MarinAire

The recommended thru-hull fitting size depends on the total BTU capacity of all marine air conditioners connected to the system. Use the guide below to ensure proper water flow. Please note that this is just a suggestion based off the average installation. Some installations may require a bigger thru-hull. Always consult with a professional first:

• Up to 9,000 BTU → ½" thru-hull
  
• Up to 18,000 BTU → ¾" thru-hull
  
• Up to 24,000 BTU → 1" thru-hull
  
• Up to 36,000 BTU → 1¼" thru-hull
  
• Up to 48,000 BTU → 1½" thru-hull
  

When multiple units share a pump, always size the thru-hull based on the combined BTU total, not individual units. Choosing the correct size ensures proper cooling performance, reliable operation, and longer system life.

A relay panel is required when two or more air conditioning units are connected to a single pump. It allows each unit to independently signal the pump to turn on when cooling is needed.

If you have only one air conditioner and one dedicated pump, a relay panel is not necessary.

A flow switch is not required, but it is optional as an extra layer of protection against water-flow loss. While our units include built-in high-pressure safety sensors, those sensors may not always shut the system down immediately for example in heating mode, where pressure conditions can differ.

A flow switch directly monitors water movement and will stop the system if water flow is lost, helping protect the pump, heat exchanger, and overall system from damage. It’s a simple, proactive safeguard—especially useful in heating mode or in applications where water flow could be restricted.

The Premium Marine Air Conditioner Installation Kits include most of the plumbing fittings required for standard installations, but they do not include any electrical components, venting, ducting, water pumps, or hose. You can view the exact components included on each kit’s product page.

What you’ll need depends on your specific installation and the pump you are using. We recommend confirming your pump’s inlet and outlet sizes and planning your plumbing layout in advance. While the kit is designed to cover most installations, some customers may have one or two leftover fittings, and others may need to add a small number of additional fittings depending on their setup.