On grid and off grid in the same house

[MT off grid]

I have been trying to find if NEC has anything saying if you can or can't have two power sources that are not tied to eachother in the same house, my plan is to keep all of my non essential loads (220) tied to the grid through their own breaker panel and another breaker panel that has all essential loads (120) tied to my off grid system, the two panels would have no connection between the two that could cause me to accidentally feed the grid, if its possible I would like to add a manual transfer switch between the two panels just incase I run out of battery power but im not sure if that complicates my idea or not

 

[Steve_S]

What you want to do is not uncommon, generally, there is no problems doing so because there is no possibility of pushing power to the grid. The use of the grid power as input for a charger is also fairly common, and simply put, you are just plugging in a charger to your wall socket, it's irrelevant what kind of battery it is charging. They can't tell you to not plug in a car battery charger... not much difference.

There are Inverter/Chargers which can do this with programmable settings, as well as AIO's (All in Ones). These features with programming & built -in ATS (Transfer Switch) do add to the cost and you will not find such functionality on "value" grade gear. Samlex EVO Inverter/Chargers, some Growatt & MPP AIO's are capable and of course much of Victron and other similar tier products can do so as well. Dual AC Input models, allowing for Grid Input for charging & Generator Backup as well are also available.

Also I have to say, be very clear about your voltages ! North America is 240VAC Split Phase & 120VAC Single Phase @ 60Hz.

 

[MT off grid]

What you want to do is not uncommon, generally, there is no problems doing so because there is no possibility of pushing power to the grid. The use of the grid power as input for a charger is also fairly common, and simply put, you are just plugging in a charger to your wall socket, it's irrelevant what kind of battery it is charging. They can't tell you to not plug in a car battery charger... not much difference.

There are Inverter/Chargers which can do this with programmable settings, as well as AIO's (All in Ones). These features with programming & built -in ATS (Transfer Switch) do add to the cost and you will not find such functionality on "value" grade gear. Samlex EVO Inverter/Chargers, some Growatt & MPP AIO's are capable and of course much of Victron and other similar tier products can do so as well. Dual AC Input models, allowing for Grid Input for charging & Generator Backup as well are also available.

Also I have to say, be very clear about your voltages ! North America is 240VAC Split Phase & 120VAC Single Phase @ 60Hz.

I always forget the 240 split vs europe etc. When I called the local inspector I was told that if a building is fed by grid power and also has a off grid system that all equipment is required to be UL certified, I want to have two totally separate power systems that have absolutely no way to feed each other but he said it can't be done with not UL, he said of I van find it in the book he would like to see it

 

[Steve_S]

Well that is a matter of your particular region and their requirements, also don't forget that many insurance companies may also have stipulations with regards to certification & inspections etc. There is certainly equipment that is UL Certified (not just compatible) but cost is relative and choice more limited.

 

[MT off grid]

Well that is a matter of your particular region and their requirements, also don't forget that many insurance companies may also have stipulations with regards to certification & inspections etc. There is certainly equipment that is UL Certified (not just compatible) but cost is relative and choice more limited.

I am required to follow all 2017 NEC regulations so guess I have some figuring to do

 

[MT off grid]

So I have called multiple electrical inspectors nationwide (united states) and also multiple electricians and they all confirm that to have solar on my house and pass inspection It is required that all equipment be UL listed (NEC 710, standalone systems) this also applies to all off grid applications but like I was told and also assumed, if it was off grid in the mountains etc no one would call for a permit and inspection so no one would know unless you have insurance and a problem arises, this also only applies to permanent installations so if I were to build a very large solar generator (must remain portable and trailer mount applies in this situation) and install a manual transfer switch I could technically get away with it as a back up power source, apparently NEC doesn't pertain to temporary portable use power like generators which solar generators fall under the same category

 

[Clifton]

It's not the NEC you have to worry about it's your city and utility. Utility says if under 1000w no interconnect agreement needed. If an SDS not in parallel I need a UL1008 transfer switch. SDS is local city code.

 

[Ozark Tinkering]

if its possible I would like to add a manual transfer switch between the two panels just incase I run out of battery power but im not sure if that complicates my idea or not

I am required to follow all 2017 NEC regulations so guess I have some figuring to do

It's good that you are doing your due diligence before wiring yourself into a red tag on your meter.

What you are talking about is a separately derived system as defined by the NEC.

Separately derived systems are power sources with no direct electrical connection between any of the circuit conductors and supply conductors. For example, no direct connection exists between the primary and secondary winding of a delta-wye transformer. Generators, converter windings, UPS systems, and solar photovoltaic systems are separately derived systems only when all circuit conductors — including the grounded (neutral) conductor — are independent of the supply conductors. If you wish to use a separately derived system, you must use a 3-pole transfer switch for a single-phase, 3-wire system, or a 4-pole transfer switch for a 3-phase, 4-wire system [Art. 100 definition and Sec. 250-20(d) FPN No.1].

A big problem you will run into is that by dividing your house in half electrically, you will have 2 separate physical locations where your neutral grounds are established to create the 2 isolated systems and NEC requires the neutral to be grounded one time only where it enters the service from the source. That would effectively make both panels part of the "grounded conductor".

