Reverse cycle heating and air conditioning work just like the one in your home or apartment. You simply set a temperature and it will do its best to keep it there.
It works wonderfully, but it does recirculate the same air. Because of this, we like to open the hatches on nice days to completely change over the air in the boat.
One of the best features is it offers a steady air temperature in the boat. If you set it to 70F, it will get no colder than 68F and no warmer than 72F.
This may sound like the perfect way to control the temperature of your boat, but as always there are downsides. The system will cool a boat incredibly well, but it has limitations when it comes to warming the boat.
If the water temperature gets below 38F, the system stops heading the boat. This forces many people to fill their boats with space heaters when their only heat source stops producing.
The other problem with winter use comes from the fact that the unit recycles the same air over and over again. Moisture in the air will build and during the colder season, condensation will form on everything. This may only seem like a minor inconvenience, but I have seen boats where every surface in the boat is sweating and a portable dehumidifier can't keep up with the demand.
The convenient system is also a very complicated system with many places to fail. If anything stops working, the whole unit fails.
One of the weak points in the unit is the need for constant water supply. If air gets into the water line, the flow of water will be interrupted. Air locks are very frequent issues and can be tedious to manage if you are not properly equipped.
Reverse cycle heating and air condition units are very useful for making a boat a home, but they require constant supervision. It is not recommend that weekend boaters leave their units on all week (or longer) while they are away. If the unit runs dry and fails to shut itself down, the unit can become a fire hazard as it becomes dangerously hot.
While this may seem like a major downfall to this unit, I can assure you that with proper care and maintenance, these units will make your boat feel like your home!