Question for Jim Wier (or other electrical guru)

On Fri, 07 Jan 2005 16:50:30 GMT, "Mike Rapoport"
wrote:

There is no breaker protecting the wire going to the bus.

Mike
MU-2

There should be - - - somewhere along the line. What about on your AV
master switch?

In my Bonanza there are auto reset breakers that protect all sorts of
things. They are behind the panel and you never see them.
Just because breakers aren't visible doesn't mean they aren't there.

Dave

Jon A. wrote:
On Fri, 07 Jan 2005 16:50:30 GMT, "Mike Rapoport"
wrote:


There is no breaker protecting the wire going to the bus.

Mike
MU-2


There should be - - - somewhere along the line. What about on your AV
master switch?

On Sat, 08 Jan 2005 08:35:40 -0600, wrote:

In my Bonanza there are auto reset breakers that protect all sorts of
things. They are behind the panel and you never see them.
Just because breakers aren't visible doesn't mean they aren't there.

Are they still using those thermal breakers in the newer airplanes?

Dave

Jon A. wrote:
On Fri, 07 Jan 2005 16:50:30 GMT, "Mike Rapoport"
wrote:


There is no breaker protecting the wire going to the bus.

Mike
MU-2


There should be - - - somewhere along the line. What about on your AV
master switch?

Mike Rapoport wrote:

I have that chart but I am unclear on how it applies to my question.

Look at the point at which the 12ga wire size line hits curve 3. That is
approximately 2/3 of the way between the 30 amp line and the 50 amp line. I take
that to mean that that wire size can take that amperage for a short period of
time. If you follow the horizontal line from that point over to the length
scale, you get a maximum length for a 14 volt system of 12 feet. And, yes, the
voltage drop and temperature considerations you mention apply.

I think it says that if I load a 12ga wire with
30A at 14V at 20C the wire can be a maximium of 16 feet long if the voltage
drop is limited to 1V.

That too.

It also doesn't define intermittent.

If you take a closer look at the label in the lower right corner, it states
"maximum of two minutes." This is also stated in the text.

George Patterson
The desire for safety stands against every great and noble enterprise.

"Jon A." wrote in message
...
On Fri, 07 Jan 2005 16:50:30 GMT, "Mike Rapoport"
wrote:

There is no breaker protecting the wire going to the bus.

Mike
MU-2

There should be - - - somewhere along the line. What about on your AV
master switch?


Well that is the whole point, it is just two wires with the same origin and
destination points. AFAIK the avioniics master sends current to the field
on avionics contactor which is supplied directly from the master contactor
which recieves its field current from the master switch. Both the master
and avionics switches are simple MS toggle switches, not circuit breaker
type switches.

Mike
MU-2
Helio Courier

Do they fit inside a wire? From the avionics contactor to the avionics bus
there is nothing expect two wires. I haven't looked upstream of the
avionics contactor. I will do that this week.

Mike
MU-2


wrote in message ...
In my Bonanza there are auto reset breakers that protect all sorts of
things. They are behind the panel and you never see them.
Just because breakers aren't visible doesn't mean they aren't there.

Dave

Jon A. wrote:
On Fri, 07 Jan 2005 16:50:30 GMT, "Mike Rapoport"
wrote:


There is no breaker protecting the wire going to the bus.

Mike
MU-2


There should be - - - somewhere along the line. What about on your AV
master switch?

"G.R. Patterson III" wrote in message
...


Mike Rapoport wrote:

I have that chart but I am unclear on how it applies to my question.

Look at the point at which the 12ga wire size line hits curve 3. That is
approximately 2/3 of the way between the 30 amp line and the 50 amp line.
I take
that to mean that that wire size can take that amperage for a short period
of
time. If you follow the horizontal line from that point over to the length
scale, you get a maximum length for a 14 volt system of 12 feet. And, yes,
the
voltage drop and temperature considerations you mention apply.

I think it says that if I load a 12ga wire with
30A at 14V at 20C the wire can be a maximium of 16 feet long if the
voltage
drop is limited to 1V.

That too.

It also doesn't define intermittent.

If you take a closer look at the label in the lower right corner, it
states
"maximum of two minutes." This is also stated in the text.

I think that your chart might be somewhat different mine certainly doesn't
have that note. I will have to search the text to see if it is there. My
copy is AC 43.13-1B CHG 1 and is dated 9/27/01 which is the most current (I
think)

Mike
MU-2

Mike Rapoport wrote:

Do they fit inside a wire? From the avionics contactor to the avionics bus
there is nothing expect two wires. I haven't looked upstream of the
avionics contactor. I will do that this week.

Well, there are things called "fusible links" that Chrysler has used for
decades. Many of them look just like wires. I've never seen one on an
airplane, however.


Matt

Mike Rapoport wrote:

I think that your chart might be somewhat different mine certainly doesn't
have that note. I will have to search the text to see if it is there.

In my copy, paragraph 444 section "d" says "The procedures in 'c' can be used to
find the wire size for any continuous or intermittent operation (maximum 2
minutes) voltage ..."

My
copy is AC 43.13-1B CHG 1 and is dated 9/27/01 which is the most current (I
think)

Ah. Mine is AC 43.13-1A CHG 3. It's dated 1988, though I bought it in the late
'90s.

George Patterson
The desire for safety stands against every great and noble enterprise.

Mike Rapoport wrote that his copy of AC 43.13-1B CHG 1 doesn't have a note
reading, "maximum of two minutes" on the wire chart.

I don't see that note on Figure 11-3 (Conductor chart, intermittent flow)
either, but it's in the text in paragraph 11-68(d): "d. Procedures in
Example No. 1. The procedures in example No. 1, paragraph 11-68c, can be
used to find the wire size for any continuous or intermittent operation
(maximum two minutes). Voltage (e.g. 14 volts, 28 volts, 115 volts, 200
volts) as indicated on the left scale of the wire chart in figures 11-2 and
11-3."

Jon