JRCS JACOM-22
JRCS / Japan marine control equipment
New product
The JRCS JACOM-22 Main Unit is the central generator-control module used in the JACOM-22 fully distributed marine Power Management System (PMS).
JRCS describes JACOM-22 as the world’s first fully distributed marine generator controller, developed to decentralize generator power-management and protection functions for increased reliability in shipboard electrical plants.
The system is designed around individual generator sections, where each generator has its own:
Main Unit
Display Unit
Operation Unit
communicating across the JACOM-22 system network. The JRCS system diagram also shows these generator sections connected through CAN-BUS and interfacing with the vessel’s alarm/monitoring system.
The photographed SM MARINE SERVICE™ stock unit carries the following nameplate information:
Manufacturer: JRCS
System: JACOM-22
Unit: MAIN UNIT
Order / Item No.: 1001223559/9 – 20345000021H
Measurement Voltage: 100/110VAC
Measurement Current: 1A or 5A class input
Control Supply: 24VDC
Type Approval No.: 00A126
Application: Marine Generator Control / Power Management System
The JACOM-22 Main Unit performs the primary generator control and monitoring logic for one generator section of the vessel’s electrical power plant.
JRCS's official JACOM-22 architecture places one Main Unit with each generator, alongside its Display Unit and Operation Unit.
This distributed configuration means the system does not depend entirely on a single central controller.
Instead, each generator section can perform local control and monitoring while communicating with the other generator controllers.
This architecture was a major design advantage for shipboard reliability.
JRCS officially categorizes JACOM-22 as a:
Power Management System
and describes it as a fully distributed power plant control and monitoring system for automatic control of generators.
In a shipboard installation, such a PMS can coordinate several generator-related functions including:
Generator monitoring
Automatic synchronization
Load sharing
Frequency control
Load transfer
Standby generator operation
Power management
ACB control
Generator protection and alarms
The exact functions enabled depend on the vessel’s JACOM-22 configuration and switchboard design.
One of the major functions associated with JACOM-22 is automatic synchronizing.
A marine spare-parts reference describes the JACOM-22 Main Unit specifically as an:
Auto Synchronizing and Load Sharing Unit.
Before a generator can be connected to the live busbar, the system must ensure that generator voltage, frequency and phase relationship meet the necessary conditions.
The Main Unit works as part of this sequence before commanding the generator Air Circuit Breaker to close.
Once multiple generators are connected to the bus, the JACOM-22 system can manage load sharing.
Load-sharing control helps distribute electrical load across running generators so that one generator is not overloaded while another remains lightly loaded.
JACOM-22 is therefore commonly searched under terms such as:
Auto Load Sharing Controller
Generator Load Sharing Unit
Automatic Power Sharing Controller
Marine PMS Controller
These search terms are relevant to the same functional requirement.
Shipboard PMS systems also perform controlled load transfer between generator sets.
For example, when transferring load from one generator to another, the PMS can coordinate generator connection and load redistribution before opening the outgoing generator breaker.
This reduces unnecessary voltage/frequency disturbances.
Power management systems commonly maintain one generator in standby condition.
Depending on the JACOM-22 vessel configuration, the PMS may initiate a standby generator when additional electrical power is required or when the running generator condition requires backup capacity.
This function is especially important when avoiding a total electrical blackout.
A key purpose of any shipboard generator PMS is maintaining continuous electrical power.
JACOM-22 monitors generator and bus conditions and coordinates automatic generator operation to support continuity of supply.
If vessel load increases beyond available generator capacity, the PMS can use configured generator-management logic to increase available generation before critical power loss occurs.
The exact blackout-prevention strategy is vessel-specific.
The photographed JACOM-22 Main Unit is clearly labelled:
MEAS VOLTAGE: 100/110V AC
This is the voltage-measurement input used by the controller for generator/bus electrical monitoring.
A separate documented JACOM-22 Main Unit also shows 110/110VAC measurement voltage, supporting this type of arrangement.
This measurement input should not be confused with the Main Unit’s own electronics supply.
The nameplate also specifies:
MEAS CURRENT: -/1A or -/5A
This indicates compatibility with standard current-transformer secondary circuits.
Marine switchboards commonly use either:
1A CT secondary
or
5A CT secondary
depending on the switchboard design.
This measurement information is critical when selecting a replacement unit.
The photographed unit is clearly marked:
SUPPLY: 24VDC
A documented JACOM-22 Main Unit reference also specifies 24VDC supply.
Therefore the following search terms are technically relevant:
JACOM-22 Main Unit 24VDC
JRCS 24V Generator Controller
JACOM22 PMS 24VDC
JRCS’s official JACOM-22 system drawing shows individual generator Main Units linked by CAN-BUS.
