![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/marine-ups-shipboard-power-distribution-1024x576.png\")
On most vessels, the UPS sits between the switchboards and the systems that must never black out. A typical arrangement:<\/p>\n
- \n
- The main switchboard<\/strong>, fed by the main generators, supplies the UPS rectifier. Ships commonly use 440 V or 690 V, 60 Hz, three-phase, often as an unearthed (IT) system.<\/li>\n
- The emergency switchboard<\/strong>, fed by the emergency generator, supplies the UPS bypass.<\/li>\n
- The battery<\/strong> carries the load during the gap between a blackout and the emergency generator coming online, and beyond if required.<\/li>\n
- The UPS output feeds a dedicated distribution board<\/strong> for essential consumers.<\/li>\n<\/ul>\n
Typical UPS-fed loads include:<\/p>\n
- \n
- Bridge and navigation equipment<\/strong>: radar, ECDIS, gyro compass, autopilot.<\/li>\n
- GMDSS radio<\/strong> and other communication systems.<\/li>\n
- Alarm and monitoring systems<\/strong> for machinery.<\/li>\n
- Fire detection<\/strong> and related safety systems.<\/li>\n
- Engine and propulsion control<\/strong>, and dynamic positioning (DP) control on DP vessels.<\/li>\n
- Public address and general alarm.<\/strong><\/li>\n<\/ul>\n
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Sector Solution: Marine & Ship<\/a><\/strong><\/p>\n<\/blockquote>\n
On offshore platforms and FPSOs, the UPS also supplies process control, ESD and fire and gas systems, and the requirements overlap with those of oil and gas facilities.<\/p>\n
The blackout scenario<\/h2>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/marine-ups-blackout-sequence.gif\")
Animation: from blackout to emergency generator. The UPS covers the gap that SOLAS cares about.<\/figcaption><\/figure>\n SOLAS requires ships to have an emergency source of power that comes online automatically, typically within 45 seconds, after a main power failure. It also requires a transitional source of power for certain essential services during that gap. On many ships, the UPS is that transitional source, or part of it.<\/p>\n
The animation shows the sequence:<\/p>\n
- \n
- The main switchboard feeds the UPS. The battery is on float.<\/li>\n
- The main generators trip. The UPS switches to battery instantly, with no break. Essential loads keep running.<\/li>\n
- Emergency generator online.<\/strong> The emergency switchboard is energised. The UPS continues to supply the load and recharges the battery, or transfers to bypass depending on the design.<\/li>\n<\/ol>\n
The required autonomy depends on the ship type, the flag state, the class rules and the specific loads. For transitional power, 30 minutes is a common figure. Some systems, such as GMDSS radio, may have their own specific requirements. The designer should confirm the applicable rules and size the battery accordingly.<\/p>\n
Supply conditions on board<\/h2>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/ship-supply-voltage-transient-envelope-1024x576.png\")
Ship supply voltage tolerance per IEC 60092-101: \u00b120 % transients for up to 1.5 s, then back inside the steady band.<\/figcaption><\/figure>\n A ship’s electrical network is much smaller and “softer” than a land grid. When a large motor such as a bow thruster, cargo pump or compressor starts, the voltage dips significantly. Generator load changes cause frequency swings. Load shedding and synchronising events add more transients.<\/p>\n
IEC 60092-101 defines the voltage and frequency variations that shipboard equipment must tolerate. In summary:<\/p>\n
- \n
- Voltage<\/strong>: +6% \/ \u221210% continuously, and \u00b120% transiently, recovering within 1.5 seconds.<\/li>\n
- Frequency<\/strong>: \u00b15% continuously, and \u00b110% transiently, recovering within 5 seconds.<\/li>\n<\/ul>\n
The chart shows the voltage envelope and an example transient from a large motor start. A marine UPS input must ride through these without switching to battery unnecessarily or tripping. The output must remain within the tolerance of the loads it supplies, which is generally much tighter.<\/p>\n
Many ships also use an unearthed (IT) distribution system. The UPS must be designed for IT input and, usually, provide an isolated IT output, with insulation monitoring on the output network. Input and output isolation transformers are standard in marine UPS designs for this reason.<\/p>\n
