AC300 to Transfer Switch

I know what you mean about the fan noise – that was one thing that turned me off to using it!

I would try disconnecting everything and reconnecting one at a time to see if charging works: e.g. see if you can charge the B300 when it’s disconnected entirely, then connected to the AC300 when no solar, etc. Like I said, it definitely charged for me. Not sure why your’s would be different. I have only one B300, don’t know if you have more than one…

I just tested T500->B300 direct (no AC300 plugged in) which the manual shows should work. Unfortunately, that’s not working either. I’m thinking my B300 is messed up. Going to contact support again. This is getting ridiculous.

Try the following…when you recharge the unit using the grid, disconnect the cable between the battery and the transfer switch before recharging from the grid. When you’re fully charged, unplug the charging cable to the battery(from the grid) first and then reconnect the transfer switch cable. See if this helps.

I had a similar issue with the ep500 and found that if i disconnect the transfer switch before hooking up to the grid i won’t trip any breakers anymore. I had a unit teplaced because something shorted out. I haven’t had any issues as of late.

I have 3 PV panels supplying power most of the time but once in a while i still need to hook to the grid.

This is what helped me. I don’t know if it was actually a fix or if there was an issue with the first unit to begin with.

Thanks Felton. That is interesting the EP500 behaves similarly. Yes, your suggestion will work with the AC300. But we are trying to get to get it to work without detaching the cable, so we can leave the unit attached 24/7 and have UPS-functionality that will turn on and off as needed without human intervention.

I understand that you want the unit to work unhindered. I was suggesting the above to possibly help Bluetti troubleshoot.
I hope you get the issue resolved soon.

I notice on another thread about the EP500 and Bluetti’s sub panel, an upgrade from Bluetti was apparently released that isolated the neutrals on the panel to avoid errors. (Also see this post.) Looks like the same problem us transfer panel users are having.

Since their fix is to modify their own sub panel, I’m not hopeful our transfer switches will have a fix… Not that @BLUETTI has said anything to us…

I’m planning on getting a AC200Max to power a small load (lights etc) during blackouts, but do not have a transfer switch yet.

Is the key to ask the electrician to install a sub-panel with a transfer switch which specifically switches neutral ?

Yes, I believe that is the key. (Note the neutral has to be switched for each circuit.) It requires a lot more wires and it’s not common for a transfer switch so an electrician may think it’s unnecessary at first. Note I have only tested this with an AC300, I don’t know if the AC200 products are the same.

Any updates on this as a long term fix?

I was using a reliance transfer switch for my AC300 and 2 B300’s and it turned itself off and would not turn back on, This is the message I sent Winnie from Bluetti when she asked how it was hooked up when it happened.

I did have the unit connected to a transfer switch, (which I purchased exclusively for this >configuration) My transfer switch is running only 5 circuits, mostly lights and a few LED >televisions and a computer.

I ran a test of the unit for about 3 hrs running these circuits (well below it’s capacity) when the >AC300 shut off with the .008 OCP (Over Current Protection) -Hardware alarm. Overall I have >been running the AC inverter for roughly 5 or 6 hrs total on and off including the 3 hour >continuous ac inverter test of the system.

The manual did not indicate that any of this would be a problem.

Winnie replied with this:

Sorry for the late reply because of the holiday. And thank you for sending it back.

  1. We will send the new AC300 to you, so it will include all the accessories.
  1. We have a batch of the AC300 which is solved this problem. I have already sent one of them to >you. Here is the tracking number: 274014686896 FedEx
  1. Sorry that we currently do not have a plan to release a smaller switch. I will report your >suggestion to the correlate department to see if we can develop one.

Best regards,


Now, as stated from previous posters, My Transfer switch routes the hot to the switch but not the Neutral. If Winnie was not just giving me lip service The replacement should not have a problem with this configuration. Because, I hope that I do not have to return the replacement with the same issue.
We’ll see.

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Thanks Mudpuppy… that is interesting. Someone over at the Bluetti Facebook forums said the same thing (Winnie was sending him a unit that “solves” the transfer switch issue).

Would love to know your results once you get it and have it tested…

what model reliance are you using?

