diy solar

diy solar

4 Circuit Manual Transfer Switch (Goal Zero, Reliance)

If you set the switches to Gen and feed this manual transfer switch with an automatic switching inverter that takes grid power (like an MPP Solar) does it essentially transfer automatically to solar/battery if grid is down?

That should do it.

Main panel feeds inverter AC in.
Main panel feeds manual transfer switch
Inverter feeds manual transfer switch.

Inverter should pass grid through to manual transfer switch, to protected loads. And backfeed PV.
If grid goes down inverter disconnects from grid and produces AC.

That's what I've done, except rather than a panel with many individual switches to select grid/inverter for each load, I have one 63A manual transfer switch feeding an entire panel of protected loads.

I had said reserve one circuit of manual transfer switch back to interlocked breaker in main panel (to manually feed anything in the house), but I think it would be inverter output back to interlocked breaker. No need to go through manual transfer switch and its smaller breakers.
 
That's what I've done, except rather than a panel with many individual switches to select grid/inverter for each load, I have one 63A manual transfer switch feeding an entire panel of protected loads.

What does that look like? Is that a separate critical/protected loads panel?
 
Something like this (I now see similar one listed for $10), and an entire house is the protected loads. Entire garage with arc welder etc. is on grid, not protected. (but manual interlocked breaker lets me power garage for loads such as extra fridge; I would turn off or not operate heavy loads.)


I have a 6 awg run to my pool house, which has its own breaker panel. Eventually I plan to pull 2 awg as well and have interlocked breakers in the panel, so I can have 70A straight from grid (main panel) or 100A from battery inverter. But pulling 200' of heavy wire is tough, need a cable tugger to do that.

So for now I have this interlocked dual DPDT transfer switch. One side goes to main panel fed by grid. Other side goes to output of battery inverter. (With a load-shed relay to disconnect in case of deep battery discharge, because my AC coupled system needs to keep grid-tie inverters connected.) The 6 awg wire to pool house is on other side of transfer switch, and I used split bolts to connect output of the two interlocked DPDT (because there is no busbar joining them.)


(Like figure B, then wrapped in rubber tape and vinyl tape)

I have this transfer switch inside a rain tight square-D box I gutted and mounted DIN rail in. Companies offer busbars used in combiner boxes to parallel breakers which might work, but I'd need something to work with interleaved breakers (two hots on each phase.) The following combiner has fingers for three adjacent SPST breakers, shows two installed, but wouldn't exactly do what I needed:


The problem with how it is set up now is that I may not notice a power failure, and battery will try to run A/C, laundry, electric heat after sun goes down, which won't be for long. I want to add relays to shed those excessive loads. In the case of A/C, it'll be a small relay in the thermostat circuit. Or, once I pull 2 awg, move some loads (electric heat) to grid-only not battery inverter. Goal is to run A/C and laundry on surplus PV while sun is up during grid failures, but disconnect them at night so battery is there for balance of smaller loads in house.

With your transfer switch panel, you keep refrigerator on battery inverter and A/C on grid (looks like the panel has individual 120V circuits, no 240V circuits?) If a power failure comes you can manually switch over A/C knowing you need to turn it off when the sun gets low.
 
@Hedges, thanks for answering my question in the SMA/AIMS thread. I wanted to ask another question without taking that thread off course.

I haven't been interested in a grid-tie system due to cost, unsure how long we will be in our current house, and really my original goal was just to get backup when grid is down. But seeing that SMA the Secure Power Supply (SPS) got me interested.

Would it be practical to have my DIY battery inverter system as backup, and a grid-tie using the SMA SPS to be able to charge my DIY battery when grid is down?
 
Yes, I think it would. With PV panels feeding Sunny Boy, Assuming you do NOT have "Rapid Shutdown", you can draw up to 2000W from Sunny Boy so long as PV panels produce enough. Later in the day when production drops below what your battery charger draws, it would shut off.

So Secure Power plus a "power station" with batteries and inverter/charger would be practical.
But if "Rapid Shutdown" is required, then it won't work. In that case you need a battery inverter that tells the PV panels on your roof to keep operating during power failures (except if fireman throws the disconnect switch.)
Something like Sunny Island or Outback Skybox is a battery inverter that will produce a local grid, so grid-tie inverter sees AC and doesn't do Rapid Shutdown. A disconnect switch so grid tie inverter loses AC lets Rapid Shutdown work.

