Getting AFCI faults (Growatt)

[lapsmith]

I have a Growatt MIN 11400, although this question may apply to any inverter with ACFI. Now that all my panels are installed in their permanent location, I rearranged the string wiring layout. I have 4 strings. The next day I got an AFCI fault, then again the following day.

What would be a likely cause? I'm thinking loose MC4 connection at one of the panels since that's the only thing that's changed. There was slight rain during the changeover, so there may be some moisture inside the connectors, but it has been sunny and the outside of the connectors are dry and they are not close to each other or ground.

What else might cause an AFCI fault? What would be the best way to trouble shoot?

 

[MajicDiver]

I would just disable AFCI. I had a well pump with brushless dc motor, 3 conductors of a 5 conductor cable, other two conductors were for a PV string. Every time the pump started or ramped speed the inverter would trip. I expect that if you have wires for different PV strings next to each other it would do the same thing.

So, unless you want to call Growatt and learn to tune AFCI settings to be less sensitive, probably best to just disable it - there are other posts with people who had same issue.

 

[Oldphile]

I turned off AFCI. The optimizers cause sporadic current waveforms when shadows occur. When I get a cloudless day, I'll turn it on to check for wire faults.

 

[lapsmith]

I would just disable AFCI. I had a well pump with brushless dc motor, 3 conductors of a 5 conductor cable, other two conductors were for a PV string. Every time the pump started or ramped speed the inverter would trip. I expect that if you have wires for different PV strings next to each other it would do the same thing.

So, unless you want to call Growatt and learn to tune AFCI settings to be less sensitive, probably best to just disable it - there are other posts with people who had same issue.

I actually did call Growatt and they lowered the sensitivity to the the lowest and it still happened. (Previously, they told me how to access service level functions, but I didn't try it myself as I didn't know it was adjustable).

Since it never occurred for the past 3 months until I rearranged the string layout the other day, I kept thinking it had to do with a bad connection. So I went through all of my field-made MC4 connections and I found two where the pin wasn't fully inserted into the housing. I'm hoping that solved the problem, but it hasn't been sunny enough since to know for sure.

Funny, I almost ran the PV conductors right where the well pump is located since it is half way to the barn, but I didn't want to risk digging near those wires and pipes. Brushless well pump? How do you like it, other than the AFCI faults? Does it have soft start?

 

[lapsmith]

I turned off AFCI. The optimizers cause sporadic current waveforms when shadows occur. When I get a cloudless day, I'll turn it on to check for wire faults.

That's too bad about the optimizers. Have you tried adjusting the ramp rate? Maybe that will minimize sudden current changes. I guess I could turn mine off too since the panels are on a metal roof and less chance of fire (although the supports are wood). If it continues, that's what I'll have to do.

 

[Oldphile]

That's too bad about the optimizers. Have you tried adjusting the ramp rate? Maybe that will minimize sudden current changes. I guess I could turn mine off too since the panels are on a metal roof and less chance of fire (although the supports are wood). If it continues, that's what I'll have to do.

Ramp rate? Can you explain? I'm not aware of such a setting.

 

[lapsmith]

My understanding is that ramp rate adjusts how fast the inverter responds to changing loads, such as when a motor starts or stops. I'm only familiar with the MIN series of Growatt inverters; others may not have that setting. In the Growatt app, it is under the Grid Code menu.

 

[MajicDiver]

Brushless well pump? How do you like it, other than the AFCI faults? Does it have soft start?

Love it, bought it in 2021 and put in well for irrigation system used couple times a week during growing season - also piped to house for backup, we live a long way from the county water line and have issues with leaks repeatedly. It’s an RPS800 and is what got me started with solar. Originally bought it and eight 100 watt panels- it has a controller that takes 48-96 VDC input and ramps up/down slowly just like a mini split does. When saw how easy the solar part was I laid cable in trench when put water line to house and started installing soar and inverters and the solar disease took hold.
I highly recommend the RPS brushless DC pumps - I’m using their controller but I’m sure you can get those many places.

 

[lapsmith]

Love it, bought it in 2021 and put in well for irrigation system used couple times a week during growing season - also piped to house for backup, we live a long way from the county water line and have issues with leaks repeatedly. It’s an RPS800 and is what got me started with solar. Originally bought it and eight 100 watt panels- it has a controller that takes 48-96 VDC input and ramps up/down slowly just like a mini split does. When saw how easy the solar part was I laid cable in trench when put water line to house and started installing soar and inverters and the solar disease took hold.
I highly recommend the RPS brushless DC pumps - I’m using their controller but I’m sure you can get those many places.

I looked at the RPS website and I see that they are for solar only. For some reason, I thought they ran on AC and used an inverter, like a VFD to drive the motor. It wouldn't work for me, but it sounds perfect for your application.

 

[MajicDiver]

I looked at the RPS website and I see that they are for solar only. For some reason, I thought they ran on AC and used an inverter, like a VFD to drive the motor. It wouldn't work for me, but it sounds perfect for your application.

Well, brushless DC actually is AC, actually is a VFD in a sense, just not what most people think of when you say VFD.

With water level 85’, and another 20’ vertical to house it delivers >= about 10 gpm to pressure tank in basement with switch set to on at 40 off at 60. Not many homes need more than that.

 

[lapsmith]

Copy that. So is the controller powered by DC or AC?

My water level is about 160'. Not sure what my GPM is, but with several acres of irrigation, probably similar to yours. Except no basements in Houston:-(

 

[MajicDiver]

Copy that. So is the controller powered by DC or AC?

My water level is about 160'. Not sure what my GPM is, but with several acres of irrigation, probably similar to yours. Except no basements in Houston:-(

I’m powering the controller with a 72 VDC 1,000 watt power supply (120ac) so can have those 8 solar panels connected to inverter full time.
The RPS800 would have very (if any) low gpm if the static water level is 160’ - don’t have the pump curve handy. For our well, once thru the rock it hit water at 265’ but it rose to a static level of 85’. Some wells are artesian in this area.

 

[lapsmith]

I've never looked for one, but I imagine a 72V 1kw power supply is either hard to find or expensive, or both.

I saw they have other models that may work with 160 ft lift, but they won't work for me for other reasons. Thanks for the info.