Output current capacity of my system....

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louie

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I currently have (2) inverter, each of which are 5000VA, 240V, 60Hz.
The full load capacity of each inverter is 21A. I have these inverters connected in parallel, so my total full load capacity is actually 42A @ 240V.

This system is feeding a panel which is loaded with only 120V circuits.

Is my thinking correct in saying that my actual capacity is 42A per phase and that since my circuits are only 120V...I really have a system with a 84 A capacity (at 100% load).

Clarification please......
 
I would call it a 42 amp 120/240V service. You can either get 42 amps at 240V, or you can get 42 amps off of either 120V leg. There shouldn't be 84 amps flowing anywhere.
 
Clarification: You have a capacity of 10 Kva, no matter how it's delivered. You can supply 42a @ 240v or 84a @ 120v, or you can deliver 21a @ 240 and 42a @ 120v, or any other mixed combination, as long as the total does not exceed 10 Kva.

The line-to-line loads will draw evenly from both hots, so the concern is to not attempt to use more than the remaining capacity of either hot. For example, if you have 20a of 240v load running, that leaves only 22a capacity on either hot, or both.
 
LarryFine said:
Clarification: You have a capacity of 10 Kva, no matter how it's delivered. You can supply 42a @ 240v or 84a @ 120v, or you can deliver 21a @ 240 and 42a @ 120v, or any other mixed combination, as long as the total does not exceed 10 Kva.

The line-to-line loads will draw evenly from both hots, so the concern is to not attempt to use more than the remaining capacity of either hot. For example, if you have 20a of 240v load running, that leaves only 22a capacity on either hot, or both.
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That would depend on the specifications for the inverters. I would guess that they are probably designed to deliver 21A @ 240V, and that the phases aren't built to handle 42 amps. Again, thats just a guess. You need to get the specs on the inverters and verify it can handle 42A before you place that much load on it.

Steve
 
Larry, I guess what I should have said was, there might be 42 amps @120V flowing to each leg, but there shouldn't be 84 amps @120V flowing in any single wire. In other words....a 10kVA 120V load could not be fed as a single circuit. Am I wrong?
 
steve66 said:
That would depend on the specifications for the inverters. I would guess that they are probably designed to deliver 21A @ 240V, and that the phases aren't built to handle 42 amps. Again, thats just a guess. You need to get the specs on the inverters and verify it can handle 42A before you place that much load on it.
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Steve, read again:

louie said:
I currently have (2) inverter, each of which are 5000VA, 240V, 60Hz.
The full load capacity of each inverter is 21A. I have these inverters connected in parallel, so my total full load capacity is actually 42A @ 240V.
Click to expand...

These inverters can be paralleled.


bcorbin said:
Larry, I guess what I should have said was, there might be 42 amps @120V flowing to each leg, but there shouldn't be 84 amps @120V flowing in any single wire. In other words....a 10kVA 120V load could not be fed as a single circuit. Am I wrong?
Click to expand...
Not at all. Just like a 200-amp service, you can draw a maximum of 200 amps on any or all phases at once.
 
Right. 200 amps per phase (or leg, for 120/240V). If he's serving 120V loads, the maximum aperage of any circuit is the maximum amperage of the leg. So, for 42 amps at 240V, the most he can pull off of one leg, is 42 amps, 5kVA, or half of the service.
 
Larry:

I'm not sure I understand what you are saying (two inverters is making this more complex than it needs to be).

Say you have one single inverter rated 10KVA at 240V, or equivalenty rated 42 amps at 240V. That is no guarentee that you can pull 84 amps at 120 volts out of the same inverter.

(Earlier I meant you may not be able to pull 42A from each inverter for a total of 84 amps on one phase.)

Steve
 
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steve66 said:
Larry:

I'm not sure I understand what you are saying (two inverters is making this more complex than it needs to be).

Say you have one single inverter rated 10KVA at 240V, or equivalenty rated 42 amps at 240V. That is no guarentee that you can pull 84 amps at 120 volts out of the same inverter.

(Earlier I meant you may not be able to pull 42A from each inverter for a total of 84 amps on one phase.)

Steve
Click to expand...

Agreed. You do understand it. That there are two inverters is not relevant. The total source is 240/120v @ 42 amps. If one uses only one hot, the limit is still 42 amps.

42a @ 120v is half the power of 42a @ 240v; 5 Kva instead of 10 Kva. The max current per leg is not dependent on the voltage between cirtcuit conductors.
 
My main point was, we typically describe a 120/240V system by how many amps it can deliver at 240V. While Louie can accurately state that he can serve 84 amps of 120V loads, it might not be a good idea to state it that way.

Imaginary Job:

Me: Yes, install a 200A 120/240V panelboard.

Evil Contractor: Sure. I'll get something in there.

Me (two weeks later): Hey!....this is only a 100A panel!

Evil Contractor: It delivers 200A at 120V.

Me: !@#$%^$@
 
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