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Old 02-27-2018, 09:17 PM   #1
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Transfer Switch Overcurrent Protection

Hello, this is my first post!

I've ordered 1000 Amp Hours of Lithium Ion batteries feeding a 3000 Watt Hybrid Inverter.

Rather than changing my existing panel and creating a sub-panel which is what most installs seem to do I've purchased an 50A Automatic Transfer Switch (ATS) that will choose between the inverter and shore-power as the supply to the main panel.

This will leave my main panel intact, and I will load shed accordingly when running from the inverter. This gives me greater flexibility by greater choice of what loads I want to run from the batteries.

Has anyone done this configuration? Are there any downsides that I'm not seeing?

Do I need to protect the ATS upstream on the shore-power side with an additional 50A CB to be NEC compliant, (or more importantly, safe)?

Thank you so much for your time in helping me figure this out!
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Old 02-27-2018, 10:08 PM   #2
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Not sure I follow - if you have a hybrid inverter it will have a pass-through capability with an internal transfer switch already integrated.

Why would you need another transfer switch?
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Old 02-27-2018, 10:51 PM   #3
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Not sure I follow - if you have a hybrid inverter it will have a pass-through capability with an internal transfer switch already integrated.

Why would you need another transfer switch?
The advantage of having the entire main panel powered by the inverter is that you have flexibility of which loads you want to run.

Think of this large inverter acting just like a generator.

I can theoretically achieve a total of 5900 watts surge capacity using a small quiet 2kw generator supporting the hybrid inverter.

My goal this summer is to go boondocking only with a small quiet generator. Charge the batteries during the morning. Have the ability to run both my ACs during the afternoon, and run one AC at night without any generator.

So given the typical passthru setup - If the inverter was on a 50amp branch circuit of the main panel powering one AC and *some* sockets, a small 2kw generator wouldn't have the ability to start the second AC compressor.
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Old 02-28-2018, 12:26 AM   #4
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You’ve obviously given this a good deal of thought. If it were me and were going to this expense (1000ah of lithium!) and was dead set on on running two AC units (!) I’d explore doubling up with two hybrid inverters running in tandem. I know the Victrons can do this and I think the Magnums can. That way as far as your panel is concerned it’s just always plugged into shore power. You’d wire all of your inverter outlets to normal power.

You’d want a maxed out solar system as well as your small generator to keep the batteries charged and the dual AC running.

Quite a system. I’ve never heard of someone running two ACs on a small generator.
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Old 02-28-2018, 10:19 AM   #5
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Not enough info , you using terms generically , so no idea of what you have ?
In " quality " solar / alternative energy systems / components , one of the 1st choices up front is weather you want grid connected or not , most any quality " grid connected inverters " have transfer switches in them by code / law .
This part of why most builders do sub-panels , in most cases they are adding , alternative energy system [ solar ] to an existing grid power supply .
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Old 02-28-2018, 10:32 AM   #6
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Thanks guys! Wow I'm glad I posted here.

With the info above I found an alternative inverter, the 'Go Power IC Series 3000W', which has full 50-amp split phase bypass. It has the "hybrid" functionality of the Magnum (it seems different manufactures have different terms for it, originally I thought they were the only game in town).

So there will no panel modifications, just add a new main breaker before the Inverter and I'm NEC compliant. I'll have 6800W surge, 5000W nominal during generator hours using the quiet little Honda.

I'm placing the batteries under the bed, so unfortunately that will require underbelly penetration to run cables due to the layout of the Globetrotter there's no good inside alternatives. I hope Amazon takes the gear I no longer need back.

Super happy about this! I'm really excited for boondocking this summer, this will really make it more comfortable. Thanks for all the help.


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You’d want a maxed out solar system as well as your small generator to keep the batteries charged and the dual AC running.
That's my next upgrade, unfortunately the roof space is so limited.
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Old 02-28-2018, 10:38 AM   #7
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30A Airstreams come with two shore power inputs and an automatic transfer switch (ATS) to select between the inputs. Both shore power inputs feed into the ATS, which in turn feeds into the main breaker panel. On my trailer, the default input is on the road side near the rear of the trailer and the secondary one is at the front of the trailer. The theory is that you would use the rear input for hooking up to a campsite pedestal and the front one for a generator. But they are really interchangeable.

There is no additional CB protection for this setup, other than what is in the main breaker panel.

Not sure of this helps to answer your query.


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Old 02-28-2018, 11:16 AM   #8
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I'm impressed with your plan. Most of all, I'm impressed with a focus on ability to run both AC units while boon docking. A kindred spirit! Keep us posted on the progress. Many happy trails to you and yours!
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Old 02-28-2018, 11:38 AM   #9
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Quote:
Originally Posted by russellt View Post
Thanks guys! Wow I'm glad I posted here.