Environmental requirements<\/h2>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/marine-ups-environmental-test-requirements-1024x576.png\")
Typical environmental requirements for marine electrical equipment. Check the exact class rules for your vessel.<\/figcaption><\/figure>\n Marine electrical equipment is tested to environmental requirements set by IEC 60092-504 (and IEC 60945 for bridge and navigation equipment), and by the classification societies’ own type-approval rules. The table above summarises typical levels. Each class society publishes exact figures, which can differ.<\/p>\n
Vibration.<\/strong> Typical requirements are \u00b11 mm displacement from 2 to 13.2 Hz and 0.7 g acceleration from 13.2 to 100 Hz. Higher levels apply to equipment mounted on engines or in steering gear rooms. The design answers are stiffened frames, components rated for vibration, locked fasteners, secured cables and, where needed, anti-vibration mounts.<\/p>\n
Inclination.<\/strong> Equipment must operate at static inclinations of up to 22.5 degrees and under rolling of 22.5 degrees. Emergency equipment has stricter requirements in some rules. For the UPS, this mostly affects the battery: cells must be restrained, and flooded cells need to be suitable for the angle. VRLA batteries are the usual choice on board because they’re sealed and position-tolerant.<\/p>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/ship-roll-and-pitch-motion-ups.gif\")
Animation: roll and pitch the UPS and its battery rack must survive in service.<\/figcaption><\/figure>\n The animation shows roll and pitch motion over 30 seconds. Every component in the UPS, from relays and capacitors to battery terminals, spends its life moving like this.<\/p>\n
Damp heat and condensation.<\/strong> Relative humidity up to 95%, with temperature cycling that causes condensation. Conformal coating on PCBs, anti-condensation heaters and corrosion-resistant materials are standard.<\/p>\n
Temperature.<\/strong> Typically 0 to 45 \u00b0C for enclosed spaces, up to 55 \u00b0C in some machinery spaces. The UPS should deliver its rated output at the specified maximum, which may require derating or additional cooling.<\/p>\n
Salt mist.<\/strong> For equipment exposed to sea air, paint systems and hardware must resist salt corrosion.<\/p>\n
EMC.<\/strong> Emission and immunity requirements, especially strict near bridge equipment where interference with radios and navigation systems is a safety issue.<\/p>\n
Choosing the UPS rating<\/h2>\n
Marine UPS sizing follows the same principles as on land, with a few shipboard twists. Start with the load list for the essential consumers, using real consumption figures where available. Add the inrush of any equipment that starts after a blackout, because many consumers restart at the same moment when the UPS returns them to service. Allow margin for future equipment: bridge systems in particular tend to grow during a vessel’s life as navigation and communication equipment is upgraded.<\/p>\n
Then check the rating against the maximum ambient temperature of the space where the UPS will be installed. Electrical rooms close to machinery spaces often run warmer than designers expect, and a UPS that derates in those conditions may no longer cover its load.<\/p>\n
Class approval<\/h2>\n
Most commercial vessels and offshore units are built to the rules of a classification society: DNV, ABS, Bureau Veritas, Lloyd’s Register, RINA, T\u00fcrk Loydu, ClassNK, KR and others. Essential electrical equipment, including the UPS on most ships, requires class approval.<\/p>\n
There are two main routes:<\/p>\n
- \n
- Type approval.<\/strong> The product design is tested and certified once by the class society, and the certificate covers subsequent units of the same design. Faster per project, but the design is fixed.<\/li>\n
- Case-by-case (unit) approval.<\/strong> The specific unit or order is reviewed and tested. Necessary when the design is tailored for the project, or when no type approval exists for that class.<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/marine-ups-class-approval-process.gif\")
