Inverter input breaker question

mervin101

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Hello all.

My first post so here goes. I built a small test system to try and learn. I have an 12V 3500W EDECOA Pure Sine Wave Power Inverter powered by a bank of six
Renogy 12 Volt Solar Panel 100 Watt High-Efficiency Monocrystalline Modules. They are running through a
Epever MPPT Solar Charge Controller 20A 150V PV to a bank of six Everstart 27DC 80 Amp Hour deep cycle batteries wired in parallel. I have 30 amp breakers between the charge controller and the battery bank. I have 100 amp breakers between the battery bank and Inverter. When I connect a 1500 Watt load the 100 amp breaker pops. I cannot find anything that shows the max amp draw allow for inverters. Do I need the 100 amp breakers?

Thanks in advance
 

rmaddy

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1500W load / 12V battery = 125A. That's why your 100A breaker trips. To fully support a 3500W inverter at 12V (which is really too much) you need wire capable of handling 340A and a 425A breaker. To handle 340A you should have a pair of 2/0 wires between each connector. I have no idea what wire size you actually have but it's unlikely you have sufficient wire.

Does the manual for your inverter offer any suggestions on wire size and fuse/breaker size?
 

sunshine_eggo

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1500W / 12V / 0.8 (inefficiency) = 156A

Your inverter may pull as much as:

3500W/12V/.8 = 365A

EDIT: 600W of solar?

600W/12V = 50A. With a 20A charge controller, you're potentially leaving a lot of juice unutilized.

If these 6 panels are in series, depending on their Voc, they may get dangerously close to 150V PV input on cold days.
 

mervin101

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1500W / 12V / 0.8 (inefficiency) = 156A

Your inverter may pull as much as:

3500W/12V/.8 = 365A

EDIT: 600W of solar?

600W/12V = 50A. With a 20A charge controller, you're potentially leaving a lot of juice unutilized.

If these 6 panels are in series, depending on their Voc, they may get dangerously close to 150V PV input on cold days.
Presently the panels are in parrallel. Also I forgot to mention I am using 2 AWG wire between charger controller and batteries to the inverter.
 

sunshine_eggo

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Presently the panels are in parrallel. Also I forgot to mention I am using 2 AWG wire between charger controller and batteries to the inverter.

Low PV voltage/high current = wiring losses. A 3S2P array would likely be about optimal.

Regardless, to capture your array's full potential you need a higher current MPPT.
 

mervin101

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1500W load / 12V battery = 125A. That's why your 100A breaker trips. To fully support a 3500W inverter at 12V (which is really too much) you need wire capable of handling 340A and a 425A breaker. To handle 340A you should have a pair of 2/0 wires between each connector. I have no idea what wire size you actually have but it's unlikely you have sufficient wire.

Does the manual for your inverter offer any suggestions on wire size and fuse/breaker size?
No, I am using 2 AWG wire.
 

rmaddy

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2AWG wire is currently safe because the 100A breaker is well below what 2AWG can carry. But 2AWG wires are very, very undersized for a 3500W inverter at 12V. Please note that 2/0AWG is not the same as 2AWG. 2/0AWG is a lot bigger.

Edit: You don't need dual-2/0AWG to the charge controller. Just between the batteries and the inverter. For a 20A charge controller you could use 14AWG. But you need a 50A charge controller which would need 6AWG wire.
 
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mervin101

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Low PV voltage/high current = wiring losses. A 3S2P array would likely be about optimal.

Regardless, to capture your array's full potential you need a higher current MPPT.
Yes I will look at a larger MPPT, just trying to figure out the safest breaker size to install to allow the inverter to run a 1500 Watt load without tripping
 

rmaddy

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trying to figure out the safest breaker size to install to allow the inverter to run a 1500 Watt load without tripping
2AWG wire isn't really big enough even for a 1500W load. You should have 1AWG for 1500W at 12V. And you would then use a 175 or 200A breaker. But do not use such a breaker with your existing 2AWG. It's dangerous.
 

sunshine_eggo

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But the 2AWG will have a large voltage drop. And really 200A is going get 2AWG wire really hot. I like the Blue Sea Systems wire and fuse chart. It covers both ampacity and voltage drop.

LOL.. I was just typing as post with that realization on my part... too true.
 

rmaddy

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trying to figure out the safest breaker size to install to allow the inverter to run a 1500 Watt load without tripping
With your existing 2AWG wire you shouldn't really try to use more than a 1200W load. It would be safe to use up to a 200A breaker with your existing 2AWG wire. But this assumes you have high quality stranded copper wire with 105ºC rated insulation. Lower all of the numbers if you have lower quality wire.
 

mervin101

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2AWG wire is currently safe because the 100A breaker is well below what 2AWG can carry. But 2AWG wire are very, very undersized for a 3500W inverter at 12V. Please note that 2/0AWG is not the same as 2AWG. 2/0AWG is a lot bigger.

Edit: You don't need dual-2/0AWG to the charge controller. Just between the batteries and the inverter. For a 20A charge controller you could use 14AWG. But you need a 50A charge controller which would need 6AWG wire.
Just checked I have 2 AWG between everything, wire diameter .28. I will look at getting some 2/0 AWG for the battery to inverter connection. any recommendations on where to get a breaker of that size?
 

mervin101

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With your existing 2AWG wire you shouldn't really try to use more than a 1200W load. It would be safe to use up to a 200A breaker with your existing 2AWG wire. But this assumes you have high quality stranded copper wire with 105ºC rated insulation. Lower all of the numbers if you have lower quality wire.
I am really looking to run the 1500 watt load so I will look to upgrade the wire sizing.
 

sunshine_eggo

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Just checked I have 2 AWG between everything, wire diameter .28. I will look at getting some 2/0 AWG for the battery to inverter connection. any recommendations on where to get a breaker of that size?

In addition to size, the temperature rating matters. The same size wire may have 60, 75, 90, 105 or 200°C rated insulation and can carry different currents.

Don't have a breaker source.
 

rmaddy

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Is the 1500 load the max you ever plan to use? What is this 1500W load? Does it have a motor or something that will cause a big surge on startup?

Even though you have a 3500W inverter you can wire and fuse for a lower usage. But then why not just buy a much cheaper 2000W inverter?
 

mervin101

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Is the 1500 load the max you ever plan to use? What is this 1500W load? Does it have a motor or something that will cause a big surge on startup?

Even though you have a 3500W inverter you can wire and fuse for a lower usage. But then why not just buy a much cheaper 2000W inverter?
the 1500 load is a space heater
 

rmaddy

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A space heater won't have a big surge so if that space heater is the most you ever plan to use, you would be better off with a smaller inverter.

If the space heater has a few heat settings you could try a lower setting. A setting that uses about a 1000-1100W would probably work with your existing 100A breaker.
 

Bvillebob

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Let's see, you have 480 amp hours of lead batteries, meaning you shouldn't be using more than about 240 amp hours from them. A 1500 watt space heater will need perhaps 160 amps or a little more to allow for inverter and wire losses, so your system will run that heater for about an hour and a half.

Unless that's your plan your system is really undersized for the size of the inverter and your desired load. both in amp hours of storage and panels.
 
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