How to add an external gfdi

davidwillis

Hi, I am setting up an 1800w grid tie system. The inverter I purchased says I need to install an external gfdi (to meet ul codes), but gives no instructions on how to do that. My solar array consists of 8 panels run in series. I have searched for a gfdi, but I can't find one rated to 300v. Also, I am not sure on how it is supposed to be wired. I need to do this as inexpensively as possible, but will need to pass an inspection.

Thanks
David

p.s.

Here is my inverter: http://www.exeltech.com/xlgtproducts.htm

And my panel specs:

Maximum Power (Pmax)*: 224 Watt
Tolerance of Pmax: +10%/-5%
Type of Cell: Polycrystalline silicon
Cell Configuration: 60 in series
Open Circuit Voltage (Voc): 36.6 Volts
Maximum Power Voltage (Vpm): 28.9 Volts
Short Circuit Current (Isc): 8.33 Amps
Maximum Power Current (Ipm): 7.58 Amps

BB.

Re: How to add an external gfdi

Just to be clear, what is a GFDI?

If you are looking for a DC Ground Fault Interrupter, the inverter you pointed at is a "non-isolated" Grid Tied inverter... I did not find any details/installation instructions with a quick look at the website.... But a DC GFI may not be appropriate for that guy.

-Bill

davidwillis

Re: How to add an external gfdi

BB. wrote: »

Just to be clear, what is a GFDI?

If you are looking for a DC Ground Fault Interrupter, the inverter you pointed at is a "non-isolated" Grid Tied inverter... I did not find any details/installation instructions with a quick look at the website.... But a DC GFI may not be appropriate for that guy.

-Bill

Ground fault detect & Interrupter is what I thought it meant. All I know is in the instruction manual it said something like this device must be used with an external GFDI device required by ..... some code. I can get the exact wording when I get home. But if I can pass the inspection without it, that would be even better.

davidwillis

Re: How to add an external gfdi

I have no idea about the virus. It is just a link to the manufacturer of my inverter.

As for the exact wording in my instructions, here it is:

"Warning Compliance to UL1741 Requires the following statement:
this unit is not provided with a GFDI device. This inverter or charge controller must be used with an external GFDI device as required by article 690 of the National Electrical Code for the installation location."

davidwillis

Re: How to add an external gfdi

Although it does say the inverter employs a Residual current detection system used to detect ac and dc residual ground current, and immediatly disconnects from the utility. And it complies with IEC62109-2, but it is for fire hasard protection only and is not intended to be used as a GFDI device.

BB.

Re: How to add an external gfdi

I would still like to see the manual for the Exeltech GT inverter (website seems fine to me--no problems).

But, you can purchase external DC GFI setups:



Midnite Solar 63 amp 150VDC DC Ground Fault Protector





63 amp 150 Volt DC ground fault protector (GFI - UL listed breaker assy). The 2011 NEC requires a ... on the roof of a dwelling. Now even if you Solarize your doghouse, a ground fault protector is required in order to pass inspection.




The above is around $50... There are others (including enclosures) available too from NAWS (our host).

Ground Fault Protection Circuit Breakers

And if you look around on their website, you will find Outback has DC GF breakers for sale too.

Again, I don't know anything about non-isolated GT Inverters--I would be a bit surprised if the DC GFI does [remove "not"] work correctly with these types of units (vs fully isolated GT Inverters with internal transformers). Not saying non-isolated GT inverters are unsafe--just I wounder if DC GFI's will work with them.

-Bill

PS: I believe these are dangerous to use... But until or unless NEC drops the requirements--You are pretty much required to use them.

davidwillis

Re: How to add an external gfdi

I will scan in my instruction an see if I can upload them.

I see there actually is a 300v breaker for about $90. What kind of box would you put that in, and how would you wire it with the inverter? I see there is a wiring diagram for a charge controller, but not for an inverter.

Thanks

solarvic

Re: How to add an external gfdi

David the first time I clicked your message I got the warning I got the warning it was unsafe, After I posted again it seemed ok so I deleted that post. When you get the Exeltech inverter in operation hope you can give some feedback on it and let us know how well it works. I was a little interested in one but most of the solar dealers don,t seem to be selling it yet. :Dsolarvic:D

BB.

Re: How to add an external gfdi

You do have to be careful, there is a huge difference between a 300 VAC breaker and a 300 VDC rated breaker. DC breakers (of equal rating vs AC rated breakers) are built much larger and may have different internal construction to turn off a DC current (DC sustains arcs very nicely).

-Bill

davidwillis

Re: How to add an external gfdi

anyone know what the maximum attachment size is? I tried to upload the scan but it is too big 9.9 MB

BB.

