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Growatt 6k Thinks it's a 3k

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Kornbread

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Sep 16, 2021
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What's up with this? spf6000t with loads of 1.3kw showing almost 50% load. Didn't notice this until the shop ac was running off solar. The actual loads, measured using a watt[-meter and amp probe are right around 1.3k. It thinks it's a 3k.
1657579262629.png
 
The load is split between L1 and L2. ~1k on one leg and ~400 watts on the other.
 
Imbalance on the transformer legs reduce theoretical output. Same thing happens with external auto transformers.
 
BradCagle said:
@Traviss224
Here's a victron autotransformer:


Read the part here:
"Theoretically, the total power that can be drawn from a 30A 120/240V supply is 30 x 240 = 7,2 kVA. In case of 20A unbalance, the practical maximum will be 30 x 120 + 10 x120 = 4,8kVA, or 67% of the theoretical maximum"

I know this is a different product, but the concept is the same with Low Frequency inverters
Click to expand...
Thanks I'll check it out
 
I was under the impression the low freq inverters somewhat balanced their loads?
BradCagle said:
@Traviss224
Here's a victron autotransformer:


Read the part here:
"Theoretically, the total power that can be drawn from a 30A 120/240V supply is 30 x 240 = 7,2 kVA. In case of 20A unbalance, the practical maximum will be 30 x 120 + 10 x120 = 4,8kVA, or 67% of the theoretical maximum"

I know this is a different product, but the concept is the same with Low Frequency inverters
Click to expand...
As far as we can tell, the spfxxxx units have their transformer wired as an isolation transformer in inverter mode, and autotransformer in bypass mode.
 
Kornbread said:
I was under the impression the low freq inverters somewhat balanced their loads?

As far as we can tell, the spfxxxx units have their transformer wired as an isolation transformer in inverter mode, and autotransformer in bypass mode.
Click to expand...

How is that supposed to work when they are on two separate circuits? Legit question..maybe something I'm missing about the inverters but I thought it was like the panel in our home where it was our responsibility to balance the legs.
 
Kornbread said:
I was under the impression the low freq inverters somewhat balanced their loads?

As far as we can tell, the spfxxxx units have their transformer wired as an isolation transformer in inverter mode, and autotransformer in bypass mode.
Click to expand...

Be interesting to see what it says the load is if you load down the leg that only has 400w on it more. Not sure if this is the problem, but the first thing that came to mind is the unbalanced loading.
 
realpinochet said:
How is that supposed to work when they are on two separate circuits? Legit question..maybe something I'm missing about the inverters but I thought it was like the panel in our home where it was our responsibility to balance the legs.
Click to expand...
It's not two circuits. It's a single 240/120v circuit.
In battery mode. This model inverts the DC bus high voltage , to high voltage AC. Then the transformer steps it down to 240/120v split-phase.
 
realpinochet said:
How is that supposed to work when they are on two separate circuits? Legit question..maybe something I'm missing about the inverters but I thought it was like the panel in our home where it was our responsibility to balance the legs.
Click to expand...
What Tim said. For ac input, the manual states two hots and one ground, no neutral.
@BradCagle Working a lot of overtime this week but when time allows, I'll see what is laying around that can be used to load down the inverter ac output legs and how it reacts.

This is completely off grid. No grid input.
 
Kornbread said:
What Tim said. For ac input, the manual states two hots and one ground, no neutral.
@BradCagle Working a lot of overtime this week but when time allows, I'll see what is laying around that can be used to load down the inverter ac output legs and how it reacts.

This is completely off grid. No grid input.
Click to expand...
Isn't that just the input, the sticker says output is 120/240 so the only way to get that is to split the single phase with a mid way point aka neutral. I said circuit but what I meant was the two legs of the single phase. I don't think you can have one leg balance to the other leg auto magically like that...again unless there's something I'm missing. David poz did a video on this about the solark being very finicky about being out of balance. I asked here on this forum and was told you still have to manually balance your loads.
 
realpinochet said:
Isn't that just the input, the sticker says output is 120/240 so the only way to get that is to split the single phase with a mid way point aka neutral. I said circuit but what I meant was the two legs of the single phase. I don't think you can have one leg balance to the other leg auto magically like that...again unless there's something I'm missing. David poz did a video on this about the solark being very finicky about being out of balance. I asked here on this forum and was told you still have to manually balance your loads.
Click to expand...
David Poz proved that a split-phase high frequency inverter (like Sol-Ark) is limited to separate ratings for each leg. This is a low frequency inverter. High frequency split-phase inverters are just two 120v inverters in one unit.
 
I wonder if there is a setting buried somewhere in there with a max the inverter can draw from the battery+solar and the unit might figure that into the maximum ac output equation?
 
timselectric said:
David Poz proved that a split-phase high frequency inverter (like Sol-Ark) is limited to separate ratings for each leg. This is a low frequency inverter. High frequency split-phase inverters are just two 120v inverters in one unit.
Click to expand...
Ok, thanks for that. But, lets say that the inverter did have the capabilities internally to balance L1/L2 but you had a case where you had various things plugged into the same leg down stream and the inverter started to pull from the other leg to balance it internally but it still has to push that current all out the same leg those appliances are attached to? Wouldn't that cause a potential over load situation and fire risk? Interesting topic...I'm intrigued to learn more about this.
 
realpinochet said:
Ok, thanks for that. But, lets say that the inverter did have the capabilities internally to balance L1/L2 but you had a case where you had various things plugged into the same leg down stream and the inverter started to pull from the other leg to balance it internally but it still has to push that current all out the same leg those appliances are attached to? Wouldn't that cause a potential over load situation and fire risk? Interesting topic...I'm intrigued to learn more about this.
Click to expand...
The inverter doesn't balance anything. The transformer does it. It's still best to balance the loads as best you can. But, you're not limited to only half per leg.
 
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