Marine Refrigeration: What Type of Refrigeration is Best for Your Boat?

A Guide to Marine Refrigeration Systems 

Is your marine fridge on the fritz? Or are you looking to maximize your marine refrigeration system with an upgrade? 

Modern boat fridges are no longer considered to be simply a place to store your fresh catch and a few cold drinks. Instead, you can enjoy the luxuries of ‘boating life’ with a marine fridge that has the extra space to keep your lunch cool and your ice cream frozen. 

The following guide to marine refrigeration systems will help you identify which type of refrigeration is best for your boat, depending on your available power options, space considerations and the boating lifestyle you live.

What is Marine Refrigeration?

Marine refrigeration is another way to describe your vessel’s fridge and freezer systems. Whether used primarily to store freshly caught seafood or as food storage for longer voyages, marine fridges work the same way as the refrigerator in your kitchen.

• Refrigerant gas is compressed to a liquid and expands back to gas on the cold plate or holding plate. 
• Heat is absorbed and dissipates outside the insulated box when the gas expands. With a boat fridge, this heat may transfer directly to the air, a seawater heat exchanger or both depending on your chosen system. 
• The expanded gas then returns through the compressor, and the cycle continues. 

Most marine fridges have the following components:

• Thermostat
• Refrigerant
• Condenser
• Compressor
• Expansion Valve
• Evaporator Plate

Types of Marine Refrigeration

Marine fridges can be categorized into three main types: drop-in units, cold plates and holding plate systems. Each type of system has its pros and cons. The right system for your boat will depend on how your system is powered, what you need marine refrigeration for and where you store your boat.

1. Drop-in Units or Self-contained Units – These all-in-one units are easy to install and have top-opening and front-opening options. Typically, the components are integrated into the case, and the compressor sits below the insulated compartment on a metal tray. 

Before considering if this type of marine fridge is right for you, evaluate your boat’s battery size and recharge rate. These units draw relatively little current, but the total amperage throughout the day may be greater than your boat’s electrical system can handle.

1. Cold Plates or Thermoelectric Units – These electric fridges are quiet, long-lasting and simple to install. Thermoelectric refrigeration systems do not use refrigerant. Like self-contained units, they are also powered with 12v DC. However, they operate using the Peltier effect, which only requires powering for short periods and has no moving parts outside the fan. 

These systems are less efficient than other refrigeration solutions as they require more amps to cool the chamber, making them ineffective for hot weather locations. 

Replacing and or upgrading the insulation around your box is recommended before installation.

1. Holding Plate Systems – If you want ice and lots of it, this is the marine refrigerator for you. These engine-driven systems are robust, and with adequate insulation, the compressor only needs to be operated for short periods once or twice daily. Usually professionally installed, the compressors are mounted on the engine to minimize vibration and extend life. Sometimes these systems offer two refrigerant channels with options to run DC or AC power sources when docked.

These units are more expensive, and installation is more complicated. Also, they contain more componentry that may require a larger skill level to repair.

For more insight into the features of each system, see this independent review of some of the marine refrigeration systems on the market. 

Tip: Investing in marine-grade materials such as holding plates made with cupronickel, powder-coated stainless steel or that are electropolished will extend your marine fridge’s life. 

Which Marine Fridge is Right for Your Boat?

Now we have reviewed how marine fridges work and the different systems available, how do you know which is the right one for your boat? To decide, you need to consider:

• Your vessel’s power source
• Whether you require air or water cooling
• How much space do you have?

What Power Source Does Your Boat Use?

When looking for a replacement boat fridge, knowing your power source is a useful place to start. There are three options for powering your marine refrigeration system:

1. AC (alternating current) Systems – These are powered from your connection to the shore, usually 110V, or through an onboard generator. Marine fridges using 110v are dependable, relatively inexpensive and easy to install.
2. DC (direct current) Systems – These operate from an onboard battery, typically 12V or 24V. Boat batteries are charged by running your engine or generator while on the water or plugging your battery charger in while on shore. Wind generators and solar panels are alternative energy sources that can be used to recharge batteries.
3. Engine-driven Systems – These are powered by an engine belt that drives the compressor when the engine is running.

Note: Dual-voltage AC/DC refrigeration systems are also available. With these systems, once you unplug from shore (AC), your fridge will automatically switch to DC.

Is Air Cooled or Water Cooled Best?

Refrigeration systems don’t create cold, they transfer heat. In this process, the compressor and condenser get hot and require cooling which can be done using air or water.

If you are boating in cool or temperate climates, an air-cooled compressor may be all you need. When the ambient temperature (outside your fridge) increases, air-cooled systems become less effective, running almost constantly and using up your battery power.

Water cooling systems are over 25% more effective than air cooling, making them a better choice in warmer locations. If you move between different climates, consider using a combination air-cooled/water-cooled compressor.

How much space do you have?

How much space do you have to install a new marine fridge on your boat?

• Replacing an existing boat fridge is easiest as you can look for something with the same dimensions.
• If you currently have an ice box on board, you can use that space or convert it.
• If there is no space for a built-in marine fridge, there are portable options that can sit on a countertop and be used only when on board.

South Island Mechanical for All Your Marine Refrigeration Needs

Whatever marine refrigeration system you choose, rest assured South Island Mechanical is here to ensure smooth installation and long life through routine maintenance and service. 

Our team of red-seal certified technicians can come to you wherever you are moored. We also offer marine HVAC installation and servicing for all your marine needs.

Located in Victoria, BC, and serving Vancouver Island and the Gulf Islands, South Island Mechanical is your one-stop shop for all your heating, ventilation, air conditioning and refrigeration needs. Contact us today for more information about our marine, residential or commercial services.