Parallel Inverter Load Balancing

[webbbn]

See link #5 in my signature for how Victron "load balances" (hint: it's in the AC wiring section)

Thank you! That makes perfect sense, but please wait while I pound my head against the desk! ... Okay.

Actually that does make perfect sense. The wires are simply being used as current limiting resistors, and they're assuming the resistance along a wire is more consistent than the resistance across a (apparently) mechanical relay. You just need to "right size" your wires. Not too big, and not too small!

Thanks for all the feedback. I don't know if I am any closer to a solution, but at least I know more now than I did previously, and I have some more references to study.

 

[CableGuy]

No
As stated above, you can not parallel these existing circuits. Because they're too small to be paralleled.
You can use one or the other to feed the stacked AIO's. Or feed one to each, with separate loads.
What I would do is run the stacked AIO's off grid completely. And feed one or both existing circuits to chargeverters for grid assist.

Aside from code, the OP's existing 240 circuit likely has a shared neutral, if any at all. If they were to parallel the 2 hot conductors on the same phase, the current on the neutral conductor would be way too much. Citing code alone is not enough to stop everyone so it's worth mentioning if anyone else is reading this down the road.

 

[timselectric]

Aside from code, the OP's existing 240 circuit likely has a shared neutral, if any at all. If they were to parallel the 2 hot conductors on the same phase, the current on the neutral conductor would be way too much. Citing code alone is not enough to stop everyone so it's worth mentioning if anyone else is reading this down the road.

I think that you misunderstood the question and therefore answer.
They didn't want to parallel two conductors in one cable. They wanted to parallel two cables.

 

[CableGuy]

I think that you misunderstood the question and therefore answer.
They didn't want to parallel two conductors in one cable. They wanted to parallel two cables.

there was some discussion of paralleling existing unused wires in a home to double current capacity, in reference to what the OP is "a pair of existing 50A 240V lines that run to the exact spot". I think it would be rare to have two 50amp 240 circuits run to the same place, and it's more likely a single 240v 50a circuit which would be a tandem breaker connected to 2 hot conductors on separate phased with a single neutral wire, or no neutral.

Even if this is not what he has, I think some readers could infer this comparing it to what they may find in their own home, such as an old 240v circuit for a basement clothes drier. if a reader is along that line of thinking, they will have a bigger problem (than code violations) if they try and parallel the hot conductors into a single phase with only 1 neutral cable.

i realize this is not what the OP was asking.

 

[CableGuy]

on a separate note, if he did have (2) true 50 amp 240 circuits, what would prevent him from parallel the inverters by not simply not paralleling the input circuits, just connect each inverter to 1 of the existing 50amp circuits on the other side of the basement, just as you would if they were 6 feet from the main panel. Each inverter even in parallel is going to have it's own breakers anyways?

 

[timselectric]

I think it would be rare to have two 50amp 240 circuits run to the same place,

Rare or not. We can only answer the questions that we are asked.
If someone else has a different circumstance, then they would have to ask a question pertaining to their situation.

 

[CableGuy]

Rare or not. We can only answer the questions that we are asked.
If someone else has a different circumstance, then they would have to ask a question pertaining to their situation.

There's no harm in confirrming that's what the OP is really working with, or mentioning he could be mistaken.

200 amp service is 100 amps on each leg. He says he has (2) 50 amp 240 circuits is (4) 50amp breakers run to the other side of the house. So the unused circuit is rated to max out what is likely his entire 200 amp service?

Highly unlikely....

 

[timselectric]

200 amp service is 100 amps on each leg.

It's actually 200a on each leg.

There's no harm in confirrming that's what the OP is really working with, or mentioning he could be mistaken.

I'm sorry, but you are the only one who is mistaken.
And you are 6 months behind.

 

[CableGuy]

It's actually 200a on each leg.

I'm sorry, but you are the only one who is mistaken.
And you are 6 months behind.

