inverter-powered breaker panel

elesaver · July 2014

I'm in the process of "sorting out info." I am working to create an off-grid mini-system. It is "mini" at this time as I will not be trying to run a heat pump/ac or water heater. I would like to be able to take the circuit breakers for the circuits that run lights, TV, computer, refrig., etc. from my current main breaker box and put them into a separate breaker box that is powered by an inverter. At this time, I will be using a Cotek 1500W true sine 24V inverter until I am able to obtain a different one.

The inverter will be closer to the charge controller and the batteries but I will need to run wiring from the inverter to the area of the currect breaker box where the original circuit breakers are. That distance is approx 75 feet. Would it be safe to run a 10AWG extension cord for that 75 feet, plug it into a heavy-duty outlet and then wire that outlet to the bus bars on the new breaker box so that I could just install the circuit breakers in a manner similar to the original setup?

I mentioned this earlier but someone said to bring the inverter to the area of the new panel with the outlet and plug it in there. I don't understand the rationale for this. Having the inverter closer to the batteries seems a better set up. It would also allow me to know if there is a problem if the inverter alarm sounds, I would more likely hear it.

In other words, how do I get the 120V ac from the inverter into an off-grid breaker box? Having extension cords from the inverter inside the house doesn't seem very practical. Obviously I'm not an electrician but I can be quite good at following instructions. :-)

Thanks for those who will take the time to help me learn.

westbranch · July 2014

Re: inverter-powered breaker panel

Yes, there will be far better returns, ie minimal V loss, having the inverter as close as possible to the batteries. 110v is far better to send to the Panel box than 24v... you might consider 10 ga , not mandatory, from the inverter to the new distribution box... just less line loss. Depending on where you run the wire you may need conduit. Better to have the model with the transfer switch than without and designed to be hardwired into the system.

AuricTech · July 2014

Re: inverter-powered breaker panel

You might want to use a different color for the outlet faceplates on the circuits powered by your PV system. That way, you'll know at a glance which outlets are always hot.

elesaver · July 2014

Re: inverter-powered breaker panel

AuricTech wrote: »

You might want to use a different color for the outlet faceplates on the circuits powered by your PV system. That way, you'll know at a glance which outlets are always hot.

That's the thing...I can't run new wiring into the house to make outlets. How in the world would I get the wiring behind the walls? My plan is to remove the circuit breakers currently in place and hook those up into the breaker panel that is wired to the inverter. So, in my mind, the same outlets in the house and the same wiring will be used for lamps, TV, refrig., etc. Those outlets will be energized by the 120V output of the inverter. I'm trying to learn how to set up a new breaker box into which I will move the current circuit breakers from the original home electric system. There will be no connection between the two. Anything in the inverter-powered breaker box will be separate.

AuricTech · July 2014

Re: inverter-powered breaker panel

All you would need to do is identify which outlets are powered by which circuits, and change the inverter-powered outlets' faceplates to a color different from that of the grid-powered outlets. No need to run new wire at all.

elesaver · July 2014

Re: inverter-powered breaker panel

AuricTech wrote: »

All you would need to do is identify which outlets are powered by which circuits, and change the inverter-powered outlets' faceplates to a color different from that of the grid-powered outlets. No need to run new wire at all.

Yes, changing the faceplates would be a simple thing. What I need is some help as to how to wire the inverter to the new breaker box. Perhaps I'm not explaining this too well? An extension cord would run from the inverter to the location of the new breaker box which would be directly alongside the current box that is servicing the house. I want to move some of those breakers to the new box but I have to get the power from the inverter to the box. How do I get the inverter 120V to the new box? That's where I'd like some direction, if possible. Thanks again.

westbranch · July 2014

Re: inverter-powered breaker panel

Please do not use the term 'extension cord', a lot of us will see it as a beat up piece of wire that has many defects, repairs etc... that is used for a temporary connection. You will be wiring this in permanently

Use a new piece of NMD 10/2, or 12/2 or last 14/2 from the Inverter to the new distribution box. Some may say this is overbuilt but less line loss as you indicate it may be a fair distance. Better to use those watts than lose them in the wire. Wire the box up as normal to CODE.

