Backyard Aquaponics
A place to discuss aquaponics

What do you mean Chappo - I don't have either as yet.

Theoretical solution:
If one could work out a heat exchanger that would not get gunked up then one would send warm water from the FT and it would end up cold in the GB, the cold return water would be nearly completely warmed by the time it gets back to the FT. A looooooong pair of pipes would do it (insulate around the pair, not between), but I think the pipe length needed is exorbitant. Still, the magic of reverse-flow is nearly as cool as AP: the cold grow beds would not take much heat from the hot FT. The water heat is not averaged as one might think, but is nearly all transfered....draw a couple pipes and think about it...

Realistically: run some numbers on what power you might need if you insulate. How much will it cost to run through the winter with var options? Is that worth it? Sure would be sweet to keep the buggers going....nice harvest next summer!

Good luck!

This is exactly what I would like to do F&F, it is the most basic form of pool heat collector controller. Of course the flash controllers that measure the heat of the suns rays and crap are at least $350, which is why I'd be happy with a differential thermostat setup as you describe.

Only problem is I'm trying to do this on the cheap (well truth is I need to do it on the cheap if I'm to keep my balls ). I have one thermostat (not a double one) which I'm assuming can be wired to be used. If I had a second then I guess I could rig to operate as you describe (:-/), but don't have a second. Cheapest ones on ebay were about $75 bucks last time I looked, so will have to wait for another time.

Reminds me - I must dig out the one that I do have (still in box somewhere) and get sparky to have a look at it for me. Has a digital display and buttons to change settings and stuff - so seems to be a fairly good one, but although it has the probe it does not have any other wiring or plugs or anything. Also as I've said before it turns on when hot, not off, so is kinda the opposite of what I want if operating as a single thermostat, but would suit to rig as a double if I had another that turned on when cold (I think ).

you have 2 kids, you don't need your bollocks any more.

I need to clarify something before I give an update. Last night as part of my post I said:



This was not actually correct. It seems I actually decided to turn off the one with the bung thermostat (I would have been worried about overheating the fish last night). Now for some updates - quite promising:

This morning the temp in the tank was 23.5 (or maybe 23.2 - can't quite remember). Temp in sump was about 18.4. Now considering my note of clarification above, theoreticaly there were not heaters running in the tnk last night and I only had a drop of about 3 degrees. This is despite outsie temps last night of about 10 I estimate (not even close to zero, but coldish all the same).

Tonight, just now at 10pm, the temp in the tank was 23.7 and there were not heaters on - though they are not far from the temp that will make them switch on. The fish were back on their small mid day feed and they appear to have eaten this.

I'm tempted to buy a power meter - these are pretty cheap in Jaycar these days I think, and hook all of the heaters up to this one plug. This would then give me a better indication of what I am spending to maintain these temps. Of course once it gets colder out, it will be harder to maintain the temps (given that it will be colder day and night).

So, main priority remains building the structure over the beds this weekend to maximise daytime temps and minimise the temp losses from the beds (and sump) at night (during period they are not pumped to).

On top of this I should look at getting a digital power meter plug and also it seems to me that it would be worthwhile investign in a new 200 watt heater that has a thermostat that works. This one could be set a little higher than the other 2 so that temps are kept at a good level through the night (potentialy just on one 200 watt heater and the other 2 are there to kick in if temps drop to a lower than satisfactory level. These 2 would most likely not operate much of the time - until the coldest part of winter, at which time they may well operate quite a lot (but this remains to be seen).

Solar collector still on list, but just not as high a priority at this poitn given the relative investment required for the gain.

Will continue to monitor the temps and keep updated.

On the weekend I'll be able to monitor more frequently and this will give some interesting info.

VB, if you have a spare timer floating around you could put the bung heater on that and have it switch on and off at some interval that gets the temp close...Then the other heaters could take up the slack...

Myles - yep, plenty of spare timers. Was doing this with the 150 watt heater until recently - having it run just in the night. Given that the heaters are very cheap at ageofaquariums, next time I'm out that way I may just bite the bullet and buy one. The one that works came to me from them for free when I let them know the other one had a bung thermostat :-). In the meantime, if I find the bung one is needed - I will do as you suggest and regulate it through use of a timer :-)

On your heating you only need one thermostst just set it 5 deg higher than the water temp so when your solar water gets to the high temp it turns on to cool

I'm not sure I'm getting the picture F&F. Are you just saying to set the thermostat at 25 degrees for instance and have the probe outside sitting on the collector so that the pump only turns on when the temp gets to that point (will need a relay for mine of course).

I thought your earlier post was talking about operating on a differential - ie if the temp at collector is higher than temp in tank, then turn on pump. Of course would also need to manage to ensure doesn't get too hot :-/. Maybe too late for me to be thinking about these things

In the thread I started about greenhouse fabric, I've talked a bit about the design of the temporary structure that will go over my beds (and have also discussed a bit here). In my last post to that thread, I said that I had a bit of an idea regarding the back of the greenhouse - which is the shed wall. I am thinking that I may put some insulation on the outside wall of the shed - which is therefore inside the greenhouse - to reduce the heat lost to the expanse of colourbond which goes well beyond the greenhouse structure (both up and to the side. But on top of that I have been thinking of making a bit of a heat sink to hang on this wall inside the greenhouse. For ages I've had some PVC pond liner that I picked up cheap at Kmart as a discontinued line. It is only 4 metres by 3 metres, but will be big enough for an experiment. What I'm thinking of doing is folding it in half, sealing the edges to each other using my hot air gun and a suitable roller and then also sealing it further to make some compartments running from top to bottom for further satbility. The top will be open, but the rest will be sealed. I will then fill with water (or maybe even gravel depending on what will do a better job). What I'll be left with is a 2 x 1.5 metre container (actually - somewhat less than that due to the pleating I'll need to do to make the compartments hold the water/gravel) that hangs on the wall and heats up during the day and lets off that heat at night. I know it will only have a limited effect given the relatively low amount of water or gravel in it - but it will be an intersting thing to test and will cost me nothing. I can then consider expanding this to cover the rest of the back wall of the greenhouse if it seems to be working. I'll have to take a look at how much of this wall gets a decent amount of sun during the day. It may get bugger all - in which case I won't bother

Veeber, if you want a differential controller then check out Jcar, last time i checked i think they had a type K thermocouple temp display controller kit.

to make it a differential controller you just need to wire two thermocouples in series opposed.

i'm fairly sure i posted this last time you started on this idea must have been winter last year

Will they run 240volts Steve, or is this for 12 volts.

Is it something I could safely do myself, or should I get the sparky next door or the one at work to do it?

What are your thoughts on how it would turn off if the tank got too hot (maybe not an issue of course).

http://www.jaycar.com.au/productView.as ... &SUBCATID=
can be wired as differential.

http://www.jaycar.com.au/productView.as ... &SUBCATID=
not differential but can be set for heat or cool

12V i think, but just wire the outputs through a relay or contactor.

can you use a soldering iron? (needed to assemble the kit)

whats your price limit VB? i'll get a cost price on a 240v PID controller type K thermocouple (off the shelf) tomorrow...............might be easier than rooting around with a kit with the luck you have

See comments above. Also, where does it indicate that the first is a differential device. I must read it again. They do look to be for 12 volt though - not what I'm after.