WARNING! Do not use any NON GFI transfer switch with your Bluetti product

@Wuastr i just bought a 3 pole sub panel to replace my pro/tran2, but now I see your post that a 4 pole is needed. Is it possible to isolate the ac300 neutral with a 3 pole sub panel?

I chose a Reliance XRC series 3 pole panel because it was recommended specifically for commercial generators and should work with my AFCI/GFCI breakers.

@Wuastr also, it sounds like we cannot plug the AC300 to a house circuit to charge from the grid in PV priority UPS mode while running load from the AC300 to the sub panel, as that would connect the AC300 to house neutral and undo the AC300 neutral separation - or am I missing something?
It also sounds like I need a grounding rod at the solar panel array once the neutrals are isolated.

I am not the expert here but what I know and what has been confirmed multiple times in forums and by my question to Bluetti is that the AC300 Neutral CANNOT be connected to your house grid Neutral. Typically this will occur when you plug in the AC300 to charge IF your loads are not plugged directly into the AC300 but through a transfer system that doesn’t take the need to isolate neutrals into account. I looked up the Reliance you mentioned and it sounds like it might work. http://www.reliancecontrols.com/Documents/XRC%20Tech%20Spec%20108A.pdf

„ The New Reliance Panel/Link X Series is a double-pole manual transfer switch with an exclusive third-pole for the neutral that switches sequentially. The X Series is perfect for use with generators having GFCI protected outlets, bonded neutral generators and installations requiring a separately-derived system.“

The GFI 4 pole I mentioned is for a 3 phase wire system (240 volt in the US). Not to be confused with the Reliance single phase switch box - if that is what it is.
Note. My background is avionics not house electricity.
I did become quite concerned when I took my multimeter to the normal plug ground and to one of the plug outputs. Normally I would expect either supply voltage (120 volts in the US) or Zero volts. Hot or Neutral. What you see is half voltage on (60 volts) in reference to the ground in both. 120 volts of course between Hot and Neutral. Floating Ground in other words. I want to see supply or zero. I want the plug Gnd to be GROUNDED. So I force the AC300 to be referenced to my house ground by tying Neutral and Ground together and running an extra wire to house earth. If this earth tie point is done in the transfer switch no problem.

No such thing as GFI switching…Its a transfer switch that switches both legs. GFCI and Arc fault devices will not allow a downstream connection of the following: neutral to ground/neutral to phase/phase to ground. Bluetti as well as other battery power units will not tolerate “bonding” their neutral to ground. so >>> you switch BOTH legs if you are using a transfer switch

1 Like

@EZGeneratorSwitch thank you for the concise and informative clarification. This will get me set up correctly.

@EZGeneratorSwitch Hi. I am attempting a critical load UPS with three circuits. Not a complete transfer, but 3 individual choices between sources (Grid and AC300). In Germany there are no commercial transfer switches available. I used three On-Off-On 2 pole CB type switches mounted directly in the panel between the GFI and the output CB‘s.

My issue is the AC charging circuit CB in the house panel will open when output circuits are connected and AC is selected ON on the AC300. In addition the GFI breaker does not trip when test button pushed.

I was told to tie earth and neutral together as close as possible to the AC300 and run a separate ground wire to earth and you state apparently the opposite. “ units will not tolerate “bonding” their neutral to ground”
I was concerned about the floating ground on the AC300.

Tonight I removed the Neutral and Ground tie jumpers I had installed and issue is resolved.

Still working the inoperative GFI. Maybe bad from stock.


That’s a really useful information

1 Like


August 9


  • | - |

@EZGeneratorSwitch Hi. I am attempting a critical load UPS with three circuits. Not a complete transfer, but 3 individual choices between sources (Grid and AC300). In Germany there are no commercial transfer switches available.

Not sure why there are no transfer switches in Germany, how often do you lose power?

