Interesting day today, lots of smoke in the cockpit!

[Bevan]

Originally Posted by Walt

The reason they (LSE) wants it that way is to prevent noise (hence the shielded power wires), with little/no concern for aircraft safety or standard practices.
And I agree, a fusible link would also be an acceptable method of protecting the wiring.

Walt, I think the reason LSE does this is to allow the engine to continue to run when the master is shut off (in case of some other electrical problem). The LSE needs power via another path to do this. I agree a fuseable link could be considered as is all the wire gauges on that (and every) circuit.

Bevan

[David Paule]

Walt, what kind of wire was involved here?

Thanks,
Dave

[Aluminum]

Originally Posted by Champ

This thread got me thinking.

My battery and master solenoid are rear mounted with a #2 wire to the engine side of the firewall where it connects to the starter solenoid and ANL fused #8 line back into the cockpit buss.

Is the master solenoid at the battery enough protection on the #2 line or should it also have an ANL fuse? It would have to be a pretty big fuse to handle starter current.

The standard master relay circuit design still baffles me. As in, who in their right mind could have come up with such a failure-prone design in the 1950s, and why does it endure. I did different on my first build, and will repeat on my second as I see no downside to what I did after five years of use.

Install a big mechanical master switch as the only thing the positive battery terminal connects to. Pass the starter current through the switch. Much safer and easier to debug. Esthetics can be improved I'm sure.

[Walt]

Originally Posted by David Paule

Walt, what kind of wire was involved here?

Thanks,
Dave

Well I haven't removed all the remains yet but it looked to be standard Tefzel single cond. shielded wire, the good news is it did 'self extinguish'.

[rv7charlie]

Dan V,
Is your battery mounted directly behind that switch? The reason for a master contactor is the ability to disconnect the fat wire *at the battery*. So if you can put that style switch within a few inches of the battery, it's a great solution. Many others have done the same.

[vic syracuse]

Yes, I know the LSE manual has it connected directly to the battery, but I have ALWAYS put an in-line fuse there right at the battery. One of the ones that are made to hold an in-line blade auto fuse works well. It usually has a cover on it and can be secured with zip ties right to the main battery cable so it won't come loose.

Vic

[DanH]

Originally Posted by vic syracuse

Yes, I know the LSE manual has it connected directly to the battery, but I have ALWAYS put an in-line fuse there right at the battery. One of the ones that are made to hold an in-line blade auto fuse works well. It usually has a cover on it and can be secured with zip ties right to the main battery cable so it won't come loose.

Vic

I suspect a well built fusible link is more reliable than the typical inline fuse holder, which tends to be manufactured to a very low price point. The terminal crimps are molded in; you can't see them. Won't say they're bad, just that your own fusible link work is probably better.

Traced an intermittent power supply to one yesterday (strobes and rotating beacon on a service truck).

[DanH]

Good warning Walt. Somehow folks got thinking tefzel wire is fireproof, or low smoke, and it's not.

One demonstration worth 1000 words...everybody torch some wire scraps.

[Walt]

Originally Posted by DanH

Good warning Walt. Somehow folks got thinking tefzel wire is fireproof, or low smoke, and it's not.

One demonstration worth 1000 words...everybody torch some wire scraps.

This was certainly a "lively" demonstration of this.

Something that actually aggravated this situation was the shielded wire, after evaluating the damage it looks like the center conductor quickly burned thru to the shield, so now both the shield and the center conductor was effectively a 'hot' wire. That explains why the LSE connector at the box also got cooked along with all the LSE wiring from begining to end even though the LSE switch was off (the now 'hot' shield found a ground path thru the LSE box and toasted it as well).

Trust me when I say you don't want to experience this in flight!

[Mike S]

Originally Posted by Walt

Trust me when I say you don't want to experience this in flight!

That was my initial thought when I read your first post