Can this be done safely?

Project

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I'm still building my powerwall and making a list of things I need and working on the layout for my solar and was wondering if I could use a transfer switch between solar power and grid except use the solar as primary. If I have several cloudy days and the battery's drop to cutoff, the transfer switch will move from powerwall to grid instead of the normal way it's usually wired. I have no interest in grid tie but will still have the grid connected.
 
Project said:
I have no interest in grid tie but will still have the grid connected.
This makes no sense.
If you are feeding into your main service panel, and that panel has power from a power company, you are grid tied.

You could feed your main panel with AC from an inverter, but the MAIN BREAKER MUST ALWAYS BE OFF, unless you have a proper utility interactive (aka grid-tied, aka UL1741) inverter.
If you dont have a utility-interactive inverter, and you feed your panel when the grid is on, it goes boom.
If the grid is down, and you feed your panel without the main breaker shut off, you can kill a utility worker, and when the grid comes back on it goes boom.

Yes you can have a transfer switch.
What you are looking to do is either DC coupling or AC coupling, depending on what type of solar system you have.

There are transfer switches for both arrangements, but they are costly. If you are unwilling to do grid tie, you will probably not like the additional $3000-$8000 for proper DC or AC coupling.

AC and DC coupled systems use a second service panel for "CRITICAL LOADS", it is powered by the grid during normal use, and when the grid is down it is powered by your battery and inverter. There are transfer switches that insure only one source is feeding the panel.

If you dont want to do it properly, you are best off just creating an off grid subpanel that is not connected to your main. Dont feed the main panel unless you know what you are doing!
 
The best bid I got for grid tie was $61,000 and when the grid goes down so do I. In my area I'm not even allowed to install the panels, I can't touch it . If I was just grid only and had a generator backup a transfer switch would be used to switch from grid to gen. I was just wondering if I could go the other way and use the grid as a backup. I have no problem doing it properly, I'm just not going to spend $60k to still be in the dark when the grid goes down


When I say grid tied I mean feeding excess to the grid.
 
Based on what you said there, you won't be able to have a ligit legal grid tie system. The power company won't allow you to install a grid tie system. You have to go through your contractor; and you said your lowest bid was $60k. So, you're out of luck there.

However, you should be able to do what you mentioned with the generator. That might cost a lot less. You probably would have to get the generator and transfer switch installed professionally, then be inspected and cleared. After that, you could install your other gear, or battery storage and install a secondary transfer switch that would start the generator and re-charge the batteries/power the house till charging is completed, then switch back.

But, it sounds like you MUST have a professional installation first before you can do the rest. Once the first stage is done and inspected, you can do the rest. However, be forewarned, that if someone complains about it and the inspector comes back out and sees the changes, you may get a fine for it.
 
You've got the concept correct, just the terminology might be a little off. I've researched this a bit and it is very simple. All you need is a change over (manual) switch, the same as used when a homeowner wants to hook up a generator. The switch goes before the main breaker between the grid and the breaker. Switch it one way, its grid and the other way it's your power source (usually off in the middle). This way, no grid feed in is possible. Yes, it's a manual change over, but not expensive. I've heard of $200 being quoted by a local electrician (South Australian).
 
I can have a transfer switch installed for next to nothing, it's when you add power back to the grid that things get expensive. I was just wondering if there was a way to run off of solar and be automatically switched from solar to grid in the event the battery's reached cutoff.
 
That's relatively easy, then. The same switch used to switch to a generator would work. If all you're wanting is basically a UPS for the whole house, that's the setup. If you want to sell back to the grid, that's not easy.

However, what I would do, unless you plan on having a large battery bank, is to have two panels. One panel is for required devices during outage; fridge, lights, water heater, etc. The other panel is for the non-essential devices; pool accessories, some AC units, some fans, etc. Then when power is interrupted, the secondary panel goes dead, the primary one is switched from Mains to Battery.

If you plan on a large battery pack, like Petes for example, then you could do it with just one panel.

Just a standard transfer switch would work just fine; as far as I can tell you, that is. ;)
 
BobMuster said:
You've got the concept correct, just the terminology might be a little off. I've researched this a bit and it is very simple. All you need is a change over (manual) switch, the same as used when a homeowner wants to hook up a generator. The switch goes before the main breaker between the grid and the breaker. Switch it one way, its grid and the other way it's your power source (usually off in the middle). This way, no grid feed in is possible. Yes, it's a manual change over, but not expensive. I've heard of $200 being quoted by a local electrician (South Australian).

Here in the US if you want to have a generator backup you can have an automatic transfer switch installed that will disconnect from grid and start the gen in the event the grid goes down. That's what I have now. I was just wondering if I could use the grid as my gen. Just thinking out loud.


Korishan said:
That's relatively easy, then. The same switch used to switch to a generator would work. If all you're wanting is basically a UPS for the whole house, that's the setup. If you want to sell back to the grid, that's not easy.

