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Forum Index : Solar : Simple Load Shedding.
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| Phil23 Guru  Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Just looking after a solution for some simple load shedding. Currently the base load on my inverter is about 1000W, before I add A/C etc. With a couple of heads running it can be in the 2-4kW range. If I lose mains, the batteries I have will give me about 45 minutes runtime without decreasing the base load. If the aircon's are on & solar is low, the load is a bit more than the batteries can supply. So Monday, I'm at Bunnings, (Employed as a Full Time Customer), bit dark & stormy looking, storm hits, power goes out, so I fly 1/2 a km up the road & throw the A/C breaker & save myself from a shutdown in the batteries deplete. First thought is to add a contactor that's held in by input mains to the A/C circuit. Absolutely simple, coil just held in by presence of the utility supply. But it's held in 24/7. What are thoughts on a simple circuit to run things the other way round. NC contactor that opens when the mains fails. Only energising the coil from the inverters output during power fail. Could also select a contactor with a manual override, so when I am home to monitor stuff during a prolonged outage, I could bring the A/C back with Solar + Genny. Am I overthinking it & should I just keep it simple & hold a contactor in 24/7 for normal usage? Phil. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have not done it yet but I plan to use an Arduino to turn an AC on and off using an Infrared Blaster. You could use a solid state relay too, does your inverter/charge controller have any auxiliary outputs? If it does and you can set it to turn off below a set voltage would be the easiest option. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| hotwater Senior Member  Joined: 29/08/2017 Location: United StatesPosts: 120 |
I run my fridge only when the battery reaches a pretty full condition and that sets a timer. At the end of that period it checks the voltage again and decided to continue or not. This is a fairly simple system that works quite well. Timed operation works well because you have a good idea how long the battery will last in any situation. I do everything with NANO's these days, but I have a simple circuit that will turn on a timer at a set voltage and turn off when the battery drops below the set voltage. I'll look for it. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
I recently got some voltage monitor relays. You can set them to open or close at a specific upper or lower voltage with Hysterisis. I am using one to turn on the hot water heater when the mains hits a certain threshold signifying there is power coming from the solar. It can also turn off or on at a certain lower voltage. Things were about $28 delivered and work as advertised, IE, very well. They only have a 6A rating so you would probably need to use a relay or contactor but hardly a big deal. You could probably set these up on the mains or the inverter to do what you want which I'm not entirely sure but think I get the gist of it. They are DIN rail mountable and have an LCD screen to make the programming easier. My tip would be DON'T read the instructions. They make the whole process of setting the things up far more confusing than the straight forward thing it is in reality! |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
I did spend some time investigating that a couple of years back with a work colleague. A Micromite was the intended devices & we planned on giving the MM full control of all parameters. The protocols were hard to sort out & the idea was shelved. Have thought about revisiting it though, as I think a better approach may be to hack a universal AC remote & connect the MM to that. For any that don't know, it seems like AC remotes send state of all settings on any button press. Phil. Edit, $12.00 for a universal remote , almost worth adding to the parts box. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have not investigated it much, there is ways to capture the output and store it to resend. So unless I am mistaken if I use the remote and store what is sent at turn on and at turn off I can then transmit that as required with an Arduino. I bought a universal remote on ebay for the same AC and it cost $6.15 delivered. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Looking at that remote, you'd probably only need to tap into half a dozen buttons to get some useful control. What happens here is I leave my office one off until about 10, then turn it on at 28° when solar production builds, lowering it progressively to 26° as solar output meets requirement. Would be dead easy (Bar the thinking out logic), to have a micro control it. Although I can view the settings before I press buttons, the remote could be reset/power cycled to a default state before each command set was sent. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I am only concerned about turning on or off the AC, I am happy to leave it on 24 degrees. The Arduino would simply turn it on if the temperature is above 28 and battery volts are above 54. If the battery volts fall below 54 it would turn off with a delay. I already have the infrared blaster and receiver and need to get on to it, I got home late on Tuesday and the AC was still running at 7PM as I forgot to turn it off. That drained the battery quite a bit and e have had very cloudy weather since then. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Work Ok? I've never got to hit the buy button due to not having real feedback from others on how they work. My two systems are a Mitsubishi 8/9kW (Japan) & a 8/9kW Fujitsu Multi head. Read a bit about Bit Banging for IR remotes & couldn't get that inspired. Probably read too many post about people having issues. Phil. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
The remote is working fine for me on the Daikin 9KW that I bought for $50. Another thought I just had which is much simpler and would do what I want. Every AC that I have seen has a button to turn it on and off without the remote. It goes to standard 24-degree auto setting but that is fine for me. So long as the logic does not go wrong and it turns on when it should be off. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
My Fuji definitely returns to it's previous state & powers up after a power interruption etc. Think I read the Mitsubishi is the same. Could just KIS & interrupt it's supply with a relay or contactor. Latching would be best, but most coil loads are small. Even if I interrupt the Fuji for just a second, when power returns it goes thru a correct start up procedure. Seems to take about 3 minutes for the compressor to resume. The Adfruit libray mentions 11 protocols, but doesn't mention anything related to the AC ones (I think). Bit of it covered here. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
the way transfer switches for backup systems are usually wired, the large load circuits like water heater, stove and a/c are wired out when the backup power is triggered. it is possible to use a relay to manually or automatically override this and add a circuit back in based on the energy that is available. I find it works quite well this way, the quality of the contactor is less critical when its cycles are low. I'm confused, no wait... maybe I'm not... |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Waiting on a couple of 1NO 1NC contactors ATM. (With Manual override). When they arrive, I'll initially put one in series with the 9kW A/Con. To start with I'll just put the coil across the mains input, so if the mains is lost it will drop the A/C off the inverter. Ultimately I'd like to add a detection circuit that energises the contactor to drop mains instead. It could either be electronic, of just a 2nd low current A/C relay. Phil. |
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