Grid-tie disconnect for interlock? Possible Shunt Trip breaker? SolarEdge W/ XW+ 6848?

jgilly69

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Jan 5, 2021
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Ok so I have this new install question for at my house so if any of you electricians or solar installers could help ?

I have a grid tied solar edge feeding main panel. I want to install a new SE XW+ 6848 as backup and grid tie.

The problem is I do not want, nor would I have a need for a backup loads panel since I can run my whole house on the SEXW+ if needed? I want to install a shunt trip main breaker in my main panel for the main disconnect, and shunt disconnect breaker for the SE GRID , and a contactor for the SE LOAD? I would really like to use the same conductors from the panel to the SE? I have considered just doing a manual interlock for a backup breaker (SE LOAD) and a double throw disconnect to pull from SE GRID to SE LOAD?

Once the grid goes back up I would manually turn on and reset?


Any thoughts? I guess I really just need a automatic transfer switch but finding one to pull my main panel on and off is crazy?
 

Hedges

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Mar 28, 2020
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Do you mean controlling two shunt-trip breakers to serve as transfer switch? Sounds to me like malfunction of control signals could result in SE XW fighting the grid. Mechanically interlocked or proper transfer switch would be safer for your hardware and the utility workers.

Manually interlocked main breaker and backfeed breaker is one way. I have that so inverter can feed the main panel.

If you're lucky and have a main breaker at meter separate from main breaker panel, then you can install something in between.
Otherwise, consider adding a protected loads panel downstream of SE XW for things you want automatically backed up (phone and refrigerator?) and manually switch interlocked breaker if you want to power other things.
 

jgilly69

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Joined
Jan 5, 2021
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14
Do you mean controlling two shunt-trip breakers to serve as transfer switch? Sounds to me like malfunction of control signals could result in SE XW fighting the grid. Mechanically interlocked or proper transfer switch would be safer for your hardware and the utility workers.

Manually interlocked main breaker and backfeed breaker is one way. I have that so inverter can feed the main panel.

If you're lucky and have a main breaker at meter separate from main breaker panel, then you can install something in between.
Otherwise, consider adding a protected loads panel downstream of SE XW for things you want automatically backed up (phone and refrigerator?) and manually switch interlocked breaker if you want to power other things.
Thanks, Sadly yes I had to install a new all in one MSE so I am stuck with finding a method to pull the panel off grid. Most shunt trips are 110v so just thinking that I could put it on the Load side of the SE and it would actually power the disconnect? But yes one small error and it would fry the SE XW+. I can get a new main breaker with a shunt trip....Maybe I am just barking down the wrong tree?
 

Hedges

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Mar 28, 2020
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11,667
A panel like this one, you could rewire critical loads into. It is interlocked so you can use your XW+ to drive it, or bypass the XW and drive from main panel.


You can also put a backfed breaker next to your main breaker and interlock them. That will let XW drive everything on main panel.

I've done both of those with my Sunny Islands. But the "protected loads" is a wire run to another panel for my entire house. I replaced the 100A and 30A breakers in the generator panel with 70A and 70A.

There are other panels available with SPDT and DPDT transfer switches so individual circuits can switch between "critical loads" and your main panel.
You probably have loads that are excessive for running entirely off PV and battery, so useful to manually enable them and know you're using backup not grid. I plan to automate that eventually so I don't run battery empty without knowing there is a grid failure.
 

copec

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Jan 23, 2021
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You probably have loads that are excessive for running entirely off PV and battery, so useful to manually enable them and know you're using backup not grid. I plan to automate that eventually so I don't run battery empty without knowing there is a grid failure.
Do you know how you’re going to do that?

My plan was to run everything after the breakers through a box of DIN mount relays and use a PLC.

With frequency shifting on your inverters you could use stuff this company (and many others that make load dumping products) makes https://www.pspproducts.com/
 

Hedges

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I can program two load-shed levels. 70% DoD disconnects everything. Other one I might set to 20%, disable AC thermostat, electric water heater, and dryer heating element. (or could use those variable dump load controllers, but probably won't for these modest power x time resistive loads.)

Another relay can signal connected to grid or not. If not on grid, I'd want to shut off refrigeration power when sun isn't up, but let another thermostat re-enable if freezer gets too warm. A fridge-temperature thermostat could enable small fan, keep fridge at desired temperature by drawing from ice in freezer.

I've picked up an assortment of power relays, contactors. Initially they will switch heating loads based on time of use.

I just wired thermocouples and CT to my DAS, want to study ice and brine as cold store for a freezer. But have to fix interference issue first. 200 mV 60 Hz is enough to clobber thermocouples?!

Electric furnace to be enabled when on-grid, gas when off grid.
(As presently wired, walked out one morning and discovered I was running 10kW heater off batteries.)

After I get my new Lambda PFC correction gizmos feeding pool pump VFD, I could servo the analog speed input in response to frequency shift, so they would be a variable dump load.

What I don't have is much dump load, unless the A/C is running, and that only uses part of production. My PV production is several times what battery charges with, so just use it or lose it. I need to transmute old car batteries into gold or something.
 
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