Could someone let me know if there is a relay state within the PLC programming that will remember the state of the relay and on power fail store that state and when power returns go back to the memorised state?

I ask as I have a control loop that should the power fail the loop will drop and can only be reset by manual intervention, I would like the PLC to knw that the control loop failed and it powered down it wouldn't reset its self but rather wait until it was reset, on the same side if the unit was running normally and the power failed when the power comes back on it would reset its self and continue running as it was.

I hope that makes sense, the only other way I can do it is if I battery back the unit so on power fail it will stay in the correct state until power returns not really ideal, and adds extra cost, its a furnace controller should you wonder.

@ buttsy,

You can use pulse relay or latching relay, the type of function is depending on the type of input. If the input is a pulse like a pushbutton and the same is used for on / off then use the pulse relay. if you have a seperated on & Off the use the latching relay.

In all cases select at the properties the renentivity function on. the help function has the following description :

I personal have used this function often.

2nd  take care for safety, in my work it is totally forbidden to automaticly restart a furnace after power cut. this is always started manual after inspection by the engineer on duty. (A build up from fuel inside the burner during starting can give a nice explosion so always the furnace after a power cut need to be purced by air and inspected.)

P.s. i made a small demo , but for unknown reason today i can not upload ...... zip files .......