Automatic Transfer Switch - Need clarification and assistance. ATS confusion overload! :)

Keith_PDX

Solar Enthusiast
Joined
Sep 25, 2019
Messages
95
Location
Portland, OR
Hello Everyone,

I have been doing solar/lithium in vans for quite some time and am finally to a point where I am ready to dive into setting my house up to be self-sustaining.

Here is my plan, in phases. I have been using an Emporia to monitor my energy usage. Luckily I am in the NW and have natural gas for heating, cooking and my dryer so my electrical needs do not have a lot of high wattage items. We rarely use our air conditioner so I am not sizing the system for that initially.

First phase is I would like to procure the following two items and setup a whole-house UPS. My goal is I would like to run off of battery during peak power times and re-charge from the grid during cheaper power times along with having the UPS functionality for power disturbances.
  1. Either a Growatt 6k SPF-6000T-DVM-MPV or MPP LVX6048 split phase hybrid inverter (still deciding)
  2. 30kWh of LiFePO4 battery capacity @ 48V.
Second phase will be to procure/install/connect the maximum size solar array that the inverter will support or potentially add another hybrid inverter to parallel and support more solar.

My confusion comes into how to do an automatic transfer relay to support Phase 1. I have watched several inverter videos on YouTube and a lot of people seem to connect them with either a manual breaker lockout to prohibit simultaneous generator/UPS and Utility power or rely on the internal transfer function but either way they appear to just back feed into the main house panel. I do not want to do this as I don't have a permit/approval to backfeed to the grid nor do I plan to get one. Grid Tie Solar is not an objective for me. I also would like to avoid from adding a critical load panel, if possible, and just feed my existing panel. Do you have any recommendations for an ATS that I can have professionally installed between the incoming utility power and my existing 200A panel that would allow me to disconnect utility power and use my battery bank in this method? It needs to transfer automatically on utility power loss or have the ability to manually be remotely operated so i can program a relay contact to perm the transfer function based upon the time of day.

Appreciate the help, knowledge and wisdom of this group. Hopefully I am not overcomplicating this... :)
Keith
 
Last edited:

mrzed001

Voice of reason
Joined
Apr 10, 2020
Messages
741
Location
Hungary - EU
Hello Everyone,

I have been doing solar/lithium in vans for quite some time and am finally to a point where I am ready to dive into setting my house up to be self-sustaining.

Here is my plan, in phases. I have been using an Emporia to monitor my energy usage. Luckily I am in the NW and have natural gas for heating, cooking and my dryer so my electrical needs do not have a lot of high wattage items. We rarely use our air conditioner so I am not sizing the system for that initially.

First phase is I would like to procure the following two items and setup a whole-house UPS. My goal is I would like to run off of battery during peak power times and re-charge from the grid during cheaper power times along with having the UPS functionality for power disturbances.
  1. Either a Growatt 6k SPF-6000T-DVM-MPV or MPP LVX6048 split phase hybrid inverter (still deciding)
  2. 30kWh of LiFePO4 battery capacity @ 48V.
Second phase will be to procure/install/connect the maximum size solar array that the inverter will support or potentially add another hybrid inverter to parallel and support more solar.

My confusion comes into how to do an automatic transfer relay to support Phase 1. I have watched several inverter videos on YouTube and a lot of people seem to connect them with either a manual breaker lockout to prohibit simultaneous generator/UPS and Utility power or rely on the internal transfer function but either way they appear to just back feed into the main house panel. I do not want to do this as I don't have a permit/approval to backfeed to the grid nor do I plan to get one. Grid Tie Solar is not an objective for me. I also would like to avoid from adding a critical load panel, if possible, and just feed my existing panel. Do you have any recommendations for an ATS that I can have professionally installed between the incoming utility power and my existing 200A panel that would allow me to disconnect utility power and use my battery bank in this method? It needs to transfer automatically on utility power loss or have the ability to manually be remotely operated so i can program a relay contact to perm the transfer function based upon the time of day.

Appreciate the help, knowledge and wisdom of this group. Hopefully I am not overcomplicating this... :)
Keith

The LVX6048 is a hybrid inverter. So it is a Grid-tie too and can backfeed to grid. I am not sure you can use it (check local code).
The LV6548 can not backfeed. That is an Off-grid with grid support inverter.
You can use an off-grid inverter this way (again, local code ...):

off-grid.jpg

If possible then this way you do not need a transfer switch (the inverter has build-in switch, it is an UPS too).
The main goes into your inverter (AC in) and the inverter powers your house (AC out goes to your house main panel)
You can have a manual transfer switch to allow grid (like a bypass) or inverter power to your house. So if you need to set inverter offline then still have power.
And with this solution you have a house UPS.
 

Keith_PDX

Solar Enthusiast
Joined
Sep 25, 2019
Messages
95
Location
Portland, OR
Thank you.
Tell me more about the manual transfer switch and now it would be wired to allow either the grid or inverter output be the power source of my existing 200A house main panel. I think that is the part my head is not clear on.

To me the problem with the LV6548 is that it takes two of them to do split phase, correct?

Appreciate it.
 

mrzed001

Voice of reason
Joined
Apr 10, 2020
Messages
741
Location
Hungary - EU
Thank you.
Tell me more about the manual transfer switch and now it would be wired to allow either the grid or inverter output be the power source of my existing 200A house main panel. I think that is the part my head is not clear on.

Main comes in
- cable to inverter AC in
- inverter AC out to transfer switch in1​
- cable to transfer switch in2
- transfer switch "out" to house (main panel)
So it you can choose which "in" goes "out"


To me the problem with the LV6548 is that it takes two of them to do split phase, correct?

Appreciate it.
Yes you need 2 of the LV6548 inverter.


Also a possibility that solution DavidPoz made: EU 240V inverter (Growatt or MPP Solar) + Auto transformer (to make split phase from it)
 
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