LarryRosen
Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ
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 Posted: Sat Sep 23, 2006 6:59 pm Post subject: Z13/8 & Z32 Relays (was Eeeeek! Another fear and question) |
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Would a solid-state relay, like the power link Jr.
<http://www.periheliondesign.com/powerlinkjr.htm> provide a more
reliable, lower current draw solution to the S-704-1 relays shown on
Z13/8 and Z32? What are the disadvantages to this type of relay other
than cost?
Other than "tradition" what is the rational for wanting a contact in a
always hot feed of more than a few amps?
Larry Rosen
RV-10
N204EN (reserved)
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
At 09:47 AM 9/23/2006 -0500, you wrote:
>
> <N6030X(at)DaveMorris.com>
>
> Well, I'll wait for Bob to justify his own schematics, but I know he
> is in Kansas at the tandem-wing fly-in today and may not be able to
> comment for a while.
>
> If it were ME, I would not use a relay to power the E-bus. I would
> use a switch. Switches handle larger current than 5A all the time,
> and if you're concerned about reliability, just use a switch rated
> for larger current. The other thing you should do here, since you're
> discovering you have an unusual e-bus, is to ask yourself whether all
> of those items really need to be on the e-bus. I had to go through
> several iterations before I finally pared my e-bus down to what was
> really going to be necessary to have running ALL THE TIME to complete
> the flight. Remember you can always power up the Main Bus for a few
> minutes if you need to, while on battery power.
>
> Dave Morris
The suggestion for adding an e-bus relay had nothing to do
with current carrying capacity of the e-bus switch. There's
be a long standing tradition in TC aircraft to limit the size
of always-hot feeders in aircraft to those protected by 5A or
smaller breakers.
Since the "FAT" e-bus feeder needs to carry more than the few
amps originally considered when the e-bus was conceived, the
idea for adding a 'mini-contactor' at the e-bus for larger
feeders was offered.
Now, fuses are much faster than breakers, and for Z-13/8
were a continuous e-bus load of 8A is PRACTICAL, then
assuming the e-bus alternate feed is fuse-fed from the
battery bus, going up to 10A fuse is a useful thing to
consider without thumbing our noses too vigorously at tradition.
Too many folks are treating the Z-figures as carved-in-
stone recommendations for details of a proposed electrical
system. These drawings are STARTING POINTS that illustrate
architectures that will in-turn drive your Plan-A/Plan-B
thinking.
Don't get yourselves wrapped around any axles here based
on sizes of wires, sizes of fuses/breakers or which
devices are fed from which busses. The drawings were
never intended to be a recipe for success, only a tool
for development. I get a half-dozen requests a week for
"Gee Bob, I like Figure Z-x but it doesn't . . . and
I want to . . . Would you please craft me a Z-y that
takes care of all my desires/worries?"
All these requests get the same reply which is not
much different that what I've written above. Nobody
promised anyone a decision free solution. One is
always on firm footing to clone the system out of
a C-172 and drive on. Any variations from that theme
WILL require thought, exploration, crafting/answering
of questions and finally understanding of the final
configuration which WILL be uniquely applicable to
YOU and your airplane.
Bob . . .
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_________________
Larry Rosen
#40356
N205EN (reserved)
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