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Old 10-05-2020, 03:51 PM   #1
Skoolie
 
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12K BTU Mini-Split Amperage Question

Hi!

Just installed a 12k BTU Mr. Cool mini-split.

Fired it up and works! Problem is it pulls 40amps!!!

Itís hooked up to a 20amp breaker!! (as manufacturer recommended)

How is this possible? Is this normal? Maybe for initial run?

Thanks

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Old 10-05-2020, 04:29 PM   #2
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Ok so what I realized is that my battery monitor is monitoring a 24v system

40amps x 24v = 960w

960w / 115v = ~8amps

That makes more sense.

This battery monitor is using a shunt that monitors my inverter.

How do fix this issue? Any ideas

Thanks for reading
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Old 10-05-2020, 05:26 PM   #3
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what type battery monitor/
do you have it wired and running 12v and the monitor is incorrect?
your battery monitor should not be controlling the load to equipment it should only be monitoring it.
your invertor/convertor is where you need to read for outs and ins voltage.
what type what guage wiring?
these are need to know questions.
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Old 10-05-2020, 06:25 PM   #4
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My monitor runs to a shunt that intercepts my batteries and a negative bus bar.

That negative bus bar is connected to my inverter, controlling my AC panel.

My Minisplit runs at 115v, telling my monitor, but my monitor interprets it at 24v.
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Old 10-05-2020, 06:49 PM   #5
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Quote:
Originally Posted by dj2109 View Post
My monitor runs to a shunt that intercepts my batteries and a negative bus bar.

That negative bus bar is connected to my inverter, controlling my AC panel.

My Minisplit runs at 115v, telling my monitor, but my monitor interprets it at 24v.
not going to play sparky hear.
you did not answer my basic questions?
is there dip switches within your monitor or did you buy the wrong one?
alot more hear to answer for electtrical than me.
give them a minute or two?
they usually holler when they think i am giving bad advice?
not bad but its a call for the more experienced opinion
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Old 10-05-2020, 11:00 PM   #6
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The battery monitor must be wired so the shunt is at the battery bank.

Measuring only that current going into and out of that bank, and **all** of that current definition of a BM.

Nothing to do with any inverter, that is just a load device to the DC side House circuit.

The AC side should somehow turn off the inverter when the shore power input is live, or cut off its input.

And the battery bank should be charging then, even if just a trickle current at Float, but the mains AC carrying all the DC loads, no draw on the battery bank.

A separate AC ammeter is required if you want to measure native AC amps fed by shore power, or coulomb-counting wattmeter to accumulater Wh, kWh, Ah etc.

When off grid, then the inverter feeds AC output to your AC panel, drawing DC from the bank, and the BM will include that in its display of net / total DC amps current and cumulative Ah.

A separate DC wattmeter can be used to log those numbers for just one load device (or charge source). An ammeter just shows instantaneous amps, not Ah.
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Old 10-05-2020, 11:00 PM   #7
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Quote:
Originally Posted by dj2109 View Post
Ok so what I realized is that my battery monitor is monitoring a 24v system

40amps x 24v = 960w

960w / 115v = ~8amps

That makes more sense.

This battery monitor is using a shunt that monitors my inverter.

How do fix this issue? Any ideas

Thanks for reading

This post makes it sound like your only issue is an improperly sized breaker and (maybe improperly sized wire) no? 960W is not excessive for a 12k A/C, so if a breaker is tripping it sounds like it is not properly sized for the load. Specifically what breaker is tripping?


Quote:

My monitor runs to a shunt that intercepts my batteries and a negative bus bar.

That negative bus bar is connected to my inverter, controlling my AC panel.

My Minisplit runs at 115v, telling my monitor, but my monitor interprets it at 24v.
This is not the way it works, everything on the DC side of the inverter operates at your battery bank voltage, everything on the AC side of your inverter operates at the 120VAC.


Your battery monitor shunt sees 24v because that is the voltage on that side of your system. It does not need to know anything about what is happening on the AC side to function properly (since it is just measuring current, voltage, and voltage drop). It can remain blissfully ignorant of any specifics on the AC (or DC) side its a rather simple device.


Furthermore it cant take actions unless it has been specifically setup to do so. Its just a monitor. So it is probably not causing your problem. What monitor are you using?
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Old 10-06-2020, 09:45 AM   #8
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I had this happen also.
My mini splits were pulling an indicated 108 amps!!!
I was concerned.

I didn’t realize this was at 24v!! ��
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Old 10-06-2020, 12:14 PM   #9
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So the readout is correct?
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Old 10-06-2020, 02:01 PM   #10
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960 watts is aboput right.. the ones in my house are around 1000 when I max them out..
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Old 10-06-2020, 03:12 PM   #11
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Quote:
Originally Posted by dj2109 View Post
So the readout is correct?

Nobody can really answer that, but we can go so far as saying the readout is not blatantly incorrect. So if there are no other issues/problems, I wouldn't worry, sounds like things are working as they should.
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Old 10-07-2020, 12:25 PM   #12
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Holy crap good thing I have a 6000w inverter.....

Thanks for replies. Basic math is not my forte
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Old 10-07-2020, 12:31 PM   #13
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We never got around to installing your AC side meters- those would show the ~8A draw on the AC side.
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Old 10-07-2020, 12:41 PM   #14
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Right, I know you were trying to take time out to help me with that, and I appreciate it. I'm still up for it when you get the chance.
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