200 amp service is 100 amps on each leg. i doubt he has 200 amp breakers from the street. 6 months is nothing on a forum people will read for years. i still highly doubt he was referring to (4) 50amp breakers and you can't be sure of it either.

 

[timselectric]

200 amp service is 100 amps on each leg.

Incorrect
It's 200a of 240v
Or 200a + 200a (each leg) of 120v

 

[sumpower]

I've been installing 3/0 cu service conductors, seems like forever. 3/0 cu is good for 200 amps on each leg between the utility and the service disconnect. Also using a 200 amp breaker.

I would hope that @timselectric post gets a thank you from someone who reads this in the future.

 

[CableGuy]

utilize a pair of existing 50A 240V lines

@webbbn were you referring to 2 separate 50amp 240 circuits, which would have been (4) 50amp breakers?

if so, what were these 2 circuits originally installed for?

 

[CableGuy]

I've been installing 3/0 cu service conductors, seems like forever. 3/0 cu is good for 200 amps on each leg between the utility and the service disconnect. Also using a 200 amp breaker.

I would hope that @timselectric post gets a thank you from someone who reads this in the future.

my line of thinking was if there is existing unused wires, his home may be older only have 100 amp breakers from the street but that's not even a fair assumption without knowing the size of the home.

me incorrectly referring to tandem 100amp breakers from the street as "200 amp service" doesn't change my original point, being:

"was the OP really talking about (4) 50 amp breakers?" (connected to an unused pair of split phase circuits leading to the other side of his home)

if the OP was mistaken, the entire discussion would be about wiring that did not exist. if my suspicion is wrong, good. I will be even more curious to know what the circuits were intended for.

I don't know why anyone has such an issue with me wanting to confirm if that's what the OP really meant. if you aren't as curious as I am, just don't read it.

 

[webbbn]

@webbbn were you referring to 2 separate 50amp 240 circuits, which would have been (4) 50amp breakers?

if so, what were these 2 circuits originally installed for?

Yes. One was intended for an electric cooktop, but we have a gas cooktop, so that circuit is unused (although it is currently the grid connection for my inverter). The other was installed as a general purpose 50A 240 circuit in the garage, which is being used for my EV charger. There's another 50A 240 circuit next to it, which is powering a wall oven, and two more nearby that power two HVAC, although neither actually use anywhere near 50A (16 and 21 max).

The larger one is now powered by my inverter, and I'm planning on switching the other one over as soon as I'm sure there will be no issues with the load.

Yes, probably 80% of the load in my house is all concentrated in about 10-15' of wall space, on the opposite side of the house as the panel. Not a great design.

I've pretty much moved past this topic. The inverter does a great job of limiting grid current using the battery on the off chance that it exceeds the circuit capacity. There is still a chance that the battery could get too low to pick up the load, and I'm currently experimenting with an external charger connected to the other circuit that could kick in to charge the battery if it gets too low.

 

[CableGuy]

Yes. One was intended for an electric cooktop, but we have a gas cooktop, so that circuit is unused (although it is currently the grid connection for my inverter). The other was installed as a general purpose 50A 240 circuit in the garage, which is being used for my EV charger. There's another 50A 240 circuit next to it, which is powering a wall oven, and two more nearby that power two HVAC, although neither actually use anywhere near 50A (16 and 21 max).

The larger one is now powered by my inverter, and I'm planning on switching the other one over as soon as I'm sure there will be no issues with the load.

Yes, probably 80% of the load in my house is all concentrated in about 10-15' of wall space, on the opposite side of the house as the panel. Not a great design.

I've pretty much moved past this topic. The inverter does a great job of limiting grid current using the battery on the off chance that it exceeds the circuit capacity. There is still a chance that the battery could get too low to pick up the load, and I'm currently experimenting with an external charger connected to the other circuit that could kick in to charge the battery if it gets too low.

Thanks for the followup. At least if you add solar (or maybe you did) it will be easy to move those 80% of loads over to the inverter sub panel.