With the info above I found an alternative inverter, the 'Go Power IC Series 3000W', which has full 50-amp split phase bypass. It has the "hybrid" functionality of the Magnum (it seems different manufactures have different terms for it, originally I thought they were the only game in town).

So there will no panel modifications, just add a new main breaker before the Inverter and I'm NEC compliant. I'll have 6800W surge, 5000W nominal during generator hours using the quiet little Honda.

I'm placing the batteries under the bed, so unfortunately that will require underbelly penetration to run cables due to the layout of the Globetrotter there's no good inside alternatives. I hope Amazon takes the gear I no longer need back.

Super happy about this! I'm really excited for boondocking this summer, this will really make it more comfortable. Thanks for all the help.




That's my next upgrade, unfortunately the roof space is so limited.
You should have room for 500-600 watts of solar. I can get 500 on my FC25 with no problem, 600 with creativity.

The Go Power 3000 isnt a hybrid inverter in that it can’t mix battery and generator/shore power together. It’s just an inverter that has a built in transfer switch. Given the expense you are going to here I’d think you’d want a hybrid system but that’s just me.

I know from experience that a little Honda 2000 generator and a Magnum hybrid inverter can just barely keep a single AC running with the Honda running at full power. Even at that it was still drawing power from the batteries to the tune of 75 amps or so at 4000’ altitude. Others have been able to convince a Honda to directly run a AC running flat out at lower altitudes. In both cases you’d want an Easy Start installed on your AC units to even have a hope.

If it were me I’d want two hybrid inverters in tandem giving me enough power to run whatever I’d want and simplify management. You’d have a 24v battery configuration so that the currents involved are slightly less scary because at 12v you are talking about 300A plus at times. I think you’ll also want a bigger generator than a little Honda, something in the 3000 watt range or two Hondas in parallel.

Boondocking with dual AC in hot climates without solar is going to require the generator(s) to run from morning to dusk to either charge the batteries and/or run the AC. Trying to do dual AC off grid is uncharted territory.

How about boodocking someplace cooler��
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Old 02-28-2018, 01:09 PM   #10
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The Go Power 3000 isn't a hybrid inverter
I'll double check this with the sales guy. He assured me it was, in the user manual under "4.5 POWER SHARING MODE 2" it seems to indicate it draws from battery to boost generator power.

http://gpelectric.com/files/gpelectr...eries_RevC.PDF

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I know from experience that a little Honda 2000 generator and a Magnum hybrid inverter can just barely keep a single AC running with the Honda running at full power.
OK interesting observation, thanks - According to Dometic the PENGUIN II's running watts is 1700W. I guess that's under ideal circumstances. We'll see how this pans out with my existing generator and I'll upgrade if required. I'll pick up those easy starts thanks for the tip, didn't know they existed!

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Originally Posted by daleyocum View Post
You should have room for 500-600 watts of solar. I can get 500 on my FC25 with no problem, 600 with creativity.
I'll go measure this out now. I've found flexible panels and I think with the right mix of 100w, 50w, and 30w hopefully I'll be able to get this done.

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How about boodocking someplace cooler
I wish. I live in Los Angeles so during the summer that will require travel very far from home.
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Old 02-28-2018, 10:08 PM   #11
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Quote:
OK interesting observation, thanks - According to Dometic the PENGUIN II's running watts is 1700W. I guess that's under ideal circumstances. We'll see how this pans out with my existing generator and I'll upgrade if required. I'll pick up those easy starts thanks for the tip, didn't know they existed!
The starting current for a AC, even with an EasyStart, can generate quite a spike of current. Thatís why a AC wonít start when you would think it would. God forbid two ACs tried to start at the same time!

I canít imagine you canít get at least 400watts from 100w panels on your roof. Hereís an example https://goo.gl/images/RGGGWG. Again 500 was no problem on my FC25. Some research will probably convince you to not do flexible panels due to their short life. I thought I wanted flexible panels until I learned how poorly they wear.
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Old 02-28-2018, 10:41 PM   #12
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I understand your setup now - the GoPower unit sounds interesting with full split phase bypass. I didn't realize such a hybrid inverter existed.

Not sure the size of your trailer. I have a 30', planning on 800w up top. I already have 2 EasyStarts installed on my AC units. They are a must if you are going to run from lithiums IMO, and generally speaking a great thing to have regardless to avoid the startup surge that a hard start devices produce.
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Old 03-01-2018, 03:18 AM   #13
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The Go Power 3000 isnt a hybrid inverter in that it canít mix battery and generator/shore power together. Itís just an inverter that has a built in transfer switch. Given the expense you are going to here Iíd think youíd want a hybrid system but thatís just me.
I stand corrected, sorry to be so hasty. It does seem that Go Power has slipped into the hybrid inverter market. They have an interesting product for those with 50 A service. Iíve not heard of anyone installing one on this forum. Anyone out there?
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