diy solar

diy solar

Rewiring the house to only use the grid for emergency backup

Skid

Solar Enthusiast
Joined
Oct 26, 2020
Messages
202
Location
Nicaragua
I have an old brick house in Central America with typical nasty wiring. I considered simply running a parallel system for the solar but would rather rip out the old and start fresh. I'd like it to go through the same panel but use breakers to isolate one from the other. I'm thinking something needs replacing I can isolate the solar and use the grid and when finished isolate the grid and revert to solar. This way if I move I can have a good reliable grid system for the new buyer.

Is this accomplished simply by using two, say, 100 amp breakers leading into the box? The grid here is 100a and the inverter, a Growatt 3k is less than that. Please excuse my ignorance. I never progressed in wiring more than connecting a stereo 30 years ago.
 
100 amps x 240 volts = 24000 watts. Good place to start is to do a energy consumption audit. Also what is your largest items and how many of those will be running at once. Knowing these you can decide what size inverter, how large of battery bank. Those determine what size solar array.
 
Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp?

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the Uber-Sun-Hours calculator site to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, some sort of DC->dc charger to charge from your alternator without frying it, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.
 
Can you clarify your goals (off-grid, hybrid, grid-tie) and size of your home's main panel or amount of power/circuits you want to support?
There are *many* options for integrating solar power consumption in your home and I'm sure others will share...

In my case... I'm off-grid / do not feed any power into the lines.

One of the things I did was run a parallel set of regular sockets in the walls (I have easy access under my house) and just labeled them "Solar X". This sub-system has larger / shared APC UPSs for computers, TV, sensitive circuits. I don't think it will mess up a future home sale - they're just sockets in the wall same as others :)

For the general house, I used several ATS(s) - automatic transfer switches - with grid the default. So the house runs on grid until I feed power to the ATSs from the inverters.... and then they auto-switch to inverter power. When the inverter shuts-down due to low battery OR I just turn off the solar system - the grid is the default, as it was with no solar at all. So my wife is not bothered when I turn off solar to work on it and by the same token, a future home owner could just leave solar off. :)

Observations since I did my system:
The rise of all-in-ones lately, with good pricing, can be used (off-grid) to combine all these functions in 1 unit. An MPP Solar or Growatt can take in 1) grid, 2) Solar, 3 ) battery, and 3) output AC with an integrated UPS and supply AC output seamlessly managing grid, solar, and battery inputs. I put an MPP 3048LV (48v battery / 3000w inverter) in my trailer and it works great!

The cheaper all-in-ones aren't at 240v100a or 240v@200a (whole house) level but I'm sure there's something like this if you have $$ - things like SolArk or Schneider level stuff.
 
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I have all the stuff here. 10kw 48v battery, Growatt 3000 LVM-ES, 3200w of panels. The house uses 5kw per day. Since I want to renew the horrible wiring of the house, mostly twisted connections held together with black tape, I will start fresh. All I'm really looking for is adequate breakers to keep the power from solar completely isolated from the grid power which will only be used when the solar is down for maintenance. Shut one side down, deal with whatever issue, shut the grid side down and back to solar. I won't live here forever and when I move want to take my system with me and the grid part intact.

Basically looking for breakers adequate for my use and how to explain to whoever replaces the wiring (there are no educated electricians here) the best way to keep the two isolated.
 
I have all the stuff here. 10kw 48v battery, Growatt 3000 LVM-ES, 3200w of panels. The house uses 5kw per day. Since I want to renew the horrible wiring of the house, mostly twisted connections held together with black tape, I will start fresh. All I'm really looking for is adequate breakers to keep the power from solar completely isolated from the grid power which will only be used when the solar is down for maintenance. Shut one side down, deal with whatever issue, shut the grid side down and back to solar. I won't live here forever and when I move want to take my system with me and the grid part intact.

Basically looking for breakers adequate for my use and how to explain to whoever replaces the wiring (there are no educated electricians here) the best way to keep the two isolated.
From what I've seen, you don't do 'parallel breakers'. You either do a manual transfer breaker setup at the main panel or you do automatic transfer switches.

The standard is to have a home main panel - and home circuits flow from this panel. One approach is that at this main panel - you can feed in grid or solar. You use a mechanical interlock method to choose which one. The mechanical interlock is just a way to make it physically impossible to have both grid and solar feeding the panel at the same time.
Here's an example youtube (there are many)

An ATS is just an automatic way to do this.

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I get that you have a idea in mind, so maybe if you could explain a bit more about what you mean by multiple breakers? and why the youtube approach does not meet your thinking. For example, trying to bridge the gap in perception here...

