Author Topic: Wall-plug Solar?  (Read 4386 times)

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Offline Kontakr

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Wall-plug Solar?
« on: March 01, 2018, 03:18:43 pm »
Has anyone used wall-plug solar units in an apartment? I understand (or at least I believe I do) the risks of backfeeding a circuit and the hazard of exceeding safe loads on the wiring, but it looks to be about the only viable way to add solar to a building I can't change.
 

Offline NiHaoMike

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Re: Wall-plug Solar?
« Reply #1 on: March 01, 2018, 06:16:22 pm »
You can use feedthroughs (copper foil sandwiched between insulation plastic) to run the wires inside without drilling any holes. Simply insert halfway in a door/window (preferably one that is not frequently used) and carefully close it so the feedthrough fits into the gap.
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Offline Seekonk

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Re: Wall-plug Solar?
« Reply #2 on: March 01, 2018, 08:16:39 pm »
Are you talking about those cheap grid tie units that plugs into a wall outlet?
 

Offline David Hess

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Re: Wall-plug Solar?
« Reply #3 on: March 02, 2018, 01:45:01 am »
In theory it can be safe to do.  Grid tie inverters are suppose to shut down if AC power is lost and should be protected against various faults like excessive current but the quality and reliability of cheap plug-in grid tie inverters is questionable.
 

Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #4 on: March 02, 2018, 04:16:26 am »
I assume we are talking the cheap chinese things on Ebay typically 300, 600 or 1000W intended for just a few panels.
My biggest concern with these indoors would be fire, I have seen pictures of these units failing badly. Next biggest concern is electrical hazard, that is no or defective anti-islanding protection (meaning the output continues to provide grid voltage into an otherwise dead grid). There have been various reports of them being unreliable but also some people very pleased with them so it seems to be a bit pot luck! Try exhaustivly to find reveiws for the one you are considering before you buy, that doesnt always work as often designs change frequently. Consider finding somewhere fire resistant or never leave it operating or plugged in unattended. One other issue is approval by your electrical company, it may be worth checking what requirements they have for the use of GTI's and also the compatability or otherwise of your electricity meter.
 

Offline Kontakr

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Re: Wall-plug Solar?
« Reply #5 on: March 02, 2018, 10:49:34 am »
Are you talking about those cheap grid tie units that plugs into a wall outlet?

Those are the ones I'm talking about. I've really only seen cheap ebay models that plug in, and one or two of those websites that look like they were made in the early 2000's way overselling what the panels can do. I was wondering if there was a more reputable manufacturer that I could trust to not kill me in my sleep, but also not skyrocket costs.

My biggest worry is fire or damage to the apartment, plus the general hassle of moving them. I'm not too worried about the electric company aspect, as I would not have enough power to overcome the idle draw of my house.
 

Offline f4eru

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Re: Wall-plug Solar?
« Reply #6 on: March 03, 2018, 07:38:10 am »
Quote
Has anyone used wall-plug solar units in an apartment?

That's illegal and dangerous.
Do you want people to die just for a few euros of solar power ???

Don't. Do. That.
 
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Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #7 on: March 03, 2018, 08:30:38 pm »
Quote
Has anyone used wall-plug solar units in an apartment?

That's illegal and dangerous.
Do you want people to die just for a few euros of solar power ???

Don't. Do. That.

Thats a bit over the top! The legality is entirely dependant on the regulations in your country for a start and they are not nececerally dangerious as some have been tested and comply with anti-islanding rules. Sweeping statements don't help anybody.
 

Offline f4eru

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Re: Wall-plug Solar?
« Reply #8 on: March 04, 2018, 11:56:51 pm »
Yeah, Could be that they are approved in a few countries
But it's still illegal in most other countries.
And it's still really bad practice to put a generator onto an uninsulated male plug.
Even if the software prevents it from  running when disconnected.
 

Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #9 on: March 05, 2018, 05:13:17 am »
But it's still illegal in most other countries.
Really, well its not illegal in my country, name some of these "most other countries" where you think it is and while you are at it perhaps you could enlighten us with your location ?
 

