Need To Add Arc Fault Detection to system

[lws2036]

I have a 3K Victron system (off grid with a generator as the backup) that is working very well. All components are Victron, including their Cerebro GX that provides very cool software for monitoring the system. I had it inspected by ESA and was told I needed to add Arc Fault and Ground Fault. Ground Fault was easily added with Midnight solar breakers in my combiner box. Arc Fault has been very difficult to find.

I got this and installed it. At first glance it seems to provide arc fault.

https://solar.se.com/us/en/product/mppt-disconnect-rs/#overview

Everything works with it wired in, but none of the lights turn on to indicate its actually doing anything. After reading the fine print off the manual, and watching some videos, I realized the arc fault this unit provides seems to require SE MPPT charge controllers to work. I really wish I had figured this out before I bought it, as it was not cheap.

I don't know what to do. I have spent a lot on this system and it works great. It would be a shame to have to replace everything. Has anyone dealt with this before?

 

[400bird]

Can you provide pictures inside the unit? I almost purchased one of those, but went with a Midnight charge controller (with integrated Arc Fault Detection)

I believe there is no power supply in there (at least for the brains) and that it needs external power which would typically be supplied by a Schneider inverter or charge controller.

 

[lws2036]

Here it is. Everything is working fine (in terms of the system is charging from the PV) with this wired in. I just can't tell if it is doing anything.

 

[400bird]

The green Tigo box in the middle is the transmitter for the RSD. Do you have RSD modules on the panels?
The Tigo transmitter has one or two LEDs on it if it is powered up.

The black rectangle below that is the arc fault detector. You'll see it goes the circuit board up top.
Are there any LEDs on it?

There's nothing in there that allows the arc fault detector to cut the connection to the panels. It might activate the RSD modules at the panels, but from memory it doesn't.

Are there any LEDs illuminated in there?

 

[lws2036]

Nothing illuminated, but I just realized I had the inputs and outputs reversed. It's corrected, hopefully, I didn't fry it. I don't have RSD modules on the panels.

 

[lws2036]

Just got a note from Schneider regarding my question on this:

The MPPT Disconnect RS complies with NEC 690.11 "Arc-Fault Circuit Protection
(Direct Current)", and includes an Arc Fault Detector. The MPPT Disconnect RS, when used in conjunction with the Conext MPPT 60 150 and Conext MPPT 80 600 charge controllers, detects and interrupts arc faults and complies with UL1699B.

So it looks like this unit does not actually provide arc fault without SE Context charge controllers. What a frustrating and expensive waste of time. I hope this helps someone else at least.

So I guess the only option left is Midnight Solar charge controllers. Unless someone else has an option for stand alone arc fault on here...

 

[400bird]

Yeah, arc fault detector I guess not arc fault interrupt. Without RSD modules on the panels all it is is a very fancy disconnect switch.

At this point would it be less expensive to buy the Schneider 60 150 charge controller?

I've got the Midnight charge controller because I couldn't come up with a stand alone arc fault solution. I even have a Schneider inverter, so the MPPT and disconnect would have fit right in for me.

 

[lws2036]

Another option would be to lower the voltage. I could put my panels in parallel. According to the code, if they are less than 80V I don't need arc fault.

 

[Hedges]

Are you not required to have RSD?

What if you fed PV through a remote-trip breaker and had arc-fault trip it?


I bought a couple of these, hope to have them trigger RSD (because I think that will be more effective at stopping an arc than simply open circuiting high-voltage series string). I don't see these available anymore.

http://ww.sensata5k.org/download/PVAF-T.pdf

 

[zanydroid]

I thought most scenarios where you need arc fault also require RSD? IE RSD at least in rooftop systems is more broadly required than arc fault (ie required starting at lower voltages). Under NEC.

 

[Hedges]

Except arc-fault has been around longer. Under older code?
Arc fault would be an NFPA concern (they may have not figured out that it is in their interest for firemen to be willing to do the job.)

 

[zanydroid]

I meant for new installs in most parts of the US.

Arc Fault = prevent a fire
RSD = make it safer to deal with a fire that is happening

Also I think RSD is probably underrated for reducing risk when servicing your own DC system.

 

[lws2036]

Are you not required to have RSD?

What if you fed PV through a remote-trip breaker and had arc-fault trip it?


I bought a couple of these, hope to have them trigger RSD (because I think that will be more effective at stopping an arc than simply open circuiting high-voltage series string). I don't see these available anymore.

[URL

Are you not required to have RSD?

What if you fed PV through a remote-trip breaker and had arc-fault trip it?


