Victron 24/3000/70 Guidance

[utkvols]

As often happens, my small project has turned into a much larger one. I originally was going to build a simple UPS for my server rack which runs fairly constant 300-370 watts. Then I thought why not replace several other UPS in the house - main desktop (2-400watt) and give some additional headroom to run an extension cord to the main fridge if power were out for an extended time. This means no more small victron and I now have the 24/3000/70 on order.
I noticed the 50A shore input- previously was going to use the existing 12ga romex but now that is no longer an option. Now that I have created a monster, I am wanting to get a bit of input to see if my thinking is the best way to do this

Victron supplied by 8 304Ah EVE cells in series
Place victron in utility closet next to main panel (instead of near server rack)
Install a new sub panel next to main panel. Pull out breaker/wiring that feeds the server rack and refrigerator and move to this new sub panel
New sub panel fed with the 50A line from the Victron

The 50A is way overkill for just these two circuits and I will probably add in another circuit or two - probably the tankless water heater as no power= no hot water. It's only power requirement is the inducer/exhaust fan which is only a few dozen watts. Still a lot of extra room.

What type of sub panel would be most suitable for this application? Does the 50A victron supply to the new panel require a breaker in between (similar to the main feeders from utility pole)? I have seen a few small, 5ish breaker panels that I assume are a very trimmed down version of a typical sub panel but with only one 120V feeder. I know the more traditional sub panel I could just bond the two lugs but I assume there's a cheaper option here. Obviously K.I.S.S. has left the building

What would you do with the second 32A victron output? I know this cannot be thrown into the new sub panel.

No solar input currently but one day that may be an option. If we ever had an extended outage, I would recharge the batteries as needed from a gas generator but in our 5 years of living here that would have only been needed once so I wouldn't want to consider this a big need in the wiring.

The other option I believe I have seen you can limit the input current to the Victron. I could keep this at 15A but that may just be a waste of a larger Victron unit?

 

[sunshine_eggo]

If you're talking about AC Out 2, this is not an "additional" output. When AC out 2 is available, a relay closes to join it to AC Out 1. This normally occurs when ac input is available. 32A is the current limit of this contactor.

It is normally used to power devices only when on grid and then automatically disconnect them when AC in is lost.

AC input limit is to simply limit the draw from the AC input. It automatically adjusts battery charging so that loads+charging < AC input limit.

With PowerAssist enabled, it also uses this value as the trigger point to terminate charging and "boost" the AC input current.

 

[utkvols]

Gotcha - I missed that part in the manual. The second output then is basically for an "optional" load that you don't necessarily want when under battery load.

So trying to clarify my understanding, the unit is essentially pass through when shore input is present. I believe I understand the powerassist - I would never experience > 20A output with my intended use case - not even with inrush current. If my current output is not going to exceed the input, I could be fine with the 20A shore input and the remaining current would go to battery charging. Thus the only downside would be having a lower charge rate (which would be totally fine from our outage experience)?
This would GREATLY simplify install obviously but the more concrete option to utilize the full functionality seemingly would be the second panel with the intended backed up circuits.

Thank you for your help!

 

[sunshine_eggo]

Gotcha - I missed that part in the manual. The second output then is basically for an "optional" load that you don't necessarily want when under battery load.

Correct. It can be programmed otherwise, but that is the default behavior/intent.

So trying to clarify my understanding, the unit is essentially pass through when shore input is present.

Correct. This can be changed to operate on the basis of loads, voltages, etc., but pass through/charging is the default behavior.

I believe I understand the powerassist - I would never experience > 20A output with my intended use case - not even with inrush current. If my current output is not going to exceed the input, I could be fine with the 20A shore input and the remaining current would go to battery charging. Thus the only downside would be having a lower charge rate (which would be totally fine from our outage experience)?

Correct. It is particularly useful if you have an undersized generator feeding the input to charge the batteries. Loads might exceed the generator, and PowerAssist would prevent generator overload.

This would GREATLY simplify install obviously but the more concrete option to utilize the full functionality seemingly would be the second panel with the intended backed up circuits.

Given that the unit is used for UPS purpose, Use of AC Out 2 does not represent full functionality. AC out 2 drops if AC input drops, so there's no point in putting anything on AC out 2. Simply leaving it grid powered has the same end result.