Online Gyro

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Re: Wall-plug Solar?
« Reply #10 on: March 05, 2018, 05:55:23 am »
Sorry??  :o

You really think it's legal to put mains on a 13A plug?
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Offline David Hess

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Re: Wall-plug Solar?
« Reply #11 on: March 05, 2018, 06:14:30 am »
You really think it's legal to put mains on a 13A plug?

If the grid tie inverter is working correctly, then there is no mains on it until it is plugged in.

Existing grid tie inverters use fixed wiring, correct?  What do you think caused the situation where a temporary grid tie inverter installation would even be desired?
 

Online Gyro

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Re: Wall-plug Solar?
« Reply #12 on: March 05, 2018, 06:21:13 am »
As you say, existing grid tied inverters are properly installed with fixed wiring at  the incoming supply meter with appropriate isolators etc.

I really wouldn't trust a cheap ebay job, which I'm sure doesn't carry appropriate approvals, with it's output on a bare mains plug and assume that it might do the right thing in all circumstances.

But it's still illegal in most other countries.
Really, well its not illegal in my country, name some of these "most other countries" where you think it is and while you are at it perhaps you could enlighten us with your location ?

I'm sure there are very strict regulations over the proper installation of a grid tied inverter.


EDIT: In the UK, grid tied inverters (up to 3.68kW) are governed by the Energy Networks Association G83 standard. This permits a properly specified inverter to continue to output for up to 5 seconds after loss of mains supply. Absolutely not safe on a mains plug!

http://www.energynetworks.org/electricity/engineering/distributed-generation/distributed-generation.html

EDIT1:
Also prohibited by BS7671 IET Wiring Regs (551.7.2 (ii)). It apparently prohibits parallel connection of a 'generating set' in parallel with the mains by means of a plug and socket.

https://www.scribd.com/presentation/259597021/17th-edition-overview-ppt
« Last Edit: March 05, 2018, 06:52:15 am by Gyro »
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Offline David Hess

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Re: Wall-plug Solar?
« Reply #13 on: March 05, 2018, 06:41:02 am »
EDIT: In the UK, grid tied inverters (up to 3.68kW) are governed by the Energy Networks Association G83 standard. This permits a properly specified inverter to continue to output for up to 5 seconds after loss of mains supply. Absolutely not safe on a mains plug!

I wonder if that standard is based on an older technology like phase locked AC generators.  The application notes I have seen for grid tie inverter design use a current driven high impedance output so if the AC power is removed, the output shuts down immediately because a fault is immediately detected.

Quote
I really wouldn't trust a cheap ebay job, which I'm sure doesn't carry appropriate approvals, with it's output on a bare mains plug and assume that it might do the right thing in all circumstances.

This is what I would worry about and I have read stories about these things burning up due to inadequate self protection or derating when too much solar power was available.
 

Online Gyro

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Re: Wall-plug Solar?
« Reply #14 on: March 05, 2018, 06:49:21 am »
David, I just edited my post above. It's also prohibited by IET Wiring Regs. That's a showstopper.

Quote
I wonder if that standard is based on an older technology like phase locked AC generators.  The application notes I have seen for grid tie inverter design use a current driven high impedance output so if the AC power is removed, the output shuts down immediately because a fault is immediately detected.

It could well be. The trouble is that it's still in there, so is permitted.

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Offline NiHaoMike

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Re: Wall-plug Solar?
« Reply #15 on: March 05, 2018, 10:46:17 am »
I had the idea to develop a grid tie inverter where a mains frequency transformer in a separate enclosure was used to interface with the grid. (That transformer could be a common AC wall wart for an experimental/educational setup.) The inverter circuit itself is then low voltage and far safer to work on. As a low voltage circuit, it would also not be subject to the UL requirements that apply to mains connected circuits.

It turns out, though, that for a small solar setup, it makes a lot more sense to not use an inverter at all. Still, I would like to see an open source grid tie inverter as an alternative to the cheap, unreliable Ebay units.
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Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #16 on: March 05, 2018, 08:26:06 pm »
As you say, existing grid tied inverters are properly installed with fixed wiring at  the incoming supply meter with appropriate isolators etc.