Re: How to add an external gfdi

Yea, we cannot host large files--generally just a page or two. Anyway, posting a copyrighted text here would not be a good idea anyway.

I will send you a PM.

-Bill

davidwillis

Re: How to add an external gfdi

solarvic wrote: »

David the first time I clicked your message I got the warning I got the warning it was unsafe, After I posted again it seemed ok so I deleted that post. When you get the Exeltech inverter in operation hope you can give some feedback on it and let us know how well it works. I was a little interested in one but most of the solar dealers don,t seem to be selling it yet. :Dsolarvic:D

It looks like it should do a good job if I can figure out the GFDi. I got what I think is a good price for it ($850 including shipping).

Chuck46

Re: How to add an external gfdi

This is what he is talking about http://www.outbackpower.com/docman/1401103030655Ground_Fault_Detector_Interrupter_REV_A.pdf Hope this helps

Chuck

OOps the llink doesnt work but its on outbacks site

Cariboocoot

Re: How to add an external gfdi

Link works fine for me.

There's a big difference between the <150 Volt arrays typically used with battery-based systems as the >300 Volt arrays often found on straight GT inverters. I haven't seen a GFDI for the high Voltage arrays. MidNite has one good for up to 300 Volt but not beyond that. Their breakers fit nicely in their boxes, btw.

Like Bill, I don't agree with this NEC regulation. Not that my opinion matters one whit.

BB.

Re: How to add an external gfdi

David sent me the first ~19 pages of the manual--and the following is contained within:

WARNING Compliance to UL1741 Requires the following Statement:

This unit is not provided with a GFDI device. This inverter or charge
controller must be used with an external GFDIdevice as required by Article
690 of the National Electrical Code for the installation location.


The XLGT Grid Interactive Inverter is a transformerless inverter, and as such, it is required to
be used in an Ungrounded Array Photovoltaic Power System as referenced by Article
690.35 of the 2008 National Electric Code. Article 690.35 does not require a GFDI device, it
does specify an updated list of requirements, and the XLGT Grid Interactive Inverter contains
all the necessary components to meet this new NEC2008 requirement.

Residual Current Detection (RCD)

The XLGT Grid Interactive Inverter employs a Residual Current Detection System used to
detect AC and DC residual ground current, and immediately disconnect from the utility
source. The RCD System is designed to comply with IEC62109-2 the International Standard
for Safety of power converters for use in photovoltaic power systems.

RCD technology addresses the specific needs of transformerless ungrounded systems, in
which an array grounding failure point could result in an AC ground current flow, a DC ground
current flow, or a combination of the two, which is the more likely case. RCD technology is
designed as a fire hazard protection system only, and is not intended to be used as a GFDI
device in any form.

RCD General operation

On initial power up the array is tested to ensure that Ground Impedance Is greater than
1kOhm/volt, or a minimum of 500kOhms, the XLGT will NOT engage the utility connection
breaker if this minimum value is not met. This test is indicated by the two green blinking
lights, if successful, the unit will then click the relay closed, and then check the Utility
conditions to attempt a grid connection. If this test is not passed, a red flashing light will
indicate a failure to meet the minimum ground impedance, and service by a qualified service
personnel may be required to fix this situation.

Upon successful start up, grid connection, and power generation, if a failure of array ground
isolation, resulting in ground fault current either AC current or DC current is detected, the
RCD will open the Utility relay and cause the system to cease power export. The RCD fault
is indicated by an alternating green and red flash. Only qualified service personnel should
clear any ground fault condition that exists. Only pressing the Reset button will clear the
RCD Detection, and allow the XLGT to resume grid interaction operation.

And later on:

WARNING! Connecting either leg of the PV Array will cause the XLGTto
become inoperative.

Electric Shock Hazard. The direct current circuit conductors of this
photovoltaic power system are ungrounded, but maybe energized with
respect to ground due to leakage paths and/or ground faults.

...

PV Array wiring
Because of the transformerless design of this inverter, neither leg of the PV is connected to
the ground terminal.

So, the DC GFI (as linked above) is not needed and if [DC GFI] used as directed, [the DC GFI] will cause the GT Inverter to shutdown.

The GT Inverter includes an RCD circuit--Which should meet the requirements of NEC 690 (alternative designs are allowed).

It appears that your local AHJ (authority having jurisdiction) must be following NEC 2008 or later (not all places do--You may have to do a bit of tap dancing to get them to allow a transformerless design GTI).

The first warning is from UL1749--Which does put the DC GFI into their requirements (and I think is a very dangerous requirement). The RCD does do the function of stopping current flow (turning off the inverter) if there is a Ground Fault in the DC Array Wiring.

At least, that is my reading of the documentation and requirements.

