Splitting Up My Home Power For Critical Backup - Opinions Please

[B-ManFX4]

If you are reading this - thank you !!! I'm looking for feedback on my system design / plan. I have thick skin - give it to me straight.

I am a visual person and I like to have clear documentation of anything I build - it helps me understand what is happening where and is a massive aid for troubleshooting. I apologize for the drawing of the breaker panels and such but it also serves as a "map" for wifey when I am on the phone with her and she is attending to an issue.

Basically, I want to add a breaker panel to my home. I will move everything I want to power during a grid outage to the new panel. I want to include a transfer switch so that if I am working on the Victron gear I can throw the switch and not interrupt power to the sub panel.

My plan is to use two Victron MP-II's in a split-phase configuration. I have two - 304AH, 51.2VDC LiFePO4 batteries built for this system. I will be adding solar to this system, but it will be after I get this initial re-wire and backup sorted out and installed. I may go for a 15KVA Quattro for the 240VAC stuff at some point in the future, if that matters for this discussion.

FWIW - the labels on the sub panel breakers are stupid because the idiots that labeled it made them like that. I will be re-labeling everything properly as I get each circuit identified. For the purposes of this review they should work OK. Nobody lives downstairs so the only thing actually drawing power down there continuously is the refrigerator. All lighting in the house has been converted to LED.

Thanks in advance to anyone that comments in a constructive-criticism manner. It is very much appreciated.

 

[JoeHam]

Wouldn’t your MP-II’s already pass through power without the xfer switch?

Edit: I see that you want to be able to bypass to work on the Victrons. I did basically the same thing with Schneider equipment (CSW-4048) years ago, sans xfer switch, and have not regretted it, yet.

Your system, your choice though. It looks good to me on this AC only drawing.

FWIW, other than the 4048 my system is Victron gear, with a Cerbo-GX, and it has been rock solid so far.

 

[utkvols]

I did the same sans transfer switch recently with a smaller panel and 24/3000 MP. Ran a few dedicated lines with new outlets/boxes at desired devices and kept the existing wiring in place in case we decide to remove it when we move

 

[Dagoth Ur Does Solar]

This looks like a sensible setup, I want to keep an eye on your thread, as this is the kind of arrangement I might want to move towards rather than jumping to grid-tie. At the very least, I have outbuildings with sub-panels that I might want to set up similarly.

Spoiler: Not directly related to your design but...

I'm guessing you don't have a gaspack HVAC unit. In my case if I want heat during a winter outage, I have to be able to power the entire circuit to the whole HVAC unit to run the blower fan and spark to ignite the gas. Which obviously causes problems if you have a summer outage and you don't want to burn through all your battery power running the A/C.

Haven't exactly sorted how I want to handle that. Maybe put the HVAC on the critical loads, but set up some automation with HomeAssistant to shut down the A/C in the event of a summer grid outage.

 

[JAS]

I'm about to do the same exact setup (except I'm using a Samlex EVO-4248SP). I told my wife if anything goes down with the "solar setup" (which Murphy's Law says will happen when I'm away hunting, etc.), she can just flip a switch to put all the critical loads back on grid.

My dilemma was finding a transfer switch that switches Neutral and does not cost a fortune. So I started looking at the double throw safety switches. Holy Cow! They're super expensive too . Found a used GE 100A on FB marketplace that someone is willing to let go for $40. I'm picking up tomorrow (Have to drive 2 hours round trip, but to save hundreds to maybe a thousand dollars...)

 

[ricardocello]

Nice drawing!

All of your subpanel circuits appear to be 120V only (no double pole breakers). Correct?

I want to include a transfer switch so that if I am working on the Victron gear I can throw the switch and not interrupt power to the sub panel.

It will be interrupted very briefly during the transition as the switch is break-before-make.

Do you plan on backfeeding to the main panel with ESS? If no, you are fine,
If yes, you will run afoul of the 120% rule, and the breaker needs to be at the bottom.

 

[ricardocello]

My dilemma was finding a transfer switch that switches Neutral

What is your reasoning for switching the Neutral? Two N-G bonds?