You could do a solar sub-panel off the main panel. This solar sub-panel (sometimes called a 'critical load panel') would have your solar only circuits - separate from the main panel circuits and use the same interlock as shown in the youtube... - e.g. the sub-panel get's grid from the main panel and solar from your Growatt.
 
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Thank you! That's exactly the information I needed! Fortunately a friend is visiting the US next week and can bring what I need. The interlock was the concept I couldn't grasp. Thanks again.
 
Here's what I got. All pre-wired, super easy to hook up, reasonable price, detailed installation videos on Youtube. I love it.
I just wired the solar in instead of using the generator lead, and used he generator lead in another location to feed my inverter which also functions as my backup charger.

Reliance Electric Transfer Switch Kit
 
I have an old brick house in Central America with typical nasty wiring. I considered simply running a parallel system for the solar but would rather rip out the old and start fresh. I'd like it to go through the same panel but use breakers to isolate one from the other. I'm thinking something needs replacing I can isolate the solar and use the grid and when finished isolate the grid and revert to solar. This way if I move I can have a good reliable grid system for the new buyer.

Is this accomplished simply by using two, say, 100 amp breakers leading into the box? The grid here is 100a and the inverter, a Growatt 3k is less than that. Please excuse my ignorance. I never progressed in wiring more than connecting a stereo 30 years ago.
How does your electrical setup at the residential level compare to North America?
Is it 120/240VAC 60HZ split phase?
What about premises grounding?
 
Get a couple of the Pro/Tran 2 systems and you'd have 20 circuit control. Then you only need one main service panel. Chose which circuits to be on grid and off grid.

Can also be used with a generator and or solar off grid generation.

Avaliable at most retailers. A few different versions and kits

 
Here's what I got. All pre-wired, super easy to hook up, reasonable price, detailed installation videos on Youtube. I love it.
I just wired the solar in instead of using the generator lead, and used he generator lead in another location to feed my inverter which also functions as my backup charger.

Reliance Electric Transfer Switch Kit
You beat me to it. I have 2 ... One 6 and one 10 both connected to inverter rather than generator. Works perfectly

 
It's surprising to me more people here on the forum don't use them. Simple to install and very effective. UL cert too.
Agree with this when you have individual components / larger systems. Some of the smaller power all-in-ones have ATS / UPS built-in.
I combine ATS and MTS at the main panel for 'optional circuits' and then have other dedicated ATSs for larger 'fixed circuits' like the heat-pump compressor.
1638646550585.png

Also, where I live, it's perfectly legal for a DIY home owner to 'expand' the house circuitry if done to code and these ATS / MTS are UL (meet code) so not expecting insurance company trouble or trouble selling the house later on.
 
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Agree with this when you have individual components / larger systems. Some of the smaller power all-in-ones have ATS / UPS built-in.
I combine ATS and MTS at the main panel for 'optional circuits' and then have other dedicated ATSs for larger 'fixed circuits' like the heat-pump compressor.


Also, where I live, it's perfectly legal for a DIY home owner to 'expand' the house circuitry if done to code and these ATS / MTS are UL (meet code) so not expecting insurance company trouble.
Yes I have an Conext SW Inverter that has a built in transfer switch and also takes up to 4000w AC, so I can turn off the AC input and run off grid, or I can keep the gird AC coming in to back up the battery power (or vis verse as a grid supplement) . So I am using both an Automatic transfer and this Manual transfer too. I really like because if you had a power outage, you can pick and choose what circuits you want to run so you dont tax the battery in an emergency.

I started with a Pro/Tran 2 6 circuit and added a 10 circuit.
 
Thanks all, for the great advice. My house is very simple, only LED lights, chargers, two Mac Minis that use about 15w each. Refrigerator and chest freezer together use about 1.5KWH per day. Total use per month about 160kwh so not much needed. Half of my consumption is coffee related- two coffee roasters and two espresso machines which comprise half the energy used. The house has 120v 60hz and all sockets are two wire only. All the wiring is trash so I'm starting fresh with a new panel, sockets, proper grounding etc.
OffGridInTheCity, the name being exactly what I will do here, gave me the answer to my question and I will use a simple generator interlock to keep grid power, which is absolutely horrible here, completely isolated from my solar supply which will provide 2 or 3 times what I will use year round, insolation never being an issue where I live. Unless the active volcano two miles away goes off in which case I will have other issues.
 
The house has 120v 60hz and all sockets are two wire only. All the wiring is trash so I'm starting fresh with a new panel, sockets, proper grounding etc.
That is great but is the service split phase 120/240VAC?
 
From what I've seen, you don't do 'parallel breakers'. You either do a manual transfer breaker setup at the main panel or you do automatic transfer switches.
Correct. Parallel breakers won’t isolate the grid from solar-produced AC if the grid is down. No legal basically anywhere.
 
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