NFI what a block heater timer is but they don't sell them here.
I did find a couple of interesting timers though once the penny dropped what to look for.
Came up with this:
http://www.ebay.com.au/itm/New-Digital-2Channel-Programmable-Relay-PLC-Board-Cycle-Delay-Timer-Module-R5F5-/252636090232?hash=item3ad248cf78:g:jFwAAOSwr2RYKafcAnd even more interestingly, this:
http://www.ebay.com.au/itm/Programmable-4-Channel-Relay-Module-PLC-Board-Adjustment-Signal-Trigger-New-M4C3-/262722948116?tfrom=252635960090&tpos=top&ttype=price&talgo=undefinedI can't tell if they can be set to switch alternately from the descriptions ( although perhaps they may be) but could be set as separate timers anyway.
Incredible how cheap they can do these things but I'm kinda feeling it's just not cricket at this point.
I'd like to try and build my own especially now opera has gone to the trouble of writing the code for one. I may not be successful but I'll give it a go anyway.
That said, Today I realised there is a bigger picture to what I really want.
Today was mostly sunny but a bit cooler and cloudy till about mid morning. I have been trying to test just what I can suck out of the panels by loading them with lights as well as the fridge to up the draw and pull some amps. Today we went out house shopping so I left the fridge on on it's own so as not to over draw on the batteries which were only getting about half the amps they were supplying from the panels.
Shortly after I left, the sun came out bright and strong but the fridge then only required a fraction of what was available. Hence my total power draw for the day has only been 19ah.
What occurs now is rather than just a switching off the supply, what would be hugely beneficial and in a range of applications would be monitoring of the input from the panels, the draw of each load and comparing them to a total max current. This way, if say the fridge was running but it's only using 200W of the 500w Available and the batteries are floating, It could switch in another load to make the best use of all the power available.
I know motors have a high amp start but this could still work if the other load was on another inverter. I have several so this would work fine for me.
Another useful function would be the ability to switch from solar to mains power. In the case of my Fridge, it's running off a UPS atm so I change it over at night to make sure I don't over discharge the car batteries at night. When the solar input as nil, a relay could be tripped that kicked in the mains power so the fridge was never left unpowered.
As getting the most from your household grid tied set-up is also important, this set-up would be useful here. If you are generating say 5 KW, the thing kicks in the water heater. You have say 2 Kw left so it kicks in the Clothes Dryer but that isn't pulling any current so it goes to the next priority in line which is the pool pump. You have a few hundred watts left so It goes to the septic circulation pump to give that a stir. And so it goes. Each channel could be prioritised and checked every so often so if it's cloudy and then the sun comes out, one load that was missed could be come back to.
I think something like this would have great appeal given all the solar being installed these days. New inverters can sense when the PV is working and kick in the water heater and there are modules to add it in but their cost is inflated and they are single channel. Something Arduino could be made cheap and multifaceted.
Maybe in 10 years I'll be up to speed enough to give it a go! :0)
I'll start with the diverter as a base and go from there!