Plug-in PV backfeeding a receptacle? Is this legal?

[Ricko1980]

I've recently been in a discussion with some policy people about plug-in solar panels. Apparently there are a few products out there that are "plug-and-cord" PV panels, with an integrated microinverter, and some of these are marketed to be simply plugged in to a regular 120V receptacle. This is for a 300W maximum AC generation, using a 380W DC panel.

In one case that I was told to look at, the product manufacturer provides some kind of "smart hub" and CTs that clip in to the main service panel on the service wires, and this "smart hub" communicates with the PV module, turning off the PV supply if there's no demand in the unit. In this way, the grid is never backfed, and the manufacturer says that clients therefore don't need any utility interconnection agreement.

The prices were pretty expensive for something that can just shave off a bit of your load most of the time, in my opinion.

According to the folks I was talking to, these require no permit, and no interconnection agreement... they say, "They're like plugging in a toaster, no permit required."

Does this violate some NEC rule? It's not clear to me if the NEC applies to people plugging things in "like a toaster." Does the NEC regulate owner appliance use? I'm in California, and the California Electrical Code includes "use and occupancy" in its scope, but then I can't find any section that seems to really apply. Where in the NEC (or some other code?) would we find any requirements for occupants (such as not plugging in a toaster on an otherwise oversubscribed circuit)?

 

[don_resqcapt19]

If the panel is physically installed, then the requirements of the NEC would apply.

 

[GeorgeB]

Legality, I agree with Don. It sounds like your unit's design prevents any backfeed. But I cannot understand Don's point about physically installed if cord-and-plug connected unless it is perceived as substituting for permanent wiring.

Although unlikely to occur with just 300 Watts, most POCO meters do not identify the direction of power flow. If your home is using less than 300W and your "system" is supplying the grid, in that case you are being charged for the power you are generating. The anti-backfeed makes this issue moot.

Generally speaking, in the hours from 3 before and after solar noon, I'm supplying (supplementing) the grid except when my AC and/or clothes dryer are running.

I don't know when (if?) bidirectional meters will become standard replacements, but do know that there are many that are not.

When my contractor installed my ~4kW DC system my POCO (Duke Energy) had to replace the meter to reflect my generation for the NetMetering to become effective.

 

[don_resqcapt19]

Legality, I agree with Don. It sounds like your unit's design prevents any backfeed. But I cannot understand Don's point about physically installed if cord-and-plug connected unless it is perceived as substituting for permanent wiring.

Although unlikely to occur with just 300 Watts, most POCO meters do not identify the direction of power flow. If your home is using less than 300W and your "system" is supplying the grid, in that case you are being charged for the power you are generating. The anti-backfeed makes this issue moot.

Generally speaking, in the hours from 3 before and after solar noon, I'm supplying (supplementing) the grid except when my AC and/or clothes dryer are running.

I don't know when (if?) bidirectional meters will become standard replacements, but do know that there are many that are not.

When my contractor installed my ~4kW DC system my POCO (Duke Energy) had to replace the meter to reflect my generation for the NetMetering to become effective.

If you fasten the solar panel to any structure or support in the ground, I see it being installed, and when it is installed, it is subject to the requirements of the NEC.
If it has a portable stand and the panel sits on the ground, then it would be outside the scope of the code.

 

[GeorgeB]

@don_resqcapt19, playing devil's advocate, not disagreeing with the intelligence of your reply ...

If I have a wall lighting fixture with a "NEMA 1-15P" electrical connection on a #18 (or #16) AWG zip cord, that is subject to the NEC?

I agree that any generating system connected to house (or business) grid sourced power SHOULD have to meet some standards; all I can think of here is that it must be listed by an appropriate authority. I cannot imagine that UL or intertek would find any standard to list it.

 

[winnie]

I don't know when (if?) bidirectional meters will become standard replacements, but do know that there are many that are not.

_Mechanical_ meters were generally bidirectional; it required extra work to make them 'secure forward'. If you flipped a mechanical meter over in the socket, it would run backwards.

_Digital_ meters are generally 'secure forward'. It is simple(??) software setting to make them secure forward. I don't see the utility making bidirectional meters standard unless they have an appropriate agreement in place.

(I don't know how simple it really is to implement 'secure forward'. In particular, if you have any sort of displacement power factor there is negative power flow for part of the AC cycle. If the meter were secure forward on an instantaneous basis, then such meters would charge for reactive power, not just real power. So the secure forward implementation has to have some sort of time constant involved, and this starts making things more complicated.)

