1 240/208 1-60 Hz 9.0/6.8 30,709/23,885 37.5/33.7 60A 1 (1)
CLEARANCES
MINIMUM CLEARANCE SUGGESTED MINIMUM
SERVICE CLEARANCE
LEFT 1 INCH 26 MM 12 INCHES 305 MM
RIGHT 1 INCH 26 MM 12 INCHES 305 MM
BACK 0 INCHES 0 MM 0 INCHES 0 MM
FRONT 1 INCH 26 MM 21 INCHES 534 MM
TOP 1 INCH 26 MM 14 INCHES 356 MM
BOTTOM 1 INCH 26 MM 14 INCHES 356 MM
SURROUNDING AMBIENT TEMPERATURE MUST NOT EXCEED 90°F/32°C

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MECHANICAL INSTALLATION
CAUTION
Electro Industries Inc. requires the use of dielectric isolation between the boiler vessel supply
and return piping when the boiler is plumbed using copper or any other dissimilar metal.
Damage to the vessel caused by galvanic corrosion voids Electro Industries’ warranty.
Reference drawing BX306
The plumbing components and piping layout shown on drawing BX306 has been very carefully picked and
should be plumbed as shown. When following this diagram, the water fill procedure becomes very simple and
almost guarantees the removal of all air or prevents air locking problems. Experienced hydronic heating
installers may be able to eliminate components such as regulated fill valve, check valve, temperature gauge, etc.,
but the inclusion of these components guarantees installation and initial operating success.
The key mechanical components required include:
Boiler/Plumbing Kit Placement – This model series is wall hung and the vessel must be vertical.
The plumbing kit items are located adjacent to the boiler housing itself as shown on
drawing BX306.
For future servicing, the unit itself must be installed a minimum of 18” above the floor. The
elements are screwed in from the bottom.
Allow adequate space for cover removal and maintenance.
Expansion Tank – As a closed loop hydronic heating system, an expansion tank is required.
Temperature/Pressure Gauge – For convenient monitoring a temperature and pressure gauge on
the outlet (supply) is factory installed, facing the front of the boiler. For full observation of the
system, installing one on the inlet (return) is desirable.
Pressure Safety Valve - This is required at the hot outlet and is furnished as a loose component
with the boiler unit itself. Failure to install the provided 30 PSI pressure relief valve as shown voids
warranty and product listing.
Add the necessary pipe extension from the relief valve to the floor to prevent water damage on this unit
or surrounding area.
Gate Valve/Drain Valve - These are for servicing and easy fill purposes.
Circulating Pump - Depending upon system lift and system loop resistance (feet of head), the
proper circulating pump is required to guarantee the minimum GPM flow as specified on the cover
sheet.
Comment: Circulator pump should “pump away from” the expansion tank.
Air Vent Relief – The boiler system air vent should be installed at the highest point of the boiler
piping. For multi-level applications where the heat emitters are several feet above the boiler,
additional air vents may be required at those upper levels to effectively remove all the air from the
system.
Building Water Supply Connection – Reference drawing BX306, note 4, some local building
codes require sophisticated check valve or anti-syphon check valve when the hydronic heating
system is permanently connected to the domestic water system. The intent of this connection is
temporary and for fill purposes only. The installer has the responsibility of complying with local
building codes.

