ES - Marine Isolation Transformers

Isolation transformers for all marine environments.    

Marine isolation transformers are the only way to completely eliminate the risk of galvanic corrosion between the ships hull and other metal objects (other ships, pilings etc.) and ensure safety for swimmers.

The problem is caused by an earth loop forming and current flowing through the earth wire on the shore supply. The problems occur in all boats, although steel & aluminium boats are particularly susceptible. It is important to get advice from a suitably qualified marine surveyor or corrosion specialist before installing shorepower.

The isolation transformer eliminates any electrical continuity between shorepower and the ship. The shorepower is fed to the primary side of the transformer and the ship is connected to the output side (secondary).

Our standard transformer range covers 10, 16, 32, 50, 63 & 100 amp single phase shore capacities at 230v. For larger yachts, and commercial ships that want to ‘cold iron’ in port we offer custom units in single phase, three phase to three phase & three phase to single phase.

Commonly these are supplied to match shore cord capacities. So at 400 volts:

  • 45 kVA for a 63 amp 3 phase supply
  • 90 kVA for a 125 amp 3 phase supply
  • 180 kVA for a 250 3 phase amp supply

In addition to these fixed ratio transformers (normally 1:1) we supply voltage converting transformers. Smaller transformers are offered that will boost 115 volts to 230 volts or visa versa. These are available as manually configured or auto changing.

Most of the Energy Solutions range of marine isolation transformers have dual input voltages (120 and 240 volt). This is of particular use on long-distance cruising boats that may want to use 110 volt supplies in Caribbean, USA Etc.

Marine Isolation Transformers

For more information or to request a quote please contact us.



ABYC Compliant. A metallic shield is fitted between the primary and secondary windings and is electrically isolated from all other portions of the transformer. It is fault tested at 4000 volts for 1 minute. This shield is wired via an insulated lead to the transformer chassis. The shield and its connection are able to carry the full load current of both the primary and secondary windings.

UL Compliant 

Although the transformer does not carry a full UL listing they are built to conform to the necessary standards.

Lloyds Compliant 

The transformer is built to conform to the Lloyds Resister standards.

Marine Iso-Boost Transformers

The Energy Solutions Iso-Boost transformer provides a cost effective and reliable solution to isolate and manage a shore line. It provides all of the features of a normal isolation transformer, as well as providing a boost function to manage the volt drop on heavily loaded shore lines, or to cope with a 208V (phase to phase) supply. On startup, the isolation transformer automatically soft starts the transformer to prevent inrush from tripping the supply breaker. If the voltage is in range, it operates in 1:1 mode, so that the output voltage matches the input voltage. If the supply voltage drops below 215V, it automatically switches into boost mode, effectively raising the output voltage by around 10%. If the supply voltage recovers, the IsoBoost automatically switches back to 1:1 operation.

Our Marine Iso-Boost Transformers are an exact fit and form replacement for Charles Industries™ Isoboost transformers.


AC System Controller and IsoBoost Combiner

The AC System Controller and IsoBoost Combiner allow enhanced system functionality when more than one IsoBoost is required.

The AC System Controller provides a simple, automatic AC source selection and suits a wide variety of power supply configurations.

The IsoBoost Combiner allows two shore cords to be combined from the Energy Solutions IsoBoost/Marine Isolation Transformer range, allowing loads to be applied evenly across both cords.


For full details on the entire Marine IsoBoost Transformer range download the brochure;

Marine Iso-Boost Transformers


Marine Isolation Transformers Case Study

Fleming Yachts - Collaboration brings results

When you work closely alongside customers the benefits for both can be substantial. The development of the Energy Solutions’ IsoBoost range was a significant move for Energy Solutions who already had a well-established place in the marine isolation transformer market, designing and building transformers that worked for client’s specific needs.

