Fried VFX 3524

zozomike · November 2019

About a year ago, I chanced on an Outback factory rebuilt VFX 3524 for a good price. My existing VFX 3524 had a board fault that would not recognize the Mate, but it worked fine otherwise. So planning to replace the board, then wire up both in classic stacking, I installed the rebuilt, and set the existing aside. So yesterday the rebuilt was acting weird, and I pulled the cover to find the negative post burned badly. Burned so badly in fact that when I tried to remove the 4/0 cable, the post came out of the inverter and its connections internally seem melted. Not good, and the cable to post connection was tight.

So out came old trusty for a reinstall, ( still have not gotten that board replaced.) Working fine, I have ordered a new cable but temporarily cleaned and am using the existing cable, and it is cool as a cucumber. So my question is what could cause such a fault? The 24-volt battery is not grounded BTW. Has anyone experienced such? Not being an inverter tech, my best guess is I will try to salvage the board out of the fried VFX3524, put it in old trusty and scrap the one that burned. Unless someone out there thinks the whole thing can be salvaged?

mike95490 · November 2019

Often there is a slightly loose connection, which heats, which increases resistance, which causes higher heat and eventually, the heat, oxidation and time cook it till it fails .

All my connections now use copper or silver loaded grease and torque gets checked next day, next week, and next year.

Estragon · November 2019

Just curious, what type/size breaker/fuse on the inverter DC circuit? It could fail without opening, but might be worth checking while you're at it?

Dave Angelini · November 2019

Latent damage from lightning can occur most anytime. That is why we use surge protection. Connections should always be torqued.

zozomike · November 2019

Mike and Dave, Hmmm, ok I will be buying a torque wrench and some loaded grease to use when the new cables come in. It sure seemed like the problem came from inside out, based on the condition of the post. And I am the opposite of frail when tightening connections. But both of you know more than me. I do have lightning arrestors LA 302DC on the charge controllers. But ????. Estragon I have this on the battery positive, Is that appropriate?

JLLN-250 - Littelfuse Power Fuse

• Authentic Littelfuse Product
• Class T
• Fast Acting Characteristics
• 300 Vac/125 Vdc
• 250 Ampere
• Interrupting Rating 200000 Ampere (Symmetrical) 20000 Ampere (Dc)

Estragon · November 2019

250a might be a bit on the large side of ok (IMHO), but still ok (IMHO).

Sometimes "the opposite of frail" can be a problem too. You can overtorque an initial connection, which can do much the same thing, but in the guts of the bolt connection?

zozomike · November 2019

Estragon, It is beginning to appear that I may have cooked my own goose. All of you bring up plausible points. And I reckon Dave just brought up lightning to salve my ego.

BB. · November 2019

Other things could have happened too... Over torque, flexing of the heavy cable, etc. could have cracked/weakened the connection to the circuit board too.

As could an assembly error (poor process at the factory for bonding to circuit board).

-Bill

Dave Angelini · November 2019

That was my point about torque. It often is too loose and you probably would see evidence of that. Over torque damages the internal PCB or however the bolt is connected to the power bridge circuitry. Since the breaker did not blow and the unit still worked (sort of) it would be logical that the factory over tightened it or the user did. I doubt Outback would do this but it is possible.

I always bring up lightning because so many are unaware. The same as torque, if you do all the right things it make it easy to point fingers.
In this case it is impossible to say what caused this.

zozomike · November 2019

So I pulled the Negative connection lug yesterday. ( Not sure what to call that as try as I might I find no parts lists) And it is just through-bolted to an aluminum plate which then is connected to the board. It seems it would be impossible to " over-torque such) The blackish stuff on the plate is molten plastic. The cause is as Dave says, indeterminate. All I need to do is find a source for the replacement negative terminal. And despite Google's skill, And unanswered calls to Outback sales, I do not know where to find a replacement. It is just a bolt with a 10mm nut on the back of the plate and plastic surround and nuts. Anyone out there know where to source replacement parts?

Estragon · November 2019

IIRC, there are a total of three boards in the inverter.

One of the two VFXs I bought in 2014 was defective, and as I recall I ended up replacing all three boards. There was no visible damage to anything, the unit just wouldn't power up or start the power-on self test. The problem unit had a much lower serial# than the other one, and Outback was good about getting replacement boards to me. The problem happened not long after installation, and OB covered the boards under warranty.

I assume it was just a bad run of boards, as both units have run fine since. If there was a new problem now, I wouldn't expect it to be covered under warranty, but would think it likely that OB could supply replacement boards(s) at a reasonable cost.

zozomike · November 2019

Thanks Estragon, This morning I sent an email to OB Support center. They do have a service center in Pheonix ( this inverter was rebuilt there) I will look for a phone number. If I find that I will post for others benefit.

Estragon · November 2019

FWIW, I did all comms with OB by email, with responses within a day or two.

zozomike · November 2019

So this is a Shout out about Inverter Service Center In Tn. Outback never replied to emails or phone messages. So I called ISC. While they did not stock the terminal post, they pulled one off of a scrap inverter, it was in my mailbox in a few days, and they charged only postage. Wow.

Fried VFX 3524

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JLLN-250 - Littelfuse Power Fuse

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