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ELECTRICAL HOOKUP
Reference drawing BH311
WARNING
DISCONNECT ALL ELECTRICAL POWER BEFORE ELECTRICALLY CONNECTING OR
SERVICING THE UNIT. FAILURE TO DISCONNECT THE ELECTRICAL POWER BEFORE
WORKING ON THIS PRODUCT CAN CREATE A HAZARD LEADING TO PERSONAL INJURY
OR DEATH.
1. Panel breaker sizes – based upon the installed unit capacity, cover page shows model
number/amps/kW, service from appropriate size panel breaker based on NEC code.
2. The larger EMB-R models include a factory provided circuit breaker. This qualifies for a local
disconnect at the product or appliance.
3. 240/208-Volt Power Source – route and install the proper current carrying conductors, suggested by
local codes, from service panel fuse or circuit breaker. Nameplate shows current & KW rating. Use
only copper wire within this unit enclosure or at the circuit breaker connection.
The source is either from the standard service panel or may be part of an off-peak separately metered
panel/CT metered enclosure. Consult with local utility if questions on off-peak installations.
WARNING
USE ONLY COPPER WIRE FOR CONNECTION TO THE CIRCUIT BREAKER TERMINALS AND
INSIDE THIS PRODUCT’S CABINET.
WARNING
TO AVOID THE RISK OF ELECTRIC SHOCK OR DEATH, WIRING TO THE UNIT MUST BE
PROPERLY GROUNDED. FAILURE TO PROPERLY GROUND THE UNIT CAN RESULT IN A
HAZARD LEADING TO PERSONAL INJURY OR DEATH.
NOTE: This model series is designed and equipped for 240-volt residential single phase. If this unit is
used on 208-volt, energy capacity is reduced by approximately 25%. The installed transformer has a primary
tap for 208-volt. Rewire internal transformer so the boiler is using this primary tap for 208-volt applications.
4. Circulating Pump – the orange pigtail wires, at the cube relay, represent a switch closure (see drawing
– 10-amp maximum) to operate the circulating pump motor. Voltage for the pump must come from a
separate source. Wiring entrance must be through the left knockout, do not combine with thermostat
cable or other control wiring.
5. Operating Thermostat – this Mini-Boiler is designed to be used for one or multiple zone applications.
For single thermostat or external zone operating relay use thermostat connection labeled Zone 1.
Temperature set point for Zone 1 is adjusted by using the temp set point dial on the front control panel
of the boiler. For multi zone applications simply, connect two independent thermostats or end switches
to Zone1, or use a zone control panel. On the EMB-R1 series the thermostat connection labeled Zone 2
does not function. Do not connect to the Zone 2 terminal block.
6. Examples of thermostats that are compatible with this boiler include:
Standard Mechanical – connect to control board “R” and “W”. IMPORTANT – set thermostat
internal heat anticipator to 0.2.
Wi-Fi Thermostats – most brands of Wi-Fi thermostats will work with the EMB-R Mini-Boiler.
Wiring connections will typically be R-W-C.
Slab Thermostat – 3-wire connection required.
R to R, W to W, C to C, green to ground

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Power robbing thermostats – power robbing thermostats can be used with the EMB-R Mini-Boiler
models depending on thermostat brand and power consumption.
7. Load Management Interrupt Control (LMC) – this Mini-Boiler product has been pre-wired and
designed for a power company load management receiver connection. This should not be altered in any
manner! If load management is not used, simply leave the terminal labeled “load man” jumped. When
connecting to load management observe the following:
A. Remove jumper from load man terminal.
B. Insert two wires at load man and extend to the power company load control device.
As shipped, this unit is only equipped for off-peak = N.C. logic. If reversed logic is required,
contact the factory for modification.
Optional 1– if the power company disconnects 240V for load control, please reference BH029 for
special wiring requirements.
8. Zone Valve – the installer may elect to totally wire in the zone valves where paralleling the end
switches activate the control board R and W. The EMB-R Series has a 40VA, 24-volt transformer which
is capable of driving 1 or 2 external zone valves depending on valve power requirements.
9. Inspection/final check – Verify all electrical connections are tight (including factory connections),
verify there is proper spacing between all power and electrical wire/terminals, and verify top high limit
manual reset is “in”. During shipping freight vibration there are times when the boiler vessel top
manual reset high limit is “popped out”.

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WATER ADDITIVES
1. Water treatment is strongly suggested to prevent scale deposits, corrosion from acids, oxygen, and other
harmful elements within the specific water supply. Unless the source water is unusually poor and/or rust
elements, additives are not required for use, but strongly suggested. Failure to manage the proper water
voids the element warranty.
2. Impurities within a closed loop hydronic boiler are considerably less damaging than the typical domestic
water heater as new impurities are not introduced constantly. In a closed loop electric boiler, the initial
filling of the water should be as pure as possible. As a closed system, this “pure water” becomes the
operating mode.
3. If there is an auto fill connected from the domestic water source to the boiler system, it is recommended
the water source as shown on drawing BX306 comes through the household water softener. If additives
are required, use the recommendations and source from your local professional plumber specializing in
hydronic heating systems.
-It is the installer or user’s responsibility to verify water quality and maintain acceptable water
quality throughout the life of this product. As a requirement the following water properties must
be considered:
i. Hardness (ppm): 0-10
ii. pH: 7.5-10
iii. Iron Content (ppm): 0-20
iv. Oxygen Content (ppm): 0
v. Total Dissolved Solids: 0-5000
WARNING
FAILURE TO MAINTAIN THE PROPER WATER QUALITY INCREASES THE RISK OF PREMATURE
ELEMENT FAILURE OR POOR ELEMENT PERFORMANCE AND WILL VOID THE ELEMENT WARRANTIES.
4. Up to a 50/50 propylene glycol mixture is acceptable for use in these boilers in cold weather
applications.

