Marine HVAC Smart Thermostat Conversion Board

Upgrade an older marine air conditioner with modern 24VAC thermostat control

The Signal Dynamics Marine HVAC Smart Thermostat Conversion Board replaces aging or obsolete marine A/C control electronics with a simple, robust relay-based control system designed to operate from a standard 24VAC HVAC thermostat.

The board provides independent control of the compressor, seawater cooling pump or pump relay, blower fan, and reversing valve, making it suitable for converting many conventional self-contained marine air-conditioning systems regardless of the original control manufacturer.

Use virtually any compatible standard 24VAC thermostat, or pair the board with a Google Nest thermostat to transform an older marine A/C system into a modern connected HVAC system.

Control Board: $199.00

Add Smart Control to an Older Marine A/C

When used with a compatible Google Nest thermostat, your marine A/C can gain many of the features found in modern residential HVAC systems:

• Remote Wi-Fi control from your phone
• Remote cabin temperature monitoring
• Remote humidity monitoring
• Programmable temperature schedules
• Presence/location-based temperature automation
• HVAC operating and usage history
• HVAC notifications and alerts provided by the thermostat
• Google Home and compatible Amazon Alexa voice control
• Change temperature or operating mode without being on the boat

These features are provided by the thermostat and associated smart-home services, so available functions may vary by thermostat model, configuration and service.

Know What's Happening on Your Boat When You're Not There

For many boat owners, remote monitoring may be the biggest benefit of the entire conversion.

When you leave the A/C running to control cabin temperature and humidity, a compatible smart thermostat lets you check conditions aboard the boat from virtually anywhere with an Internet connection.

If cabin temperature or humidity begins climbing unexpectedly, you have an early indication that the air conditioner may not be operating normally. Instead of discovering a hot, humid cabin on your next visit, you have information that can help identify a problem sooner.

Simple, Heavy-Duty Control

The Signal Dynamics board separates the high-voltage equipment control from the thermostat and user interface.

Our board controls the equipment. Your thermostat provides the intelligence.

Heavy-duty electromechanical relays control the marine HVAC loads while the thermostat operates safely at conventional 24VAC control voltage.

The board provides outputs for:

Compressor • Seawater Pump/Pump Relay • Blower Fan • Reversing Valve

Thermostat connections use familiar HVAC terminals:

R • C • Y • G • O

This eliminates dependence on an aging proprietary thermostat, keypad or display and replaces it with widely available 24VAC thermostat technology.

Built-In High-Pressure Fault Protection and Lockout

Marine air conditioners depend on adequate seawater flow to remove heat. Loss of cooling water or other problems can cause the system's high-pressure safety switch to open.

Our board incorporates a dedicated high-pressure fault protection and lockout circuit.

If the existing high-pressure switch opens, the HVAC control relays are immediately disabled. Even if the pressure switch subsequently closes again, the system remains locked out.

The fault is indicated at the control board and requires a power cycle to reset.

This prevents an unattended air conditioner from simply restarting repeatedly after a high-pressure fault and gives the owner or technician a clear indication that a fault has occurred.

Designed as a Universal Marine HVAC Conversion

This product is a conversion controller, not simply a reproduction of one obsolete marine control board.

It can potentially replace the control functions of many conventional marine HVAC systems where the original controller operates:

120VAC compressor
120VAC blower
120VAC reversing valve
120VAC seawater pump or pump relay
High-pressure safety switch

This makes the board useful for upgrading many older Dometic, Cruisair, Marine Air Systems and other conventional self-contained marine HVAC installations, provided the equipment uses compatible loads and control functions.

Because marine A/C systems vary considerably, this is not necessarily a connector-for-connector replacement for the original controller. Installation requires identification of the existing compressor, blower, pump, reversing-valve, high-pressure-switch and power wiring.

Google Nest Recommended, But Not Required

A Google Nest thermostat is not required to operate the board.

Any suitable conventional 24VAC thermostat capable of providing the required Y, G and O control signals may be used.

We recommend a compatible Nest because it adds the remote monitoring, Wi-Fi control, scheduling, smart-home integration and other advanced features that make this conversion particularly useful aboard a boat.

Optional Remote-Mount Enclosure — $29.95

Relocating the controller may require extending the existing HVAC wiring, but the result can make future service dramatically easier.

With the controller mounted in an accessible location, you can readily see the power indicators, fault indication and wiring connections, and the board can be reached for troubleshooting or replacement without digging into the air-conditioning unit.

The enclosure is supplied undrilled, allowing the installer to determine the best locations for high-voltage, low-voltage and equipment wiring.

Enclosure: $29.95

Important: The enclosure itself is manufactured with an IP67 rating. Drilling or otherwise modifying the enclosure for wiring penetrations can affect that rating. Appropriate sealed cable glands or fittings should be used when maintaining a weather-resistant installation is required.

Why Convert Instead of Installing Another Proprietary Controller?

Many older marine air conditioners are mechanically capable of providing years of additional service while their proprietary electronics, displays and control boards become increasingly difficult or expensive to replace.

This conversion takes a different approach.

Instead of recreating the original proprietary electronics, it gives the air conditioner a straightforward relay-based interface to standard 24VAC HVAC controls.

The result is a system with:

Modern thermostat choices • readily available replacement thermostats • remote monitoring capability • Wi-Fi control with compatible thermostats • accessible troubleshooting • conventional HVAC wiring • heavy-duty relay load control • high-pressure fault lockout

And if the thermostat technology changes years from now, the basic marine HVAC equipment does not need to change with it. The control board simply provides the interface between the A/C equipment and conventional 24VAC thermostat commands.

Signal Dynamics Marine HVAC Smart Thermostat Conversion Board

Control Board: $199.00
Optional IP67-Rated Remote-Mount Enclosure: $29.95

Dealer and marine HVAC installer pricing available.

Thermostat sold separately. Google Nest, Google Home, Amazon Alexa and other referenced trademarks belong to their respective owners. Smart features depend on the thermostat selected, Internet connectivity, configuration and services available from the thermostat manufacturer.