A Sunny Island, 48V AGM battery, and a power cord would serve as a 120V power station. Costs around $3500 right now if 100 Ah battery.
 
Something like this (I now see similar one listed for $10), and an entire house is the protected loads. Entire garage with arc welder etc. is on grid, not protected. (but manual interlocked breaker lets me power garage for loads such as extra fridge; I would turn off or not operate heavy loads.)


So for now I have this interlocked dual DPDT transfer switch. One side goes to main panel fed by grid. Other side goes to output of battery inverter.

I do NOT trust this 63A DIN-mount transfer switch. Just heard it buzzing. Either it has a problem holding off 240V from the non-selected source, or its magnetic trip on the selected source is rattling even though current draw is low. I've disconnected alternate source from it.

I am ordering another interlocked Square-D QO breaker/box (sold as generator transfer switch) to do this with equipment I trust.


I have seen other DIN switches (not breakers) offered overseas from what may be more trusted vendors. They ganged two On-off-off switches to two off-off-On switches.

 
Who or what defines if rapid shutdown is required?

NEC and/or local codes.
Old systems are grandfathered, but new systems in areas with these rules require "rapid shutdown." When power fails, or when a switch is thrown, all PV panels are isolated from each other (or each clamps its output to low voltage) so no where is there more than 80V or 300W available.

It is not an issue for micro inverters, because max volts and watts is a single panel.

For high-voltage string inverters like I use, could approach 600V on a cold morning, and 480Voc is typical, with 2500W or more available.
If a fireman needs to hack a hole in the roof, or is applying water and thinks have broken, he could be electrocuted.
 
NEC and/or local codes.
Old systems are grandfathered, but new systems in areas with these rules require "rapid shutdown." When power fails, or when a switch is thrown, all PV panels are isolated from each other (or each clamps its output to low voltage) so no where is there more than 80V or 300W available.

It is not an issue for micro inverters, because max volts and watts is a single panel.

For high-voltage string inverters like I use, could approach 600V on a cold morning, and 480Voc is typical, with 2500W or more available.
If a fireman needs to hack a hole in the roof, or is applying water and thinks have broken, he could be electrocuted.

Ah okay. Well we don't have any PV so I'm sure we would require rapid shutdown. I don't know of anybody in Houston that could do a custom installation of used PV panels and a Sunny Boy. All the companies I've seen only install their chosen system.
 
Just googling, I find "Rapid Shutdown" systems installed in Houston


If PV panels are mounted somewhere other than the house, for instance a free-standing structure in the yard, then rapid shutdown isn't required.

Several brands of grid-tie inverters use frequency-shift to reduce power output and will play nice with battery inverters (if they are wired after the battery inverter, or have a transfer switch to put them there.) It may be that latest model inverters supporting California's "Rule 21", tolerating grid voltage and frequency variations, would work OK.

Best to select grid tie inverters that can be used with a battery inverter, or a hybrid inverter that accepts PV panels and batteries. Ideally, one that works without batteries as well, so they are an option.
 
@Hedges thanks again, I'm afraid that's out of my league. I got my hopes up seeing somebody mention the affordable pricing on used panels and SMA inverter thinking I could use the SPS with my existing equipment.

And no chance of ground mount, we have a 3 story connected townhouse without yard :-(
 
Ah okay. Well we don't have any PV so I'm sure we would require rapid shutdown. I don't know of anybody in Houston that could do a custom installation of used PV panels and a Sunny Boy. All the companies I've seen only install their chosen system.

Most of the time and labor is attaching standoffs/rails to the roof, and mounting panels on them.
That is basically mechanical work, but there is usually special hardware to properly ground the metal parts together. Manufacturers like Unirac and Iron Mountain sell systems of hardware with ground clamps.
Micro inverters, optimizers, or rapid shutdown boxes attach to panels or rails. The MC cables just plug in, with touch-safe connectors. You just need the correct number in series or possibly series/parallel.

Actually wiring an inverter to the breaker panel is the only place where live dangerous voltages occur (assuming you don't stick a screwdriver or your tongue into an MC connector.)

