Alternating Pumps

[Lancie1]

Per your PM, here is some alternating logic that works, and is optimized to use only normal relays, no latches or one-shots. (The one-shot function is wrapped up into the alternator logic).

One-Shot Relay needs 1 NO contact.
P1/P2 Toggle Relay needs 2 NO, and 2 NC contacts.
Stop Float Switch needs 1 NO, 4 NC contacts
Lead Float Switch needs 2 NO, no NC contacts
Lag Float Switch needs 2 NO, no NC contacts

You can probably use your 10 on-hand DPDT ice cube relays for all. You could use 2 relays controlled by the Stop Float to increase the number of NC Stop Float contacts to 4.

If the Lead and Lag Float Switches only have 1 contact, use a DPDT realy for each of those also.

This relay-oriented version has the advantage that the Lag Float does not interfere with the altenator function.

 

[dronai]

Wiring in old style relay logic is a daunting task !!! Looking at the logic also looks strange in some places.

First rung, the stop float closes, goes through a set of NC contacts, and out to the coil. Upon stop float closing, that NC contact opens disconnecting the coil immediately ? The holding contact can't keep it open, so why is it there ?

Even the toggle gets disconnected by the Stop NC contact opening.

 

[Lancie1]

Upon stop float closing, that NC contact opens disconnecting the coil immediately ? The holding contact can't keep it open, so why is it there ?

The circuit works as shown in the attached sequence of 6 pictures.

Step 1: Pump 1 has been started by the Lead Float.

Step 2: Lead Float is OFF, Stop Float has triggered, sealing in the One-Shot relay B3:0/0. B3:0/0 must stay ON to maintain power after the Stop Float goes Off again.

Step 3: Stop Float goes back Off, causing the NC Stop Float contact on the 3rd rung branch to turn on the P1/P2 Toggle. The P1/P2 Toggle goes ON and seals itself ON. Now the Alternator logic is ready to start Pump 2 the next time the Lead Float goes ON.

Step 4: Lead Float goes on again, starting Pump 2.

Step 5: Lead Float goes OFF, then the Stop Float goes ON, stopping Pump 2. The P1/P2 Toggle B3:0/1 is still ON at this point.

Step 6: The Stop Float goes Off, turning off P1/P2 Toggle, and returning the circuit to its initial state. It is now ready to start Pump 1 the next time that the Lead Float goes ON.

Looking at the logic also looks strange in some places.

Yes, it does. Strange circuits require strange logic. This relay-only alternator logic depends only on the float switch sequence, so it will alternator correctly even if the Lag float is triggered (will not skip an alternation cycle).