To tell which lights and plugs are on a specific CB, leave all the lights in the house on and at least one item plugged in on, then turn all the rest of the breakers off and look to see what is still working. In the kitchen check to see if the top and bottom plugs are on the same circuit, some are separately wired to different CBs. Repeat for each breaker...

enjoy

vtmaps · July 2014

Re: inverter-powered breaker panel

Why do you want breakers in the inverter-powered electrical panel? They will not be needed... the inverter cannot make enough power to trip a 15 amp breaker. If you were going to use a transfer switch so that you could choose between grid and inverter to power the electrical panel, then of course you would need breakers. Also, if you are planning to put in a larger inverter sometime then you might as well put in the breakers now.

--vtMaps

TucsonAZ · July 2014

Re: inverter-powered breaker panel

If I were going to do this I would do something like what was mentioned by westbranch, I would use 10/2 wire for sure, I would get a simple little current tester, they're like $10 at a big box store and if you get them within about an inch of a live wire they make a noise and light up. Turn off all the breakers but the one you want to use and see what it powers testing anything in the area to be certain.

I would be more concerned with how to get the wiring out of the old extension box and into the one powered by the inverter. If you're disconnecting at the breaker box you could feed that line from anyplace remember, for example, if the line goes more in the direction of the battery bank you may be able to feed that line from the outlet closest to the inverter by removing the outlet and installing the new breaker there. Just make sure to take safety precautions so it's clear to yourself others what you did. I don't like splicing at the main breaker which is why I mentioned all this. Though I did do it once on a property I bought that had the main panel stolen and all lines cut short, no issues from that.

elesaver · July 2014

Re: inverter-powered breaker panel

First, thanks all for the suggestions. I had seen 10/2 "extension cords" at Lowe's and thought it would be easier to run the one than individual wires. It is not cheap! It's close to $100, I think.

This kind of thing must be so simple for all of you that my puzzle is not clear. Let me go one more time on this and then I'll mush. The house is already wired with the current main breaker panel, circuit breakers and outlets. The plan is to put in a breaker sub-panel powered by the inverter alongside the main breaker box and move the current circuit breakers from the main panel into the inverter-powered sub-panel so that I can choose to use some of the existing wiring and outlets in the house to run on solar. I have never put in a breaker panel...I guess that's obvious. My questions are not on which circuits or anything other than installing a sub-panel. Here's what I thought would work and I'm trying to confirm that this is not totally bizarre and I end up burning up the house, or worse.

The wires (be it "extension cord 10/2" or NMD 10/2) will come from the inverter to the location of the new sub-panel. I was going to mount and wire a heavy-duty outlet near the sub-panel to plug in the inverter. I would then have a "disconnect" from the inverter by unplugging it if I chose, wiring the positive to the positive, neg to neg, gr to gr. From there, I would remove the circuit breaker for the devices and/or outlets that I want to run with solar (instead of the grid )from main panel and put them into the sub-panel.

I do have an outlet power tester so it will be easy to determine what outlets are powered.

"...if you are planning to put in a larger inverter sometime then you might as well put in the breakers now." Yes, I will be getting a larger inverter in the future so I'd rather do this now.

You gentlemen are very kind to try to help and I appreciate your interest and patience. If anyone has additional clarification, it would be great. If not, I'll continue on. Thanks again.

Cariboocoot · July 2014

Re: inverter-powered breaker panel

A sub panel is installed just like a main panel: it has input to the bus bars and output through breakers. So step one is the breakers in the main panel have to be removed and put in the sub panel. This will also mean the wiring to those breakers has to be stripped out and moved over. That is why it is difficult as installed wiring can sometimes be buried beneath things (drywall, other wires) and may be too short to make the transition to the new box even if it is right beside the old one.

Step two is feeding those bus bars in the sub panel. Obviously new wire, and a transfer switch may be employed so that it can be fed either from the inverter or the original main service panel (which will need a breaker installed for the sub panel). Wiring here has to be able to handle the full load of the sub panel, which adds up fast. Two 15 Amp circuits is 30 Amps and there's your 10 AWG maxed out. This is a code issue, not a practical one: as vtMaps said the inverter will fault before any breaker trips but just try explaining that to an inspector.