Solar Edge has a per-panel optimizer that allows panels of various orientations to be connected together, and allows more in series than normal because each regulates its voltage output. When not operating, each delivers 1.0V, so safely shut down.

Townhouse. You might encounter rules about who can work on the roof, since you can cause a leak.

You should be able to select a grid-tie system from a vendor that's compatible with adding battery backup later. Or one that has a hybrid inverter, just add batteries.

SMA latest model Sunny Boys are officially supported by Sunny Boy Storage (lithium battery to shave peak loads), and separate Automatic Backup Unit (relay to disconnect grid during power Failures.)

Enphase I think has some kind of backup. Also Schneider, Outback, and others.
 
Rent out the townhouse
Buy a place in the country.

Condos in particular have high HOA fees, not tax deductible.
Latest standard deduction makes smaller mortgages effectively not deductible, too small to make a difference.
Same property as a rental, and all that can be deducted, while you still take standard deduction.

Cash-out refi (2.5% !!), buy a lot with water but no electricity, live out of an RV to begin?

(You will then learn to do all your own wiring, plumbing, removing fallen trees ...)
 
You should be able to select a grid-tie system from a vendor that's compatible with adding battery backup later. Or one that has a hybrid inverter, just add batteries.

SMA latest model Sunny Boys are officially supported by Sunny Boy Storage (lithium battery to shave peak loads), and separate Automatic Backup Unit (relay to disconnect grid during power Failures.)

We don't really need a large battery bank, I think we are covered with the generator and 100A battery we have. But I would like the panels to provide a little bit of power during grid outage, hence the interest in the SMA SPS since it could charge my battery. The hybrid inverter would not work for my 12v system correct?
 
We don't really need a large battery bank, I think we are covered with the generator and 100A battery we have. But I would like the panels to provide a little bit of power during grid outage, hence the interest in the SMA SPS since it could charge my battery. The hybrid inverter would not work for my 12v system correct?
I think there are some 12V hybrid inverters - AC input, PV input, battery connection, AC output.

Here's an inverter which does all of those except PV; a separate charge controller is used:


That model uses a 12V battery, might be for an RV or boat typically.

Outback sells other models to backfeed the grid. This one just charges from the grid (maybe passes grid through a relay, I haven't looked in detail.)
The model numbers have "V" for vented (better air cooling but not weather tight), "G" for grid tie, etc.
 
I'll second the sma.
Hedge talked me into it. Now I have2 6048 islands and 2, 7.0 sunny boys.13k of panels , and 14kwh of the total of 62kwh of 280 litium.
It's a good start?
 
I'll second the sma.
Hedge talked me into it. Now I have2 6048 islands and 2, 7.0 sunny boys.13k of panels , and 14kwh of the total of 62kwh of 280 litium.
It's a good start?

Tell me how using lithium batteries in the system works out, what BMS, what settings. I'm going to put my old AGM on my pickup with one Sunny Island, but would consider lithium to replace it.
 
I'm the odd man out right now. Didn't plan on bms yet. To many options and bickering.
What I would like is ...
1 head unit , multiple shunts. 1 for each string of batts.
The calb 170s that I have set up in my shop is a 24 v system. No BMW, been running 1.5 wars flawlessly on a electric car parts 3k low frequency inverter. Been running 24 /7 in a remote location. 2k of panels. Runs swamp cooler , fridge, lights inside and out .and the air compressor.

As soon as the well is punched , we start assembling the power system. 1100 feet down. That's why the over abundance of power.
Also when the house is built , we dont have to be frugal with the juice. Couldn't do it without the cheap panals from santan and Michael and his bulk buying. You know very well what this would have cost only 3 years ago. Holy smokes!!
 
I think there are some 12V hybrid inverters - AC input, PV input, battery connection, AC output.

That would be more like what we want. Ideally we could buy a a few kW of used panels and find somebody to install them, if that doesn't hurt the value of the house.

Then use an inverter/ATS, no grid-tie, so we could use the PV to power some circuits during the day.
 
Mpp has an 800watt model that is 12v,

and sigineer and aims have them as well.

solar, grid, generator with start contacts, and charging many types of 12V battery chemistry.
 
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