Looking for mains latching timeout relay to prevent water pump flooding

[JohnW2]

Flow detector on the output. If it detects flow for an excessive length of time it shuts down the pump.

Indeed, but I doubt that one could find a 'flow detector' which, itself, actually offered that functionality - the OP would still have to add some electronic logic (be it with the "latching timeout relay" {if one existed} that the OP mentioned or something else).

Kind Regards, John

 

[flameport]

name of the latching relay

They are called latching relays, such as these: https://uk.rs-online.com/web/c/relays/general-purpose-relays/latching-relays/

hanks for that - would this suit for the delay-on timer? The voltage, price and functionality seem right!

Not really, that is an exposed circuit board thing.
These: https://uk.rs-online.com/web/c/?sra=oss&r=t&searchTerm=on+delay+relay
would be more suitable.

Quasar appear to sell hobby electronic kits, which are entirely not what you want.

Relays and similar items are all standard parts used for industrial controls, and suppliers such as RS and Farnell have a vast selection of them.
They may cost a bit more, but are designed for the purpose, will last for years, and are easily and quickly replaced should anything fail.

 

[lardconcepts]

Thanks - well, I don't want a DIN mount, so this looks close https://uk.rs-online.com/web/p/latching-relays/9143963/
But... useless datasheet. I'll give them a call later!

 

[JohnW2]

Thanks - well, I don't want a DIN mount, so this looks close https://uk.rs-online.com/web/p/latching-relays/9143963/

Despite what you say about your wishes, it looks as if the item to which you have linked IS a DIN-mounted relay.

I'm still not clear as to how you are planning to get the time delay which you also want (in addition to the latching).

Kind Regards, John

 

[JohnD]

I don't want a DIN mount

Why?

 

[ericmark]

If the timer is after the float then when float switches off so does timer, so it will in most cases auto reset when float switches off, so no real reason why it should latch, simple timer is good enough. If you want to stop auto reset, then have a latching relay triggered by NO contacts keep the two functions separate.

I have to admit with multi pumps where we wanted automatic operation we tended to use a PLC.

 

[lardconcepts]

Timer should be unrelated to float switch. Thanks for all the ideas - I'm going to let this bounce around in my head over the weekend and I'll let you know what dribbles out next week...

 

[mattylad]

They are not and cannot be unrelated - the float switch must be part of the timer circuit.

You have 2 float switches there, one on string to start/stop the pump and the other on the tank side, what does the one on the side actually do?
I suspect that it turns off the pump to prevent overfilling, in which case this also needs to be in the timer circuit to stop it once it is filled.

 

[AlanE]

Reading this thread is a classic how to complicate and over engineer a simple problem!

All you need is a standard 240volt relay with two sets of N/O contacts.

Take live supply via a limit (float) switch that has N/C contacts to detect the upper water level to one side of the coil of the relay. Other side of the coil connect to Common terminal of one set of relay contacts. The N/O terminal goes to the neutral side of supply. You now lave a 'latching relay'. (Once relay has operated the circuit is maintained via these relay contacts).

Wire your float switch accross the same set of relay contacts so it is effectively in parallel with the contacts.

Operation then follows the sequence:

1. Water level drops and level switch contacts close compleating relay circuit.

2. Relay closes. First set of contacts now bypass float switch. Second set of contacts operate pump which fills tank with water.

3. As water level rises the water level switch opens but relay is held on by first set of contacts so pump continues to fill tank.

4. When water level reaches the level set by the top limit switch it open circuits, power drops from relay, pump stops running and the relay will not energise again until water level drops enough to operate water level switch.

Backup in case upper level switch becomes defective? Add a second one, both wired in series either on will then switch off the system. Oh plus replace overflow discharge pipe with one capable of discharging more than the pump can supply.

If you need it will do an actual diagram but it might be a bit rough!!

 

[JohnW2]

Reading this thread is a classic how to complicate and over engineer a simple problem! ... All you need is a standard 240volt relay with two sets of N/O contacts.... Operation then follows the sequence ....

What you suggest is all very well, but does not seem to address what I understand to be the OPs main concern, which, as I understand it, is not to do with the tank overfilling but, rather, is that he wants the pump to be disabled (and remain disabled until manually 'reset') in the event that there is a flow of water out of the tank for more than a specified period of time (e.g. due to a burst pipe or a tap left 'on').

Kind Regards, John

 

[lardconcepts]

What you suggest is all very well, but does not seem to address what I understand to be the OPs main concern, which, as I understand it, is not to do with the tank overfilling but, rather, is that he wants the pump to be disabled (and remain disabled until manually 'reset') in the event that there is a flow of water out of the tank for more than a specified period of time (e.g. due to a burst pipe or a tap left 'on').

Exacccctly!

 

[AlanE]

Exacccctly!

Ok so add a countdown timer. Wired in parallel with pump so countdown starts when pump starts its output relay is connected in series with limit switches. After countdown period pump stops.

Incidently leak scenario problem you are trying to solve is common to everybody connected to the mains water supply in event of a leak. Regards to leaving a tap on whynot timed taps or proximity operated ones?

 

[JohnW2]

Ok so add a countdown timer. Wired in parallel with pump so countdown starts when pump starts its output relay is connected in series with limit switches. After countdown period pump stops.

Yes, provided that, after the 'countdown period', the 'countdown timer' kept the pump in the 'off state' until the timer was manually reset.

However, I agree with you that the OP appears to be trying to address a problem which exists with any water supply (regardless of what is producing the pressure/flow) - so, unless I'm missing something, I don't know why he is specifically concerned because he has a local pump.

Kind Regards, John

 

[lardconcepts]

the OP appears to be trying to address a problem which exists with any water supply

Correct

 

[JohnW2]

Correct

That being the case, and given that 99%+ of people don't have a local pump which they could disable in the event of a major 'leak', I wonder why you are so concerned about this. For that 99% of people, the only option would be some sort of electrically controlled shut-off valve which activated in the event of a prolonged flow, but I've never heard of anyone doing that in a domestic context. With outdoor hosepipes, yes, there are (non-electrical) devices that do that, but I've never heard of anyone doing it with their main water supply.

Kind Regards, John