Now about that wire to the inverter. Flexible 10 AWG extension cords, as you've already discovered, are expensive. Also not necessary if you can run much cheaper 10-2/G and fasten it down. There's the rub; solid wire shouldn't be used if its going to be flexed. And that brings us up to the inverter itself: if there's no hard-wire capability (only an outlet on the inverter) you need a couple of feet of flexible wire with a plug on it. This means there should be a junction box where you splice the flexible to the solid. All nicely fastened down to that point.

And yes, I for one have a hard time explaining how to wire things for having done it so much it's second nature. Having to think about it and explain it clearly is more difficult than doing the job!

vtmaps · July 2014

Re: inverter-powered breaker panel

elesaver wrote: »

I was going to mount and wire a heavy-duty outlet near the sub-panel to plug in the inverter.

When you say "heavy duty outlet" what exactly do you mean? It sounds like you may be planning what we call a 'suicide cord'... Are you planning that the power from the inverter be to a male plug with exposed prongs?

elesaver wrote: »

I would then have a "disconnect" from the inverter by unplugging it if I chose, wiring the positive to the positive, neg to neg, gr to gr.

You need to figure out about where to have the neutral-ground bonding... is it in your inverter or will it be in the new panel? Do you plan to ever power the new "inverter' panel from the grid? If so, you need to have a way to disconnect the bond if it's in the new panel. Or have a transfer switch do it.

--vtMaps

westbranch · July 2014

Re: inverter-powered breaker panel

what VT just said tweaked a thought, do you plan on this inverter use to be permanent for the second Distribution box or , if needed, will you need/have to switch back to grid power? If so you will want to use a transfer switch, not the plug in arrangement you are describing.

elesaver · July 2014

Re: inverter-powered breaker panel

Cariboocoot wrote: »

A sub panel is installed just like a main panel: it has input to the bus bars and output through breakers. So step one is the breakers in the main panel have to be removed and put in the sub panel. This will also mean the wiring to those breakers has to be stripped out and moved over. That is why it is difficult as installed wiring can sometimes be buried beneath things (drywall, other wires) and may be too short to make the transition to the new box even if it is right beside the old one.

Step two is feeding those bus bars in the sub panel. Obviously new wire, and a transfer switch may be employed so that it can be fed either from the inverter or the original main service panel (which will need a breaker installed for the sub panel). Wiring here has to be able to handle the full load of the sub panel, which adds up fast. Two 15 Amp circuits is 30 Amps and there's your 10 AWG maxed out. This is a code issue, not a practical one: as vtMaps said the inverter will fault before any breaker trips but just try explaining that to an inspector.

Now about that wire to the inverter. Flexible 10 AWG extension cords, as you've already discovered, are expensive. Also not necessary if you can run much cheaper 10-2/G and fasten it down. There's the rub; solid wire shouldn't be used if its going to be flexed. And that brings us up to the inverter itself: if there's no hard-wire capability (only an outlet on the inverter) you need a couple of feet of flexible wire with a plug on it. This means there should be a junction box where you splice the flexible to the solid. All nicely fastened down to that point.

And yes, I for one have a hard time explaining how to wire things for having done it so much it's second nature. Having to think about it and explain it clearly is more difficult than doing the job!

All right...now we're getting someplace. Actually, we've gotten to another hurdle. I think I should be running heavier duty wiring from the inverter to a junction box and then to the heavy-duty plug. The heavier duty wiring would allow the system to grow without having to replace the wire. I've seen that 4 AWG wire will handle 60 amps.

I will have to say that I am surprised by the "small" amount of amps that a 10-2 wire can handle safely. I've looked at the specs for the Cotek 1500 24V inverter and I do not see output amps. Sad to say, but I've been focusing more on the watts,volts and, amp hours needed than on amp-carrying capacity of wiring. This makes me want to configure the batteries to a 48V system and get a 48V TSW inverter before I got too much further into the rabbit hole.

elesaver · July 2014

Re: inverter-powered breaker panel

"what VT just said tweaked a thought, do you plan on this inverter use to be permanent for the second Distribution box or , if needed, will you need/have to switch back to grid power? If so you will want to use a transfer switch, not the plug in arrangement you are describing. "

No, nothing will be ever connected with the main breaker panel. If I need to go back, I would move the circuit breakers from the sub-panel back to the main panel.

