Charger Ground Fault

metalguy21

I needed to shut down my system to clean the battery terminals.  On powering up it has a Ground Fault in the panels according to the panel readout. This first requires replacing a fuse in the main panel that of course is an oddball and I don't have.  But even once I get it I'm not sure where things went wrong.

I've done this numerous times with out issue.  My first guess is perhaps things need to be shut down and powered up in a certain order  I typically shut the breaker to the house off, then the breakers at the combiner at the array, then the PV breakers in the panel, then the charge controllers (I have two), and finally the main breaker from the inverter to the batteries. I power it up in the reverse order.  

I've ordered the fuse and it will be here late tomorrow but till then I thought I'd ask if anyone thinks there is a specific order this stuff needs to be turned off/on in.   Again I've done this a half dozen times without a problem.  Hmmmmmm.  

BB.

What charger do you have (I guess where the GF fuse is located)?

Did you pop out the fuse and check with an Ohm Meter to see if it is open (blown) or not?

Normally, as I have seen in other systems, the fuse is connected between the negative battery/solar panel bus and safety ground (chassis ground of charge controller, ground rod, etc.).

The fuse is typically around 1 amp, and will blow if there is a short between anything on the DC bus that is "Hot" (positive battery bus, positive panel connections, anywhere in the DC + wiring (such as shorting Battery bus to "chassis/safety ground", DC + input on AC inverter, etc.).

Note, is is possible, especially when there is a good amount of DC current flow in the system, to blow the 1 amp fuse with NEgative to 

You can clip a 45-100 Watt 120 VAC filament lamp between Chassis/Safety ground and DC Negative battery bus (assuming negative grounding). And use a volt meter to measure voltage between DC Negative and Safety Ground. Voltage drop in the DC wiring could cause enough voltage differential to blow the 1 amp fuse.

Using the filament lamp will bring negative bus and safety ground to zero voltage (see with DMM). If there is a "real" short, then you will see non-zero voltage between negative bus and ground bus--At least without blown another fuse (or more).

With lamp clipped between negative bus and ground bus, if you see (typically) Vbatt or Vpanel (during day) voltage, then there is more than likely a hard short between some positive bus and safety ground bus.

If you see very near zero volts (with sun up), then you should be able to install the "detection fuse" and then remove the lamp.

There should be no special order in bringing the system up (other than don't short + to ground with a wrench/screwdriver, etc.).

PSW/TSW inverters have isolated AC output--So any AC issues (shorts, etc.) should not be an issue.

MSW inverter typically have non-isolated outputs--And it is possible an AC output short from one of the 120/240 outputs to safety ground could blow the GF Fuse.

That is all I can think of at the moment.

-Bill

Dave Angelini

They are Schneider mppts in the Sig.  You should power down mppt solar first and then mppt battery. Reverse this in power up. If there is sun on the array's, you should first select disable charger. This will take any loads off the solar first. You can wrap the old fuse in foil for testing to see if this is all that is wrong. Power down solar first then inverter. reverse on power up. Always remove any large ac loads during any of this.

BB.

Dave is correct--I missed the Signature, and, in general for battery powered systems, connect/turn on the battery bank first, then connect/turn on the solar array. And power down the array first, then the battery bank. This is so the charge controllers can sense the battery bank voltage and boot first, before being exposed to solar power.

-Bill

metalguy21

Okay, thanks this is good information. The fuses are in a little removable cover panel at the bottom of the two charge controllers. I'm going to pick up a couple more here in a while. Someone mentioned shorting positive out to ground. Not sure if it matters but while cleaning the positive battery terminal with a brush I arced against the grounded container of it and got a nice big Arc. I didn't think much of it but could this maybe be with blue the fuses.

metalguy21

And on the power up power down order, I did the array first and then turn the controllers on then turn the inverter batteries on. Clearly not the order you guys are talking about. I get your logic I'll do it the way you suggest once I swap out these fuses

BB.

Sounds like the wire brush/positive terminal/grounded metal container--More than likely that is what popped the fuse(s).

-Bill

metalguy21

Agreed.  I've always been careful to not do that and never have till now.  And sure enough I have an issue.  1amp fuse so it doesn't take much. 

metalguy21

Ok, just to follow up on this thread.  I pulled the fuses in the two controllers and they were indeed both blown.  Replaced them and powered up and things are humming again.  Clearly the arc on the batteries when cleaning them caused this. 

I did pay attention to your guys advice on the startup order to whit;  Staring with all breakers off I first booted up the charged controllers, then turned on the inverter and its panel, then the five small PV breakers at the combiner, then energized the PV to the controllers.  Lots of blinking lights and clicks but after a couple minutes all was back to normal.  Thanks for your help and suggestions.