Backyard Aquaponics
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I currently have a backup 12v bilge pump which comes on when mains power fails, I'd like to set up a backup 240v water pump which would come on if the main pump fails due to seizure. As it is now, if my main pump fails due to seizure or blockage , my backup 12v bilge won't come on. So my question is how can i switch a backup 240v water pump on useing a sensor or something which detects a cease of water flow out of my main pumps pipe/outlet?

Thanks in advance
JORGY

Gday Jorgy,

I had a lot of problems early on with blockages. Can you make a simple covered pump box with screens instead of trying to make the a circuit for a back up pump.

The back up pump could be triggered using a pressure switch and a relay but its not going to be pretty.

You'd need a 24V power supply for the relay and possibly the pressure switch. An enclosure as you would have 24V switching 240V (deadly). If you had a mate the was a sparkie I'd get him to do it. Its not impossible but it could be highly hazardous if done wrong.

The Miner.

Yeah, should be able to get a small plc to handle it, with perhaps an in-line flow meter, and if you have it cycling on timed pumping it would be fairly easy to arrange a program so that if there's no flow for a certain period of time, it turns off the dodgy pump and switches on the second one.

Hey Jorgy

Go to automationdirect.com.au they sell little PLC's and pressure switches, if thats the way you want to go.

You can do it with relay logic to as described previously.

If you want a hand drop me a line and I'll do my best to draw something up for you..

The Miner

G'day Miner
I don't have any issues with blockages, I was just useing it as a possible reason for a pump to stop while still having mains power.



Hey EB
PLC is a bit beyond me, was hoping for a more simpler sollution. I run my pump 24/7 and just think it would be like having extra insurance having another pump ready to switch on if the main one fails. I did think about having 2 main pumps running opposite each other but I don't like switching pumps on and off constantly. I'll have a bit more of a think about it and if i nut something out I'll put it here for criticism

Thanks for your suggestions

The most appropriate device would be a flow switch. If there is flow, the main pump is running. No flow combined with a timer (there are electrical timers available), indicates the main pump has failed and hence start the backup.

Not sure about your budget but a mechanical flow switch would be integrity problems after a while due the build-up of biofilm. Maybe you should try a thermal dispension flow switch. No mechanical parts.

Thanks Ivan, I'm trying to keep it as simple{also meaning cheap} as possible, I just checked out water flow switchs on ebay and there are water flow switchs for aircons that i think would be ok.They are the only ones i have checked out so far, so there might be better ones around. I could mount the switch on the top side of the fishtank ibc plastic which would keep the electrics away from water, and just direct the water coming out of the outlet against the paddle. I could just get it wired into the middle of an extension lead, then I can just plug my pump straight into it. What do yous think about that? I think that might be as simple and cheap as possible.

Well just be careful if you are wiring 240VAC. A wiring might look safe and harmless on a dry day, but improperly terminated circuits on a wet day could be fatal... Personally I will terminate the circuits into a terminal box with proper ingress protected cable glands.... Use proper terminals to connect the circuits... Also make sure that the flow switch is rated for AC operation and what the maximum currrent it can take through its contacts.