One of the biggest misconceptions about self regulating heat cables is whether or not they turn themselves off in warm temperature. The simple answer is they do not turn themselves off when temps rise above freezing. To turn heat cables on and off, a switch is required. The switch can be as simple as a literal switch. Some customers use a literal light switch (sometimes with a pilot light or lighted switch feature) to control their systems. When they want the heat cables to warm and melt snow and ice, they turn the switch on. When they want the system off, they turn the switch off. Other property owners use simple or sophisticated thermostat controllers to turn the heat cables on and off.
Why the confusion then? Self regulating heat cables do regulate the amount of power used based on the temperature of the cable itself. The colder the cable is the more power required. Power usage goes up also when the cable is wet as in the case of a cable lying in a gutter bottom. This power usage is adjusted along the entire length of cable. However, even in summer, if power is fed to the heat cable it will be consuming some amount and not be 'off'.
Which thermostat option is right for you?
A simple switch is the most economical way to go. There is a drawback. Forget to turn the system on and ice dams may form which will be difficult for the ice dam prevention system to overcome. Every year customers forget to turn their roof and gutter ice melt systems on and then complain about their systems not working properly. Forget to turn the system off when it is not need and operating costs skyrocket. For the customer who is home and knows they will monitor the functioning of their ice dam system, it is a great choice.
Moisture and Temperature Sensors. Another popular option is a thermostat with moisture sensing capabilities. The concept is that the system will not turn on unless it has snowed and temperatures are below freezing. These controllers are a great choice for customers who are able to monitor their roof ice melting systems periodically. This is required because the controllers turn the system off after the snow has stopped and may not retrigger when snowmelt reaches the gutter or eave edge. These systems come with a manual override feature to account for this. These systems are not a set it and forget it option. Under some conditions, ice dams can and do form if these controllers do not pick up the melted run off. The moisture sensors also require annual maintenance to insure proper functioning.
Ambient Sensing Controllers. A reliable temperature controller for your heat cable ice melt system is an ambient sensing controller. These controllers turn the heat cables on at a predetermined set point - usually @ 34 degrees. Another option is a secondary shut off point at @ 10 degrees. The concept is that the controller will turn on the ice dam prevention system when temps are between 10 and 34 degrees - the temperature at which ice dams form and snow falls. On the Bylin AS Digital Controller, these settings are completely adjustable. The drawback on this controller is that it is on during those temps even when no snow is present on the roof. The AS Digital Controller has a manual override switch to account for this. This controller is priced for the residential market making it available even for smaller roof ice melt systems.