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WATER FILL PROCEDURE
The following procedure only applies to the prepackaged plumbing kit and/or when the system is plumbed
exactly as shown on drawing BX306.
1. Do not apply 240/208 volt power during water fill sequence.
2. Connect the temporary household water supply source (probably hose connection) to the "supply water
connection" input.
NOTE: If supply water connection is permanent, some local building codes may require special anti-
siphon check valve, PRZ check valve, or equivalent between the Mini-Boiler fill regulator and the
domestic water source or the city water connection.
3. Connect a drain hose to lower hose bib, "drain valve".
4. Open "drain valve" and close "inlet gate valve" (between drain valve and boiler bottom inlet).
5. Verify “top gate valve” is open.
6. Open "water supply valve" and open household water supply source.
This may be at normal household pressure (40 to 60 PSI), the auto-fill value regulator keeps the
hydronic loop at its proper low pressure.
7. Allow system to circulate, discharging through drain valve, for at least 10 minutes.
8. Put your ear against the metal pipe and listen for air bubbles. If the water flow is consistent and quiet, the
system is probably purged and water filled.
9. Close the "drain valve". Open the "inlet gate valve".
10. The cold system pressure at the gauge should be approximately 10 to 14 PSI.
11. Close "water supply valve" and disconnect water supply.
12. Optional – The circulating pump can be energized during this fill operation by having the 240/208-volt
power main source breaker off and simply jumpering the 2 screw terminals for the pump wire connection.
AQUASTAT OPERATION
Determine the design or anticipated outlet temperature. If this is a radiant floor system this typically could be
as low as 90°. If it is staple-up or water coil, satisfactory operation may be at 140° to 160°. If this is baseboard
or radiators, start with 170° and during very cold weather this may need to be 180°.
The front temperature set point is selected by a small screwdriver dial switch. See next section for higher
temperature settings.

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WARMFLO HI TEMPERATURE MODE & EMERGENCY HEAT
Adding a jumper on the header marked “E HEAT” on the control board automatically
sets the temperature setpoint to maximum 180 °F. See image to the right. In other
words, with the jumper installed, the system will command full on to reach 180 °F and
control to that temperature. Note: Zone Call is still required. To test functionality,
jumper R W with E Heat jumper installed.
Adding a jumper on the header marked “HI TEMP” on the control board automatically
shifts each temperature setpoint up 20°F as follows:
90°F 110°F
100°F 120°F
110°F 130°F
120°F 140°F
130°F 150°F
140°F 160°F
150°F 170°F
160°F 180°F
Note: Basic 24V power must be present for this control board function to work.
Flow Switch Statement
A flow switch is not included with the boiler. However, one can be added to the LMC circuit. Simply place the
field provided flow switch in series with this circuit.
CAUTION
ELECTROCUTION IS A RISK INSIDE THE ENCLOSURE OF THE BOILER. ALWAYS TURN POWER OFF TO THE BOILER
PRIOR TO MODIFYING THE ZONE 2 TEMPERATURE SETPOINT OR ACTIVATION LOCATED INSIDE THE BOILER.
HAZARDS OR UNSAFE PRACTICES COULD RESULT IN PROPERTY DAMAGE, PRODUCT DAMAGE, SEVERE PERSONAL
INJURY AND/OR DEATH.

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OPERATIONAL TIPS
1. Indicator lights – there are nine indicator lights on the front cover. Figure 1 under Aquastat
Operation is a reproduction of the front decal giving definition and information for using these
indicator lights.
2. Boiler Power green LED indicates 24-volt is present on the control board. On the EMB-R1
models an outdoor sensor is not included. In normal operation, the green power LED will have
a steady flash indicating no outdoor sensor. See table to the right for temperature sensor
diagnostic information related to the boiler power LED, etc.
3. 240/208-volt element power current flow can only be measured when the external operating
thermostat is calling for heat. In the EMB-R* models there is a 30-second delay before stage 1
turns on, this allows the pump to circulate and sample temperature. Stage 2 will depend upon
the temperature differential at the sensor in the supply pipe, see sequence (assumes off-peak
mode).
4. The operating thermostat heat call can be verified by the red LED marked
Thermostat Call located on front cover. The ‘R’ to ‘W’ heat call is indicated on the
control board in the upper left when the upper door is opened. See image to the right.
5. Electric Mode yellow LED is on when the boiler is not being load controlled (blue
wires closed).
6. The 205°F Manual Reset Limit red LED is on when the vessel top manual hi-limit
switch has opened due to high temperature.
7. The 190°F Auto Reset Limit red LED is on when the vessel top auto hi-limit switch
has opened due to high temperature.
8. The pump output on the control board provide contact closure to the pump
relayunder the lower chassis door (See image to the right). Ensure the pump
connected does not exceed the rating of the relay. Power must be removed to open
the chassis doors for external wiring of the pumps.
9. At outlet temperatures of approximately 160F, the maximum operating system
pressure should be approximately 18 PSI (124 kPa). If the PSI (or kPa) increase
from cold water to operating hot water is more than approximately 3 to 4 PSI
increase (20.6 to 27.5 kPa), the expansion tank is too small, or there is air in the
system.
10. At the top of the vessel is a manual reset, 205° F, primary manual hi-limit. This is
behind the upper control board cover, at the top of the vessel. In the middle of the
manual reset wires there is a tab between the wire terminals. This is the reset
button. With power off and the device cooled, press the tab in to reset. *Seek
professional maintenance before restarting boiler.
11. Check for water leaks and repair as required.
12. If flow seems to be a concern, determine both inlet and outlet water temperature and apply GPM (L/min) formula
detailed in previous section “Information/Water Flow Calculations”.
WARNING – HIGH VOLTAGE
MUST SHUT OFF HIGH VOLTAGE BEFORE
ATTEMPTING TO RESET.
WARNING
PROFESSIONAL MAINTENANCE IS
REQUIRED WHEN THE MANUAL RESET
TRIPS. THE SYSTEM IS LIKELY TO TRIP
AGAIN IF THE UNDERLYING ISSUE IS NOT
FIXED.
PUMP1
PUMP2

