L1 to L2 voltage is ~1v coming into SolarEdge inverter

kurtjx

Hello! I am a homeowner that has had this solar install since 2018.  My installer is out of business since 2021 and my inverter has gone offline - entirely unresponsive - no lights, no error codes, nothing.  I've been trying for _months_ to get someone out to help me and no one is available or interested!

So I started doing it my damn self.  I assumed the SolarEdge inverter died and so I went around w/ SolarEdge tech support. I measured the input AC voltages and it turns out they are wrong!?!

I understand that L1 to L2 should actually be ~240v (I'm in USA near Boston MA).  RN that voltage is ~1v but the L1-N and L2-N are 124v and 125v respectively.  Voltages to ground are about the same. So it seems like these L1 and L2 should be 180 degress out-of-phase but they're not.  Note everything worked up until a few months ago.  It all worked for years.

Is there some "phase inverter" or similar part that maybe failed upstream?  I've been googling around a bit and so far I don't understand how L1 and L2 are supposed to be made out-of-phase.

BB.

Welcome to the forum Kurtjx,

Here is a good article on 120/240 VAC split phase power (what we typically have in homes in North America):

https://en.wikipedia.org/wiki/Split-phase_electric_power

Note: The only way to reliably diagnose this issue is to remove the AC cover from your GT Inverter and to remove the cover from your Main AC breaker panel. This exposes dangerous electrical voltage and current. A slip of a hand, ring finger, screwdriver, cover, etc. can electrocute you or start a fire. Only do this if you are trained/experienced with working on home panel wiring.

The first question would be has there been any rewiring at your home or has the utility power been changed (assuming your voltage readings are correct)?

Do you have any 240 VAC appliances in your home such as AC, Heating, electric stove, electric drier, water heater? Are they working correctly? These larger appliances tend to use 240 VAC power...

Do you feel comfortable/safe removing the cover from your main electrical panel so you can access the wiring/breakers/etc.?

If not, you probably need to have an electrician come by and check your panel.

More or less, what I would check:

1. Pull main panel cover
2. Check AC power in L1/L2/N... As you understand (correctly). L1 to L2 should read 240 VAC, and L1 to Neutral and L2 to Neutral should read 120 VAC.
3. You should have a 2 pole circuit breaker that has L1 and L2 going to your AC inverter (should also have a green wire ground and mayu or may not have a White Neutral too).
4. Check the L1 and L2 voltages at the breaker. Should read 240 VAC
5. Check the L1 to ground--Should read 120 VAC (neutral and green wire safety ground/electrical panel metal box are all tied together inside the main panel/bus bars).
6. Check the L2 to ground--Should read 120 VAC 

There are several things that could have happened....

1. L1 and L2 are not wired to your home correctly... You could have (for example) two L1 connections from the pole transformer. All 120 VAC power/appliances work correctly. No 240 VAC appliances work (probably not what is wrong).
2. Look for signs of water/rust/corrosion inside the AC panel (and your AC box for the GT inverter)... Sometimes water/rain follows wiring into an electrical box and corrodes an electrical connection. Look for corrosion and/or browning/blackened connections at binding screws, etc.
3. Assuming your L1/L2/N connections are correct to your home, and any other 240 VAC appliances are working correctly, the assumption is you have a failed electrical connection (loose screw, corrosion) between the 240 VAC 2 pole breaker and your GT inverter AC power box (most likely). Or possibly a failed AC breaker (L1 from bus bar to breaker terminal is "good" and L2 bus bar to breaker terminal has failed open).

What could have happened... L2 (just an example) electrical connection has failed from breaker panel to AC box of GT inverter... And L1 is "powering" L1 terminal of GT inverter, and you have no L2 connection... And the L2 terminal voltage is just leakage current from the L1 terminal... That way your meter reads the 120 L1 voltage, and the L1 to L2 leakage current via the inverter AC wiring as 120 VAC too... But when you measure L2 to Neutral (or to safety ground), you see 120 VAC, but L1 to L2 shows zero volts (because L2 is "powered" by L1 thru inverter).

The 120/240 VAC wiring is very simple:


The transformer outside your home provides the 120/240 "phases".

Loose/corroded electrical connections can cause "strange" voltage readings. Small animals can chew through wiring, etc...

A relatively common sign of a bad electrical connection somewhere can be seen in a home when a large electrical load is turned on (washing machine, plug in electric heater, etc.) and some lights "go dim" in the home, and other lights "go bright". That is a typical example of a corroded/failing Neutral connection.

I have had that happen in two separate homes I have owned. Water from the "weather head" (where AC power comes into the home)--Just a few drops over many years or decades) corroded a neutral terminal (one home behind the AC meter socket, another inside the main breaker panel)... Water following wiring into an electrical connection is a common issue). Dressing the wiring entering the weather head so that all wiring went "up" into the weather head stopped water from going into the weather head and further problems.

Your main breaker panel may look something like this inside (this is a sub panel, but similar to typical main panel wiring):


If you hare not "comfortable" working in areas like this--Time to call an electrician.

-Bill "be very careful" B.

littleharbor2

Solar Edge Optimizers are supposed to drop to one volt when there are issues. I'd look to a problem from the PV array down to the inverter.

kurtjx

update: there are 2 fuses in my AC shut-off box.  One of them appears to be dead - continuity test fails on multimeter. My local hardware store didn't have a matching fuse, I will go to electric supply store today.  It's an FNLR 20a - I think not really a special fuse, but I assume the $4 NON fuse wasn't a good idea.

BB.

Sounds like you found the fault. Fuses do fail over time.

What is the size of solar array that you have? Fuses/breakers for solar should be operated at ~80% of current rating:

• 0.80 * 20 amps = 16 amp suggested 240 VAC solar current maximum

In North America, fuses/breakers/wiring at really designed to operate at 80% of rated current for "continuous current" applications (such as solar arrays that may run at rated current for 3-6 hours per day (depending on weather, size of array, etc.).

I have had those types of fuses fail.. But usually in older buildings (>50 years old). The fuse failing after 6 years--Sounds like the fuse/wiring could be a bit underated for your array...

But just keeping a couple of spare fuses around is a cheap way to address the issue (vs rewiring the solar power branch circuit).

Could just be an early life fuse failure too... That does happen.

-Bill

kurtjx

UPDATE: I got a new fuse and we're up and running again! Freaking stoked that it's fixed! Embarrassed it took me so long to just figure out it was a fuse to change!