However, what I would do, unless you plan on having a large battery bank, is to have two panels. One panel is for required devices during outage; fridge, lights, water heater, etc. The other panel is for the non-essential devices; pool accessories, some AC units, some fans, etc. Then when power is interrupted, the secondary panel goes dead, the primary one is switched from Mains to Battery.

If you plan on a large battery pack, like Petes for example, then you could do it with just one panel.

Just a standard transfer switch would work just fine; as far as I can tell you, that is. ;)

I'm aiming for 100kw battery backup so 1 panel should work. I thought about 2 separate panels but I don't think it will be needed. What you described is exactly what I'm wanting to do.
 
Project said:
The best bid I got for grid tie was $61,000 and when the grid goes down so do I. In my area I'm not even allowed to install the panels, I can't touch it . If I was just grid only and had a generator backup a transfer switch would be used to switch from grid to gen. I was just wondering if I could go the other way and use the grid as a backup. I have no problem doing it properly, I'm just not going to spend $60k to still be in the dark when the grid goes down


When I say grid tied I mean feeding excess to the grid.



....and when I say do it properly, I mean you really have to have a utility interactive inverter if you want automatic switching.
You could do it manually like a generator back up, but that would require you to be there all the time to make the switch.

Where do you live and how many Kilowatts for $61,000????


BobMuster said:
You've got the concept correct, just the terminology might be a little off. I've researched this a bit and it is very simple. All you need is a change over (manual) switch, the same as used when a homeowner wants to hook up a generator. The switch goes before the main breaker between the grid and the breaker. Switch it one way, its grid and the other way it's your power source (usually off in the middle). This way, no grid feed in is possible. Yes, it's a manual change over, but not expensive. I've heard of $200 being quoted by a local electrician (South Australian).

The switch alone is more than $200.
Doing any work between the pole and the main breaker would require the power company to come shut it off. This means a licensed electrician and permits.
 
APD said:
Project said:
The best bid I got for grid tie was $61,000 and when the grid goes down so do I. In my area I'm not even allowed to install the panels, I can't touch it . If I was just grid only and had a generator backup a transfer switch would be used to switch from grid to gen. I was just wondering if I could go the other way and use the grid as a backup. I have no problem doing it properly, I'm just not going to spend $60k to still be in the dark when the grid goes down


When I say grid tied I mean feeding excess to the grid.



....and when I say do it properly, I mean you really have to have a utility interactive inverter if you want automatic switching.
You could do it manually like a generator back up, but that would require you to be there all the time to make the switch.

Where do you live and how many Kilowatts for $61,000????



This is in arkansas and was for 20 kilowatts. The only thing I'm allowed to do is buy approved solar panels . I can't even install the mounts. Basically I can supply a pallet of panels and they do the rest. Needless to say that was a deal breaker for me. My generator switch I havenow is automatic. It has switched when I was away from home before and ran for 3 days before I thought about it and had someone go by and check it.
 
[quote pid='4271' dateline='1491180621']

This is in arkansas and was for 20 kilowatts. The only thing I'm allowed to do is buy approved solar panels . I can't even install the mounts. Basically I can supply a pallet of panels and they do the rest. Needless to say that was a deal breaker for me. My generator switch I havenow is automatic. It has switched when I was away from home before and ran for 3 days before I thought about it and had someone go by and check it.
[/quote]

Ok that's $3/watt installed, that's just about the national average.
20 KW is a pretty big system for residential, do you really need that much?....and if you need that much, you are going to kill your DIY powerwall really fast (unless it is huge).

You might be able to put the grid as backup in an auto transfer switch like yours, but you have to consult the manufacturer. In theory it could work as long as the switch is capable of having constant AC on both GRID and GEN simultaneously. The internal circuitry might prevent this.

You already have everything you need to test whether it will work....just swap the gen / grid inputs. DISCLAIMER: this is not advise. Do it at your own risk. Im not responsible for anything you do.
 
APD said:
[quote pid='4271' dateline='1491180621']

This is in arkansas and was for 20 kilowatts. The only thing I'm allowed to do is buy approved solar panels . I can't even install the mounts. Basically I can supply a pallet of panels and they do the rest. Needless to say that was a deal breaker for me. My generator switch I havenow is automatic. It has switched when I was away from home before and ran for 3 days before I thought about it and had someone go by and check it.

Ok that's $3/watt installed, that's just about the national average.
20 KW is a pretty big system for residential, do you really need that much?....and if you need that much, you are going to kill your DIY powerwall really fast (unless it is huge).

You might be able to put the grid as backup in an auto transfer switch like yours, but you have to consult the manufacturer. In theory it could work as long as the switch is capable of having constant AC on both GRID and GEN simultaneously. The internal circuitry might prevent this.

You already have everything you need to test whether it will work....just swap the gen / grid inputs. DISCLAIMER: this is not advise. Do it at your own risk. Im not responsible for anything you do.
[/quote]
I'm not going to be trying it without a few phone calls first. Lol 20kw is large but that's what the power company said I would need because of the size of the house which is under construction now. I tried to explain that due to the efficiency of the house I should be able to do it with half their recommendation but they disagreed. Then I looked into going off grid but battery storage is very expensive until I stumbled across this. Now energy storage is within reasonable limits and can use the grid as backup. My powerwall goal is 100 kilowatts.
 