-Bill

davidwillis

Re: How to add an external gfdi

Well that is interesting. I spoke with my electrical inspector a while ago (before I got the inverter), and he said every thing needs to be UL listed, and have a GFDI. However he my not know about the transformer less inverter.

Now I am even more confused as to how to install this, and get it to pass the inspection.

One other thing, this will be installed on a shed about 150 feet from my house. Since it is not in a building with people living in it, would that make it exempt from needing a gfdi?

BB.

Re: How to add an external gfdi

The DC GFI is to reduce the chance of fire (it is not the same as the GFI outlets/breakers that you see on 120/240 VAC household branch circuits).

The DC GFI (as far as I know) was an attempt to reduce the chance of "arc faults"... For DC circuits, arc faults are more of a fire hazard than AC--DC arcs will sustain very nicely at lower voltages and currents than AC arcs (DC arc welders are very nice). In reality--the DC GFI (as linked above) just put a 1 amp fuse/breaker between DC return and Earth/Safety Ground. If there is a DC Hot to earth fault, it pops the 1 amp fuse (or some devices will stop operation). I wrote a long paper on why DC GFI's are very unsafe and of limited use as Arc Fault "interrupters".... But it will probably not be useful with the inspector unless they are really into electrical wiring and safety/design issues.

Installing this in an outbuilding would not really matter--unless you can argue that an arc fault would not be a fire hazard (don't think the inspector will buy that).

the 208 NEC was re-written to allow tranformerless inverters that use alternatives to detect DC wiring faults. And the RCD used appears to meet those requirements. Now you have to convince the inspector.

The is sort of the problem with keeping different specifications/codes in sync with each other. I don't know enough about the UL GTI Inverter specs. enough to argue their requirements (I do not have a current version of that code).

But--If your device is UL/TUV/NRTL LISTED, and your building department uses NEC 2008 or later--Or you can bring a copy of NEC 2008 and show them that transformerless GTI inverters are allowed, and alternates to the DC GFI is also allowed (which is probably even in the older code-- J Wiles always argued that NEC does not force engineers to do things in an unsafe manner--So, it the DC GFI listed was just a "suggestion" and should not be used if the engineers believed it to be unsafe)--Then I would makes a copy of the applicable NEC codes and say that this is where your GTI unit falls into.

If they push you to use the DC GFI--It will only work if the 1 amp breaker is left unconnected (i.e., not connected from PV- to earth ground through the breaker).

So as I see it:

1. Convince the AHJ (copy of NEC + GTI Installation Manual) to install without DC GFI (check with Exeltech and see if they have any documents you can give to the AHJ).
2. Install DC GFI and then disconnect ground breaker wire after inspection (note, it may be very difficult or possibly impossible to find a DC Breaker rated for >150 VDC--If inspector looks, they should fail install)
3. Save your money/time and find another project

-Bill

davidwillis

Re: How to add an external gfdi

I thought I would post the response from Exeltech.

Hello David,

The warning statement you referenced is required in our manual for the inverter to meet UL1741 compliance. If you'll continue to the paragraph immediately following that warning statement, we indicate that our XLGT is designed to operate in with an un-grounded PV array, and further references Article 690.35 wherein our inverter does not require a GFDI to be code-compliant.

This is an example where the UL1741 Safety Standard (latest revision was released in 2005) is out of step with the National Electric Code. In this case, the NEC exemption prevails.

I've attached the latest copy of the XLGT Installation Manual from our website. It was just updated today. (Changes didn't impact anything you mentioned.)


Dan

I hope that is good enough for the inspector

BB.

Re: How to add an external gfdi

Good luck David...

That is pretty much what I believe the "proper" answer to be too. Now it is up to the inspector (and if he/she was already keyed in on the DC GFI requirement--It may take some time to get a change in their thought processes).

-Bill

Cariboocoot

Re: How to add an external gfdi

davidwillis wrote: »

This is an example where the UL1741 Safety Standard (latest revision was released in 2005) is out of step with the National Electric Code.

Why am I not surprised? :roll:

Thanks for getting to the bottom of this. Let us know how "compliant" the AHJ is.

davidwillis

Re: How to add an external gfdi

well I got everything installed, and had the inspector come look at it. He is so confused he does not know what to do. I showed him the e-mails from the engineer and I thought he understood it. He read through the code, and doesn't know what it means, so he said he had to go ask someone else. That was yesterday, today I called him back, and now he says I need a GFDI without grounding ...... I am so upset with inspectors that don't know what they are doing. He is coming over again tomorrow to try and figure it out.

BB.

Re: How to add an external gfdi

Try to convince him that the RCD meets the NEC code (and UL) requirements.