Animation: the class approval route for a marine UPS, from drawings to the onboard test.<\/figcaption><\/figure>\n The animation shows a typical route: drawing submission, design review and approval, type tests where needed, a FAT witnessed by the class surveyor, issue of the product certificate, and finally installation and onboard testing.<\/p>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/marine-ups-class-approval-documents-1024x576.png\")
The document package a classification surveyor typically expects for a marine UPS.<\/figcaption><\/figure>\n The surveyor will typically ask for the documents shown above: type approval certificate or approval route, single-line diagram with ratings and protection, general arrangement and mounting drawings, battery autonomy calculation, material certificates for cables and enclosures, test procedures, heat dissipation data and the maintenance manual.<\/p>\n
Start the class process early. Drawing review can take weeks, and the surveyor’s availability for the FAT must be coordinated.<\/p>\n
Battery selection for marine UPS<\/h2>\n
VRLA batteries are the most common choice for marine UPS systems: sealed, maintenance-light, position-tolerant and widely approved by class societies. NiCd is used where long life and high-temperature tolerance justify the cost, especially offshore. Lithium-ion is increasingly used on vessels with large battery systems, but for UPS applications it brings additional class requirements around fire safety, BMS integration and ventilation.<\/p>\n
Whatever the chemistry, the battery installation must consider:<\/p>\n
- \n
- Restraint<\/strong> against roll, pitch and vibration.<\/li>\n
- Ventilation<\/strong> for any gas emitted during charging.<\/li>\n
- Temperature<\/strong>: battery life falls sharply above 25 \u00b0C for lead-acid.<\/li>\n
- Access<\/strong> for inspection and replacement.<\/li>\n<\/ul>\n
AC UPS or DC system?<\/h2>\n
Not every essential consumer on board needs AC. Many ships have a 24 V DC emergency system, with its own chargers and batteries, feeding navigation lights, some alarm panels, GMDSS equipment and engine control circuits. Larger vessels and offshore units may also have 110 V or 220 V DC systems for switchgear control.<\/p>\n
The choice between an AC UPS and a DC system depends on the equipment. Bridge electronics and alarm systems designed for 230 V AC need a UPS. Equipment with native DC inputs can often be fed more simply and efficiently from a charger and battery, without an inverter in between. On many new builds, the best answer is a combination: a marine UPS for AC consumers and marine-grade chargers for the DC networks, both designed to the same environmental and class requirements.<\/p>\n
Maintenance at sea<\/h2>\n
On land, a failed UPS module can be replaced by a technician who arrives the same day. At sea, the crew is on its own until the next port. That changes how a marine UPS should be designed and supported:<\/p>\n
- \n
- Modular, accessible components<\/strong> that the crew can replace with basic tools.<\/li>\n
- Clear diagnostics<\/strong> on the local display, in plain language, with an event log.<\/li>\n
- An onboard spares kit<\/strong> covering fans, fuses, control boards and the most likely power components.<\/li>\n
- A maintenance bypass<\/strong> so the load stays powered while the UPS is worked on.<\/li>\n
- Documentation written for engineers on board<\/strong>, not only for factory technicians.<\/li>\n<\/ul>\n
Ask suppliers what their recommended onboard spares list contains, and what support they can provide remotely while the vessel is at sea.<\/p>\n
Specification checklist for a marine UPS<\/h2>\n
When writing a marine UPS specification, cover at least:<\/p>\n
- \n
- Classification society<\/strong> and notation, and the approval route required.<\/li>\n
- Input supply<\/strong>: voltage, frequency, phases, earthing system (IT or TN), tolerances per IEC 60092-101.<\/li>\n
- Bypass supply<\/strong>: source (usually the emergency switchboard) and its characteristics.<\/li>\n
- Output<\/strong>: voltage, phases, frequency, earthing, isolation, distribution board and breaker list.<\/li>\n
- Load list<\/strong>, with power, power factor and inrush.<\/li>\n
- Autonomy<\/strong>: required duration, at what load, and the rule it derives from.<\/li>\n