-Jon

 

[GoldDigger]

_Mechanical_ meters were generally bidirectional; it required extra work to make them 'secure forward'. If you flipped a mechanical meter over in the socket, it would run backwards.

_Digital_ meters are generally 'secure forward'. It is simple(??) software setting to make them secure forward. I don't see the utility making bidirectional meters standard unless they have an appropriate agreement in place.

(I don't know how simple it really is to implement 'secure forward'. In particular, if you have any sort of displacement power factor there is negative power flow for part of the AC cycle. If the meter were secure forward on an instantaneous basis, then such meters would charge for reactive power, not just real power. So the secure forward implementation has to have some sort of time constant involved, and this starts making things more complicated.)

-Jon

The mechanical meters had a smoothing mechanism in the form of the inertia of the rotating disk. The mechanical secure-forward generally consisted of a pair of overriding clutches from oppositely rotating shafts.
Digitally, since you know the frequency of the delivered voltage, it is easy to construct an integrating mechanism and flip the sign of the output if needed on a multiple cycle accumulation period.

 

[Joethemechanic]

If I have a wall lighting fixture with a "NEMA 1-15P" electrical connection on a #18 (or #16) AWG zip cord, that is subject to the NEC?

I was thinking of these under cabinet lights

 

[PWDickerson]

If you fasten the solar panel to any structure or support in the ground, I see it being installed, and when it is installed, it is subject to the requirements of the NEC.
If it has a portable stand and the panel sits on the ground, then it would be outside the scope of the code.

It is true that the NEC does not apply to cord and plug connected appliances, but the NEC is not the only voice we have to listen to. Power companies routinely restrict backfeeding the grid, and PSE, my local utility, will send out a meter foreman to knock on your door and ask uncomfortable questions when they see a reverse rotation alarm at a site that doesn't have a net metering agreement in place.

 

[don_resqcapt19]

@don_resqcapt19, playing devil's advocate, not disagreeing with the intelligence of your reply ...

If I have a wall lighting fixture with a "NEMA 1-15P" electrical connection on a #18 (or #16) AWG zip cord, that is subject to the NEC?

I agree that any generating system connected to house (or business) grid sourced power SHOULD have to meet some standards; all I can think of here is that it must be listed by an appropriate authority. I cannot imagine that UL or intertek would find any standard to list it.

did you attach it to the wall in a way that needs tools to remove? If so, it is within the scope of the NEC. It it has keyhole slots, it isn't.
That is exactly how it works with the power strips. The listing standard says you can't attach them, but they have keyhole slots so you can set them over a screw...that is not installed or attached

 

[ggunn]

Although unlikely to occur with just 300 Watts, most POCO meters do not identify the direction of power flow. If your home is using less than 300W and your "system" is supplying the grid, in that case you are being charged for the power you are generating.

Although I have heard of that happening, it is only rarely the case. The company I just retired from has installed thousands of residential and commercial grid tied PV systems on services with existing revenue meters of different kinds and I do not know of a single case where exported energy was metered as consumption.

 

[winnie]

I believe that @Hv&Lv has described this from the utility side of things, and that his POCO installs secure forward meters without unless there is an interconnect agreement, and I think mentioned a few cases of people being charged for export.

I presume @ggunn that your company installed many systems with proper interconnect agreements

-Jon

 

[electrofelon]

Although I have heard of that happening, it is only rarely the case. The company I just retired from has installed thousands of residential and commercial grid tied PV systems on services with existing revenue meters of different kinds and I do not know of a single case where exported energy was metered as consumption.

All of the newish digital meters In my POCOs territory are indeed secure forward - that is for self contained, I haven't had the opportunity to check a CT metered.

 

[mtnelect]

The Southern California Edison replaced all their analog meters with digital meters several years ago. No more theft of electricity and know all your electrical habits every minute of the day. And are read remotely like Southern California Gas did shortly after SCE. And, if you forget to pay your bill it also can be disconnected remotely. I know, I didn't pay my bill and it was turned off.

 

[jaggedben]

If the panel is 'installed' then plugging it into an existing receptacle circuit violates the requirement for a dedicated disconnect in 705.12(A). (Unless it's a purposefully installed single receptacle, which you know it won't be.) The bit about the CT and 'smart hub' implies both that it is indeed 'installed' and that there's willful violation of that requirement. It's raised my eyebrows that a few of these things seem to be genuinely listed. Not sure how that is happening or if it's for real.

Beyond that, legally, just because you may keep the utility from knowing doesn't mean it's legal to connect a parallel source to their supply. 99.9% chance it isn't. Also it's harder for a controller like the one described to completely stop exports that it sounds (there's an open loop response time). So utilities probably have the data to detect exports, if they look.