ES Case Study - Flemings IsoBoost



Marine Iso Transformers

We offer a range of single and three phase isolation transformers of all capacities. Our standard range of isolation transformers offer the following features:

Complete range – 10,16,32, 50, 63 & 100amp single phase shore capacities at 230V

Dedicated output - our larger transformers come configured to provide either 120 – 0- 120V 4 wire  USA output or 0-230V 3 wire Euro output.

ABYC compliant – all transformers are built with a screen between primary and secondary windings capable of carrying twice the full load current of the transformer. This exceeds the requirements of ABYC E-8.20.1 by 100%.

Lloyds compliant – all transformers are built to comply with the requirements of the LRS.

Resin coated – all transformers are protected with a UL approved vacuum impregnated polyester varnish.


For the full information download the datasheet

Marine Isolation Transformers

ES DockPower - Dual shore cord isolation transformer

The demand for shore power means that larger motor yachts often have dual 32A or even dual 63A shore power sockets. This requires the boat’s internal AC circuitry to be split into two entirely separate groups - normally air conditioning and domestic. But if one circuit tries to pull more than the maximum rating there’s nothing to be done to stop the dockside load circuit breaker tripping, even if the other cord has plenty of capacity left.


The DockPower isolation transformer range from Energy Solutions solves this problem by allowing boat owners to bring two shorepower leads onto a boat and combine them into a single supply to feed all the boat’s loads. The two cords are loaded equally which ensures you get the maximum amount of power on board. Suitable for a range of vessels from large sailing boats to mid-sized motor yachts, DockPower provides an important solution to their specific power requirements.


For the full information download the datasheet

DockPower - Dual shore cord isolation transformer


Options and Configurations

Standard Insulation

The standard transformer is protected by being immersed in a resin bath. This is done under a vacuum to ensure total coverage. This protects the transformer from air borne moisture and normal corrosion.


Double Dipped Insulation Option

In addition to the standard insulation the transformer receives a second water proof coating. The take off ends of the coil windings are also sealed to prevent water ingress. This additional insulation is suited to transformers that maybe subjected to water contact.


Soft Start

When first connected to the shore supply the hull isolation transformer will draw a very high initial current. This can often trip the shore supply circuit breaker. Energy Solutions are able to install a soft start on the input of the transformer to greatly reduce the inrush current.


Input Configuration

Most of the smaller, single phase, transformer range is offered with a dual wound primary. This allows the transformer to be connected to both 110 volt and 230 volt shore power supplies.

Most three phase transformers are supplied as a Delta input (no neutral connected).



Output Configuration

The output configuration of the transformer can be requested as:

  • 230 volt for European systems
  • 240/120 volt for American systems
  • 208 volts three phase for USA spec boats
  • 400 volts three phase for Europeans spec boats



Purchasing your ES Marine Isolation Transformer

To discuss your shore power requirements please contact us 

01634 290772




Dockside Transformers

We can also design and build bespoke dockside isolation transformers for use in marinas and boatyards enabling ships with no isolation transformer on board to safely ‘cold iron’.

Available sizes from 15kVA to 250kVA with special options such as IP54, multi-tapped outputs, integral protection and control gear.




Custom Transformers

Most of the Energy Solutions range of marine isolation transformers have dual input voltages (120 and 240 volt). This is of particular use on long distance cruising boats that may want to use 110 volt supplies in Caribbean, USA Etc.

They also help to protect swimmers against the risk of electrocution. This is a particular risk on fresh water moorings.

Safety for swimmers

Energy Solutions are able to supply specific transformers for individual applications. These may be single or three phase. We have supplied transformers up to 250 kVA.



Victron Isolation Transformers & Galvanic Isolators

2000VA / 3600VA / 7000VA

For smaller applications we can also provide the Victron range of isolation transformers. This range is indispensable in professional marine energy systems. It prevents electrolytic corrosion and above all serves as a device to guarantee a safe electric system. Toroidal wound technology for quietness and high efficiency. Soft start circuitry will ensure that the shore circuit breaker will not trip when plugged in.



Galvanic Isolators are a low cost solution to prevent galvanic corrosion that occurs on boats with electric power feeds.