- Battery<\/strong>: chemistry, location, restraint, ventilation.<\/li>\n
- Environment<\/strong>: installation space, ambient temperature, vibration category, IP rating.<\/li>\n
- EMC<\/strong>: particularly if near the bridge.<\/li>\n
- Alarms and monitoring<\/strong>: interface to the ship’s alarm and monitoring system (Modbus, dry contacts).<\/li>\n
- Mechanical<\/strong>: dimensions, weight, cable entry, mounting and access for maintenance (often very constrained on board).<\/li>\n
- Documentation and testing<\/strong>: class documents, FAT with surveyor, onboard test.<\/li>\n<\/ol>\n
Common mistakes in marine UPS projects<\/h2>\n
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- Using a land UPS with a marine label.<\/strong> Without proper vibration design, coating and IT-system compatibility, it will struggle.<\/li>\n
- Ignoring the IT system.<\/strong> A UPS designed for TN networks can create earth paths or nuisance alarms on an IT ship network.<\/li>\n
- Underestimating space constraints.<\/strong> Marine electrical rooms are tight. Agree dimensions and access early.<\/li>\n
- Late class engagement.<\/strong> Approval delays can hold up delivery.<\/li>\n
- Battery restraint as an afterthought.<\/strong> It should be in the GA drawings from the start.<\/li>\n<\/ul>\n
Frequently asked questions<\/h2>\n
What makes a marine UPS different from a standard UPS?<\/h3>\n
Marine UPS systems are designed and tested for vibration, inclination, humidity and salt; tolerate shipboard supply transients per IEC 60092-101; usually support IT (unearthed) networks with isolated outputs; and are approved by a classification society.<\/p>\n
Which standards apply to marine UPS systems?<\/h3>\n
IEC 60092 series (especially 60092-101 for supply quality and 60092-504 for environmental testing), IEC 60945 for bridge equipment, IEC 62040 for UPS performance and safety, SOLAS for emergency and transitional power, and the rules of the relevant classification society.<\/p>\n
Does a marine UPS need class approval?<\/h3>\n
For essential services on classed vessels, usually yes, either through type approval of the product or case-by-case approval for the specific unit.<\/p>\n
What battery is used in marine UPS systems?<\/h3>\n
VRLA lead-acid is the most common because it is sealed and position-tolerant. NiCd is used where long life and high temperature tolerance are priorities. Lithium-ion is possible but brings additional class requirements.<\/p>\n
How long should a marine UPS battery last during a blackout?<\/h3>\n
It depends on the vessel type, applicable rules and loads. A common requirement for transitional power is 30 minutes, but the specification should state the exact autonomy and its basis.<\/p>\n
Marine UPS from EPC Energy<\/h2>\n
EPC Energy designs and builds IEC 60092 compliant marine power systems<\/a>, including industrial UPS, rectifiers and inverters with conformal coating, vibration-resistant construction and isolated outputs for IT networks. Our projects<\/a> include a 145 V DC, 700 A modular rectifier system for a Greek marine customer. Send your vessel’s requirements to epcas@epcas.com.tr<\/a> and we’ll prepare a tailor-made proposal ready for class approval.<\/p>\n
- Ignoring the IT system.<\/strong> A UPS designed for TN networks can create earth paths or nuisance alarms on an IT ship network.<\/li>\n
- Input supply<\/strong>: voltage, frequency, phases, earthing system (IT or TN), tolerances per IEC 60092-101.<\/li>\n
- Clear diagnostics<\/strong> on the local display, in plain language, with an event log.<\/li>\n
- Ventilation<\/strong> for any gas emitted during charging.<\/li>\n
- Case-by-case (unit) approval.<\/strong> The specific unit or order is reviewed and tested. Necessary when the design is tailored for the project, or when no type approval exists for that class.<\/li>\n<\/ul>\n
- Frequency<\/strong>: \u00b15% continuously, and \u00b110% transiently, recovering within 5 seconds.<\/li>\n<\/ul>\n
- Voltage<\/strong>: +6% \/ \u221210% continuously, and \u00b120% transiently, recovering within 1.5 seconds.<\/li>\n
- GMDSS radio<\/strong> and other communication systems.<\/li>\n
- The emergency switchboard<\/strong>, fed by the emergency generator, supplies the UPS bypass.<\/li>\n