Fuses in general

[Tuno]

Okay, neither my flight manual nor maintenance manual say what kind of
fuses I should be using between the batteries and instruments. The
printing on one looks to be T500L250V, which I understand to mean 0.5
amps, slow-blow, 250 Volts. (It's 5x20mm.)

I know that to protect my wiring I need something in the 2 to 3 amp
range, but slow-blow or fast-blow? Does it matter? In choosing the
fuse, do I consider only the wiring to the instrument, or do I
consider the instrument itself? (If it draws 300 mA peak, I imagine
the fuse must be at least 600 mA.)

I need to replace the blown T500L250V and get some spares for the
others -- I just don't know what to order.

~ted/2NO (software guy)

[Tim Mara[_2_]]

Borget B400 uses quick acting 0.5amp fuse type "M205" (meaning 5 x20mm)
5x20mm 250Vac
Borgelt B500 uses the same type in 1 amp
any fuse manufacturers 5x20mm fast acting fuse would be acceptable in the
proper value
these should be easy to find wil almost any electronics supplier
tim
Please visit the Wings & Wheels website at www.wingsandwheels.com


"Tuno" > wrote in message
...
> Okay, neither my flight manual nor maintenance manual say what kind of
> fuses I should be using between the batteries and instruments. The
> printing on one looks to be T500L250V, which I understand to mean 0.5
> amps, slow-blow, 250 Volts. (It's 5x20mm.)
>
> I know that to protect my wiring I need something in the 2 to 3 amp
> range, but slow-blow or fast-blow? Does it matter? In choosing the
> fuse, do I consider only the wiring to the instrument, or do I
> consider the instrument itself? (If it draws 300 mA peak, I imagine
> the fuse must be at least 600 mA.)
>
> I need to replace the blown T500L250V and get some spares for the
> others -- I just don't know what to order.
>
> ~ted/2NO (software guy)

[[email protected]]

Ted:

You've gotten a good answer from Tim about the proper fuse to use, but
you asked another good question that went unanswered and that is all
too often overlooked. That is, what does the fuse protect? The
answer is, as you suggested, the wiring. AC43.13 has wiring size
tables for common A/C wires and the size fuse needed to protect them.
It is a table worth having available somewhere in your shop. By
referring to that table you can know what size fuse will safely
protect the wire (gauge and run) it is connected to. The other
question you asked -- does the fuse protect the instrument -- is more
problematic. Generally speaking it does not because the instrument
has an internal fuse to protect it. Not all do, of course, and some
fuses are so difficult to access and replace that you'll wonder if
you're better off putting a low value fuse before the instrument.
These are individual decisions based on the instrument you're
installing. Fred

Fred LaSor
SoaringNV
Minden, NV

[ContestID67]

Fred had some really great thoughts. One thing to add.

Fast blow versus slow blow? Slow blow seems like the easy way to
helping to prevent blown fuses. Slow blow (slo-blo) fuses were
created to handle devices with high "inrush" currents. That is, when
you turn on this type of device, there is a high initial current draw
for a short period (maybe 1-2 seconds) which settles down to a lower
level. Simplistic examples are motors and incadesent light bulbs.

Do you have any devices in your glider that need a slo-blo? Highly
doubtful. I don't know of any "modern" (last 10+ years) avionics/
instruments that need slo-blo. I don't use any. Check the manual on
all your devices to be sure.

Finally, as to using one fuse total or using one fuse per
device...this is a question in which you will get equal proponents on
each side. I prefer one fuse directly at the battery. I run two
batteries.

My $0.02.

- John DeRosa

[Andy[_1_]]

On Dec 9, 12:11*pm, ContestID67 > wrote:
> Finally, as to using one fuse total or using one fuse per
> device...this is a question in which you will get equal proponents on
> each side. *I prefer one fuse directly at the battery. *I run two
> batteries.

I don't there is a choice to either fuse at the battery or to fuse at
the instruments. There must be a fuse at, or in, each battery or you
risk an in flight fire. The battery fuse (or circuit breaker) should
be large enough to support all equipment but no larger than required
to do that.

The advantage of also having separate fuses for each item, or groups,
of avionics is that a short at the panel or an internal avionics
short, will only blow the local fuse and leave other equipment still
working. This of course requires all fuses to be properly rated.

I've never blown a fuse in flight in nearly 30 years of flying
gliders, but I have blown fuses when working on the glider on the
ground. For that reason I chose not to give up any panel space for
fuses. They are all behind the panel and can be reached by raising
one side of the canopy (ASW 28).

Andy

[[email protected]]

Another consideration on fusing batteries is that some battery
connectors allow you to plug one battery into another when they are on
the charging shelf. The results are VERY messy and occasionally
dangerous. If your batteries are ndividually fused the fuse will go
before the wires melt and swell the battery case. Well worth the
small cost of installing a fuse on each battery.

