Abstract: A moisture sensor with two heatable concentric moisture electrodes and a temperature sensor detecting the electrode temperature is set into the roadway surface to be monitored. The moisture electrodes are heated by a heating current circuit. The heating current circuit is connected to a computer which has a store for storing device-specific parameters, desired values and a processing program. During each measuring cycle the computer processes the temperatures of the moisture electrodes measured by the temperature sensor and a signal which is representative of the surface moisture. A control signal is produced therefrom which heats the moisture electrodes. An alarm or switching signal is produced when the moisture electrodes have reached a temperature characteristic of the formation of ice and a conductivity indicative of moisture is present between the moisture electrodes.

Abstract: The volume of water in circulation is controlled by means of a bell-type mixer (4) which has a stationary section disc (6) and a somewhat sickle-shaped rotary distributor bell (7). The section disc has at least three separate passage openings, the first of which is connected with the boiler feed pipe (KV), the second (12) with the heating pipe (HV) and the third with the boiler return pipe. The distributor bell (7) is acted upon externally by the heating return water pressure and internally housing a communication duct (19). The distributor bell shunts the boiler feed pipe over a limited area of rotation via the second passage opening (12) with the heating pipe and simultaneously frees a variable area of the opening into the second passage for the admixture of return water. In this way optimal regulation is achieved with little structural, maintenance or operational outlay.

Abstract: A method of controlling the ratio between the water flow rates in the primary and secondary circuits of hot water heating systems, particularly of low-temperature hot water heating systems, by mixing flow water with return water passing through an adjustable bypass by means of a multi-way mixing device. To make maximum use of the rangeability of said mixing device and to optimize overall heating system control, the bypass water flow rate is controlled as a function of the mixing device position and the bypass is substantially closed when the way from the primary circuit flow piping to the secondary circuit flow piping is fully opened and/or an appropriate signal is given by the heating system controller.