 

[B-ManFX4]

Nice drawing!

All of your subpanel circuits appear to be 120V only (no double pole breakers). Correct?


It will be interrupted very briefly during the transition as the switch is break-before-make.

Do you plan on backfeeding to the main panel with ESS? If no, you are fine,
If yes, you will run afoul of the 120% rule, and the breaker needs to be at the bottom.

Thanks. Like I said, I'm a visual person so drawings really help me to plan and execute and troubleshoot.

All of the subpanel circuits are indeed 120VAC. The wifey did ask about putting the water heater over there. Thoughts?

I understand the break / make operation of the MTS. I just want something to allow me to take the Victron stuff down if I need to and not interrupt all of the 120VAC circuits everywhere else in the house.

I have no plans of backfeeding. This is simply me being tired of power outages screwing up so much stuff (I work from home and rely heavily on PCs, the Internet, etc.). Once I get my solar install done I hope to get to a point where the grid only powers the ovens, dryers and A/C units. We'll see...

 

[B-ManFX4]

I'm about to do the same exact setup (except I'm using a Samlex EVO-4248SP). I told my wife if anything goes down with the "solar setup" (which Murphy's Law says will happen when I'm away hunting, etc.), she can just flip a switch to put all the critical loads back on grid.

My dilemma was finding a transfer switch that switches Neutral and does not cost a fortune. So I started looking at the double throw safety switches. Holy Cow! They're super expensive too . Found a used GE 100A on FB marketplace that someone is willing to let go for $40. I'm picking up tomorrow (Have to drive 2 hours round trip, but to save hundreds to maybe a thousand dollars...)

I too am wondering why you feel you need to switch the neutral? Please share.

 

[ricardocello]

All of the subpanel circuits are indeed 120VAC. The wifey did ask about putting the water heater over there. Thoughts?

The only 240V circuit I put on my critical loads is my well pump, because a house without running water is a nightmare.

I did not put my 6 kW electric water heater on there, because for short outages the water stays hot.
The water heater alone will take most of your 10 kVA. But at least it is pure resistive (power factor 1.0).

You can also rewire the hot water heater to use 120V and take twice four times as long to heat up at 1.5kW.
Wouldn’t fly in my house, too many people.

I did rewire the panel to allow a 7500w generator to connect directly to the water heater for extended outages, using a special Leviton 30A DPDT switch.

 

[JAS]

What is your reasoning for switching the Neutral? Two N-G bonds?

Yes, I have the Samlex receiving AC Input from the Main panel (where the N/G Bond exists). If using a "traditional" generator transfer switch (most do not switch N and share the N/G Bond from the main source panel), there's a weird behavior that exists when passing through the AC (like a loop from main panel -> Samlex -> Gen Transfer Switch -> back to the main panel). When I tested this originally, I instantly tripped the GFCI receptacle I was using for the AC Input. Upon research, it seemed due to the GFCI seeing another N/G bond "downstream" (even though it is technically the same N/G bond)

Note: This was only a problem when passing through the AC and not while Inverting (as long as Inverter has N/G bond removed/disabled). One way to avoid this would be to not use the AC Input at all and charge the batteries via a separate ChargeVerter... EDIT: OR switch the neutrals as I have decided to do

 

[B-ManFX4]

The only 240V circuit I put on my critical loads is my well pump, because a house without running water is a nightmare.

I did not put my 6 kW electric water heater on there, because for short outages the water stays hot.
The water heater alone will take most of your 10 kVA. But at least it is pure resistive (power factor 1.0).

You can also rewire the hot water heater to use 120V and take twice four times as long to heat up at 1.5kW.
Wouldn’t fly in my house, too many people.

I did rewire the panel to allow a 7500w generator to connect directly to the water heater for extended outages, using a special Leviton 30A DPDT switch.

There are just the two of us, although we do entertain guests at least once a month it seems. I have been looking into swapping one of the water heater elements to a DC unit and wiring in solar power to it.