Fred LaSor
SoaringNV
Minden, NV

[Brian Bange[_2_]]

This is a timely thread for me...
I've been given the onerous task of maintaining the radios in our club's
6 gliders. This winter we are going to wire all 6 the same. The plan is to
have a fuse at the battery, a main switch on the front panel that switches
everything on and off and when off ties the battery to the charge
connector. We also will move the charge connectors to the front of each
ship. We are loosing a lot of batteries due to user stupidity or laziness.
If they stay deeply discharged during the week, they lose most of their
capacity.

I am a proponent of a fuse at the battery. I am afraid that if the power
wires got shorted somehow, they could either start a fire or create enough
smoke to cause an accident. I have 2 ships that use a metal hose clamp to
hold the battery down. I personally think that is a bad idea, as if the
battery shifted, it would short to the hose clamp.

Two questions:
1. What can I use instead of the hose clamps and where do I get it?
2. Any comments on our plan?

Brian Bange
At 19:11 09 December 2008, ContestID67 wrote:
>Fred had some really great thoughts. One thing to add.
>
>Fast blow versus slow blow? Slow blow seems like the easy way to
>helping to prevent blown fuses. Slow blow (slo-blo) fuses were
>created to handle devices with high "inrush" currents. That is, when
>you turn on this type of device, there is a high initial current draw
>for a short period (maybe 1-2 seconds) which settles down to a lower
>level. Simplistic examples are motors and incadesent light bulbs.
>
>Do you have any devices in your glider that need a slo-blo? Highly
>doubtful. I don't know of any "modern" (last 10+ years) avionics/
>instruments that need slo-blo. I don't use any. Check the manual on
>all your devices to be sure.
>
>Finally, as to using one fuse total or using one fuse per
>device...this is a question in which you will get equal proponents on
>each side. I prefer one fuse directly at the battery. I run two
>batteries.
>
>My $0.02.
>
>- John DeRosa
>
>

[brianDG303]

First, a nit-pick; incandescent lamps are resistive and not inductive
and inrush isn't a common component. But low voltage lighting systems
with a core and coil transformer is exactly what will pop a fast fuse.

I would use Anderson Powerpole connectors and strap the batteries down
with good-sized nylon ties, you can get quite large ones if needed. Or
you could heat-shrink some parts of the hose clamp. Also, it sounds
like the battery connectors you are using leave the connections
exposed, if so an insulated connector is suggested. If using crimp
connectors use Panduit brand or maybe AMP and NEVER use the cheap ones
that you see everywhere.

Anderson powerpoles will allow two batteries to be connected, but it
will be + to + and - to - and that might be less entertaining. I guess
if the batteries are at the same voltage nothing would happen.
Anderson uses a small roll pin to join two connectors together, I
really don't like the pins and let a little glue wick between them
instead.

[Steve Koerner]

My opinion is that low current fuses on the panel (or behind it) are
more likely to cause problems than prevent them. I use just one fuse
per battery circuit. I prefer a 10 amp automotive blade fuse mounted
at the battery. If it might be of interest, I've prepared a short
treatise on glider battery wiring and fusing including a picture which
is accessed at this page:

http://www.wingrigger.com/wingrigger5_005.htm

Steve Koerner
GW

[[email protected]]

Brian:

Sounds like a good plan. I like the Anderson powerpole connectors
mainly because they have enough friction during connection to wipe the
surface clean of any oxidation, so give a good connection. I don't
use the roll pin to hold the two terminals together -- just squirt a
little hot melt into the matching indents. And yes, the automotive
blade fuses are an excellent installation on one of the battery
terminals. As for holding batteries down, I agree a metal hose clamp
is an accident waiting to happen. What's wrong with a short piece of
bungee cord?

Fred LaSor
SoaringNV
Minden, NV

[Tim Mara[_2_]]

I always use automotive type flat spade fuses on the battery itself...the
fuses and fuse holders are far more durable than round glass fuses.

I honestly have no idea where we come up with some of these ideas for
battery holders and hold down's...
nowhere in AC4313 or any aviation mechanics books will you ever see bungee
cords (these are for holding your lunch box on your Schwinn, Hose clamps
(these are for....you guessed it...hoses!), Tie wraps....these are for
wrapping up your Christmas tree lights after January 1st ...or duct tape,
Velcro, handcuffs....or??? I've even found packaging tape and pine 2x4's in
gliders...Keep in mind these are still aircraft we are talking about and
even if they weren't, even automobiles has simple but strong bolts and
brackets to anchor their batteries....just like normal aircraft do...it
doesn't take too much imagination to make a simple and secure battery anchor
using real nuts and bolts...and if it's done right it is as or simpler to
remove and replace the battery with a wingnut or an over-center latch and a
safety pin...
tim