" It sounds like you may be planning what we call a 'suicide cord'"

I see what you're saying here. If the inverter is running and the cord unplugged at the sub-panel, those outlet plug leads are hot and if I would touch them at the same time (or something else touch them) there would be a big problem. I'm glad you have brought this to my attention. I'm going to have to have a switch. Thanks for the tip.

Cariboocoot · July 2014

Re: inverter-powered breaker panel

elesaver wrote: »

All right...now we're getting someplace. Actually, we've gotten to another hurdle. I think I should be running heavier duty wiring from the inverter to a junction box and then to the heavy-duty plug. The heavier duty wiring would allow the system to grow without having to replace the wire. I've seen that 4 AWG wire will handle 60 amps.

Actually 4 AWG will handle 90-100 Amps. 10 AWG is standard for 30 Amp circuits, 8 AWG for 50 Amp circuits, 6 AWG for 60 Amp, 4 AWG for 80 Amps et cetera. A lot has to do with how those wires are run because much of it is about heat dissipation. You may notice as wire size increases the increase in Ampacity is not direct; this is because of the cross-section to surface area (which allows heat dissipation) ratio change.

I will have to say that I am surprised by the "small" amount of amps that a 10-2 wire can handle safely. I've looked at the specs for the Cotek 1500 24V inverter and I do not see output amps. Sad to say, but I've been focusing more on the watts,volts and, amp hours needed than on amp-carrying capacity of wiring. This makes me want to configure the batteries to a 48V system and get a 48V TSW inverter before I got too much further into the rabbit hole.

The inverter is rated for 1500 Watts, so that's 1500W / 120V = 12.5 Amps basically. How big of an inverter are you planning on going to? 30 Amps out is about what a 3600 Watt unit will do.

Don't confuse input with output. The DC side of the inverter, being lower Voltage than the output, will have more current on it for the same Watts. This is also where you have the most problem with V-drop for the same reason.

elesaver · July 2014

Re: inverter-powered breaker panel

"The inverter is rated for 1500 Watts, so that's 1500W / 120V = 12.5 Amps basically. How big of an inverter are you planning on going to? 30 Amps out is about what a 3600 Watt unit will do."

Sorry, Carriboot. I should've figured that one myself. (Shame on me.) Anyway, the fog continues to lift. A larger inverter...3000W and 48V inverter instead of 24V would about double the amp output. That may be worth going on with it...if the price is right, of course. :-) After you're in so far, what's a few more hundred. :-) :-)

westbranch · July 2014

Re: inverter-powered breaker panel

elesaver wrote: »

No, nothing will be ever connected with the main breaker panel. If I need to go back, I would move the circuit breakers from the sub-panel back to the main panel.

Please post a drawing of what it is you plan on having.

I am having trouble with what you just said and I am thinking it is different to what I think I read...
A transfer switch would eliminate having to move Circuit breakers AND wires back to the main panel when the SHTF... and you 'need' those circuits to be powered...

elesaver · July 2014

Re: inverter-powered breaker panel

westbranch wrote: »

Please post a drawing of what it is you plan on having.

I am having trouble with what you just said and I am thinking it is different to what I think I read...
A transfer switch would eliminate having to move Circuit breakers AND wires back to the main panel when the SHTF... and you 'need' those circuits to be powered...

I don't have a way to do a drawing as such. The plan is to run wiring from the inverter to the location of the main breaker panel)approx 50' away) where I will install a sub-panel. (If the term "sub-panel" means that it is a panel connected to the main panel, that is not what I am trying to say. My "electrical language" is sadly lacking, so I'm having to pick up terms as I go.) I am planning to install a disconnect box into which wiring from the inverter will be hardwired and then run wire from the disconnect to the sub-panel. That sub-panel is going to be used to power the house circuits that I want to power with the solar. I will move the circuit breakers from the main panel to the new (sub-panel) location. The two panels will not be connected in any way in order to prevent any back-feed or other problems with the main power supply. When I am using the solar circuits, I will still be using some of the main circuits...heat pump, water pump, clothes dryer, etc., as I do not have the capacity to solar power those at this time.