These companies must know they're skirting the law and they don't care. One could make an argument it doesn't really matter much. They may fly in part because the economic impact of such small systems is ... not very much.

 

[winnie]

Here is a previous discussion on this topic:

Zero export system without interconnection agreement

I've been told by a few people that there is no need for POCO interconnection agreement/PTO if the grid-tied solar system ensures zero export. That doesn't seem correct to me but I can't find any explicit POCO rules or local/federal laws/codes that address this situation. Can anyone point to...

forums.mikeholt.com

Using terms I previously used, these plug in panels would be 'virtual zero export', and based upon what other people said, these panels are likely not UL listed.

They are likely built using UL listed components (including the micro inverter) but used in a way that the listing does not anticipate.

Jon

 

[ggunn]

I presume @ggunn that your company installed many systems with proper interconnect agreements

All of them, of course.

 

[analog8484]

I've recently been in a discussion with some policy people about plug-in solar panels. Apparently there are a few products out there that are "plug-and-cord" PV panels, with an integrated microinverter, and some of these are marketed to be simply plugged in to a regular 120V receptacle. This is for a 300W maximum AC generation, using a 380W DC panel.

In one case that I was told to look at, the product manufacturer provides some kind of "smart hub" and CTs that clip in to the main service panel on the service wires, and this "smart hub" communicates with the PV module, turning off the PV supply if there's no demand in the unit. In this way, the grid is never backfed, and the manufacturer says that clients therefore don't need any utility interconnection agreement.

The prices were pretty expensive for something that can just shave off a bit of your load most of the time, in my opinion.

According to the folks I was talking to, these require no permit, and no interconnection agreement... they say, "They're like plugging in a toaster, no permit required."

Does this violate some NEC rule? It's not clear to me if the NEC applies to people plugging things in "like a toaster." Does the NEC regulate owner appliance use? I'm in California, and the California Electrical Code includes "use and occupancy" in its scope, but then I can't find any section that seems to really apply. Where in the NEC (or some other code?) would we find any requirements for occupants (such as not plugging in a toaster on an otherwise oversubscribed circuit)?

That sounds like the portable Craftstrom unit I asked about on the forum a while back. It likely violates POCO rules for parallel generation but does not appear to directly violate any law passed by state/local governments. So, POCO's may go after users of such units for service agreement violations. However, in my research I have found there is already 10's of thousands or more inverters popular with RV's (11+ million) in the US that connect to the grid (shore power) and generate power in parallel with the grid but not exporting for years without an interconnection agreement. Such systems have not resulted in any known case of legal actions or disconnections by POCO's. It appears that relatively small parallel generation systems is not a high priority issue for POCO's.

 

[jaggedben]

That sounds like the portable Craftstrom unit I asked about on the forum a while back. It likely violates POCO rules for parallel generation but does not appear to directly violate any law passed by state/local governments.

Sure it doesn't 'directly violate any law', but it indirectly violates the law by violating approved regulations so what's the difference. In Calfornia at least, and probably most states, the utility rules are approved by public utilities commission, which is empowered by the legislature to approve such rules, which in turn gives the utility for all practical purposes the same power to sue you (or turn off your power) as if it was a law passed by the legislature itself. A distinction without a real difference.

So, POCO's may go after users of such units for service agreement violations. However, in my research I have found there is already 10's of thousands or more inverters popular with RV's (11+ million) in the US that connect to the grid (shore power) and generate power in parallel with the grid but not exporting for years without an interconnection agreement. Such systems have not resulted in any known case of legal actions or disconnections by POCO's. It appears that relatively small parallel generation systems is not a high priority issue for POCO's.

Probably really depends on the utility, but you're last sentence is not wrong at least in many cases. I've found and heard that local public power entities are a lot more uptight than the large IOU (which is probably just strapped for resources). I mean, for a private company, if you're going to spend a few hundred dollars sending a rep out to give someone a stern talking to, you'd better have that much revenue to recover. Public entities seem more likely to operate on principal.

 

[pv_n00b]

These have been around since microinverters became available. I will point out one thing that has not been mentioned yet. Usually, the manufacturer shows these portable AC modules on a patio and plugged into an outside outlet. Outside outlets have been required to have GFCI for quite a while so the chances are high that someone using this will plug it into a GFCI-protected outlet and no GFCI sold today is listed for back feed. They are all designed so that if the GFCI trips and there is a source on the plug side the GFCI circuit will most likely be damaged. The outlet may or may not continue to be energized; if it is energized, it no longer has GFCI protection.