Product Update
July 12, 2007
High Limit Thermostat
RE: EUR–5A, APS–3C, APS–4C, and SC–40C Snow Switches
These new products all feature calibrated high limit thermostats for heater and property protection. The original range was 40°F to 50°F (4°C to 10°C). Several customers suggested increasing the range to ensure proper melting when the heating cable was buried to its maximum depth. A new range of 40°F to 90°F (4°C to 32°C) was selected to ensure effective heating under worst case conditions.
The APS–3C, APS–4C and SC–40C add a DIP switch selected high limit thermostat operating mode for installations that make it impractical or impossible to thermally couple the temperature sensor to the deicing heaters. These systems include roof and gutter deicing and control upgrading when it may be cost prohibitive to break up the pavement and risk heater damage.
This new feature provides additional over temperature protection in other than pavement deicing applications. These include roof and gutter deicing, systems using only an aerial sensor such as the CIT–1 or GIT–1. When upgrading controls there is no need to break up the pavement to install the temperature sensor since this is expensive and risks damaging the deicing heater cable.
At temperatures above the thermostat setting, the new feature inhibits heater operation if the deicing heaters are operating due to a sensor failure or unusual weather conditions. If the system is being serviced when it is warm outside, heaters can be checked by operating the HEATER CYCLE switch. This causes the heaters to operate with a duty cycle of 30 seconds on and 2 minutes off.
The standard mode causes the heaters to cycle at the thermostat setting thus regulating the pavement temperature, which prevents overheating. This requires thermal coupling between the temperature sensing bulb and the deicing heaters. Checking heaters at higher temperatures requires a temporary change in controller wiring connections.
In systems using only aerial or gutter/downspout sensors, the temperature sensing bulb can be in ambient air. However, the limitations noted above still apply.
EUR–5A Snow Switches with the new high limit thermostat range of 40°F to 90°F (4°C to 32°C) are in stock. APS–3C, APS–4C and SC–40C Snow Switches with the new feature are available from stock to 6 weeks with seasonal inventories planned for mid August.