I bought a couple of these, hope to have them trigger RSD (because I think that will be more effective at stopping an arc than simply open circuiting high-voltage series string). I don't see these available anymore.

http://ww.sensata5k.org/download/PVAF-T.pdf

From what I understand it just need to show the system has arc fault protection. As I was explained it need to show it can detect an arc fault and then protect the system in that event. My inspector seems pretty reasonable. If I could show the protection came from RDS, I think it would be fine

 

[lws2036]

I thought most scenarios where you need arc fault also require RSD? IE RSD at least in rooftop systems is more broadly required than arc fault (ie required starting at lower voltages). Under NEC.

I have a ground mount. Which normally does not require arc fault. My issue is I built a structure for the equipment and batteries that is large enough to be considered a building (the structure I am powering in a bunkie and I didn't want to lose the space. One option is to make that structure smaller I suppose.

 

[sollap]

I'm not familiar with this RSD box, TIGO's, SE, or Victron gear. But, I have some thoughts on what I see in your picture above.

Looking at the circuit inside that box, I don't think you did any damage by reversing the PV in/out. The PV wires don't connect to anything in the box other than the switch, and otherwise just pass through sensors. This box needs external power. There is a small connection block to the right of your PV wiring that has the inputs for your 48v battery. The manual says to use a 2A fuse. With suitable power, I think you'll see some lights.
When it's on, I believe the circuit board monitors the arc fault sensor, and the external RSD initiator. If either of those trips, the circuit board tells the TIGO transmitter to send out the signal to shut down your panels. It also sends a signal via Xanbus to shutdown the SE equipment. I believe it treats RSD and Arc fault the same way. Different initiators, but same results.
If you have the TIGO receivers installed on your panels, you would be part way there. You'd just need to figure out how to get the Victron equipment to shutdown. Is there an RSD connection on your Victron gear?
I don't know how the TIGO transmitter works, but the wiring in your box suggest it only has a + and - power supply. The other wires go to a coil which I assume is the antenna which injects the signal into your PV lines to communicate with the receivers. What that means, is that you could connect a small low coil current relay to the power supply of the TIGO transmitter. When it gets power, the box is reacting to a fault. Your small relay can drive other relays (with battery power) or maybe could directly open/close the RSD contacts on your Victron gear, if it has those.

 

[lws2036]

I'm not familiar with this RSD box, TIGO's, SE, or Victron gear. But, I have some thoughts on what I see in your picture above.

Looking at the circuit inside that box, I don't think you did any damage by reversing the PV in/out. The PV wires don't connect to anything in the box other than the switch, and otherwise just pass through sensors. This box needs external power. There is a small connection block to the right of your PV wiring that has the inputs for your 48v battery. The manual says to use a 2A fuse. With suitable power, I think you'll see some lights.
When it's on, I believe the circuit board monitors the arc fault sensor, and the external RSD initiator. If either of those trips, the circuit board tells the TIGO transmitter to send out the signal to shut down your panels. It also sends a signal via Xanbus to shutdown the SE equipment. I believe it treats RSD and Arc fault the same way. Different initiators, but same results.
If you have the TIGO receivers installed on your panels, you would be part way there. You'd just need to figure out how to get the Victron equipment to shutdown. Is there an RSD connection on your Victron gear?
I don't know how the TIGO transmitter works, but the wiring in your box suggest it only has a + and - power supply. The other wires go to a coil which I assume is the antenna which injects the signal into your PV lines to communicate with the receivers. What that means, is that you could connect a small low coil current relay to the power supply of the TIGO transmitter. When it gets power, the box is reacting to a fault. Your small relay can drive other relays (with battery power) or maybe could directly open/close the RSD contacts on your Victron gear, if it has those.

Wow! This sounds promising. Thanks!

 

[CoolWill]

I suppose the panels are mounted on the house? If they were on a separate rack, you wouldn't be required to have arc fault, ground fault, or rapid shutdown.

 

[lws2036]

I suppose the panels are mounted on the house? If they were on a separate rack, you wouldn't be required to have arc fault, ground fault, or rapid shutdown.

They are on a separate rack, my issues is the structure I made to house the batteries and solar equipment is large enough to be considered a building. According to my inspector, this is enough to warrant needing arc fault.

 

[CoolWill]

They are on a separate rack, my issues is the structure I made to house the batteries and solar equipment is large enough to be considered a building. According to my inspector, this is enough to warrant needing arc fault.

But does the structure housing the equipment have the panels, or are they still on a separate rack? Because just housing the equipment without panels doesn't require arc fault. The arc fault requirement kicks in when the building has panels on it.

 

[lws2036]

But does the structure housing the equipment have the panels, or are they still on a separate rack? Because just housing the equipment without panels doesn't require arc fault. The arc fault requirement kicks in when the building has panels on it.

Ah interesting. So I might be able to push back on this then.