Load status, by way of “current proving”, is an important criteria in BMS / HVAC applications to determine if loads such as fans, pumps, motors and heaters etc are operating once called for. Operation can be determined in one of two ways, either physically by way of an air movement, flow or heat, achieving this can be invasive and expensive with long cable runs back to a control panel. Far simpler to monitor a “current draw” within the control panel. Just because a load has been called for doesn’t mean it has happened, the load being called for could have failed or there could be a wiring fault. Invariably the “current proving” requires to be as simple as “is there a current draw, or isn’t there”, rather than a precise Amperage measurement.

Our inline current proving switch type YRI-41 available in five ranges from 1mA to 10 Amps FLC has been very popular in achieving the above, complemented by our “CT” style switches FOX.CS-020 and FOX.CS-200 for larger loads up to 20 Amps and 200 Amps respectively. 

However, whilst many BMS / HVAC loads are single-phase, some are not.  Correct monitoring of a three-phase load really requires all three phases to be monitored.  Achieving this would necessitate three single-phase units to be used, often cost-prohibitive and therefore resulting in a pragmatic approach of monitoring just one phase, but this does not give 100% correct status monitoring.

Our new YWRI-43 self powered In-Line Three Phase Current Proving Switch overcomes the above dilemma for FLC loads up to 10 Amps per phase, thus achieving full three-phase current proving for small three-phase balanced loads.  Each phase passes in series through the YWRI-43 and should current be lost or falls on any of the phases below the adjustable setpoint 250mA - 10 Amps the output C/O relay will de-energise.  

View the product range here.