Move critical loads from load center to standalone inlets to safely use PPS as UPS

[jester74]

Hi all!

Long-time lurker, first time posting. First of all, thank you to all contributors here, I've learned a TON. Truly appreciate the shared knowledge.

My current question:
I have an EcoFlow Delta mini which I hope to as a UPS strictly for my fridge (typically 70 watts, no more than 500w when using ice-maker heat strip), a small freezer (about 150 watts) and minimal electronics (router and NAS another 150 watts). The Delta runs them fine when plugged directly in to the unit.

I have read just about every thread regarding the nightmares of using portable power stations as a parallel-to-grid UPS (or EPS) where the portable power station is plugged to the inlet of a transfer switch that typically does not switch the neutral wire, which then clashes with the neutral feeding the AC-in of the PPS and things trip, give errors or release smoke.

My idea around this is the following:
What if at the main panel I completely remove the romex going to my critical loads (confirming there's only one outlet per each circuit... the kitchen fridge, the garage freezer, and the router/NAS outlet) and instead terminate them at three separate 120v male inlets immediately outside/beside the main panel? Basically turning those three circuits into code-friendly in-wall romex extension cords. I could then plug those inlets to the Delta while the Delta itself is plugged in to a separate circuit from the grid. This would make it so there's zero chance of neutral loops, and would still let me have GFCI outlets (not breakers) at the fridge and freezer (though I'd have to use an adapter to connect the plug's ground at the Delta's AC out to actual ground since it only has a dummy hole for ground). If the inverter ever needs to be removed from the picture temporarily, I could plug in cords from those inlets to separate nearby outlets fed from the main panel and thy'll be back in business, and of course, reverting back permanently would only require running the romex back to the main panel and removing the inlets.

I would label the outlets by the three circuits with something clear, such as "This outlet is fed from Main Inlet 1 next to Main Panel in Garage" etc. And "Inlet to feed Kitchen Refrigerator outlet" etc. at the appropriate inlet. Maybe use different-colored outlets, like hospitals do?

Any flaws in this approach? Do you see any code violations? Although I only plan to have one outlet per "extension", would having more than one outlet on the same extension circuit be allowed since the Delta can't put out more amps than the romex is rated for?

There's more to the plan, but I didn't want to make this too convoluted, but ask away if necessary.

Thanks in advance!

 

[SamDeleted]

So stick a plug on the cables feeding your chosen outlets , plug it into the power station, and then feed mains electricity through the power station to the critical load, then if / when there's a blackout it'll switch onto battery and act as a ups

Why not just get a ups ?

 

[jester74]

So stick a plug on the cables feeding your chosen outlets , plug it into the power station, and then feed mains electricity through the power station to the critical load, then if / when there's a blackout it'll switch onto battery and act as a ups

Why not just get a ups ?

There’s already a UPS at the router/NAS, no room for one at the fridge. Regardless, main reason is endurance.

With the delta (which I’ve already had for a while, so less to buy) I can run everything for several hours. The switchover speed isn’t all that important to me so long as it happens automatically. I just want those circuits to run for as long as possible even if/when there’s an outage and I’m not at home.

I also already have a 10-circuit ProTran2 transfer switch which I hope to install and use later with an AIO or hybrid (no solar though) and battery bank that can run a few more circuits or these same ones for much much longer. Only have the MTS so far though. Have to keep researching the neutral-switching issue when it comes to AIOs or hybrids.

 

[SamDeleted]

Ah ok yes an AIO with battery would be a good step moving forward I think

 

[Mattb4]

Depending on how handy at wiring you are you could create a Transfer control box to switch both hot and neutral. I use one at my Main panel and a AIO as the alternative power. The MTS is two pole rather than a Reliance that only has 1 pole MTS

 

[jester74]

Depending on how handy at wiring you are you could create a Transfer control box to switch both hot and neutral. I use one at my Main panel and a AIO as the alternative power. The MTS is two pole rather than a Reliance that only has 1 pole MTS

Hmmm, you've given me another idea that might be cleaner than what I was thinking above, and even cheaper (though I don't mind spending a bit more to get a better result).

Since the critical loads I want to run don't add up to much, and I'd have to either place them all on the same bank of the MTS (or use an adapter that ties the two line legs of the MTS inlet so the single phase from the inverter reaches all circuits)... well, what if I wire the inlet of the MTS so that L1 from the inlet plug is for the hots, and L2 is for neutrals? So long as I bind the neighboring switches together (which the MTS lets me do) it should be fine to run the neutral through a breaker since it would be switched together with the hot. The black/red wires being repurposed to neutral-switching would have to be replaced with white ones since they'll be neutrals now, but I don't see any other expense. Even if someone unknowingly plugged in a 240v generator to the inlet, all that would happen is that the loads would feed off of one leg because L2 would not be connected inside the MTS. Only downside I can think of right now is that my ten circuit MTS would now only handle five, but again, where I'm at now, five is more than enough.

Any thoughts anyone?

 

[Mattb4]

Hmmm, you've given me another idea that might be cleaner than what I was thinking above, and even cheaper (though I don't mind spending a bit more to get a better result).

Since the critical loads I want to run don't add up to much, and I'd have to either place them all on the same bank of the MTS (or use an adapter that ties the two line legs of the MTS inlet so the single phase from the inverter reaches all circuits)... well, what if I wire the inlet of the MTS so that L1 from the inlet plug is for the hots, and L2 is for neutrals? So long as I bind the neighboring switches together (which the MTS lets me do) it should be fine to run the neutral through a breaker since it would be switched together with the hot. The black/red wires being repurposed to neutral-switching would have to be replaced with white ones since they'll be neutrals now, but I don't see any other expense. Even if someone unknowingly plugged in a 240v generator to the inlet, all that would happen is that the loads would feed off of one leg because L2 would not be connected inside the MTS. Only downside I can think of right now is that my ten circuit MTS would now only handle five, but again, where I'm at now, five is more than enough.

Any thoughts anyone?

Not entirely sure of your proposed setup. So long as you keep the neutrals (the one from your main panel and the one from your inverter) separate but switchable to the load it out to work. Be aware that a common neutral for many circuits will need to be of sufficient size wire. If you are powering 3 circuits wired with 12awg you likely want to use 8awg wire to feed the 3.

 

[jester74]

Not entirely sure of your proposed setup. So long as you keep the neutrals (the one from your main panel and the one from your inverter) separate but switchable to the load it out to work. Be aware that a common neutral for many circuits will need to be of sufficient size wire. If you are powering 3 circuits wired with 12awg you likely want to use 8awg wire to feed the 3.

Gotcha, yeah, with my latest idea I'd be foregoing the "common neutral" design that the MTS comes with and using a separate wire for each circuit's neutral so it'd be fine in that regard.

In a nutshell, what I'd be doing is taking the 10-circuit MTS (which has 5 single-pole switches per bank; meant to accommodate L1 and L2 of split-phase) and using the second bank for neutrals instead of for L2, turning it into a 5-circuit MTS now with dual-pole (L1 and neutral) switching per 120v circuit. The switches can be tied together so there's never a chance of leaving a hot powered without its neutral. Only "big" change required is swapping the second bank's wires to white for code.

 

[miltonschreiber]

Depending on how handy at wiring you are you could create a Transfer control box to switch both hot and neutral. I use one at my Main panel and a AIO as the alternative power. The MTS is two pole rather than a Reliance that only has 1 pole MTS

Who makes that transfer switch?

 

[Mattb4]

I went with Etek.