 

[MrM1]

@Ozark Tinkering so using something like a Reliance Controls Prp/Trans multi circuit manual Transfer Switch that shares the main panel N/G bond for your critical loads panel, would be a problem to use with the grid, when the grid is not down?

These Reliance panels are common for generator use for critical loads in a grid down situation. What you seem to be saying is, you couldn't use that panel if the grid was operational regardless of your alternate source (Gen, inverter, hamster wheel, etc)

Top-Quality Transfer Switch Kit | Reliance Controls

We provide top-quality generator transfer and safety switch, generator transfer panel, power transfer switch for generator, and house generator transfer switch.

reliancecontrols.com

 

[MT off grid]

It's not the NEC you have to worry about it's your city and utility. Utility says if under 1000w no interconnect agreement needed. If an SDS not in parallel I need a UL1008 transfer switch. SDS is local city code.

NEC 720 says otherwise, I have confirmed it with several inspectors and electricians and all of them say the exact same thing

 

[MT off grid]

@Ozark Tinkering so using something like a Reliance Controls Prp/Trans multi circuit manual Transfer Switch that shares the main panel N/G bond for your critical loads panel, would be a problem to use with the grid, when the grid is not down?

These Reliance panels are common for generator use for critical loads in a grid down situation. What you seem to be saying is, you couldn't use that panel if the grid was operational regardless of your alternate source (Gen, inverter, hamster wheel, etc)

Top-Quality Transfer Switch Kit | Reliance Controls

We provide top-quality generator transfer and safety switch, generator transfer panel, power transfer switch for generator, and house generator transfer switch.

reliancecontrols.com

A generator is a temporary power source so it doesn't need to follow NEC 720, a solar power system in most cases is a permanent installation so it is required to follow NEC 720, I will be building a large solar generator so that I can avoid NEC

 

[Ozark Tinkering]

A generator is a temporary power source so it doesn't need to follow NEC 720, a solar power system in most cases is a permanent installation so it is required to follow NEC 720, I will be building a large solar generator so that I can avoid NEC

Then the whole conversation has been wasted from the beginning.

@Ozark Tinkering so using something like a Reliance Controls Prp/Trans multi circuit manual Transfer Switch that shares the main panel N/G bond for your critical loads panel, would be a problem to use with the grid, when the grid is not down?

These Reliance panels are common for generator use for critical loads in a grid down situation. What you seem to be saying is, you couldn't use that panel if the grid was operational regardless of your alternate source (Gen, inverter, hamster wheel, etc)

My response was based on your original scenario and my comment opened with ;

It's good that you are doing your due diligence before wiring yourself into a red tag on your meter.

...after you said;

I am required to follow all 2017 NEC regulations so guess I have some figuring to do

So I made my last comment this morning after thinking about it and before I'd seen that you put a set of wheels on your project. Of course you can get it done with a well placed 3-pole transfer switch and especially since you have cunningly made a case to avoid the need for UL or NEC compliance, you probably don't need to concern yourself with NEC 215.11 either?

So I have called multiple electrical inspectors nationwide (united states) and also multiple electricians and they all confirm that to have solar on my house and pass inspection It is required that all equipment be UL listed (NEC 710, standalone systems) this also applies to all off grid applications but like I was told and also assumed, if it was off grid in the mountains etc no one would call for a permit and inspection so no one would know unless you have insurance and a problem arises, this also only applies to permanent installations so if I were to build a very large solar generator (must remain portable and trailer mount applies in this situation) and install a manual transfer switch I could technically get away with it as a back up power source, apparently NEC doesn't pertain to temporary portable use power like generators which solar generators fall under the same category

 

[MT off grid]

Then the whole conversation has been wasted from the beginning.

My response was based on your original scenario and my comment opened with ;

...after you said;

So I made my last comment this morning after thinking about it and before I'd seen that you put a set of wheels on your project. Of course you can get it done with a well placed 3-pole transfer switch and especially since you have cunningly made a case to avoid the need for UL or NEC compliance, you probably don't need to concern yourself with NEC 215.11 either?

Not wasted, just brain storming with ideas on what I have been told and what can be done with equipment I already have

 

[50ShadesOfDirt]

It seems to always boil down to constraints and variables, and the choices one makes after discovering and reviewing them all. AHJ's, building codes, insurance ...

Did one choose *wisely*, or *poorly*, after navigating that maze ...

I'm always impressed when someone comes up with an alternative choice to a set of constraints and variables ... as opposed to the "default" choice. I might be able to make use of that alternative, so I appreciate hearing about it!

 

[Ozark Tinkering]

I'm always impressed when someone comes up with an alternative choice to a set of constraints and variables ... as opposed to the "default" choice. I might be able to make use of that alternative, so I appreciate hearing about it!

Ikr!?

cunningly made a case

 

[Clifton]

If you are off grid and an SDS, the NEC isn't knocking on your door. If it is not wired as an SDS and running it parallel with a shared neutral then your utility could know and then your AHJ. "Most" utilities do not require an interconnect agreement if under 1kw or under parallel or if it's an SDS. Stay SDS, so now it's just your AHJ. If you need a permit is, every aspect NEC matters.

If you are an SDS and connect with a transfer switch it needs to be UL 1008 to make the utility happy.