Fuses, Yes, Fuses

[SV_Classic]

Hi all,

It's been an interesting and unexpected side effect of thrashing with all y'all, I've grown to have more appreciation for the light weight, reliable, and inexpensive fuse!

But with so many automotive grade or worse products out there, what is a good quality inline fuse holder for an aircraft?

Thank you.

 

[GKC Aviation]

I use the FHP-1 fuse holders.
They come with the different spring inserts to accommodate three different AGC fuse types.
Great quality compared to some others I've seen. Won't just come apart on you.
You can get them through Aircraft Spruce, etc.

 

[Marc_J._Zeitlin]

But with so many automotive grade or worse products out there, what is a good quality inline fuse holder for an aircraft?

You asked about in-line fuse holders, but those are used only in situations where a fuse bus cannot be used. I'm partial to:

Fuse Holder 6-20 Slot - B&C Specialty Products

These fuse blocks offer a low-cost, space-saving solution to power distribution circuit protection, without the expense, fabrication-time, and higher parts-count of a panel comprised of miniature circuit breakers attached to a rigid bus bar. Designed for use with ATC-style fuses, these fuse...

bandc.com

but there are many high quality fuse buses from Littlefuse and other MFGs, with varying features (included ground bus, indicator lights and the like).

For in-line fuses, when I need to use one, I use something along the lines of:

https://www.amazon.com/10-Gauge-Fuse-Holder-Inline/dp/B08BWRSPY1

which is overkill with 10GA wire, but similar weather protected holders are available with smaller gauge wire as needed (usually with 14 GA or 12 GA wire at the auto parts store). I splice them into the wiring with AMP high quality butt splice terminals:

Butt Splice Terminal - B&C Specialty Products

Sold individually or in a pack of 10. Constructed of high conductivity copper per ASTM B-152 and tin-plated per ASTM B-545, with nylon insulation per UL 94V-2. Genuine AMP

bandc.com

Hope this helps.

 

[SV_Classic]

Thanks for the replies, I'll give those links a look.

 

[SkippyDiesel]

But with so many automotive grade or worse products out there, what is a good quality inline fuse holder for an aircraft?

Thank you.

What's so wrong with automotive grade???

I have four 12v mini blade fuses fitted in my aircraft.
They have been used in non aircraft critical systems eg 12V power supply plug.
They are secure, completely enclosed in a moisture/dust resistant insulating cap/housing, won't dislodge through an aircraft movement/vibration requiring a significant pull to be removed.
Are relativly cheap and can be had through most electrical/automotive retail outlets - what's not to like?

 

[SV_Classic]

I assumed there was an aircraft grade product, I guess I was wrong! lol

 

[Rhino]

What's so wrong with automotive grade???

I have four 12v mini blade fuses fitted in my aircraft.
They have been used in non aircraft critical systems eg 12V power supply plug.
They are secure, completely enclosed in a moisture/dust resistant insulating cap/housing, won't dislodge through an aircraft movement/vibration requiring a significant pull to be removed.
Are relativly cheap and can be had through most electrical/automotive retail outlets - what's not to like?

Every installation is different, and you are free to do as you please. And, as you demonstrate, how they're used makes a difference too. But, generally speaking, automotive inline fuse holders are comparatively large and heavy because they typically use heavier gauge wire than is seen in aircraft installations, and they often have water/dust resisting features you don't need in an aircraft. You shouldn't install a fuse holder in the engine compartment, so those features aren't necessary. A fuse block can use automotive style fuses, blade or tube, while using less space and weight. So, there's nothing wrong with inline fuse holders, but they usually aren't the best choice for aircraft installs.

I also highly, emphatically and strongly recommend you purchase or download the Aeroelectric Connection by Bob Nuckolls.

http://aeroelectric.com/Connection/R12%20Searchable%20Merged%20Chapters.pdf

 

[SkippyDiesel]

" ........there's nothing wrong with inline fuse holders, but they usually aren't the best choice for aircraft installs."

I just love it when aviation buffs (no offence intended) make unsubstantiated negative comments (however diplomatically put) about alternative materials & parts.
The reality is, much in the automotive world, in particular but also elsewhere, is perfectly suited to home built small aircraft , without any loss of efficiency or safety, at a much lower price.
HOWEVER I would council anyone contemplating using non aviation sourced components/materials, to have done their due diligence, before committing to use in an aircraft. This means knowing what standard is required - often the engine / aircraft manufacture will post standards or the name of a product that you can research the standard for - in my opinion this is the minimum required that you should equal or better.

Back to fuese - As stated I have four of the mini fuse holders (shown), two on the firewall (in the engine compartment) and two, in an accessible position, under the instrument panel. The fact that they came in a dust & moisture resistant "package" is actually a bonus, in that the fuses within, already very firm, are doubly secure - no fear of dropping out at all and electrolysis ( the ban of 12 volt connections) is extremely unlikly.

Note: I would council against automotive fuses for critical aircraft systems - use the aviation grade resettable types, commonly known as a circuit breaker.

 

[Rhino]

I gave the reasons why, and I gave a good reference, so there's nothing unsubstantiated about them. The parts I mentioned using are also from the automotive world. They're just better suited for use in aircraft, because they're smaller, lighter, and more accessible. As I said, some applications, like the non-critical ones you cited, would be more suited to inline fuses.

You should not be so quick to malign aviation buffs when those aviation buffs were the ones whose advice was asked for. I've worked avionics, electronics and computers for over 40 years, and earned my living doing it for most of those years. I even got a college degree in it. You might want to consider the possibility that I might know what I'm talking about.