CAN communication is important because it allows individual generator controllers to exchange system information.
This supports coordinated actions such as:
generator synchronization
load sharing
standby-generator control
system-status sharing
while maintaining the distributed architecture.
JACOM-22 can also communicate with higher-level vessel monitoring systems.
Official JRCS documentation shows JACOM-22 interfacing with systems such as:
SMS-22-K
SMS-32 / SMS-32-K
OASIS / IAS
for remote control and monitoring.
JRCS documentation states that remote functions can include:
engine start
ACB closing
standby setting
and that measured values such as:
electrical power
current
frequency
can be transferred through the communication system.
The Main Unit is the central processing and generator-control module of each JACOM-22 generator section.
It handles electrical measurements and generator-control logic according to the vessel configuration.
When sourcing a replacement Main Unit, matching should include:
Order / Item Number
Measurement Voltage
Measurement Current
Supply Voltage
Hardware revision
Vessel PMS configuration
because two JACOM-22 Main Units may not necessarily be configured identically.
The Display Unit provides generator and system information to the operator.
JRCS documentation shows a separate Display Unit as part of every JACOM-22 generator section.
Market references separately list JACOM-22 DISPLAY UNIT, confirming that it is an individually replaceable spare.
The Operation Unit provides local generator operating controls.
JRCS’s official system diagram clearly shows it as a separate module from both the Main Unit and Display Unit.
Replacement buyers therefore frequently search:
JRCS JACOM-22 Operation Unit
JACOM22 Operator Panel
JACOM-22 Generator Operation Panel
Another JACOM-22 spare found in the marine replacement market is the:
Alarm Interface Unit
A market reference identifies:
JACOM-22 Alarm Interface Unit – item no. 2034500007I.
This is an important related keyword for a full JACOM-22 technical page.
However, an Alarm Interface Unit is not a direct substitute for the Main Unit.
Some JACOM-22 installations also include a Remote Interface Unit / Remote Interface Main Unit.
A Japanese vessel maintenance specification specifically calls for replacement of:
JACOM-22 MAIN UNIT with Remote Interface Unit
along with separate Display and Operation Units.
This shows that several configuration variants exist.
JACOM-22 was a major product in JRCS history.
JRCS states that JACOM-22 was developed as a fully distributed Intelligent Generator Plant Control & Monitoring System, and its successor documentation says more than 1,000 vessels received JACOM-22 over its service history.
That installed base is one reason legacy JACOM-22 replacement parts remain valuable in the marine spare-parts market.
This is especially important for buyers today.
JRCS’s support listings show JACOM-22 regular-sales discontinuation as a formal product-support issue.
A published JACOM-22 discontinuation notice states that the discontinued units include:
Main Unit
Alarm Interface Unit
Display Unit
Operation Unit
and identifies JACOM-55 as the successor system.
The notice also explains that conversion to the successor can require switchboard/control-circuit modification rather than being a direct plug-in replacement.
This makes original or professionally refurbished JACOM-22 modules particularly useful for ships that want to keep an existing PMS operational.
JRCS officially describes JACOM-55 as the successor to JACOM-22.
JACOM-55 retains the distributed PMS concept while adding newer hardware, improved display, redundant communication and separate CPUs for generator control and engine protection.
However:
JACOM-22 Main Unit and JACOM-55 are not direct plug-and-play replacements.
JRCS's discontinuation information specifically notes that conversion can require changes to the switchboard surface and control circuits.
Before JACOM-22, JRCS produced the JACOM-21, a 16-bit generator controller.
JRCS corporate history states:
JACOM-21 – developed in 1996
followed by:
JACOM-22 – developed in 1999.
JACOM-21 is therefore an important related-model search term, but it should not be presented as interchangeable with JACOM-22.
JACOM-22 is used in vessel power-generation and main-switchboard systems.
Relevant shipboard applications include:
Main Switchboard Generator Control
Generator Monitoring
Power Management System
Automatic Synchronizing
Automatic Load Sharing
Standby Generator Control
Generator Protection
ACB Control
Power-plant automation
The system can be found on a broad range of merchant vessels because of its long installation history.
Check the 24VDC supply at the Main Unit first.
Inspect:
24VDC feed
fuse/protection circuit
terminal connection
DC common/return
connector seating
If correct supply voltage is present but the unit remains inactive, further internal diagnosis may be required.
Check the voltage measurement circuit.
The photographed unit expects 100/110VAC measurement voltage.
Inspect:
PT output
measurement wiring
fuses
terminals
Main Unit measurement input
before replacing the controller.
