Our solution revolves around our BS6173 certified interlock control, the EMX50. It has been fully certified to comply with the standard by Advantica, an independent NAMAS laboratory. The EMX50 requires an input signal from each fan. This may be from a standard differential pressure switch, in the most basic and most economic form. Alternatively an electronic version can be employed, as in our EPS10, depending upon the amount of differential air pressure available from the fan. Additionally, if preferred, an indirect method of air flow detection may be used, for example our motor current sensor, the ECS10. Whilst not our preferred method, our tests have shown that the ECS10 can be used reliably and in complete safety. All our sensors employ the internationally accepted ‘safe start’ procedure.
The choice of sensor can make a considerable difference to the cost of a system and depends on the specific application. If there is enough air pressure difference, at least 0.3 mbar (33 Pa), then a low cost mechanical diaphragm switch can be used. Where appropriate, we can measure for pressure drop and advise on the installation of a suitable set of sensors. In all cases it is important that the volumetric flow is sensed and not the static pressure.
In installations where gas burning equipment without flame failure operate, our gas leakage (or proving) GLT10 control must be fitted to comply with BS6173. This would operate after the fan interlock had passed start up, to check if for example an unprotected gas tap has been left open. In this instance, the gas valve would be held shut until the gas tap is closed and the installation re-tested.