Please visit the Wings & Wheels website at www.wingsandwheels.com


"brianDG303" > wrote in message
...
> First, a nit-pick; incandescent lamps are resistive and not inductive
> and inrush isn't a common component. But low voltage lighting systems
> with a core and coil transformer is exactly what will pop a fast fuse.
>
> I would use Anderson Powerpole connectors and strap the batteries down
> with good-sized nylon ties, you can get quite large ones if needed. Or
> you could heat-shrink some parts of the hose clamp. Also, it sounds
> like the battery connectors you are using leave the connections
> exposed, if so an insulated connector is suggested. If using crimp
> connectors use Panduit brand or maybe AMP and NEVER use the cheap ones
> that you see everywhere.
>
> Anderson powerpoles will allow two batteries to be connected, but it
> will be + to + and - to - and that might be less entertaining. I guess
> if the batteries are at the same voltage nothing would happen.
> Anderson uses a small roll pin to join two connectors together, I
> really don't like the pins and let a little glue wick between them
> instead.

[Todd]

> What's wrong with a short piece of bungee cord?

Batteries are heavy, hard objects that I would prefer not hit me in
the back of my head in heavy turbulence or worse, a crash landing. I
would never trust a bungee cord to restrain a few pounds of lead! I
use a 1" nylon strap (heavy duty) with a METAL BUCKLE (I have broken
too many plastic buckles to trust them in a critical application)
attached to some solid structure of the glider. Buckle is positioned
to keep it far away from the terminals (which are insulated too)

In my glider, the (2) 12 Ah batteries are sitting in a aluminum angle
(1.5") tray bolted to the structure. This way the tray absorbs most
of the g forces and the straps keep the batteries in the tray. By the
time the straps break or the tray tears loose, I probably no longer
have to worry about the batteries hitting my head.

I also use PowerPole connectors with fuses on each battery.
Connectors are double sided taped to the battery as a strain relief.

I also carry a auto cigarette adapter with a powerpole connector and
my cell charger so I can charge my cell if I get stuck somewhere.

[Bob Kuykendall]

On Dec 9, 3:15*pm, Todd > wrote:
> I use a 1" nylon strap (heavy duty) with a METAL
> BUCKLE...

I've used a very similar setup with good results. The battery box I
built for my HP-11 was one of my very first sheetmetal projects, and I
tested it and the retention strap to about plus or minus 12g. That
means I could stand my 140 lb weight on it without yielding, and I
could safely apply the same force upwards to the strap.

However, one thing I didn't know at the time is that nylon is rather
sensitive to acids, and loses strength quickly when so contaminated.
Given that the S in SLA is for "sealed," under most circumstances
there's no chance of spillage. But the A does stand for "acid," so it
pays to keep an eye on the battery to make sure it doesn't leak, and
on the strap to make sure it isn't becoming brittle or discolored.

Thanks, Bob K.

[Andy[_1_]]

On Dec 9, 2:28*pm, brianDG303 > wrote:
> First, a nit-pick; incandescent lamps are resistive and not inductive
> and inrush isn't a common component.

Sorry wrong nit to pick. The resistance of an incandescent lamp
filament is temperature dependent. Anyone that has used lamps as
current control devices is well aware of this.

Andy

[Andy[_1_]]

On Dec 10, 8:44*am, Andy > wrote:

> Sorry wrong nit to pick. *The resistance of an incandescent lamp
> filament is temperature dependent. *Anyone that has used lamps as
> current control devices is well aware of this.

I suppose I should have completed the information. The resistance is
low when the filament is cold. There is a large inrush current which
reduces as soon as the filament gets hot.

Anyone old enough to have used equipment with vacuum tubes (valves or
bottles) will remember how bright the heaters glowed when the
equipment was first turned on. The thermionic valve was a marvelous
device - heat, light, and RF out of one component ;).

Andy

[brianDG303]

OK Andy, I'll bite. Lighting loads are generally considered to be
resistive and not inductive. While not perhaps true in some examples,
for the subject of this thread I think the nit was picked correctly.
For example, if you connect 16 amps of lighting load to a 20 amp fast
fuse (or 'Quick Operating' magnetically enhanced circuit breaker) you
will have a reliable circuit. If you connect a 16 amp capacity core
and coil transformer to that same fuse, or if you connect 16 amps of
old style HID lighting with the reactive ballasts acting as inductors,
you will pop that fast fuse most of the time in an AC circuit. I think
that if in an AC circuit the contact closure is timed exactly as the
sine wave crosses the 0 volt line there is sometimes sufficient lag to
slow the inrush enough to keep the fuse from popping. That's my theory
anyway.

