mitchell_t
Member
Hi guys,
I know that "this has been covered lots of times in the past and I should just search it"... But I am struggling to find the correct method to rectify this problem...
So, I have an existing program from a Micrologix1500 that is running on a Boiler, I have ZERO PLC training and / or experience... Now, I am quite proud of the fact that I have managed to go from a program that had absolutely NO descriptions on any of the inputs/outputs/bits/Integers etc and have managed to label 95% of it, so I have a vague idea of what it is doing...
Ok, onto the issue at hand:
I have a boiler with 2 Feed water pumps running into the boiler, which used to run on a duty/standby cycle of 7 days (However the day counter would only ever tick over if the pump was running at the given time), the pump on duty would come on when it seen a low water input, then go off when said input went away, standby pump would come on if extra low water input was made. Every time the PLC was turned on, all counters reset to 0 and pump 1 would be duty pump, every time extra low water occurred counters would reset to 0 and pump 1 would be duty.
Anyway, Client has had us change the way the feed water system works, rather than pump coming on and off at low water, we now have 1 pump running at all times with a modulation valve allowing water into boiler as required and returning to feed tank when not required. So I have need of one pump running at all times (easy, just removed the requirement of low water needing an input, so pump runs at all times). What I am having issues with is the cycling, I have changed it so that pumps alternate every 12 hours (at clients request) But what I would like is for the PLC to remember what its current duty pump is, I don't want pump 1 to be duty every single time I power up the PLC, I don't want it to reset back to pump 1 after every time the Extra low water is triggered.
Your help is greatly anticipated & appreciated,
Tim
I know that "this has been covered lots of times in the past and I should just search it"... But I am struggling to find the correct method to rectify this problem...
So, I have an existing program from a Micrologix1500 that is running on a Boiler, I have ZERO PLC training and / or experience... Now, I am quite proud of the fact that I have managed to go from a program that had absolutely NO descriptions on any of the inputs/outputs/bits/Integers etc and have managed to label 95% of it, so I have a vague idea of what it is doing...
Ok, onto the issue at hand:
I have a boiler with 2 Feed water pumps running into the boiler, which used to run on a duty/standby cycle of 7 days (However the day counter would only ever tick over if the pump was running at the given time), the pump on duty would come on when it seen a low water input, then go off when said input went away, standby pump would come on if extra low water input was made. Every time the PLC was turned on, all counters reset to 0 and pump 1 would be duty pump, every time extra low water occurred counters would reset to 0 and pump 1 would be duty.
Anyway, Client has had us change the way the feed water system works, rather than pump coming on and off at low water, we now have 1 pump running at all times with a modulation valve allowing water into boiler as required and returning to feed tank when not required. So I have need of one pump running at all times (easy, just removed the requirement of low water needing an input, so pump runs at all times). What I am having issues with is the cycling, I have changed it so that pumps alternate every 12 hours (at clients request) But what I would like is for the PLC to remember what its current duty pump is, I don't want pump 1 to be duty every single time I power up the PLC, I don't want it to reset back to pump 1 after every time the Extra low water is triggered.
Your help is greatly anticipated & appreciated,
Tim