In essence, I will have two breaker panels that are totally separate in operation at the same time. One is the main panel and one is smaller sub-panel that will be installed dedicated to solar. If the grid power is out, I will still be able to use the circuits that have been moved to the "solar" sub-panel.

Now, if there's an easier way...I'd surely like to know. I have read about a transfer switch but from what I thought it described, it's an EITHER/OR situation for grid vs solar. I need to have a mix of both. Hopefully, the explanation is understandable. Now whether it's practical or not is another matter.

Cariboocoot · July 2014

Re: inverter-powered breaker panel

It depends on where you put the transfer switch.
For example it could switch you sub panel (proper name for it but doesn't exactly describe the usage in this case) from the inverter to the main panel with one.
You could use an inverter-charger which has a transfer switch built-in: its AC IN fed from the main panel and its AC OUT going to the sub panel.
You can keep the grid AC and inverter AC entirely separate. The downside there is not being able to power the items on the sub panel if the inverter goes down without having to rewire. Hence the transfer switch suggestion.
You would not use a 'whole house' transfer switch to take all of the main panel off grid and put it on the inverter.

AuricTech · July 2014

Re: inverter-powered breaker panel

Cariboocoot wrote: »

It depends on where you put the transfer switch.
For example it could switch you sub panel (proper name for it but doesn't exactly describe the usage in this case) from the inverter to the main panel with one.
You could use an inverter-charger which has a transfer switch built-in: its AC IN fed from the main panel and its AC OUT going to the sub panel.
You can keep the grid AC and inverter AC entirely separate. The downside there is not being able to power the items on the sub panel if the inverter goes down without having to rewire. Hence the transfer switch suggestion.
You would not use a 'whole house' transfer switch to take all of the main panel off grid and put it on the inverter.

If I understand both this post and the OP's intent, this would be a case where the transfer switch would normally be set to OFF (allowing the OP's PV system to power the circuits on the subpanel), and would only be set to ON in the event of a failure somewhere in the PV system (such as the inverter or CC going down, or an extended period of insufficient PV production to keep the batteries charged).

Cariboocoot · July 2014

Re: inverter-powered breaker panel

AuricTech wrote: »

If I understand both this post and the OP's intent, this would be a case where the transfer switch would normally be set to OFF (allowing the OP's PV system to power the circuits on the subpanel), and would only be set to ON in the event of a failure somewhere in the PV system (such as the inverter or CC going down, or an extended period of insufficient PV production to keep the batteries charged).

Yes, although the terms 'OFF' and 'ON' don't really apply to selector switch. More like NC is inverter and NO is grid.

westbranch · July 2014

Re: inverter-powered breaker panel

Exactly, with the transfer switch you NEVER have to re-wire those circuits in the sub panel, just 'the flip of a switch' and you are back in business AND .... no worries about cross-feeding /back-feeding as you suggested.

TucsonAZ · July 2014

Re: inverter-powered breaker panel

Cariboocoot wrote: »

A sub panel is installed just like a main panel: it has input to the bus bars and output through breakers. So step one is the breakers in the main panel have to be removed and put in the sub panel. This will also mean the wiring to those breakers has to be stripped out and moved over. That is why it is difficult as installed wiring can sometimes be buried beneath things (drywall, other wires) and may be too short to make the transition to the new box even if it is right beside the old one.

This would be my biggest concern in your entire project. I think the 10/2 wire is fine, avoid the extension cord, see if you can, I know we have the same inverter and I just looked into mine, seems the power outlet connects via a simple male/female connector so you could remove that outlet with ease and hardwire into the inverter without much effort.

Also, if it were me, I would pull off the sheetrock around the breaker box, if the breaker you're converting is going out the bottom I would mount the solar breaker box one stud over and 18" lower, if it's coming out the top do the same but above it. This will allow you to not cut or splice that wire at all, you can put the rock back up or patch the holes and call it a day fairly easily.

Everything else seems doable and fine.

inverter-powered breaker panel

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