Using PAC to switch on relays

I need to find a way of switching a master fan on, which is connected to a c-bus relay channel, whenever another fan is operated. For example, if the master fan is connected to relay channel 1, and there are 3 other fans are connected to relay channels 2,3,4, then I need some way of sensing that any one of channels 2,3, or 4 are active, and automatically switching on channel 1. Similarly, I also need to switch off channel 1 when none of the other relay channels are activated. Can anybody help?

I seem to recall that there is a pascal statement which is included with the PAC, which recognises changes in state, and can thus be used to initiate a programmed response. For example, if the fan on relay channel 3 is operated, and thus channel 3 is switched on, then switch on relay channel 1, and when channel 3 ceases to be active, switch off channel 1. Does this sound logical, and if so, can anybody advise what the pascal code should be?

Alternatively, is there a simpler way of doing it, without having to write custom code?

 

You don't need to use a PAC or any code for this.

You can use the logic groups in the relay channel. There are four groups avaible to use under the logic tab of the relay, which thus gives you Five group addresses to control the one relay channel.
All you need to do is add the groupd addresses for channels 2,3,4 as an "or" function under channel 1.
This will mean that when ever the address for Fan 1 or 2 or 3 is ON, the master fan channel will turn ON and then when ALL fans are OFF then master fan channel will turn off.