Today's Message Index:
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1. 10:06 AM - Re: Z8 Ground Power test switch (jonlaury)
2. 02:13 PM - Re: Z8 Ground Power test switch (user9253)
3. 04:50 PM - Ground Power Lite (Robert L. Nuckolls, III)
4. 05:56 PM - Ground Power test (Fergus Kyle)
5. 06:17 PM - Re: Z8 Ground Power test switch (jonlaury)
6. 06:17 PM - Re: Ground Power test (Robert L. Nuckolls, III)
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Subject: | Re: Z8 Ground Power test switch |
Hi Joe,
Yes, I came to same conclusion about the advantage of separate contactors, after
Bob McC pointed out the shortcomings :) of my drawn circuitry of using a single
contactor for double duty.
The genesis of this idea was that in an electrically dependent airplane (EDA),
one should have a GP jack, rather than having to pull the cowling to get to a
battery with jumpers, and the GP contactor is dead weight for most of it's life.
Why not make it pull it's weight by having it be the aux alternator contact
as well?
Not as easy as it sounds. And I just got latched on to the idea about saving the
weight of a 4th contactor.
For all the weight of the separate ice cube relay, like you showed, I could just
leave my pocket change on the hangar bench before flying.
I still would like to see the modified schematic in your post, but it's pretty
low resolution as a .jpg file, and gets really fuzzy when I blow it up. Could
you post a .pdf of it?
Yes, Z-8 is a work in progress and the 9024 is not available yet. But Bob N was
making rumblings that it will be soon. If it's not by the time that I want to
fly, I will use a crowbar OV and LVW system on both Alts.
And I did start out using Z-13/8, and then Z-12 but BoB N objected to using the
E bus for the loads (20a +) of an EDA and Z-12 puts both alternators on the same
bus, eliminating redundancy if the problem is with the bus and it needs to
be shut down. It was then that Bob decided that Z-13/20 needed to be revisited
for EDA's and came up with Z-8. And I think that by itself, Z-8 is simple and
to the point.
Now that I've been brought back to reality with your's and BoB McC's sobering examination
and weight/cost/benefit analysis, I am happy with Z-8 and an additional
few ounces of contactor for Alt 2.
Thanks for all your help,
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=315353#315353
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Subject: | Re: Z8 Ground Power test switch |
http://eepa2a.bay.livefilestore.com/y1plAbE8KEJcAHS_99-BEHNUEuTebEghFVpbGTGXcDSdcGIgz3wNjVeCrStKgWRL1tO4_KOaV8-Js_dlVyMBgBn_admIrw7c2-d/z8_188-a.pdf?download&psid=1
John,
Above is a link to a pdf. I know that it is not exactly what you want. But the
main thing that I wanted to do was to eliminate the parallel circuit around
the OV circuit breaker which would prevent it from tripping. I am not saying
to use this circuit. Just look at how the ground power contactor is wired and
make sure that you do not connect another wire from the bottom of the coil through
a switch to ground, in effect bypassing the circuit breaker.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=315378#315378
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Subject: | Ground Power Lite |
>The genesis of this idea was that in an electrically dependent
>airplane (EDA), one should have a GP jack, rather than having to
>pull the cowling to get to a battery with jumpers, and the GP
>contactor is dead weight for most of it's life. Why not make it pull
>it's weight by having it be the aux alternator contact as well?
Keep in mind that the "electrically dependent" airplane
can generally be operated on a few tens of amps . . . perhaps
even 20 or less. So a ground power connector suitable
for both charging a battery -OR- operating a cockpit full
of electro-whizzies doesn't need to be the same device that
you might use to crank an engine using the FBO ground power
cart.
In about 1000 hours of flying over a period of 20 years,
I've had only two occasions to seek ground power assist
for getting an engine started. Both times the weather was
0F or below and neither airplane had an RG battery or
a modern high performance starter.
So allow me to suggest that since all readers of the
AeroElectric-List know how to craft a cranking system that
will get them going 99.99% of the time without a ground-
assist, a boss-hogg ground power connector and contactor
offers marginal to negative return on investment.
You can build your own ground power cable from say 6AWG
wire and use a trailer connector to mate it to the airplane.
Emacs!
Mount the connector close to the battery to minimize
length of always hot wire. Connect three pins to battery
contactor input using 12AWG wire. Three other pins to
battery(-) ground. If it makes you feel better, put
a mini-ANL 60 in series with the (+) wire right
at the battery contactor.
Now, since this is a ground power connection under YOUR
control, you can be sure that polarity issues are dealt
with for every instance. You can hood this cable set
to an automobile with the engine running and wait
10 minutes to recharge a dead battery before you attempt
engine cranking. You can use a similar cable assembly
permanently wired for proper polarity to your switch-mode
ground power supply to light up the panel on the ground.
Emacs!
Lighter, simpler, and likely to meet 99.99% of all your
ground power needs. Actually, stay home in front of the
fireplace when the weather goes to 0F and this rig
will cover 100% of your ground power needs.
Bob . . .
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Subject: | Ground Power test |
Perhaps I'm being too simple, but I run an LED from the base of the
GPU fitting such that if it shows about 12-14Vdc in correct sequence, the
LED lights and I know I can power the GPU contactor to the ship. Won't that
do?
Cheers, Ferg
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Subject: | Re: Z8 Ground Power test switch |
Joe,
Thanks for the PDF. I understand about not building parallel circuits bypassing
the OVP now. And I decided to use a separate contactor for the #2 Alternator
aftter all, so I feel a little like the guy who yells "FIRE!" in the theater.
[Embarassed]
Best,
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=315393#315393
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Subject: | Re: Ground Power test |
At 07:52 PM 10/11/2010, you wrote:
> Perhaps I'm being too simple, but I run an LED from the
> base of the GPU fitting such that if it shows about 12-14Vdc in
> correct sequence, the LED lights and I know I can power the GPU
> contactor to the ship. Won't that do?
Sure . . . as long as you have control of the power
being fed to the rest of the airplane. The system I
proposed a few minutes ago applies power to the ship's
battery as soon as you hook up the external power source . . .
which puts battery-bus powered things at-risk before
the battery master is turned on . . . and everything
else after the master is on. There is a fist
full of ways to connect, pre-test, control and protect
for the various ground power faults.
Reality of the ground power situation is that it's
seldom needed and then mostly under conditions
controlled by the owner/operator.
Bob . . .
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