Priority Programming

[mcallahan]

I'm trying to setup an ATO (dual float switches from autotopoff) such that when the low switch is activated (low water in sump), the ATO kicks on as long as the high switch is off (the high switch is the fail safe).

However, the APEX looks at the float switches and sees that the high switch is off so it turns on the ATO pump.

How I can tell the apex to give priority to the low switch?

 

[WaterHazard]

So if I understand correctly, evaporation will take the water level all the way down to the low float switch before topping off at all, but then when it does top off, it tops off all the way to the high switch, then turns off? (Hysteresis built in between the two float switches - on the order of...inches?? Depends on mounting.)

Alternatively, I could interpret your intended setup as the low switch controlling top off alone. In that case, the ATO pump turns on when water drops below the low switch, then turns off when the water is back up to the low switch. The high switch would only be used if the low switch fails. (The only hysteresis is that which is inherent to the float switch - on the order of millimeters, maybe?)

Which of the two are you attempting?

 

[mcallahan]

I talked to Neptune and I had to switch around the code. Here is the fix (code-wise)

If Switch2 OPEN Then OFF
If Switch2 CLOSED Then ON
If Switch1 CLOSED Then ON
If Switch1 OPEN Then OFF

 

[swearint]

I don't think that code will do what you want. The Apex executes code top to bottom, so later code has priority (a couple exceptions). Since Switch1 is later and has both conditions (ON/OFF), Switch2 is irrelevant.

The general approach is to start with the default condition and then add exceptions.

Assuming:
Switch1: low sump, closed when down
Switch2: high sump, open when up

[ATO]
Fallback OFF
Set OFF
If Switch1 = CLOSED Then ON
If Switch2 = OPEN Then OFF

This will activate ATO when the sump is low (Switch1 = CLOSED). If Switch1 were to fail CLOSED, then Switch2 will act as a backup and turn ATO OFF (Switch2 = OPEN). Also keep in mind that the default state for switches is OPEN. In the case of ATO, if they were to be accidently disconnected, you want it to be OFF when OPEN.

Todd