DIY my Auto Pump Cutoff II

[chrisyew]

Before I proceed, it's best to refer to the APC I in this thread;

APC I

since most of the basic operation and construction is the same.

Credit : Thanks to fellow hobbyist with the nick whoami for pointing out the miniature relay used is not solid state relay thus it can be connected in the normally closed position.

The Auto Pump Cutoff II comes with an External Monitor - a 12V red bulb and an buzzer (with optional switch to turn it on or off).

Advantages of APC II;

- Relay is in the Normally Closed position when pump is running; i.e. the relay in not turn on.

- If there is an power outage, the return pump will automatically turn on again when the power is restored compared to APC I.

- APC II comes with external monitor - red light indicator and optional buzzer switch.

- When any of the float switches is closed caused by either the main tank water level is too high, or the sump tank last chamber (where the return pump is) water is too low; the APC II will turn off the return pump. Once the pump is off and even if there is a back siphon, the float switch will not turn on the pump again even if the float switch is turn on. You need to turn off the Reset switch to turn on the pump.

[chrisyew]

Here is the External Monitor which is optional; you can do it or without it. Since the main unit is usually hidden behind the sump or tank, so I decided to have an external monitor so that it's easier for me - at least visually or with the buzzer on.

[chrisyew]

How the APC II works;

Float switches arrangement :

- The top float switch for the main tank must be arranged in such a way that it is normal open when the water level is below it. When the main tank level is too high, the float switch will be closed position. If not, remove the C-clip below the float switch, take the float out and reverse it then put it back together with the C-clip.

- The bottom float switch in the sump must be in such a way that it is normally open too when submerged in the water. When the water in the sump tank last chamber where the return pump is falls below the float switch - the float switch will be closed. If not, reverse the float switch position as above.

The Circuit;

Basically the same as APC I except that the float switches are arranged in parallel with one of the relay contact. In normal operation, the relay is in the normally closed position so there is a main supply to the return pump and turning the pump on.

Once any of the float switch is activated, the 12V transformer will supply voltage to the bridge rectifier (the Reset switch must be on position) thus activating the relay coil. This will turn the relay on and cut off the main supply to the return pump. Even if there is a back siphon causing the float switch to open again, the relay will not be turn off as one of the relay contacts is connecting the 12V transformer supply to the bridge rectifier.

The relay will be turn off when the Reset switch is turn off. Once the Relay switch is turn off, the return pump will turn on again.

When any of the float switches is turn on causing the relay to activate, the External Monitor Red light indicator will turn on and the buzzer will sound.

[chrisyew]

Step by step of setting up the APC II;

- Connect the return pump, the 2 float switches and the external monitor to the main APC II unit.

- Turn on the main switch of the APC II. Once the main switch is on, the return pump will turn on.

- Now turn the Reset switch to on. This will not turn on the relay as the float switches still in the open position.

- Should any of the float switches activate (in closed position), the relay will turn on causing the relay to turn on. The return pump will be turn off and the red light indicator and buzzer will turn on.

- Ensure everything is alright in the main tank and sump tank before you turn off the Reset switch.

- Once you turn off the Reset switch, the Return pump will be turn on again. Now you may arm the Reset switch again by turning it on.

[chrisyew]

Basically the same components used as APC I except the Main Switch and Reset switch is best to change to the same like the Main Switch type (not the push switch type as it's easy to indentify the position).

For the external monitor, get a small box ($1.20) with a 12Vdc RED light bulb, a 12V buzzer and a toggle switch.

Here is the external monitor tied to the rack on the sump;

[hammerhd]

good job

how much the whole thing cost?

[chrisyew]

good job

how much the whole thing cost?

Thanks. The cost breakdown is in the thread APCI. Actually not much if you got all the parts right the first time. For me, it's a bit more as I got standby parts and some others to try out.