Abstract: An electrode water boiler, preferably for the humidification of air, comprising a boiler having two or more electrodes connected to an electrical supply source between which current flows through the water in order to heat the water, the boiler also having a steam outlet, a valve for feeding water into the boiler, a valve for discharging water from the boiler, a sensor for sensing the current in one or more electrodes, and control means responsive to the sensed electrode current arranged to initiate the feed water valve when the electrode current is below a predetermined lower value and to initiate the water discharge valve after the electrode current has risen above a predetermined higher value and, following the initiation of the feed water valve and the electrode current subsequently rising to a predetermined intermediate value between the said lower and higher values, to effect the introduction, into the boiler, of a fixed measured quantity of feed water.

Abstract: A humidifier boiler has a plurality of electrodes supplied with electric current through circuitry which includes at least one solid state switch or relay such as inverse parallel thyristors or triacs arranged to switch at zero voltage so that, when the humidifier is called upon to vary the quantity of water vapor output from the boiler through an outlet pipe in response to a control signal from a humidity controller, the control signal causes the duration of the "on" and/or "off" periods of the, or each, solid state switch or relay to be varied in order to vary the power to the electrodes.

Abstract: An air condition monitor unit for monitoring the temperature and/or relative humidity of the ambient air. It comprises an air temperature sensor and a relative humidity sensor, and a plurality of memory means capable of retaining set values of respective thresholds comprising the maximum and minimum acceptable values of air temperature and relative humidity. Membrane switch means are connected to the plurality of memory means, operation of which switch means changes a set value retained in the plurality of memory means. Further membrane switch means are connected to the first switch means and the plurality of memory means, successive operation of which further switch means changes the memory means for the time being addressed by the first switch means from memory means to the next in a predetermined cycle.

Abstract: A multi-electrode boiler, especially for use as a humidifier, comprising water-changing means arranged to allow at least some of the water in the boiler to be changed, monitoring means arranged to monitor the electrical-current which flows through at least one of the electrodes of the boiler, control means responsive to the monitoring means to control the change of at least some of the water in the boiler to maintain the electrical-current in said at least one monitored electrode within a predetermined range of values, in which switching circuitry is provided to switch in and out electrodes of the boiler to vary the boiling rate.

Abstract: An electrode boiler includes a plurality of veritcal electrodes arranged in a container having an open steam outlet at its top whereby the boiler operates at substantially atmospheric pressure. The boiler is provided with electrically controlled feed and drain valves and a water level sensing electrode is provided in the container. Electronic solid state control circuitry includes means response to the water level sensed by water level sensing electrode for controlling operation of the feed valve to replace water boiled away thereby maintaining a constant water level in the boiler. The electronic control circuitry also includes current responsive means operative to open the drain valve when the electrode current reaches a predetermined maximum magnitude irrespective of the water level and to close the drain valve when the electrode current falls to a predetermined lower value.