If you still don't buy what I am saying, I'm perfectly happy to
concede the point. However, the original post implied that motors and
incandescent light bulbs require slow-blow fuses. (Many) motors do and
incandescent light bulbs do not, so if you are designing an electrical
system and the only "Inductive" loads are incandescent it would be
fine to use a fast blow fuse in order to protect electronic gear.

I guess this brings up another point, if there is more than one fuse
certainly the battery fuse or CB could be a slow blow and the fuses at
the gear would want to be fast blow in most cases.

On Dec 10, 11:39*am, Andy > wrote:
> On Dec 10, 8:44*am, Andy > wrote:
>
> > Sorry wrong nit to pick. *The resistance of an incandescent lamp
> > filament is temperature dependent. *Anyone that has used lamps as
> > current control devices is well aware of this.
>
> I suppose I should have completed the information. *The resistance is
> low when the filament is cold. *There is a large inrush current which
> reduces as soon as the filament gets hot.
>
>
> Andy

[Big Wings]

My glider has multiple batteries with a switch to change between them
during flight. To, hopefully, eliminate loss of logger data during the
brief interruption of power during the switching process there is a large
capacitor to ensure continuity of supply to selected instruments during
switching. Although there is a resistor to limit the inrush current to
the capacitor this type of circuit needs a slow-blow fuse. (Factory wired
in last two years.)

[Tuno]

This looks like a major clue that changes everything. (Well, almost
everything.)

My ASG29 also has two main batteries and a dial switch on the panel
that selects which battery is providing power to all of the
instruments. I wonder if the transition from B1 to B2 is popping the
(fast-blow) fuse on the back of the B40. And it would explain why
there was a T500L250V fuse in the panel fuse holder; I understand that
the "T" means slow-blow ("T"imed?), where an "F" would indicate fast-
blow.

2NO

[bod43]

On 10 Dec, 22:53, brianDG303 > wrote:
> OK Andy, I'll bite. Lighting loads are generally considered to be
> resistive and not inductive. While not perhaps true in some examples,
> for the subject of this thread I think the nit was picked correctly.
> For example, if you connect 16 amps of lighting load to a 20 amp fast
> fuse (or 'Quick Operating' magnetically enhanced circuit breaker) you
> will have a reliable circuit. If you connect a 16 amp capacity core
> and coil transformer to that same fuse, or if you connect 16 amps of
> old style HID lighting with the reactive ballasts acting as inductors,
> you will pop that fast fuse most of the time in an AC circuit. I think
> that if in an AC circuit the contact closure is timed exactly as the
> sine wave crosses the 0 volt line there is sometimes sufficient lag to
> slow the inrush enough to keep the fuse from popping. That's my theory
> anyway.
>
> If you still don't buy what I am saying, I'm perfectly happy to
> concede the point. However, the original post implied that motors and
> incandescent light bulbs require slow-blow fuses. (Many) motors do and
> incandescent light bulbs do not, so if you are designing an electrical
> system and the only "Inductive" loads are incandescent it would be
> fine to use a fast blow fuse in order to protect electronic gear.
>
> I guess this brings up another point, if there is more than one fuse
> certainly the battery fuse or CB could be a slow blow and the fuses at
> the gear would want to be fast blow in most cases.
>
> On Dec 10, 11:39*am, Andy > wrote:
>
>
>
> > On Dec 10, 8:44*am, Andy > wrote:
>
> > > Sorry wrong nit to pick. *The resistance of an incandescent lamp
> > > filament is temperature dependent. *Anyone that has used lamps as
> > > current control devices is well aware of this.
>
> > I suppose I should have completed the information. *The resistance is
> > low when the filament is cold. *There is a large inrush current which
> > reduces as soon as the filament gets hot.

I too vaguely recalled that the initial current in a cold
incandescent bulb might be rather high. I cant however
remember precisely. It is though easy to find out
if you have a bulb and a multimeter. Just measure the
resistance when the bulb is cold and check
the expected current with V = IR. Well I = V / R.

This article
http://en.allexperts.com/q/Physics-1358/Incandescent-lamp-surge.htm
states that the initial current is 10 times the
running current for a domestic light bulb.
Bulbs used in gliders are likely to run cooler
so that they can be tougher to better resist
vibration, and so the initial vs final current
ratio will likely be lower.

The other aspect to this is of course that the bulb
does warm up very quickly and so even a fast blow fuse
may well be unable to respond quickly enough to
fail 'inappropriately'.

[Andy[_1_]]

On Dec 11, 9:00*am, Tuno > wrote:
> I wonder if the transition from B1 to B2 is popping the
> (fast-blow) fuse on the back of the B40.


I have the same factory standard rotary power switch and an unmodifed
B40 that is always left on and selected to external power. My B40
fuse has never blown. (There are no external capacitors in my glider
nor do I need any).


Andy