| 摘要 |
The circuit is provided in particular for a multi-stage safeguard against freezing of the heat-transfer medium (water) in freezing weather, it being intended that even a failure of one or the other component does not threaten the safety. In a typical embodiment, the circuit has a thermostatic switch (4) which in the event of a risk of freezing switches the fan (10) of an outside-air heat exchanger off via the control contactor (15). A further thermostatic switch (5) additionally switches heat from the heating device into the heat-transfer medium circuit by means of a solenoid valve (6) when the temperature falls below a limit temperature. A regulator (9) with a temperature sensor (7) behind the outside-air heat exchanger likewise additionally conducts, according to demand, heat into the heat-transfer medium circuit via a solenoid valve (8). The heat circuit pump (1) is monitored by a thermal excess-current release device (2). The operating states are indicated by signal devices (17-20). In spite of these comprehensive functions, the circuit is simple and manages with a few inexpensive circuit elements so that its costs are low in relation to the costs as a result of operational faults and damage which would otherwise be expected in the course of time. <IMAGE> |