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TROUBLESHOOTING HELPS
Front Cover LED Indications
The two red LEDs labeled “MANUAL RESET LIMIT” and
“AUTO RESET LIMIT” are an indication of whether the
manual or auto temperature limits have failed.
The green LED labeled “BOILER POWER” is an indication
of whether the boiler control board is powered/unpowered.
See diagnostic chart on previous page or inside boiler top
cover.
The yellow LED labeled “ELECTRIC MODE” is an
indication of if the power company is allowing electric
boilers to operate (led ON) or not (led OFF).
The red LED labeled “THERMOSTAT CALL” is an
indication of whether a thermostat call is active/inactive.
The two red LEDs labeled “STG1” and “STG2” are an
indication of whether elements of the boiler are on/off.
The green LED labeled “PUMP ON” is an indication of
whether the zone pump relay is on or off.
Sequence EMB-R1-*-*-1
At thermostat call, pump turns on.
Elements remain off for 30 seconds.
In this series, if the supply sensor is detecting supply water temperature below the setpoint, the elements
turn on.
As the outlet temperature approaches the set point, the control algorithm automatically stages the
elements to match the BTU load and maintain set point temperature output.
Above the set point elements 1 and 2 staging is reduced according to the control algorithm.
The staging of the elements continues to adjust to optimize element usage based on realized heating
demand.
Mechanical auto hi-limit, top vessel surface mount, automatic reset – this opens at 190 ± 5°F, which opens
the red/white wire indication to the board. This opens all 24V element relay power thus preventing element
activation power. This can be monitored by the “Auto Reset” front indicator light. As the water cools to
approximately 160° F it should self-reset and restart.
Mechanical manual hi-limit, top vessel surface mount, manually reset – surfaced mounted to the top of the
vessel, opens at 205°F. This opens all 120V/240V element power thus opening all power conductors to the
elements. The observed action is realized through the “Manual Reset” front indicator light. Note: the boiler will
not operate until the unit cools down and this limit is manually reset.
In the middle of the manual reset wires there is a tab between the wire terminals. This is the reset button. With
power off and the device cooled, press the tab in to reset.
Note: In typical abnormal operation the auto hi-limit will always trip prior to the manual limit. In
general if the system is properly setup, the manual limit should never trip.

12/28/2023 14 BI312
AVAILABLE, ELECTRO INDUSTRIES, INSTALL PARTS OR KITS
EMB-PK MINI-BOILER INSTALLATION PLUMBING KIT PREFERRED, 3/4"
EMB-P2 PUMP KIT 1/25HP CIRCULATOR
5590 EXPANSION TANK 40K BTU 2.1 GALLON
5576 AIR ELIMINATOR 3/4" ROLLAIRTROL
5453 VALVE RELIEF 30 PSIG .75” NPT MALE
5456A GAUGE PRES/TEMP 75 PSI/320DG F .25"
EMBR5625 REPLACEMENT CONTROL BOARD
5402KIT THERMISTOR, SUPPLY TEMP
5128C RELAY, 24VDC, 40A
5541 TRANSFORMER, 24V/40VA

Mini-Boiler
"BASIC" MECHANICAL PIPING DIAGRAM
BX306 P.1
REV A 07/20/22

Mini-Boiler
"PREFERRED" MECHANICAL PIPING DIAGRAM
BX306 P.2
REV A 07/20/22

MINI-BOILER BASIC HOOKUP (EMB-R*-*-*-1, EMB-M*-*-*-1)
BH311
Rev. A
PG 1 OF 2
Rev A 08/02/22: Released

MINI-BOILER HOOKUP (EMB-R*-*-*-1, EMB-M*-*-*-1)
BH311
Rev. A
PG 2 OF 2