Mike, thanks for your detailed post here, we are on a one week break here, after which I will reply in detail. As well as put a push to get you a programmable case controller. The hardware is just waiting for a developer of which I am short on these days.
Updated:
The line 30 is rather complex, I would make a mode variable and flip that true or false based on the conditions. Then use that to open & close valves, etc.Keeping it simple to one action per line rather than bunching them up into a single line like this. Its much easier to debug and much easier to follow the logic when you find yourself re-debugging this program on site in a year or two from now. Also note the deadband in my line 31, in your case if the DAT is near the setpoint you could get valves chattering without some deadband.
30 IF NOT DEFROST AND DAT > CASE_SP THEN START VARX
31 IF DEFROST OR DAT < CASE_SP - 1 THEN STOP VARX
32 IF VARX THEN EEPR = PID1 ELSE EEPR = 0
33 IF VARX THEN STOP EEPR
Graphics: Here’s a post I did a while back about how to put graphics into the displays. THere are other posts as well, search for ‘graphics’.
Schedules: It would be a simple work around to add a second schedule and incorporate 4 more events into your defrost schedule. Another option would be to add some timers, more like my program at the firsts posts. Set the intervals and you have fine grained control over the number of defrosts, hundreds per day if you like.
