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Old 10-17-2021, 08:03 PM   #1
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How many amps can an inverter put out?

Could someone smarter than me explain this? I have a Magnum Energy Inverter/Charger Model MS2000. Its spec sheet says that the "Output power continuous watts" is 2000 which converts to 16.67 AC amps. However my inverter box has a 30 amp breaker on it and it has tripped twice when I tried to use over 30 amps. I tried several watts to amps converters online and they all say 16.67, which by the way is about 1/10 what batteries alone can put out, 170 DC amps before tripping it's breaker. So what piece am I missing to understand the difference between 16.67 amps and 30 amps AC?
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Old 10-17-2021, 08:08 PM   #2
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Are you on shore power? If so, the inverter passes the current from the shore power connection through the inverter (bypassing the circuitry which inverts power from DC -> AC)

This bypass must have a 30 amp limit.
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Old 10-17-2021, 08:18 PM   #3
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you have a problem with 12v amps vs 120 volt amps. You are taking 12volt power and inverting to 120volt power. Factor of 10 = 166.67 amps?
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Old 10-17-2021, 08:22 PM   #4
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The 30 amp breaker is on the AC side of the inverter.

Which breaker is tripping - the input or the output (1 or 2)?

The inverter’s internal AC transfer relay is rated for 30 amps per leg. The
pass-thru current must be no greater than 30 amps per leg or damage to the relays may occur.


file:///C:/Users/Andy/Downloads/64-0007%20Rev%20F%20(MS%20Series)_Web_1.pdf
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Old 10-17-2021, 08:25 PM   #5
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1 amp at 120 volts is 10 amps at 12 volts. Same the other way around. Both = 120 watts.

An inverter will need 160 amps at 12 volts to create 16 amps at 120 volts. Plus some loss in conversion.

Volts times amps = watts.

Watts are watts no matter what the volts or amps are.
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Old 10-17-2021, 08:29 PM   #6
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Your inverter will output 3300 watts for 5 seconds, most do have starting and operating ratings. If the breaker is a little weak that would trip it.
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Old 10-17-2021, 09:52 PM   #7
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Quote:
Originally Posted by andy29847 View Post
The 30 amp breaker is on the AC side of the inverter.
Which breaker is tripping - the input or the output (1 or 2)?
The inverter’s internal AC transfer relay is rated for 30 amps per leg. The
pass-thru current must be no greater than 30 amps per leg or damage to the relays may occur.
file:///C:/Users/Andy/Downloads/64-0007%20Rev%20F%20(MS%20Series)_Web_1.pdf
The only breaker is on the input
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Old 10-17-2021, 09:58 PM   #8
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Quote:
Originally Posted by pasdad1 View Post
Are you on shore power? If so, the inverter passes the current from the shore power connection through the inverter (bypassing the circuitry which inverts power from DC -> AC)

This bypass must have a 30 amp limit.
So if I upgrade to a 4000 watt inverter, will it have a 60 amp limit?
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Old 10-18-2021, 03:46 AM   #9
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Originally Posted by RV Vagabond View Post
So if I upgrade to a 4000 watt inverter, will it have a 60 amp limit?
No, the best your going to get is 50 amps.

That's the standard amperage for most RV nowdays.
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Old 10-18-2021, 05:16 AM   #10
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Quote:
Originally Posted by RV Vagabond View Post
The only breaker is on the input
You haven't told us enough about your coach and inverter to offer best advise. On my coach (Alpine Coach) the inverter is powered by AC and that circuit is protected by a 30 amp breaker in the main panel. The inverter has 2 circuits that feed AC power (passed through when connected to shore power or generator, produced from the inverter function when on bettery power) to the microwave and a couple of recepticles. Here is an illustration I made:



Some inverters have circuit protection as part of the inverter/charger unit (as opposed to having them in a panel).



Is the breaker that you are having trouble with in the main AC panel or is it on the side of the inverter/charger?
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Old 10-18-2021, 08:37 AM   #11
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Originally Posted by twinboat View Post
1 amp at 120 volts is 10 amps at 12 volts. Same the other way around. Both = 120 watts.

An inverter will need 160 amps at 12 volts to create 16 amps at 120 volts. Plus some loss in conversion.

Volts times amps = watts.

Watts are watts no matter what the volts or amps are.
Twinboat again is 100% correct, the 2000 watts output is not in question the conversion rate to the final voltage dictates how many amps are available for consumption. At 2000 watts the conversion from 12v to 120v is approximately 16.67 amps available to run 120v electronics. The higher the inverter watts the higher the potential amps that would be available at the end on the conversion process, but, since the inverter is sourcing the power needed for the conversion from the coach's battery bank the available energy to enable the process will be limited to the battery bank's storage amps combined with whatever power replenishment rate exists to restore the battery amps through shore, generator, solar or alternator power, etc.

Your 30 amp circuit breaker appears to be performing as intended since it is tripping when you attempt to consume over 30 amps, a situation, that is normally relegated to the wire gauge size utilized to support that circuit. If that circuit breaker did not trip, the additional amps being pulled through that circuit would potentially exceed the wire gauge capacity to support and the end result is increased heat that can easily lead to an electrical fire.
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Old 10-18-2021, 09:04 AM   #12
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Quote:
Originally Posted by RV Vagabond View Post
So if I upgrade to a 4000 watt inverter, will it have a 60 amp limit?



I assume you are talking about amps for your 120v appliances, right?


4000w / 120v AC = 33.33 AC amps (theoretical since breaker would trip at 30)


Remember: watts / voltage = amps



or another way to write it: voltage * amps = watts


Also, watts are watts, same unit of energy no matter if talking AC or DC.


ETA: if you are plugged into shore power then your inverter is passive. Shore power is passing through and the inverter portion of the device is not doing anything. This is only true for inverters that have a built in auto transfer switch. Mine does not, so it does not have an input for AC power. My auto transfer switch is a separate external device.
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Old 10-18-2021, 01:12 PM   #13
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I think it has been explained, but I'll say it again in slightly different words (just in case).


Your inverter unit can source power from either 12vdc batteries (inverting) or from external (shore/genset) 120vac power. Sourcing from external 120vac power is often called "pass-through". External power can be greater than what is available while inverting (changing DC to AC), but typically limited to 30A by an internal circuit breaker in the inverter unit. Maybe by an external breaker too.


When sourcing from 12v batteries, the inverter circuitry is limited by its design to 2000W, which means the 16.67 amps you calculated. To do that, it has to draw a lot more amps from the battery at 12v, roughly 10x as much. The watts-volts-amps relationship has already been explained, so I won't repeat. The inverter circuitry is unable to produce the 30A, so it can't trip the 30A breaker. If you had a bigger inverter capacity, it might get to the 30A limit.
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Old 10-18-2021, 04:38 PM   #14
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RVvagabond are you convinced? You have received several excellent detailed explanations.
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