WARM Enough to Swim- Jump Right In
ICING BELOW 42-47°F (5-7°C)** is a Heat Pump Issue
For most humans, if it is warm enough to swim, the average daily air temperature will be above 60°F (15°C).
That usually means at night it will go down to 55°F (13°C) and mid-day it will hit 65°F (18°C) or higher.
Still pretty chilly but YOUR HEAT SIPHON WILL RUN 24/7 if needed to keep the water as warm as you want.
It is when the air is BELOW 42°F that heat pumps have an icing issue.
That means an average daily air temperature around 50°F or lower - POLAR BEAR SWIM CLUB TIME.
In order to take heat out of the air, the refrigerant inside HEAT SIPHON's evaporator tubes must be about 10°F-15°F COLDER THAN THE AIR so at about 42°F (5°C) to 47°F (8°C) air temperature the tube is approaching 32°F (FREEZING-0°C) and any moisture in the air will begin to FREEZE on the coil and ice it up.
Icing clogs the small fins, insulates the tubes and stops air flow all of which severely reduce the efficiency. If a lot of ice is allowed to build up it will take a long time to thaw out and melt.
**Why The Range in Icing Temperatures?
The more heat you remove from the air the larger the temperature difference required since the fan size and airflow stay about the same (for noise and other technical design reasons). This means that smaller heat pumps with relatively larger air flow per btu will be able to operate at lower air temperatures before icing begins. In addition, the lower the relative humidity, the longer a given heat pump can run until significant icing occurs.
Heat Siphon is designed to shut off when the air can cause icing and automatically restart when it is safe again as the air temperature goes over 50°F. In swimmable weather this off period is not more than a few hours in the spring or fall and should have no significant effect on your water temperature.
**Actual low air temperature icing limit between 45°F-47°F also depends on the model and the relative humidity