My issue is the AC charging circuit CB in the house panel will open when output circuits are connected and AC is selected ON on the AC300. In addition the GFI breaker does not trip when test button pushed. The GFCI breaker is bad if it doesn’t trip when the test button is pushed

I was told to tie earth and neutral together as close as possible to the AC300 and run a separate ground wire to earth and you state apparently the opposite. “ units will not tolerate “bonding” their neutral to ground”
I was concerned about the floating ground on the AC300.

These are BATERRIES not AC current. Batteries can not tolerate grounding any leg. Think of your car…you don’t ground either leg of the car to earth. All the AC300 is doing is taking power from the Battery DC and making it a AC sine wave with a inverter.

Still it can’t be grounded. Both legs must float. HOW are you making 230 volts? Doesn’t the AC300 put out 120 volts or is that unit special to Europe and supply 230 volts?

I Built my own Critical Load (3X) circuit in Germany. Integrated into existing CB panel. 3 separate heavy gauge AC plugs.



Neutral from AC300 kept completely separate from House Neutral. Ground and Neutral tied together. Neutral separation to protect AC300 when charging from House grid.

3 ON-OFF-ON 2 pole switches to switch Hot and Neutral. With this I can individually select feed source (House or AC300) to critical circuit.



So the solution is to stop tying neutral and ground together?


Thanks for your input. I believe I have solved my basic issue, but appreciate your help. Removing the ground - neutral connection at the AC300 before the junction box solved the CB opening . I still have the GFCI breaker not testing correctly. During the night both the main house GFCI and my newly installed AC300 GFCI opened and the house was completely without electricity. Still some work to do. In the meantime I unplug the AC300 when charging is not needed.

Yes in Europe the AC300 matches the voltage used here, 240 volts. This may be why Bluetti transfer switch is not available since it requires different connection and multiple approvals.
We do not have many power outages to date, but the future is uncertain. In any event I am not building a transfer switch per se, rather a 3 critical load UPS for the house - with the option to remove any of the three loads from the UPS (AC300) and supply power from the grid instead, if needed or desired. The idea is to increase self use of the excess solar capacity I have by storing excess PV during the day and feeding back during the night.

Since we are feeding into the house grid the ground on the AC300 AC output plugs MUST be referenced to the same potential as found in the house ground circuit and have negligible resistance to Earth. I have this now. Neutral however MUST have the same electrical potential as the house ground. Without this you can have shock potential if the neutral touches case and, in any event, any house installed Ground Fault protection will not work properly if ground reference is not correct. Neutral is isolated completely now which is why the GFCI doesn’t work I suspect…

Currently Neutral and Ground are not the same potential and I must find a solution.

In any event batteries don’t really care if their negative has the same potential as earth, but we are talking about AC inverters anyway.

Might check out Bluetti AC300 - Neutral Bonded Grounding and GFCI/AFCI outlets. - YouTube

Hi @Wuastr - the video you referenced on YouTube for Neutral Bonded Grounding is my video.

I’ve been working with support on the grounding issue for the last few weeks because the use of a floating generator connected to a neutral switched transfer switch in the USA is a NEC violation.

For those with a transfer switch that does not switch the neutral they have access to the bonded neutral from their main panel…

However for those of us that have a switched neutral transfer switch and connect a generator we are creating a SDS “Separately Derived System”. With a SDS we are required to have a bonded neutral and have a grounding rod. Due to the fact that the AC300 is a floating neutral generator, we are required to bond the neutral at the AC300 or transfer switch. I choose not to bond the neutral at the transfer switch because that would effect my grid configuration when I flip back to utility power.

The use of a neutral bonding plug is not a new thing for the AC300. Bluetti support has told other users to use them to make their Tesla EV Chargers work.

Hope this will give you some insight to your configuration… but obviously what I mention is related to US configurations.

1 Like

@twister36 Hi David. I am at a bit of a standstill here. Currently if the AC300 is plugged in for charging I have a quasi bonded neutral it appears via the charging plug. At least the AC300 neutral AC output no longer has voltage on it. If I jumper ground to neutral at the AC300 AC output (like you do with the bonding plug) my House GFI opens. This is with AC on selected and No loads plugged in.

