ML 1400 RSLogix 500 code problem

Hello

I have a 3 blower logic. Two modes. Mode is changes by pressing a button on a HMI screen, program is on ML 1400.


Mode ONE: One blower at a time. 3 blowers total. Each blower goes on and off for a set period of time. Next blower comes second hour, and third blower comes on third hour, fourth hour first blower comes back on again. If running blower fails(contactor), next blower picks up until first(or which ever turn) blower is fixed.

Mode TWO: Just like mode one except that two blowers run 2 at a time such as AB - BC- AC. If any of running blowers fail, third spare blower comes on.

The problem: In a situation where I am in a single blower mode, if a single running blower fails, instead of another single blower turning on, I have two blowers turning on. As soon as failed blowers(contactor) is fixed, everything goes back to a single blower mode. Somewhere I am crossing fail over logic between single mode and double mode but do not see where.

I hope my confusing description makes sense. I also have an oxygen sensor that dictates when blowers turn but please ignore that.

Any suggestions would be greatly appreciated!

Looks like you could add some conditions to your branches for one blower at a time, where your fault bits are at, so that if, for example, Blower_A is faulted and Blower_B is running, nothing happens etc.

In rungs 2, 3, and 4 there are branch rungs, in the single mode logic, that turn on the blower if another is faulted.

If blower A is faulted then rung 3 will turn on blower B through B3:21/6 and B3:4/14. Also, rung 4 will turn on blower C through B3:21/6 and B3:4/14. The same thing happens with the other blowers in some combination of these three rungs. You need to make the selection of which backup blower starts in a fault condition exclusive. XOR (one or the other but not both).

Hello
I am still missing something.
The issue is that if one of the blowers is in hand/HOA, program should ignore it. So in a single mode or two blower mode, if any of blowers are in hand, they should be ignored. I can not seem to figure out a way to accomplish that.
Please help!
ML1400