Today's Message Index:
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1. 06:46 AM - Re: Primary Power Diagram RV-14 (Mudfly)
2. 08:18 AM - Re: Re: Primary Power Diagram RV-14 (Charlie England)
3. 12:06 PM - Re: Primary Power Diagram RV-14 (Mudfly)
Message 1
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| Subject: | Re: Primary Power Diagram RV-14 |
Finally getting time to get back to my wiring plan.
John, I will hopefully be able to look at your suggestions later today.
In this post, I'll discuss the updated Stby Batt 2 interconnects with the GTN650.
The GTN650 does not have provisions/pins for a b/u power source like the
garmin devices on Stby Batt 1. Garmin advised the GTN would need to be on its
own bus with the Stby batt powering only that bus. My first drawing showed
the GTN650 on its own bus with Stby Batt 2 powering that bus as Garmin recommend.
However, after consulting with TCW I was told my plan would not work
due to the setup of the IBBS Batt. I would need to use the "pass-thru" power
connections [pins 6,7, 8] to allow the batt to operate properly.
I realize with this setup, the GTN is powered solely by the pass-thru and output
wiring of the IBBS. This wiring is protected by a single 10amp mini fuse located
on the enclosure of the battery.
The power draws (total all connectors) of the GTN650Xi published by Garmin are
2.65A Typical, 7.72A max. I placed the pass thru wires on a 7.5 cb. My thought
was I would prefer this CB to open before the 10A mini fuse on the battery.
The max current of 7.72A (probably during radio transmission) would possibly
exceed the 7.5 cb, but maybe not enough to pop the CB. If it did pop, and
I needed the GTN, I may consider re-setting the CB and using the comm 2 radio
for further radio transmission. Obviously, if this situation occurs on a regular
basis, I would need to re-think this configuration.
Attached are the latest revisions of the Primary Power System and Stby Batteries
drawings.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510185#510185
Attachments:
http://forums.matronics.com//files/stby_batts_interconnects_feb15_140.pdf
http://forums.matronics.com//files/primary_power_system_feb15_336.pdf
Message 2
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| Subject: | Re: Primary Power Diagram RV-14 |
On 2/15/2023 8:45 AM, Mudfly wrote:
>
> Finally getting time to get back to my wiring plan.
> John, I will hopefully be able to look at your suggestions later today.
> In this post, I'll discuss the updated Stby Batt 2 interconnects with the GTN650.
The GTN650 does not have provisions/pins for a b/u power source like the
garmin devices on Stby Batt 1. Garmin advised the GTN would need to be on
its own bus with the Stby batt powering only that bus. My first drawing showed
the GTN650 on its own bus with Stby Batt 2 powering that bus as Garmin recommend.
However, after consulting with TCW I was told my plan would not work
due to the setup of the IBBS Batt. I would need to use the "pass-thru" power
connections [pins 6,7, 8] to allow the batt to operate properly.
> I realize with this setup, the GTN is powered solely by the pass-thru and output
wiring of the IBBS. This wiring is protected by a single 10amp mini fuse
located on the enclosure of the battery.
> The power draws (total all connectors) of the GTN650Xi published by Garmin are
2.65A Typical, 7.72A max. I placed the pass thru wires on a 7.5 cb. My thought
was I would prefer this CB to open before the 10A mini fuse on the battery.
The max current of 7.72A (probably during radio transmission) would possibly
exceed the 7.5 cb, but maybe not enough to pop the CB. If it did pop, and
I needed the GTN, I may consider re-setting the CB and using the comm 2 radio
for further radio transmission. Obviously, if this situation occurs on a regular
basis, I would need to re-think this configuration.
>
> Attached are the latest revisions of the Primary Power System and Stby Batteries
drawings.
Haven't followed your stuff closely, but reading the above sounds like
you're focused on fusing (or CBing) to protect components. That's the
mfgr's job; not ours, and no external fuse will protect a device from an
internal fault in the device. If you fuse close to the rated draw,
you're setting yourself up for nuisance trips.
Fuses/CBs should protect wire; not devices.
It's worth remembering that while mfgr's recommendations should be
followed for the most part, they need to pass the smell test, and
occasionally, they stink.
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Message 3
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| Subject: | Re: Primary Power Diagram RV-14 |
[quote="johnbright"]Re "Primary Power System.pdf" RV-14A N144EF rev in work 02/04/2023
I have a number of suggestions that I can peck away at. Ill start with the battery
bus to make it meet FAR 23.1361:
[list]Mount it on the forward side of the firewall.
Connect it straight to the battery with no current limiter or fuse. No protection
required and each joint between the battery and the battery bus is a potential
failure point.
Short feeder length, say 6" or less fashioned with best practices to make a short
to ground practically impossible.
10 awg hookup wire is fine but 12 or 14 would be fine also. These are conventionally
rated for 30, 20, and 15 A respectively.
Keep all the fuses 7-1/2A or less.
This will meet the spirit of FAR 23.1361 which is important for service and crash
safety scenarios. Why 7-1/2A fuses instead of the 5A or less "protective device"
specified in FAR 23.1361?... because as Bob Nuckolls points out, fuses are
much faster than circuit breakers.[/list]
I personally dont use fuses smaller than 5A to reduce part numbers. Common advice
is to not use smaller than 22 or 20 awg wire anyway for mechanical robustness.
And if you dont use smaller than 20 awg you dont have to stock the 22 or differentiate
it from the 20.
Do you plan to use Bussmann 15600 fuse holders? Just curious.[/quote]
John,
I looked at installing the hot battery bus on the fwd side of the firewall during
my planning. I actually have pieces of cardboard cut out in shapes of fuse
blocks and current limiters. They are connected together with pieces of string
representing wires. Because the RV14 comes from Vans with pre-arranged
locations/holes for the battery and starter contactors, I'm somewhat limited with
how creative I can get locating devices. To keep the Bat Bus feed wire
within approx. 6" length, the bus would be mounted left side, slightly below
midpoint vertically on firewall. To inspect this bus, if needed, the upper and
probably lower cowling would need to be removed. The other location is left
side, upper area of firewall. This would require about an 8" feed wire from
the battery contactor. In this case only the top cowling would need to be
removed for inspection.
With my carboard and string, it just appeared that running a 10awg wire from the
ANL through the firewall to the hot bat bus was a much cleaner installation.
During my planning, I mostly used the Z101 and Z-36 diagrams. My endurance bus,
which really isn't an endurance bus, is mostly for dual feed purposes and easy
load shed if needed for stby alt ops. The Z36 show a MANL30 protecting the
"Robust" Endurance Bus. Z-101 shows a "Fat Wire Tie Point" off the batt contactor
feeding the Bat and Clrnc busses. My thought was to use the current
limiter base as a fat wire tie point while also protecting the 10awg wire to
the hot battery bus. Would the ANL fuses be too slow for this purpose? Also,
I didn't realize until later the battery bus on Z12 is located fwd of firewall
so I was already heading down the aft firewall path.
Like I mentioned, nothing at this point has been mounted and no wires have been
run so I can easily change my plans if needed.
Regarding fuse holders.. I have not purchased anything yet. You mentioned the Bussmann 15600. They seem to be the most used and and proven way to go. I have seen a few use the blue sea systems fuse blocks https://www.westmarine.com/blue-sea-systems-st-blade-fuse-block-6-circuits-with-negative-bus-and-cover-3733482.html , but those would definitely not be good firewall fwd.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510189#510189
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