Backyard Aquaponics
A place to discuss aquaponics

Hi, I am just about to make foundations for an aquaponic greenhouse, small compared to many of your systems - 800 litre fish tank, 1 x 400 litre sump and a backup sump of about 200 litres under the floor for about 400 litres of grow beds, rafts and a few towers. I hope to run it off grid.

It has been a while since I had to use my electricity maths and there are a couple of practical gaps in my knowledge (at least) that keep niggling at me that I would like to get settled before I lay any pipes after the foundation has gone off.

So, I'll be powering two submerged bilge pumps (I do have a worry about the longevity of bilge pumps with brushed motors but I am asking about that in another post) in each sump, one of which is an emergency backup and I reckon the 200w panel I found will do it but I would like to build in an element where, if the batteries go below what I'd like for whatever reason (English weather is as bad as you may have read) then the system will revert to a mains feed from the house. I've looked about on lots of other people's systems and I haven't found anything similar. Perhaps it is so simple that people don't mention it. Some sort of relay? Is this something I can build in to the circuit breakers?

Any thoughts welcome.

Tim

Try to keep most of your questions in one post, it makes it easier for us to answer your questions. As for your question about reverting to mains power, most people put an automatic battery charger on their batteries, but that might not be appropriate in your case. I don't know of anything premodern, but you could youse a voltage sensing circuit to power a DPDT relay with one side hooked up to your batteries, and the other hooked up to a 12v power supply. Amateur radio shops sell good 12v power supplies. As for the longevity of 12v bilge pumps, they are built for intermittent duty. In other words keep backups, and be prepared to swap them.