By resettable fuse, I assume you meant circuit breakers. Resettable fuses (polyfuses or PPTC) cannot be manually reset, so they're unsuitable for some applications in aircraft, certainly for critical systems. They reset automatically when they cool. AC 43.13-1B advises against using them.

 

[SkippyDiesel]

Ha Ha! I do so appreciate a debate with a self confessed expert in the field.

No intention to "malign" just using my observation & experince of interacting with many "died in the wool" aviation (& other) experts over a reasonably long life.

So often the expert has become so entrenched/invested in his/her orthodoxy, they lose what conceptual flexibility they may have had, before becoming an expert - it's a known, very human risk in all training in "the way".

It's not so much that you "...might know what I'm talking about." or not, it's more about the possibilities/alternatives that do not fit nicely into your training (the way).

I pride myself in not having a specific discipline - when needed, seek advice from the experts, consider it and then deciding on the way forward - for the most part it works for me.

"By resettable fuse, I assume you meant circuit breakers. " Yes as stated "... resettable types, commonly known as a circuit breaker".

"Resettable fuses (polyfuses or PPTC) cannot be manually reset, so they're unsuitable for some applications in aircraft, certainly for critical systems. They reset automatically when they cool. AC 43.13-1B advises against using them."

Could not agree more - I may be out of line, however I believe a more precise term for this type of fuse is - Resetting or Automatic (Auto) Resetting (Reset), not "resettable" which indicates a human action/involvement (press, flick. switch, etc).

 

[SV_Classic]

But, generally speaking, automotive inline fuse holders are comparatively large and heavy because they typically use heavier gauge wire than is seen in aircraft installations, and they often have water/dust resisting features you don't need in an aircraft. You shouldn't install a fuse holder in the engine compartment, so those features aren't necessary. A fuse block can use automotive style fuses, blade or tube, while using less space and weight. So, there's nothing wrong with inline fuse holders, but they usually aren't the best choice for aircraft installs.

Appreciate the input @Rhino and the replies @SkippyDiesel . I had asked about inline fuse holders because I have three switches on a side panel for nav, strobe, and landing lights that are fed by a single 10A CB on the panel. Not wanting to run 18GA wire for each circuit, I was going to use an inline 5A fuse and run 20GA wire for each of the three circuits. I didn't really see specific aircraft grade inline fuse holders so I asked about what's available that would be suitable for an aircraft expecting there to be something that is better than the next step down which mght be automotive grade.

I had already bought some smaller holders from Amazon which seem to be about the same quality as what was suggested so I'm ready to go with those three circuits.

 

[Carl_Froehlich]

The point not yet discussed is wire insluation. The insulation on auto wiring is PVC. The insulation on aircraft wire is Tefzel. PVC melting point is around 200 degrees. Tefzel is around 500 degrees.

Bundle some PVC together in the engine compartment and you compound the problem. The cost difference between Tefzel and PVC is in the grass so why do it?

If you want to use fuses and fuse holders, fine. I recommend however you buy from known sources (e.g. Stein) not Amazon or eBay.

Side note. Putting fuses or breakers in series is usually not a good idea. Make sure you look at “what happens if” senarios.

Carl

 

[SV_Classic]

all fair points, thanks for the reply. I bought from amazon to get holders for mini fuses with lighter gauge wire. Stein never replied when I emailed them about fuse holders, I suppose I can call and ask today.

I was originally pulling power directly from the switched battery bus but found I didn't have room for CB switches so had to revert to regular switches pulling power from a breaker with smaller fuses on each branch. Figured a fuse and CB with different ratings would play nice together vs. two CB's.

 

[SkippyDiesel]

The point not yet discussed is wire insluation. The insulation on auto wiring is PVC. The insulation on aircraft wire is Tefzel. PVC melting point is around 200 degrees. Tefzel is around 500 degrees.

Bundle some PVC together in the engine compartment and you compound the problem. The cost difference between Tefzel and PVC is in the grass so why do it?

If you want to use fuses and fuse holders, fine. I recommend however you buy from known sources (e.g. Stein) not Amazon or eBay.

Side note. Putting fuses or breakers in series is usually not a good idea. Make sure you look at “what happens if” senarios.

Carl

Very good advice.

I do feel that your "Bundle some PVC together in the engine compartment and you compound the problem. " is a tad hysterical. Tefzel, will not help you if you practise bad wiring/installation.

I have often found that the options available from the automotive world are far more diverse, lighter & more modern, than from the aviation industry.
For example:

FHP-1 fuse holders/ Aircraft Spruce, uses a glass tube fuse. Works. Bulky, heavy, costly and uses fuses that are relativly fragile.

 

[SV_Classic]

we're splitting hairs at this point folks

 

[SkippyDiesel]

Naturally, I don't agree. This is a genuine philosophical & practical area of debate.
The aviation industry has built up, since its departure from bicycle engineering, an elitist overly conservative position - only aviation derived products/techniques can be allowed.
To some extent this is reasonable but not when the exponents (both professiona & amature) are dogmatic in their resistance to the possibilities presented by other industries.

 

[SV_Classic]

i was ready to use amazon no-label fuse holders ten posts ago

 

[SkippyDiesel]

You weren't the target of my comment - If I may be so bold - so far, you represent the reasonable, considered fraction of this Forum

 

[airguy]

I assumed there was an aircraft grade product, I guess I was wrong! lol

Can you define "aircraft grade" for us?

 

[SV_Classic]

Can you define "aircraft grade" for us?

Well, it depends. Are we talking about aircraft grade due to its selection by a manufacturer for a certfied design or aircraft grade due to the FAA designating something via TSO or other certification that allows its use in aircraft? Or, in the case of experimentals, something deemed by me to be worth trying in my aircraft? There are variations on the theme.