I guess you can run the system and then short one of the DC legs to earth ground--If the RCD works as designed, it should (safely) shut down the GT Inverter (which is the requirement).

More fun--Ask the inspector to perform the test, himself, if he does not trust the NEC/UL Listing of the inverter (UL did LIST the inverter--So it does meet their requirements). If the inverter was not LISTED--then it would be up to you to add an external GFDI system. But, of course, the inspector should not allow an unLISTED device to be connected in the first place.

-Bill

davidwillis

Re: How to add an external gfdi

The problem is the inspector does not know the code, or understand the code when he reads it. I am going to just give him the e-mails i have received, and tell him to call or talk to them to figure out how it is supposed to be done. I am not, and cannot get a 600v external GFDI. And I don't know how connecting it to the + and - DC power to a GFDI will do anything other than cause problems. It is his job to figure out if what I have done meets code, and if it doesn't he needs to figure out how it should be done (and putting an external GFDI on is not how it is supposed to be done). I hate that I have to pay to have someone that does not know what he is doing inspect my work.

davidwillis

Re: How to add an external gfdi

Sorry about those last posts. I just had to vent a little. I think I am doing better now....

davidwillis

Re: How to add an external gfdi

well after enough talking, the inspector finally passed it off...:D

davidwillis

Re: How to add an external gfdi

I finally got my new net metering meter, so I turned on the inverter. It seemed to be working just fine, but then it stops for just a second (the LED goes orange, then back to green... sometimes it goes red then orange then green, sometimes it is really fast, and others I actually hear a relay turn off, then back on in a few seconds). I also noticed (by using an ac amp meter) that there is current going through my grounding wire (about0.10 to 0.15A). So I pulled out the ground wire and measured 61 VAC on between the ground lug, and the ground wire. I don't know what to do. I emailed the company with no response. It is very frustrating though, because it just gets up and running, then shuts off. By connecting an amp meter on the hot wire, I can see that it takes a while to get up to power, and then just as it does, it shuts off.

Any advise?

Thanks

p.s. the manual says red means low voltage on the solar panels (which I can monitor, and it stays over 200 at all times, usually about 225-235 with open voltage at 285). The orange Led is when a utility has resumed valid condition after an abnormal condition.

westbranch

Re: How to add an external gfdi

phone the inspector and have it condemned or dangerous??

BB.

Re: How to add an external gfdi

The ground current is a bit high (0.005 amps or 3-5mAmps is the limit for plug-in devices for ground current). But, since yours is hardwired to your building wiring, it should not be an issue.

Many electronic devices use some pretty good sized filter capacitors between Line 1 and Line 2 to ground. These capacitors will put some current on the ground wire (it does not cost you anything money wise, the power factor of this current is ~0.0 or ~90 degrees out of phase with the voltage because it is a "pure" capacitive current).

A GT inverter that measures an out of tolerance on the AC mains (voltage or current) should shutdown and timeout for ~5 minutes before it will restart.

In your case, it sounds more like the solar array voltage/current is not stable (is this middle of the day, or sun up / sun down?). There is no timeout required, so if something is bouncing near min/max voltage--you could get some "chatter" (just guessing, my GT inverter does not do that).

In any case, if you can measure your AC line voltage/current/frequency and your Solar Array DC voltage/current (both with internal GT display and with separate DMM) when this happens--it may be helpful.

You probably will need to call the factory--They may have seen the issue before and tell you exactly what needs to be done.

-Bill

davidwillis

Re: How to add an external gfdi

This is middle of the day (it is gets up to 12A @ 125VAC on the AC side, before it shuts off). The Solar array puts out a constant voltage (open voltage). But it fluctuates some when the inverter is turned on. I just thought it was the mmpt? I was watching the voltage when from when I turned on the inverter until when it shut off, and it started at 280 before the inverter was turned on, then it fluctuated around 220-245. It shut off at 224 (when the inverter shut of it immediately jumped back to 280V). It seems consitant (meaning it powers up and then levels out at about 12A AC, for a few seconds then shuts down again).

There is no GT display, so I have been doing everything with my multimeter.

davidwillis

Re: How to add an external gfdi

It is starting to get cloudy now (and later in the day). So the power output is now down to only 4Amps Ac, but it does not restart anymore. So it seems like when the power output is too much it resets???? Although it is a 1.8kw inverter, so it should put out more than 12 amps, and I have seen it turn off with it as low as 10.

BB.

Re: How to add an external gfdi

In general, an MPPT solar charge controller and a Grid Tied Inverter (with MPPT input function) should limit its output up to its rated wattage/amperage no matter how much (or how little) energy is available from the array (as long as the array is with-in voltage/current protection specifications).

-Bill