So that’s not true. A true transfer switch isolates the neutral wire from each source. If the reliant doesn’t do this then you have a path, not common to happen, for power to return to the main panel. It does not be rely on the rule that power returns to it’s source. As a safety measure your neutral must be isolated for each input source.

I have the Generac 50 amp transfer switch. Each hot and neutral wire are pigtailed into the transfer switch for every circuit I want to run from my main panel. When I transfer the power between sources the 2 hots and neutral are switched.

The other issue I hear on this forum is the bonding on the neutral and ground. This is only allowed at your main panel.

Lastly this has nothing to do with a transfer switch. You can repeat this issue of the ac output being interrupted by a ac grid power status change with the unit is not connected to any outbound devices. Which means it’s not a transfer switch issue.

I do agree with the comment that this is probably due to a relay that triggers when ac grid power status is changed… But I doubt there is anything that can be done for this, as this sounds like an architecture problem… Not a software problem.

Yes it is true. Some transfer switches do switch the neutral but the most common ones that people install for generator use (e.g. Pro/Tran - Products - Reliance Controls Corporation) do not. Probably the main reason being you have to run four wires for every circuit instead of two, which gets impractical when you are just ‘splicing’ into an existing panel. Sub-panels isolate the neutral which perhaps some people call a transfer switch.

You can plug an outlet tester into one of the outlets of the AC300, and see it switch from bonded to non-bonded when you switch between bypass and the inverter. I don’t think it’s technically proper, but it clearly does that.

My AC300 does not interrupt AC output when switching to/from grid power when anything is directly plugged into it. That works 100% reliably. Only when connected to my (shared neutral) transfer panel. Other people in this thread report the same behavior.

Recycle, regarding your first line - i am trying to use the Reliance 310/a pro/tran 2- are you certain this does not switch the neutral? here’s the manual

if it does not, are you saying this is not compatible with the ac300? my Reliance 310/A required me to wire a neutral and ground to the main panel, and for every circuit: you tie the panel breaker hot (black) to the Reliance black and insert the corresponding Reliance red into the individual panel breaker hot (that i just pulled the black wire from). forgive the newbie question here: i’m just curious if i’m using the wrong transfer switch

Reliance Controls 30310A Pro/Tran 10-Circuit 30-Amp Indoor Generator Transfer Switch

I also hooked-up two of these which do work:

I think yours is like mine and does not switch the neutral. Looking at this figure from your user manual (page 5):

You’ll notice there is only one neutral line (red arrow) for all the circuits. A neutral switching-one would have neutral lines for each black- and red- lettered connector. This of course would mean 24 wires instead of 12 for your 6-circuit switch, which is why I think they “cheat” and just share the neutral.

correct, i see what you mean - so are you saying that this transfer switch is problematic? because it does not switch the neutral? problematic in terms of being compatible with ac300s in split phase set up (with a 240v circuit) i mean

In order to pass local code and inspection your transfer switch must isolate the hot and neutral wires from the main breaker to ensure no back-feed to local grid. I’m not going back and forth with this, if you went with a switch that doesn’t isolate it because you wanted to save on wires that fine with me… but reliance does make an x-series that does this.

Concerning the switch from bonded to non-bounded that is not done by the AC300. When you plug your tester into the the outbound ac ports of your ac300 with no incoming grid you’ll see that its not bonded. When you plug in your AC grid, the pass-though allows your tester to see the bonding of neutral and ground from your main panel… this even happens before the AC input is turned on by the AC300.

The AC output is only interrupted when the AC Grid “Input” is introduced or taken away.

The X-series does switch the neutral. The more common Reliance ProTrans series does not. (See the wiring diagram I posted directly from a Reliance manual above.) I didn’t choose this to save wires, this is how most transfer switches were designed. Reliance still sells these switches so I gather they must still pass some codes.

Yes, that is what I said. From the perspective of the device you have plugged in, it changes from bonded to non-bonded though.

Not if you have a device plugged in directly. AC output remains on in both cases for devices directly plugged in. AC output is turned off only with certain transfer switches. And only when grid power is introduced, not when it is taken away.