I really wouldn't trust a cheap ebay job, which I'm sure doesn't carry appropriate approvals, with it's output on a bare mains plug and assume that it might do the right thing in all circumstances.

But it's still illegal in most other countries.
Really, well its not illegal in my country, name some of these "most other countries" where you think it is and while you are at it perhaps you could enlighten us with your location ?

I'm sure there are very strict regulations over the proper installation of a grid tied inverter.


EDIT: In the UK, grid tied inverters (up to 3.68kW) are governed by the Energy Networks Association G83 standard. This permits a properly specified inverter to continue to output for up to 5 seconds after loss of mains supply. Absolutely not safe on a mains plug!

http://www.energynetworks.org/electricity/engineering/distributed-generation/distributed-generation.html

EDIT1:
Also prohibited by BS7671 IET Wiring Regs (551.7.2 (ii)). It apparently prohibits parallel connection of a 'generating set' in parallel with the mains by means of a plug and socket.

https://www.scribd.com/presentation/259597021/17th-edition-overview-ppt

Ahh thank you for finding it in the wiring regs I must confess I missed that however just to be clear this does not make it illegal, it is not a criminal offence to disobay the wiring regs BUT you would be held liable for any damage caused by not conforming to them.

I agree in general with what everybody has said BUT these units may be used with care and awarness of the potential consiquences, to declare them illegal is simply misleading.  Most unit's I have seen advertised are carefull to state they are CE certified and G83 complient and I have read several articles by people who have sucsesfully used them.

A lot of equipment available to people is potentially dangerious if missused or someone with insuficient knowlage tampers with it but I personally do not think everybody else should be penalised as a result.

I quote from wiki and this is also the situation understood by many people "Electrical work does not have to be compliant with BS 7671, but if a casualty or fatality occurs as a direct result of that electrical work, and this results in a legal action, then it may be necessary to justify major deviations from the principles of BS 7671 and other appropriate standards."
« Last Edit: March 05, 2018, 08:33:14 pm by fourtytwo42 »
 

Online Gyro

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Re: Wall-plug Solar?
« Reply #17 on: March 05, 2018, 10:10:05 pm »
"held liable" and "legal action" are a good enough pointer for me.  ;)
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Offline dmills

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Re: Wall-plug Solar?
« Reply #18 on: March 06, 2018, 12:04:07 am »
I have done (and documented) installations that deviated from 7671, no big deal, you just have to be very sure that you have thought it thru, and labelled anything that deviates from what some future sparky is expecting.

If you are not prepared to stand behind your work in a court (Or, shudder, in front of a coroner), should you be doing it?

Time was that it did not list marine locations as 'special', and you want nothing to do with TN-C-S in a marina, so we used isolating transformers to separately derive power for each outlet (With RCDs on the secondary side, post secondary earth bond connection), way outside the scope of the standard, but it worked well and we had no problems with it.

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Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #19 on: March 06, 2018, 12:21:50 am »
I think the OP has enough information now to be able to see the potential hazards, good to have the discussion/debate :)

I had the idea to develop a grid tie inverter where a mains frequency transformer in a separate enclosure was used to interface with the grid. (That transformer could be a common AC wall wart for an experimental/educational setup.) The inverter circuit itself is then low voltage and far safer to work on. As a low voltage circuit, it would also not be subject to the UL requirements that apply to mains connected circuits.

It turns out, though, that for a small solar setup, it makes a lot more sense to not use an inverter at all. Still, I would like to see an open source grid tie inverter as an alternative to the cheap, unreliable Ebay units.

There are such DIY circuits available if you know where to look, low frequency transformer coupled GTI's are fairly safe to construct. The high frequency transformer type require much more high voltage circuitry and should only be attempted by the more experienced, there are a few examples on some silicon vendors websites such as TI, Micro-chip, ST & others. This comes into the same safety bracket as DIY SMPS's to me, you must understand the constructional requirements for safety, it's not just a matter of a schematic and some software :)
I didn't mention transformerless designs as they really do come into the dangerious arena IMOP.
« Last Edit: March 06, 2018, 12:23:37 am by fourtytwo42 »
 

Offline mtdoc

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Re: Wall-plug Solar?
« Reply #20 on: March 08, 2018, 06:56:49 am »
"Wall-plug" grid tie inverters are illegal in the US. Full stop.

