Backyard Aquaponics
A place to discuss aquaponics

the controllers (proper ones) usually have a secondary "alarm" o/p.

you could wire the sensor for differential controll so it turns the pump on at a +2.5C differential and then set the alarm to 28C and wire the main NO O/P through the alarm NC O/P

clear as mud?

Regarding price limit - I don't even want to spend what the kit costs. I already have what should be a good thermostat unit here and provided I can get one of the sparkies I know to wire it for me and add a relay (to reverse the way it currently switches) then this might do for starters. Shit, in fact if I do it the way F&F was suggesting, ie have the thing turning on when the temps get to a certain level at the collector, then I won't even need to reverse the switching.

Don't want to invest more heavilly at this stage because the whole thing may turn out a wast of time. Thanks anyway.

The one I have has an alarm I think. Must dig it out. I posted pictures of it for you last time (probably 12 months ago as you say). Will try and find them - maybe I emailed them :-/

does not indicate it is differential, but a "hack" for a controller that uses a T/C as the sensor is to wire two sensors in series opposed. +oooo-to -oooo+

the controller then sees the mV signal that corresponds to the difference of the two sensors and you would set the controller to switch on at say +2.5c (which is the differential.

pm or email pics again.

and then save a copy for next winters discussion on solar collectors ROFL

- can't find them . Will look on my photo disk :-)

Found

I have a little booklet that says more about it (with the thermostat if I ever find it )

yep, needs a relay to change from cooling mode as it was made for a cool room or fridge.

sensor will be a thermistor (cant do the differential hack)

does not have an alarm, defrost will almost certainly be time based

you do have the sensor, dont you?

Yep - have a sensor. Looks like you are correct regarding the alarm (was just going from memory). Yes - I seem to remember defrost being time based. Would not need a relay if I used the thermostat to turn on when the temp at the collector got to a cerain point and off when it got down to a certain point. May just do this during testing phase. Would need to get a feel for whether there was any chance I could cook the fish though

If I ever find another cheapish thermostat - perhaps I could piggy back with this one so that the new one would be used to turn off power when high temp in tank reached. The old one (pictured) would piggy back on this and turn on only if desired temp was reached at the collector. Therefore, pump would only be on when temp of tank was below a certain point (say 28 degrees) and the temp at collector was above a certain temp (say 25 degrees).

FFS veebs, i'll check the garage to see if i have any BC-9090's (my alltime favourite controllers, wish i had taxed a boxfull before i left that craphole of my last job) that i can send you. call it a loan to the backyard lab. remind me about it if i forget (which i will).

Hey - steve, remember to send me that thingy

Wot is it anyway? A thermostat . Would I use it to piggy back with the one I have?

http://www.brainchild.com.tw/detail/147723/147723.html

all in one controller, has functions like ramp and soak (which you will never use )

Thanks mate - is all french to me, but I'll remind you when you forget