Pump protection relay for swimming pool

Has anyone used a pump protection relay like you would for a borehole with a swimming pool pump?

I’m trying to get something in place for my parents’ pool. The gardener takes care of leaves & filter cleaning most of the time, but I would like things to shut down in case of running dry or filter clogged, etc. The previous pump burned out after a storm because the pipe itself was clogged, even though the filters were cleaned.

I don’t want to automate it myself using a current monitoring relay as I don’t have any other automation things setup there, but using a Shelly or a Sonoff to spy would help.

I’m thinking of something like this that auto-calibrates when you press the button: DPP1 230VAC | 1 PHASE PUMP PROTECTION RELAY 230VAC | J - Timers and Control Relays : Modular Protection relays | ElectroMechanica, but there are less fancy ones where you dial it in manually too.

Also see this:


The best way to protect motors is with sensors that are installed in the winding during manufacture/rewinding.
This is expensive and is only done on large expensive motors.
However it’s fairly easy to retrofit if you have the time: Check out Mantech https://www.mantech.co.za/ and search for ‘thermal switch’
Choose one of the correct temperature and that you can easily mount to the stator.
This will not remain tripped but it will keep the motor from cooking…

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@phil.g00 Your valuable input is required here…

The new pump is under warranty (unless it runs dry), so I can’t open it up now, but will consider for my own one. Thanks.

The thing to remember - the motor can run indefinitely without water. The pump part cannot. By the time the motor starts drawing excessive current, the pump has already failed and is either seized or mixing molten plastic. So the protection devices can only save the motor.

What you can monitor for is lower current draw (or perhaps power factor), which should happen when the water is not moving, but you will have to tune that to the pump, which means that off-the-shelf solutions don’t exist.

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Yeah, I’m hoping that an integrated “pump protection relay” would do some of the magic for me as opposed to monitoring it myself.

That’s part of the reason I want an automatic one as well: while the pump’s running normally, press the “SET” button – I’m not really sure how I would configure a manual one, since I can’t easily put the pump into different modes to find edges.

Might then just automatically turn the pump off when the filter needs to be backwashed, which might actually be helpful :slight_smile:

I’ve looked a bit, but can’t find anyone who has done this for a pool pump though. Is that because it’s a bad idea, or just that a pool requires constant maintenance anyways, so you’ll normally spot a problem fast enough?

manual and explanation of functions

“Underload Sensing: In an induction motor, the current always lags the voltage. By measuring this angular lag, an underload fault can be sensed. Loss of load will cause the angular lag to increase. When it exceeds the set limit stored during calibration, the relay will de-energise after a 1 sec response time. The restart timer will now start timing (see Restart Timer).”

So on loss of flow sense, the current will drop and that triggers protection. Quit clever lil devices, controlled by DSP most likely and using fuzzy logic is my guess.


What caused the motor to fail? Overload, underload ??
The motor is the expensive part and this is what you need to protect…

Not sure to be honest, it was replaced before I was involved, but the new pump also had no flow, which was then properly investigated.

The original pump was > 30y old, so I’m guessing it was originally a case of “Oh, jaaaa, these old pumps, you know?” :frowning: But it did actually need replacing.

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Thanks. The EM one has a much less informative pamphlet.

I use a Sonoff R2 for my borehole. It measure the current and you can use it as a timer as well. You can set the timer on the Sonoff and add a rule to cut the pump when the current falls below a preset value. No home assistant needed. Just use the Sonoff app to monitor everything.

Ok. Call in the supplier and see what they say. (Listen with one ear only…) :unamused:
Check if you agree with the diagnosis…