Any grid tie inverter in the US must meet UL1741 to be compliant with the N.E.C.  Wall plug inverters do not.

While I do not know the details, I'd be "shocked" if there were not similar regulations in other developed countries.
 

Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #21 on: March 08, 2018, 07:55:21 am »
"Wall-plug" grid tie inverters are illegal in the US. Full stop.
Any grid tie inverter in the US must meet UL1741 to be compliant with the N.E.C.  Wall plug inverters do not.
While I do not know the details, I'd be "shocked" if there were not similar regulations in other developed countries.
I am not quite sure what drives you to keep harping on and on, there are plenty of people who experiment around including in your country so you will just have to accept that not everybody has the same black and white view of the world as yourself.
 

Offline mtdoc

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Re: Wall-plug Solar?
« Reply #22 on: March 08, 2018, 09:47:28 am »
"Wall-plug" grid tie inverters are illegal in the US. Full stop.
Any grid tie inverter in the US must meet UL1741 to be compliant with the N.E.C.  Wall plug inverters do not.
While I do not know the details, I'd be "shocked" if there were not similar regulations in other developed countries.
I am not quite sure what drives you to keep harping on and on

Um - one post in this thread is "harping on and on"? :o

Quote
you will just have to accept that not everybody has the same black and white view of the world as yourself.
:wtf: I posted some factual info. Are you disputing those facts?

I really posted no opinions - other than that I'd expect other developed countries to have similar laws as the US.

As far as people experimenting with solar PV installations.  I'm well aware of that and all for it - as long as they are not jeapordizing others safety when they do it. "Wall plug" grid tie inverters are unsafe -at least all of the ones I have seen. If one is available that passes UL1741 or equivalent anti-islanding standards (as well as other common sense safety measures), I'd love to hear about it.

 I've been personally building as well as helping others design and install small and large PV systems for several years now.

It's unfortunate that there are so many uninformed people tinkering with these cheapo wall plug grid tie inverters. Like any unsafe electrical practices - the probability of an accident may be relatively low but the consequences of one are potentially fatal.

It's sad to see someone on an engineering forum promoting such practices to the naive.

If your are truly interested in things "green/eco" as your profile says and DIY then you should be interested in things being done safely.  All it will take is one accident involving a utility worker during a grid outage to give ammunition to the anti RE crowd for banning PV installations or outlawing any DIY installations.
« Last Edit: March 08, 2018, 10:03:27 am by mtdoc »
 
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Online Gyro

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Re: Wall-plug Solar?
« Reply #23 on: March 08, 2018, 10:01:09 am »
"Wall-plug" grid tie inverters are illegal in the US. Full stop.
Any grid tie inverter in the US must meet UL1741 to be compliant with the N.E.C.  Wall plug inverters do not.
While I do not know the details, I'd be "shocked" if there were not similar regulations in other developed countries.
I am not quite sure what drives you to keep harping on and on, there are plenty of people who experiment around including in your country so you will just have to accept that not everybody has the same black and white view of the world as yourself.

On the contrary - reading back through the past page, it's you who keeps "harping on" about legality, despite solid documented evidence contradicting your viewpoint! Maybe it's time you started citing something factual rather than your opinion. >:(

But it's still illegal in most other countries.
Really, well its not illegal in my country, name some of these "most other countries" where you think it is and while you are at it perhaps you could enlighten us with your location ?
« Last Edit: March 08, 2018, 10:12:06 am by Gyro »
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Offline fourtytwo42

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Re: Wall-plug Solar?
« Reply #24 on: March 08, 2018, 05:55:27 pm »
I don't think there is any more point in corrupting the OP's thread with a load of small minded rubbish!
 


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