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Autotransformer and shore power

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Glenn, there's a difference in an Autotransformer versus an Isolation Transformer and Im not sure what product or device (transformers or Inverters) you're using, what it is, and how it operates so cant answer your question absent further detail and a wiring diagram. The 120/240 Volt Single Phase Three Wire utility service such as available in an RV parks power pedestal can be replicated with an Isolation Transformer (makes a new Neutral) with the same 120/240 Single Phase Three Wire output..  I need the details and wiring diagram of whatever "transformer" or "Inverter" you're talking about .........


 John T

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As John said it is all in how it is wired.  Any power supply needs to be isolated from another supply unless one is designed to coordinate with another.  From what I see neither of the supplies you are referring to have that capability but I haven't looked at the spec's.   If the inverter chargers you are considering have pass through capabilities that you plan on using it could be complicated.  On the other hand if you isolate the circuits by relays or just a plug arrangement you can have all the options for shore power you have now OR use the inverter/transformer power.

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32 minutes ago, Randyretired said:

I am assuming you plan on using the pass through on the inverters?  If you plug 120v into that will the inverters and transformer be able to handle that and pass through the power you need?  I don't have the specifications but that could be a problem.

Ok, the inverter doesn't state pass thru. States if solar not enough, it will pull from grid as needed. Also will work without batteries but I will have. It is an all in one unit. mppt built in. They actually recommend an autotransformer for it if spilt phase needed. They sell one but it is 5k only. So I would need 2. Same cost as Victron 100 amp So going to get the Victron unit.  


Edited by GlennWest
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Only comment I see him make on generator is the neutral. But I will not have the neutral hooked up from ulility lead in wires. So if generator is hooked up, no neutral. The way the adapters are formed should have power to both legs. Generator should work with the reduced power of generator. Only reason I be concerned about a generator is a snow/ice storm like we had this winter in Texas. Solar would not have worked. If for some reason it doesn't like the generator, I could wire in a bypass. 

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3 hours ago, GlennWest said:

So if generator is hooked up, no neutral

Glenn, just a FYI in case you didn't already know or perhaps maybe help others:

1) Some gensets come from the factory with a BONDED Neutral

2) Some gensets come from the factory with a FLOATING Neutral

3) Its possible to have a straight 240 VAC only device with NO Neutral.

4) Its possible and easy to create a Bonded Neutral if it came Floating

5) Which (Bonded or Floating) should be used depends on how and where its used and how transfer/switching takes place PRIMARILY BASED ON THE PRINCIPLE OF SINGLE POINT GROUNDING IE THERE SHOULD BE ONLY ONE BOND.... 

6) Typically the RV main distribution panel (UNLIKE homes panel) has separate insulated and isolated Neutral and Ground Busses..since the ONLY ONE Neutral Ground Bond has already been created in the parks distribution system.

7) An Inverter could create a Bond using a relay such that its only present when in use

😎 Typically if an RV is running on genset or inverter power that device has a BONDED Neutral as the RV panel does not Bond.

9)  120/240 Volt Single Phase Three Wire service like for a home orrrrrrrrrr a Genset can be configured with a 240 volt output that has a center tapped Neutral so L1 is 1/2 or 120 to Neutral while L2 is also 1/2 or 120 to Neutral and again typically bonded. 

10) To figure out what all you have and may end up with requires wiring diagrams of every component as well as a wiring diagram of your whole system, so take this as general NOT specific advice when designing your system. IE consult the manufacturer and Manual NOT any of us when designing your system !!!

PS an Autotransformer has a common conductor passing through from Primary over to Secondary while a regular or isolation transformer does not.

 Best wishes Glenn, 

John T  

Edited by oldjohnt
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