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Hotspot Hybrid Mini Split w/ 1.5kw of Solar
#1
Hello!

I'm in the process of installing a Hotspot Hybrid mini split heat pump (ACDC12C). This product can take up to 300vmp direct solar input. I have four 48v panels wired in series for the input. It also can also optionally take a 240v grid connection. Here's my question.

What would I need to do, or is it even possible to make it so when mini split is off, a charge controller is taking the solar energy being produced to charge batteries then inverted to power my a frdige for example, but as soon as the mini split unit kicks on, it switches the solar energy to the mini split. I understand the charge controller, battery, inverter part of it, but figuring out how to do the switching I don't understand. 

Thank you!

David
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#2
Simple Answer: You could just tie directly from the solar input and put a junction and go to the charger controller

However, if the charge controller is pulling power when the split system kicks on, it may not like that. You may need to put a contractor switch that communicates with the split system so that when it gets ready to kick on, it kills the connection to the charge controller.

And finally, this needs to be verified with local codes to make sure it is installed and set up according to local building codes.
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#3
I saw these units and thought they were cool but in the end it just doesn't make much sense. Yes it's great that it can be powered directly off solar panels but you still need an ac grid power supply since if the clouds drop you would need to switch back to grid. So if you were to say 'oh but if i power directly then i won't have to have to use an inverter' but then if you switch back to grid then you will still need an inverter if you plan on storing the energy in batteries. So you might as well just power directly off the inverter and forget the direct solar part of it.
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#4
Just add a relay that is powered by the ac unit so when it turns on it turns off the relay disconnecting the mppt charger
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#5
(10-01-2020, 05:11 AM)daromer Wrote: Just add a relay that is powered by the ac unit so when it turns on it turns off the relay disconnecting the mppt charger


That's what I'm thinking. I DPDT relay where the MPPT charger is wired to the normally closed terminals, the AC unit to the normally open. When the AC unit kicks on the relay energizes and changes the states of both loads. I just need to figure out exactly where to connect the relay to the AC unit. I'm assuming its 24vdc, but I don't know for sure. 

Now, if only I could figure out which relay would work. It seems most relays don't handle high voltage DC (Vmp roughly 160vdc). Since all the panels are wired in series, the current will be no more than 10A. Any ideas?

Thank you,
David
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#6
(09-30-2020, 11:07 PM)deleclair Wrote: It also can also optionally take a 240v grid connection. 
[...]
I DPDT relay where the MPPT charger is wired to the normally closed terminals, the AC unit to the normally open.


Probably obvious, but you'll need to either have the fallback 240VAC connection, or keep the A/C unit connected at all times to solar... can't tell the A/C to turn on otherwise.


Not sure if this is useful in this case, just throwing it in.  Passively senses AC current, and activates switch when current above threshold.
https://www.amazon.com/Current-Sensing-N...B07N1P6TWL


KISS principle: how about attaching a microswitch on the flap of the indoor A/C unit? I'm sure there are solar chargers (Midnite Solar?) that can be (de)activated with a simple switch.
So:
A/C flap open => disable solar charger (no need to disconnect high voltage DC solar)
A/C flap closed => enable solar charger
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#7
(10-01-2020, 01:31 PM)ajw22 Wrote:
(09-30-2020, 11:07 PM)deleclair Wrote: It also can also optionally take a 240v grid connection. 
[...]
I DPDT relay where the MPPT charger is wired to the normally closed terminals, the AC unit to the normally open.


Probably obvious, but you'll need to either have the fallback 240VAC connection, or keep the A/C unit connected at all times to solar... can't tell the A/C to turn on otherwise.


Not sure if this is useful in this case, just throwing it in.  Passively senses AC current, and activates switch when current above threshold.
https://www.amazon.com/Current-Sensing-N...B07N1P6TWL


KISS principle: how about attaching a microswitch on the flap of the indoor A/C unit? I'm sure there are solar chargers (Midnite Solar?) that can be (de)activated with a simple switch.
So:
A/C flap open => disable solar charger (no need to disconnect high voltage DC solar)
A/C flap closed => enable solar charger

Not sure what happened to my response, but thanks for pointing out the obvious, because I hadn't thought about it until you pointed it out. I already ran the 240vac to the unit, so we got that part settled. Thank you.

Your KISS idea and current sensing switch idea are interesting. Would I just use a mc4 branch connector to connect the solar inputs to both the AC unit and charge controller?
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#8
(10-01-2020, 02:16 PM)deleclair Wrote: Your KISS idea and current sensing switch idea are interesting. Would I just use a mc4 branch connector to connect the solar inputs to both the AC unit and charge controller?

I guess a MC4 branch connecter would work just fine.
I should note that I've never used MidniteSolar, but heard only great things.  And this whole topic is new to me (and probably everyone else).

Browsed through the MidniteSolar Classic manual, and it seems that it indeed does support switching between Rest/Charge based on an external input.  Specifically by setting AUX2 port to "logic input 1/2" and applying <2V or >6V to Aux2.  So you're going to need some DC power source with the microswitch.
https://www.midnitesolar.com/pdfs/classi...v_1933.pdf , page 40.

BUT... on another manual they state in BOLD RED:
*NEVER connect any loads or other stuff to the PV input on the Classics (Or any charge controller) *

Perhaps it means that it'll damage the solar charger... or simply that it does not make sense to do so.

You do realize that any excess PV energy that the A/C does not use is wasted?  Starting to think it's overall more efficient to feed from the 240V side using a hybrid inverter.
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#9
Exactly. It's just stupid to try to divert by doing all that relay and crap. You already have a battery and inverter. Just power the mini-split through the inverter. If you happen not to have a battery and inverter, then it sure would be nice to be able to power the AC directly from solar panels. So their thinking is, hey if you have some spare panels you can directly hook it up to the AC and not spend anything else on controllers, etc. But it's stupid because it requires you to oversize the panels so it can be powered when not at optimal conditions, thus you're wasting a lot of the energy that could have been fed through a battery and inverter system with more efficiency.
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#10
I think the purpose of these units is to supply aircon only when the suns shining, when panels are putting out close to max. This is when aircon would really be absolutely needed. So the array wouldn’t have to be oversized by much. When there’s clouds then no aircon. In some countries they are happy if they atleast get aircon when it’s really hot and suns shining.
For me I sometimes need aircon when it’s cloudy Wink
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