MPP "Controller" with Solar Panels wired into house - "Illegal"?

[Old Jarhead]

I was told today by a friend who sells solar for a solar installation company that my planned system was "illegal" in Utah:

all numbers are approximate.

4,000 W of Solar Panels mounted on roof of house
MPP LV5048 "all in one" mounted in the attached garage and plugged in to the grid.
2,000 W LiFePO batteries in the garage
AC Circuit breaker panel from the MPP in the garage.

I plan to wire from the MPP circuit breaker panel, using a licensed electrician, to code, so that One outlet in each of 4 rooms in my house is powered from the MPP controller. (The other outlets will still be through the house circuit breaker panel that is fed by the grid)

I will have the MPP set to provide power to the circuit breaker panel with the following priority: Solar Panels, Batteries, grid.

My friend told me that it's illegal to have any other circuits in a house that is connected to the grid (in this case, Rocky Mountain Power)

Is he correct? Is it illegal? Or is he misunderstanding something?

Thanks in advance!

 

[Maast]

The only way to answer that is to dig through the current NEC code that Utah is using. He may be referring to connecting to the 'supply side' vs the 'load side' of the breaker panel or simply the roof edge clearance of the panels on the roof.
Lots and lots of reading to be done. Here's a link to the 2017 NEC code:

Edit: Removed link to copyrighted document (oops)

 

[Old Jarhead]

Thank you Maast!
Only 882 pages? Piece of cake!

 

[Maast]

Articles 690, 710, & 712. Batteries are covered in 480.1 through 480.6 and 480.9 through 480.11.

Cuts it down 95% of reading the whole thing. Still a good bit of studying and googling to figure out what it's talking about.

The NEC does seem to REALLY like disconnects...

 

[offgriddle]

Thank you Maast!
Only 882 pages? Piece of cake!

This should be no different than running a portable gas powered generator.
If the power that you generate has no possible pathway to the grid, then it's your own business what you do. If, however, there is any possibility that the power you generate could find a path to the grid through your electrical system, then you must use a transfer switch to prevent that.
Maybe code doesn't want permanent electrical fixtures installed that are fed by a second power source, to prevent an accidental combining of the grid power and your own homemade power.

 

[Steve_S]

I read this a couple of times and it bothers me. I know in some areas there are some pretty ridiculous rules but most aren't.

In a situation where there is the possibility of pushing power to the grid lines, then it has to be done properly & to code and follow a vast array of rules (depending where you are, that can be cuckoo). Just tossing somethin on your house and connecting to you panel where it can backfeed the grid is not only stupid, it's most likely illegal as well.

If you decide to install solar & batteries and decide to run a segment of our home independent of the grid power, so circuits on their own AC Panel and not connected to the homes main AC power panel, then that is usually fine. (do follow electrical codes).

As well, if you wish to "partition" a section of your home to use both Grid & "Backup UPS" without grid feed-in, again that can be accomplished with the right hardware. This is where you could connect an Inverter/Charger to your home AC for INPUT ONLY, enabling it to charger your batteries IF low and during OFF-Peak hours but also allowing for solar charging and providing power to your partitioned sub-panel. Samlex Inverters can do this (see link in my signature).

If you have the intention of connecting solar & batteries and then back feeding to the grid so they pay you for power, then you have to get the permits and follow all the rules and meet the electrical code requirements and have it all signed off.

 

[Maast]

This should be no different than running a portable gas powered generator.
If the power that you generate has no possible pathway to the grid, then it's your own business what you do. If, however, there is any possibility that the power you generate could find a path to the grid through your electrical system, then you must use a transfer switch to prevent that.
Maybe code doesn't want permanent electrical fixtures installed that are fed by a second power source, to prevent an accidental combining of the grid power and your own homemade power.

Thats one way, but code does allow and addresses having a "hybrid" installation in where you can backfeed the grid and have a "protected loads" panel. The protected loads panel is usually basically a transfer switch between the inverter connection point and your normal house panel. This is all on the supply side.

The grid connection point is at the main AC connection to the load side panel. Usually if you're going to do a hybrid connection you have to install a new panel inbtween your grid connection and your house panel and that becomes your new "main panel" and then you do your transfer switch between the new 'main panel' and the original house panel.

If you backfeed the grid then not only does your meter have to support it, EVERYTHING above 60v in the electrical path has to be UL listed. Which is a huge PITA as well as expensive.

If you go above 10kw of panels you become a 'commercial producer' and then you HAVE to be connected to the supply side of the main panel.

 

[offgriddle]

Thats one way, but code does allow and addresses having a "hybrid" installation in where you can backfeed the grid and have a "protected loads" panel. The protected loads panel is usually basically a transfer switch between the inverter connection point and your normal house panel. This is all on the supply side.
If you go above 10kw of panels you become a 'commercial producer' and then you HAVE to be connected to the supply side of the main panel.

A simple transfer switch like this perhaps.

