IO module with override functionality

The IQ4 Hand/Off/Auto (HOA) modules make it possible to override plant when the controller/strategy is not achieving the results required for whatever reason. The modules can also be used to override plant to test if it is working correctly, for instance to check that boilers are fully operational before they are switched on after summer. Additionally, the modules can be used for commissioning, as they work straight out of the box with no need to address the module or connect it to an IQ4 controller.

HOA modules have been designed to offer ease of use. Trend has produced labels that clip over the modules to give users the ability to individually identify each switch so even a non-specialist can easily identify what needs to be overridden. Both module options utilise a two-state operation and require no tools to operate – pressing the knob takes the channel in or out of override, and twisting the knob sets the status/value of that channel. This means that a controls engineer can pre-set the value to be overridden so that when the overridden state is entered – which may be by a non-specialist – the module immediately goes to the value required with no additional adjustments.

Plant that is overridden and runs for 8h a day could use up to three times as much energy. Therefore, in order to prevent wastage, the HOA modules offer various methods of indicating status. When a channel is overridden the button flashes, providing a clear indication that there is something that needs investigating. Additionally, an alarm can be configured on each channel so, when the override button is pressed, notification arrives at a Trend 963 Supervisor or IQ VISION user interface. Finally, it is possible to provide indication of the status and value of the override on a 963 Supervisor or IQ VISION schematic, so that it is clear on the page if any plant is being overridden.

"Since it was introduced, the response to the IQ4 range has been phenomenal and it is now one of the most successful products in our history," says David Field, product manager at Trend. "I’m therefore delighted that we have been able to extend its reach with the introduction of the IQ4 HOA modules, which was the missing piece of the jigsaw for those countries where the ability to override plant is a common requirement in specification documents. Not only have we addressed this issue, we have done so in a highly innovative way that offers a whole host of features and benefits, thereby demonstrating Trend’s on-going commitment to developing solutions of the highest calibre."