There is an additional source for error in our system since the house outlets have no specific Hot or Neutral position. If you make a bonding plug you can easily short the Hot to Ground. Here you can see the voltage split between Neutral and Hot referenced to ground. If I plug in the AC300 this issue is resolved.

Getting tired of resetting the oven clock every time the house looses power.

Can you explain what you mean by “quasi bonded neutral”… ?

By plugging your AC300 into the grid for charging will ground that side of the AC300, but it will not pass the ground to your AC300 outputs.

So my method of using a grounding plug may not apply to your countries method for delivering power to your home. In your country is it typical for your main panels utility wires to be bonded to ground? If so, which wires? I would assume you need to repeat this configuration on your generator side.

When AC charging plug is used I have Ground = Neutral and no floating ground and no BAD voltage on my neutral outputs on the output connectors of the AC300, hence my use of the word Quasi. When AC300 is no longer plugged in I lose the Ground = Neutral. Now yesterday I added a jumper between Ground and Neutral on the output junction according to Code and Bluetti approval of my plan. The plan showed Neutral switched separately and a common bonding ground. This jumper resulting in GFCI house breaker opening AND AC300 now has to go back to the Mothership due to Error Code 800 and the unit shutting of twice a day. Once you get the dreaded 800 the AC300 is toast. It shuts AC output off willy nilly and you have to do a complete reset including pulling solar input plug when it happens.

Next stop either EP500 Pro OR EcoFlow Delta Pro and Smart Home Panel which is made for such an installation. I suspect I am done with the AC300 for my house.

Update. After experiencing the GFCI fault for the house wiring and subsequent Error code 0800 now showing up, I measured AC300 outlet ground to Neutral with AC plugged in. Neutral is now HOT carrying half the output voltage. Before the fault I had my outlet ground and neutral at the same potential when AC300 was plugged into house AC. After repair or replacement of AC300 I will use an isolation transformer for AC input.

1 Like

Any GFCI or Arc fault will trip instantly because both monitor any loss of current to either ground or neutral or to a phase leg. A bonding plug ( which should be illegal and “most” don’t even have a label) connect the neutral to ground and your device will open in less than 5 milliamps

Canada and the USA require the neutral from the utility to be Bonded at the first means of disconnect ( first house panel). This is the ONLY place a neutral and ground are bonded together. From this point your grounding electrode conductor connect to two means of ground unbroken. It can be Ground rods, water line or ground plates… any combo of two

In my setup I have a SDS because my transfer switch also switches the neutral wire. Therefore I have no access to the bonded neutral of the main panel. This is why in my setup/environment, and per NEC requirements, the generator must be bonded. Due to my system being a SDS, the generator is the first means.

You are correct for those running a Pro/Tran or other transfer switch that does not switch the neutral wire. As they have access to the bonded neutral in the main panel and therefore do not need and should not make their generator a bonded neutral.

1 Like

I am going to try this with the upcoming AC500. Bring both into this then to the main panel.

SDS is NOT determined by the switch. It is determined by which type of source you have. If your source is a BONDED NEUTRAL then you have a SDS and it requires you use a transfer switch that switches the neutral. NEC 702.11 also requires it shall be grounded to a grounding electrode.
So if your source is a Floating Neutral ( bluetti) then you don’t have a SDS. Here is where it gets fuzzy… Bluetti is NOT like a regular generator it is a battery source converting to a AC power wave. That “new” power source has zero affiliation with ground as we know it (just like solar) and in some cases will harm that source should you ground the “neutral” as you would with a service.
Transfer switches that do not switch the neutral are for Floating neutral generators Non SDS systems.

1 Like

I can see how you read that I said that SDS was related to the transfer switch… but that’s not what I meant.

In my environment I bonded my neutral at the AC300 because my transfer switch does switch the neutral and I have no access to bonding at the grid main. Additionally I required that ground faults would cause a trip and not leave the potential at the faulty device. With this, my environment is a SDS.