Reliance Controls 60 Amp Utility / Generator Transfer Switch TCA0606D - The Home Depot

This 60-Amp, double-pole manual transfer switch is for use with any 125/240V generator up to 15,000 running Watts. Ideal for switching a 60A service or subpanel from utility to generator power. This economical

www.homedepot.com

 

[Maast]

Exactly like that. Reliance also makes transfer switches for individual circuits, but for me when I really started to plan out how to do it, it would have been so difficult and expensive for me it was a LOT easier to just install a new 'main panel' and then put in a shunt trip for the dryer circuit so I wouldnt overload the 8048 inverter if the grid went down and it started carrying the whole load with both the stove and dryer going at the same time.

Also, putting in a new main panel allowed me to address the 125% main panel bus bar rule. (lots of googling on that one)

 

[offgriddle]

Exactly like that. Reliance also makes transfer switches for individual circuits, but for me when I really started to plan out how to do it, it would have been so difficult and expensive for me it was a LOT easier to just install a new 'main panel' and then put in a shunt trip for the dryer circuit so I wouldnt overload the 8048 inverter if the grid went down and it started carrying the whole load with both the stove and dryer going at the same time.

Also, putting in a new main panel allowed me to address the 125% main panel bus bar rule. (lots of googling on that one)

Oooooh the 8048 is beautiful!
Wots this about a 125% bussbar rule,?

GS8048A-01 8,000W 48V

Outback Radian GS8048A-01 8000W 120/240VAC Inverter - UL1741-SA Listed

www.wholesalesolar.com

 

[tictag]

Whilst we could all argue the point, I'm sure your friend didn't say this just to put up an arbitrary barrier to your project. It might be worthwhile discussing the matter further with him - maybe he knows something you and us lot don't? Pitched in a way as being a learning experience, I'm sure he'll be willing to point out the specifics of why such a system would be illegal.

For example, the MPPSolar units say that they are 'Designed for US' but nowhere in their sales material does it say that they are UL listed.

 

[ghostwriter66]

Articles 690, 710, & 712. Batteries are covered in 480.1 through 480.6 and 480.9 through 480.11.

Cuts it down 95% of reading the whole thing. Still a good bit of studying and googling to figure out what it's talking about.

The NEC does seem to REALLY like disconnects...

You should see CALIFORNIA’s Solar code ... THATS the reason I asked for a transfer to S Texas .. the code here fits on the back of a napkin ... BUT going to say knowing UTAH - your friend is right .. BTW their should be a UTAH SOLAR COUNCIL u can call and they send u what u are looking for ...

 

[Maast]

Oooooh the 8048 is beautiful!
Wots this about a 125% bussbar rule,?

Yeah, awesome efficient and super flexible inverter, they aint cheap though...

Its where you can't exceed 125% of the main panels bus bar rating and if you have a 200A main breaker already you cant add any more than a 50A breaker to the panel. You can get around this by reducing your main breaker to 175A giving you a total of a 65A inverter breaker. Article 705.12 in the code is what determines this.

I have to do this because even though 8000w at 240V is only 33A the inverter has a 60A passthough which could in theory overload the breaker bus. Bloody stupid rule because in practice it'd never happen because of the way the inverter handles internal loads plus grid feed but the inspector insists thats the way it is. Pesky schmuck...

Grid-tied Solar and the Dreaded 120% Rule | altE Solar Blog

Once solar inverters get larger than 7680W, installers often will run into a NEC restriction known as the 120% rule. We go over some solutions...

www.altestore.com

 

[trippydude]

Your friend is correct, but it is only because the inspector won't accept the fact that the transfer switch contained within the hybrid inverter is a transfer switch.

 

[HaldorEE]

This should be no different than running a portable gas powered generator.
If the power that you generate has no possible pathway to the grid, then it's your own business what you do. If, however, there is any possibility that the power you generate could find a path to the grid through your electrical system, then you must use a transfer switch to prevent that.
Maybe code doesn't want permanent electrical fixtures installed that are fed by a second power source, to prevent an accidental combining of the grid power and your own homemade power.

Another aspect is safety for workers. Image if you have an electrician in doing work. He flips the main breaker (or pulls the meter) and thinks all the wiring is deenergized, then runs into one of your circuits.

Or a fireman trying to cut in through a wall to rescue someone. You see where this is going.

 

[offgriddle]

Another aspect is safety for workers. Image if you have an electrician in doing work. He flips the main breaker (or pulls the meter) and thinks all the wiring is deenergized, then runs into one of your circuits.

Or a fireman trying to cut in through a wall to rescue someone. You see where this is going.

Mm hmm and when you feed the power company's transformer in reverse from your generator, that creates high voltage on the power lines, endangering power company electrical workers and even other nearby homes and businesses.

 

[HaldorEE]

Mm hmm and when you feed the power company's transformer in reverse from your generator, that creates high voltage on the power lines, endangering power company electrical workers and even other nearby homes and businesses.

Which is why backfeeding a grid tied panel from a generator is illegal unless you use an interlock that prevents that from happening.

 

[offgriddle]

Which is why backfeeding a grid tied panel from a generator is illegal unless you use an interlock that prevents that from happening.

Yes indeed, a transfer switch, either automatic or manual, must be used to isolates the grid to prevent accidental backfeeding.