Backyard Aquaponics
A place to discuss aquaponics

Here you go..... viewtopic.php?f=8&t=3976

I like your line of thought going automated. Though from what I've seen, you shouldn't need to adjust the oil-flow rate, just light the heater and leave it running.
I think it would be easiest and most reliable though to light the waste oil burner once, manually, early during winter nights and leave it running overnight for 12 hours, keeping the air within the whole greenhouse sufficiently heated. Then automate the pump to the heat exchanger with a thermostat, or Arduino chip, to heat the fish tank water only when it dropped below a certain temp.


A well designed waste oil burner "...when adjusted for maximum efficiency, consumes less than one quart ( 0.94 litres) of oil an hour" (http://journeytoforever.org/biofuel_lib ... h/me4.html)

To prevent the water in the heat exchanger running dry, you could setup a solenoid valve on the heat exchanger pump so it is continously running but if max temp is reached in the fish tank, a solenoid opens which pumps water in a recirculating fashion into a stand alone bypass tank (eg a 200 litre drum) with nothing in it where it didn't matter how hot the water got.

Hard to describe with words, but here's a sketch:



Scenario:

1) The two purple Solenoids are open, so water in the fish tank flows through to heat pump, then through heat exchanger and recirculates back into fish tank

2) heat pump and solenoids are controlled by a thermostat monitoring fish tank temp. When fish tank temp exceeds say 28 degrees celcius, the thermostat closes the solenoids.

3) Water then flows only through the heat bypass tank


I'm sure there is a less wasteful way to do this? Any suggestions?




Indeed.. this is the reason I'm so keen to build a greenhouse to retain as much heat as possible over winter

ps Rup just reading your evacuated tubes thread. Great writeup and photos and lots of helpful info, thank you

Re-read it myself..... there's a lot of tracking data that wasn't included for some reason....

i'm trying to keep my water warm enough over winter with a couple of 30 and 20w heaters- i've got barra and 1200l of water. the heaters are keeping the water between 20-24
i'm thinking of putting bubble wrap over some of the water as an insulator- is this a good idea- or will it kill the fish? i aim to cover 80% so there is access around the sides?
cheers

i've got a 1200l system, using a 20 and 30w heater for my barra.
keeping temps between 20-24
i was thinking of putting bubble wrap on 80% of surface to insulate and maintain warmth
will this work or will it kill the fish?
thanks

The fish should be fine. Water holds twice the amount of O2 at 20°C as it does at 30°C. Depending on your stocking density, you may want to have some questions running.

How big are they now, 4 years on?

A very old thread... however...
ok so long as you have aeration running. If you block off 80% of the water-air interface, you only leave 20% for Oxygen exchange. With typical stocking densities, you may well have low Oxygen levels in the water.