Backyard Aquaponics
A place to discuss aquaponics

There has been some concerns about running bilge pump continuous, they don't appear to be designed to do that - so be aware.

Some of us are using bilge pumps, 12v deep cycle batteries and a battery charger as a power backup system...the pumps work quite well in this configuration

I have a 360gal (1,250lph) bilge pump, pumping to a metre height and get around 800-1,000lph (never really checked the volume but for the size, they are powerful)

One thing to consider about a bilge pump -- or any 12vdc pump -- it will typically require 10 to 20 times as many amps as a similar AC pump. If you will be using timers or relays -- or anything with contacts that open and close -- to control the pump, you may have trouble with them sticking unless they are rated for 12VDC and as many amps as your pump takes.

I run into the misconception that 12VDC is safer than AC quite often working with people in remote places in Alaska -- 12VDC certainly will not electrocute a person, but it can generate heat. Many people think that since 12VDC is "safer" they can get by with cheap, skinny wires -- not knowing that they actually need larger diameter wires to carry the current -- then they connect bulbs and other devices until the wire gets hot, starts a fire, and their log cabin burns down....

Indeed ems, not to mention the losses in the cable due to high current.
We have the same misconception here in Aust atm. That 12VDC halogen downlights are more efficient. They're marketed as 'Low-Voltage lighting' many ppl I know see that as 'low-power'... Each downlight has it's own little oven of a transformer sitting amongst the roof insulation, and people tend to use 200W of 'Low-Voltage' where they would use 100W of AC...

Unfortunately salesmen capitalize on what sells products -- even if they foster misconceptions.

Agreed just look at the amperage they are carrying.

BTW some of the halogen fittings have very nice toroids

Thanks for all the advice!

It looks as though I may have to investigate using a tiny switch (low actuation force) and a relay. I went into an electronics shop on Monday and physically tested every switch they had (must have looked like a total fool). Admittedly it wasn't a big shop and so wasn't a big range, but they didn't have anything that could carry the power I need without it having a substantial actuation force. So I need a low-power switch connected to a relay that powers the pump.

Thanks to my fandangled flood-drain float switch, the pump will definitely not be running continuously. In fact the whole thing will probably be put on a timer any way (timer ON = auto flood/drain, timer OFF = drain then GB empty). Any way, this means the little bilge pump will not be running for any longer than the time taken to fill the GB, and then it will get to rest for at least as long as it takes to drain the GB.

sounds good jimmy. Can't wait to see pics.

Well, we've just signed up for a 45,000L rainwater tank so funds for aquaponics may be a little tight for a while.

Thankfully I've already bought the fishtanks and got my wife's approval for using our front garden for AP :-)

Will keep you posted.