Project said:
I'm not going to be trying it without a few phone calls first. Lol 20kw is large but that's what the power company said I would need because of the size of the house which is under construction now. I tried to explain that due to the efficiency of the house I should be able to do it with half their recommendation but they disagreed. Then I looked into going off grid but battery storage is very expensive until I stumbled across this. Now energy storage is within reasonable limits and can use the grid as backup. My powerwall goal is 100 kilowatts.

Do you have a source for free or cheap lithium batteries?....I too was enticed by the "low cost" of a DIY powerwall, but it turns out they are not significantly cheaper than lead-acid UNLESS you have a good source.

Maybe the power company just gave you the 20kw number because of your square footage? Did you or they do an actual load calculation based on appliances?

Arkansas? So will you be running an air conditioner often? That is a huge load.

100 KW!?!? do you know how many lithium cells that is?
 
APD said:
Project said:
I'm not going to be trying it without a few phone calls first. Lol 20kw is large but that's what the power company said I would need because of the size of the house which is under construction now. I tried to explain that due to the efficiency of the house I should be able to do it with half their recommendation but they disagreed. Then I looked into going off grid but battery storage is very expensive until I stumbled across this. Now energy storage is within reasonable limits and can use the grid as backup. My powerwall goal is 100 kilowatts.

Do you have a source for free or cheap lithium batteries?....I too was enticed by the "low cost" of a DIY powerwall, but it turns out they are not significantly cheaper than lead-acid UNLESS you have a good source.

Maybe the power company just gave you the 20kw number because of your square footage? Did you or they do an actual load calculation based on appliances?

Arkansas? So will you be running an air conditioner often? That is a huge load.

100 KW!?!? do you know how many lithium cells that is?

I already have about 30,000 cells now but have only processed about 8000 so far. I am installing a geothermal cooling system that is far more efficient than regular a/c and have wood for heat via fireplace and outdoor wood boiler. Not even going to have a microwave and all cooking and got water will be with gas.
 
Project said:
APD said:
Project said:
I'm not going to be trying it without a few phone calls first. Lol 20kw is large but that's what the power company said I would need because of the size of the house which is under construction now. I tried to explain that due to the efficiency of the house I should be able to do it with half their recommendation but they disagreed. Then I looked into going off grid but battery storage is very expensive until I stumbled across this. Now energy storage is within reasonable limits and can use the grid as backup. My powerwall goal is 100 kilowatts.

Do you have a source for free or cheap lithium batteries?....I too was enticed by the "low cost" of a DIY powerwall, but it turns out they are not significantly cheaper than lead-acid UNLESS you have a good source.

Maybe the power company just gave you the 20kw number because of your square footage? Did you or they do an actual load calculation based on appliances?

Arkansas? So will you be running an air conditioner often? That is a huge load.

100 KW!?!? do you know how many lithium cells that is?

I already have about 30,000 cells now but have only processed about 8000 so far. I am installing a geothermal cooling system that is far more efficient than regular a/c and have wood for heat via fireplace and outdoor wood boiler. Not even going to have a microwave and all cooking and got water will be with gas.
Ha Ha, so I guess you do know how many cells that is :D ! You must have a really good source!? Damn dude, your house sounds just like my kind of place! jealous/congratulations!
 
[/quote]
Ha Ha, so I guess you do know how many cells that is :D ! You must have a really good source!? Damn dude, your house sounds just like my kind of place! jealous/congratulations!
[/quote]

I fell into a good deal about a week ago that was the bulk of my Cells. I'm still a long ways out on completing this house. It's another DIY project that's 7000sqft log house built out of very large logs. It's a tremendous amount of work and slow going but it's well worth the effort. I'm defiantly not afraid to take on a challenge.
 
Got any pics of your 30,000 cells and your charge/discharge gear?
 
Im away from home right now but you can see a pic of the first 2000lbs on another thread on here. Let's see your haul or something like that. I can only charge 40 at a time right now and have 10 opus chargers for cycling and capacity testing. I built a mobile charger that I take on the road with me so I can charge while I'm at work. I have 200 tp4056 modules and battery holders but haven't been home long enough to put anything together.



image_cjypco.jpg
. The only pic I have on my phone of my charger. It's nothing fancy but it gets the job done
 
Realy nice setup. I like that you have a mobile unit that you can take with you to keep up the pace. With that many cells, it's almost a necessity. And thats a lot of TP's you have. ;)

Looking forward the rest of your build
 
Korishan said:
Realy nice setup. I like that you have a mobile unit that you can take with you to keep up the pace. With that many cells, it's almost a necessity. And thats a lot of TP's you have. ;)

Looking forward the rest of your build


Thanks. I do most of my charging on the road. I'm away from home about 25 days per month. Hopefully I'll be able to retire in a couple more years. The TP's I got dirt cheap, $13-$14per hundred . I couldn't pass it up at that price..
 
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