Confirm whether the vessel system uses:
1A CT
or
5A CT
and verify wiring and CT secondary condition.
Installing a unit with incorrect configuration can result in incorrect current/power calculation.
Check:
generator voltage
bus voltage
generator frequency
phase sequence
breaker ready signal
synchronizing permissives
communication status
A synchronization failure does not automatically mean the Main Unit is defective.
Investigate:
generator governor
speed-control signal
power measurement
CT input
load-sharing communication
generator settings
before changing the JACOM-22 controller.
Check:
ACB ready condition
spring charged status
trip circuit
interlocks
synchronizing condition
JACOM output command
The Main Unit may intentionally block breaker closing if required conditions are not satisfied.
Check:
CAN wiring
connector condition
termination
24V supply
other JACOM generator Main Units
Because JACOM-22 uses a distributed CAN-BUS architecture, a communication fault elsewhere can affect system coordination.
Check the original unit’s:
Order number
hardware/software configuration
generator settings
measurement ratios
number of generators
remote-interface configuration
A replacement JACOM-22 Main Unit may require matching/configuration rather than only electrical installation.
When requesting a replacement JACOM-22 Main Unit, provide:
Manufacturer: JRCS
System: JACOM-22
Unit: MAIN UNIT
Order / Item Number
Measurement Voltage
Measurement Current
24VDC supply confirmation
Generator rating
Switchboard drawing number
Front/rear photographs
Associated Display/Operation Unit information
For the photographed unit, the most important search references include:
1001223559/9
20345000021H
100/110VAC
1A / 5A
24VDC
SM MARINE SERVICE™ supports worldwide sourcing and supply of JRCS JACOM-22 Power Management System components including:
JACOM-22 Main Unit
JACOM-22 Display Unit
JACOM-22 Operation Unit
JACOM-22 Alarm Interface Unit
Remote Interface Main Unit
Related JRCS generator-control modules and PCBs
Depending on stock availability, equipment may be offered as:
New / New Old Stock
Used Tested Working
Refurbished
Reconditioned
Because JACOM-22 has reached discontinuation/maintenance status, correct legacy replacement units can be especially valuable for existing vessels.
SM MARINE SERVICE™ also maintains a dedicated JRCS PCB Card & Marine Control Module page covering multiple JRCS automation and control spare parts.
JRCS reports that JACOM-22 was installed on more than 1,000 vessels during its product lifetime.
For a vessel with an otherwise serviceable switchboard, replacing one failed JACOM-22 Main Unit can be more practical than converting the complete PMS to a newer generation.
A complete JACOM-55 upgrade can require engineering work, switchboard modifications and control-circuit changes.
This is why tested legacy JACOM-22 units remain actively searched by shipowners, technical managers and marine service companies.
JACOM-22 is a fully distributed marine generator control and Power Management System developed by JRCS.
It is the principal generator-control module assigned to each generator section in the JACOM-22 PMS architecture.
The photographed unit is marked 24VDC.
The photographed nameplate specifies 100/110VAC.
The unit is marked for 1A or 5A current-transformer secondary input.
Yes. Marine spare references describe the JACOM-22 Main Unit as an Auto Synchronizing and Load Sharing Unit.
Yes. Load sharing is part of its documented generator power-management role.
JRCS's official system architecture shows JACOM-22 generator Main Units connected by CAN-BUS.
Yes. JRCS documentation shows JACOM-22 interfacing with systems such as SMS/OASIS for remote operation, alarms and measured-value transfer.
Documented units include Main Unit, Display Unit, Operation Unit and Alarm Interface Unit.
Yes. JRCS has issued end-of-regular-sales/support information for JACOM-22, while maintenance/support arrangements continue according to the published schedule.
JRCS identifies JACOM-55 as the successor.
Not necessarily. JRCS notes that conversion may require switchboard and control-circuit modifications.
SM MARINE SERVICE™ supports worldwide sourcing of JRCS JACOM-22 Main Units and related PMS spare parts, subject to current availability.
JRCS JACOM-22 Main Unit is the main generator-control module used in the JACOM-22 fully distributed marine Power Management System. The photographed unit is rated for 24VDC supply, 100/110VAC measurement voltage and 1A/5A current measurement, with references 1001223559/9 and 20345000021H. JACOM-22 supports generator monitoring, automatic synchronizing, load sharing, breaker control and vessel power-management functions. Related JACOM-22 spares include the Display Unit, Operation Unit and Alarm Interface Unit. JRCS has identified JACOM-55 as the successor to JACOM-22, but conversion may require switchboard modifications. SM MARINE SERVICE™ supplies new, used, refurbished and reconditioned JRCS marine automation and PMS spare parts worldwide.
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