System overload?

[Fitz]

mtnclmb,

Congratulations for getting the issue solved! On my van the fuse you are talking about is mounted on the side of the inverter. I recall having a conversation with Paul in Austin a year or so ago and he told me he wasn’t aware of one ever blowing, you might have to follow up with him and find out if you are the first!

Can you please do the rest of us a favor and post the specifics of the fuse? Some of us might want to order one to have on hand.

I seem to recall on my van that the wire feeding the 12 volt panel is on the upstream side of this fuse, that the big fuse is located between the house battery and the Magnum inverter/charger. I will get out the meter and do some checking.

Again, glad you are back on the road and fully functional!

Edit: Scalf77 and I posted at the same time. I am in complete agreement with his comments above and that the tap to the 12 volt panel was most likely connected on the wrong side of the fuse. On my van the wire runs from the upstream side of the fuse to the relay and then to the panel, thus my reasoning when I suggested the relay might be bad.

[velo47]

Originally Posted by mtnclmb

We found a great shop with knowledgeable technicians.

Who'd you go to in ABQ? We will need a good shop if we ever get our SMB.

[86Scotty]

Great info here. Thanks for posting your solution. I didn't even know what a class T fuse was or looked like. Had to Google it. As always, thanks for the lesson Scalf!

[mtnclmb]

The name of the shop is Action RV. They are located just south of Albuquerque in Bosque Farms, NM.

[Scalf77]

Blue Sea Class T Fuse



https://www.amazon.com/Blue-Sea-Syst...ABJRPHT1E&th=1

-greg

[arctictraveller]

Class T fuses are the type specified by most inverter manufacturers, and required by most codes such as the ABYC (American boat and yacht council). ABYC's requirements are the gold standard for 12v electrical systems. Class T fuses are extremely fast acting, current limiting, fuses that are rated to interrupt a minimum of 200,000 amps. Circuit breakers on the other hand, take much longer to trip, and under certain conditions (very high short circuit currents) can actually fail to open the circuit due to arcing within the interior of the breaker it self. That's to say that if there is a serious fault, the points inside the breaker may open, but the current supplied by the battery will be high enough to arc across the contacts and continue to flow, (like an arc welder) probably resulting in a melt down of the wire or a fire. A class T will not allow this to happen until the current supplied exceeds 200,000amps. I would simply replace the fuse, rather than installing a circuit breaker. As for moving the 12v feed to the other side of the fuse, that's fine as long as those wires are fused to match the wire's ampacity (current carrying capacity)

EDIT, It looks like the interrupt rating may be only 20,000amps, but I find it both ways when searching Google. Never the less, the benifits of a class T remain the same.

[mtnclmb]

Great explanation of what I was wondering about. So I guess we'll stay with the T fuse. I tried to post a picture of it but I can't on the mobile version of this forum. It's exactly like the one that Scalf77 posted. Thanks.

[Glider]

Here'so a pic of a class T in a Ford SMB that I saw sitting in the lot in Austin today. It is located between the battery and the inverter, as it should be. Not a great photo, as access was not easy, but you get the idea.

Mtmclmb, before you make changes to your system, I strongly recommend that you call the tech support people at Magnum, assuming that you have a Magnum inverter. The tech support people over there are extremely knowledgeable and helpful, and they know their product better than anyone. They will be able to point you in the right direction.

I had a quick look at the installation manual for the Magnum 2000, which is what I'm guessing you have. Magnum does approve either a T-class fuse or a breaker for that installation. They note that the battery and the inverter should be as close to each other as possible. That said, when the inverter is installed in one of their enclosure boxes, the T class fuse is located immediately adjacent to the inverter, not adjacent to the battery, so having the fuse close to the inverter does not appear to be an issue as far as Magnum is concerned.

Bottom line: take a few photos of your installation, and get on the phone with tech support. They will guide you appropriately. if you don't have one already, I also recommend that you download the installation manual for your inverter. It's a good resource.

I'm delighted you solved your issue, and hope you have a great trip.

[arctictraveller]

Below is some useful information about inverter instillations, from a top rated technical editor for several boating publications.

Inverter Installations; What You Need to Know | Steve D'Antonio Marine Consulting

In addition to explaining the use of class T fuses, he points out that fuses need to be installed as close to the batterys as possible. The reason for this is to protect the wire. Placing a fuse at the load end of the wire protects the device it feeds, but not the wire it self. If that wire were to short out between the battery and the fuse (say where it passes through the floor) the fuse would never open, the wire would turn to molten copper and most likely cause a fire.

It looks like Glider found reference to Magnum's approval of circuit breakers in place of a Class T, and following the manufacturers recomendations is always the best plan. Never the less, best electrical practices require the use of a class T, installed as close to the battey as possible.

[Glider]

I agree with arctictraveler on all points. In this case, the manufacturer has approved the use of a breaker, but that doesn't change arctictraveler's point that use of a class T fuse is a better solution.