Sizing the CB needs... Homebuilt wiring too

[Dave S]

I am installing a used Narco AT-150A transponder and have only acquired
the pinout.. not an install manual.. (trust me.. if/when it goes, it
will be replaced rather than repaired..)

A brief/quick google search didn't bring up anything that indicated what
size CB to use..

What size CB is considered adequate for this type of transponder that
will allow enough current but still protect the wiring from a short?

Also.. those of you with dual navcoms.. do you have both nav-coms ganged
on a single breaker or separate?

It seems that most of the power draw would be during transmit only..

How many folks have wiring that by passes the master switch.. to a
clock, a cigarrete lighter/power power, a keep-alive circuit on backup
batteries in the panel...

Dave

[mikem]

Dave S wrote:
> I am installing a used Narco AT-150A transponder and have only acquired
> the pinout.. not an install manual.. .
> What size CB is considered adequate for this type of transponder that
> will allow enough current but still protect the wiring from a short?

3A or 5A.

[Ray Andraka]

Dave S wrote:
> I am installing a used Narco AT-150A transponder and have only acquired
> the pinout.. not an install manual.. (trust me.. if/when it goes, it
> will be replaced rather than repaired..)
>
> A brief/quick google search didn't bring up anything that indicated what
> size CB to use..
>
> What size CB is considered adequate for this type of transponder that
> will allow enough current but still protect the wiring from a short?
>
> Also.. those of you with dual navcoms.. do you have both nav-coms ganged
> on a single breaker or separate?
>
> It seems that most of the power draw would be during transmit only..
>
> How many folks have wiring that by passes the master switch.. to a
> clock, a cigarrete lighter/power power, a keep-alive circuit on backup
> batteries in the panel...
>
> Dave

The encoder gets power through the transponder too. The heater in the
encoder is the highest current draw out of the transponder and encoder
set-up, so the breaker and wiring has to be sized to accommodate that load.

I believe the breakers are supposed to be sized to the wire, not to the
radio. My transponder (was an AT150 with a trans-cal encoder, now an
AT165) has a 5A circuit breaker on it.

[[email protected]]

In rec.aviation.owning Ray Andraka > wrote:
> Dave S wrote:
>> What size CB is considered adequate for this type of transponder that
>> will allow enough current but still protect the wiring from a short?
>
> I believe the breakers are supposed to be sized to the wire, not to the
> radio.

Chapter 11 of AC43.13-1B seems to agree, and tells you how to figure it
out.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAdvisoryCircul ar.nsf/0/99C827DB9BAAC81B86256B4500596C4E?OpenDocument

Matt Roberds

[Dave S]

Ray Andraka wrote:

>
> I believe the breakers are supposed to be sized to the wire, not to the
> radio. My transponder (was an AT150 with a trans-cal encoder, now an
> AT165) has a 5A circuit breaker on it.

Ray.. as many others have told me.. you are right.. you size the breaker
to the wire.. not the device..

But you also size the wire being used.. to the current carried over the
distance carried (as the nice lil FAA book shows)...

So one sizes the wires to the device,, then the breakers to the wires..

In my instance it makes a difference because I have a LOT of 5 amp
breakers. For the wire runs involved, a 1, 5 or even 10 amp breaker will
protect my wires adequately. But I also dont want to pop a breaker in
normal operation.. "while protecting my wiring run"

By they way.. thanks for the feedback on the 5A breaker.

Dave

[[email protected]]

Breaker vs wire size 43.13 All true.

But the mfgr will recommend a breaker size. To speed
approval, you should follow their recommendations.

I'd guess enc + tpx would work on a 2A breaker; not over 3.

Bill Hale

Dave S wrote:
> Ray Andraka wrote:
>
> >
> > I believe the breakers are supposed to be sized to the wire, not to the
> > radio. My transponder (was an AT150 with a trans-cal encoder, now an
> > AT165) has a 5A circuit breaker on it.
>
> Ray.. as many others have told me.. you are right.. you size the breaker
> to the wire.. not the device..
>
> But you also size the wire being used.. to the current carried over the
> distance carried (as the nice lil FAA book shows)...
>
> So one sizes the wires to the device,, then the breakers to the wires..
>
> In my instance it makes a difference because I have a LOT of 5 amp
> breakers. For the wire runs involved, a 1, 5 or even 10 amp breaker will
> protect my wires adequately. But I also dont want to pop a breaker in
> normal operation.. "while protecting my wiring run"
>
> By they way.. thanks for the feedback on the 5A breaker.
>
> Dave

[Ray Andraka]

Dave S wrote:
> Ray Andraka wrote:
>
>>
>> I believe the breakers are supposed to be sized to the wire, not to
>> the radio. My transponder (was an AT150 with a trans-cal encoder, now
>> an AT165) has a 5A circuit breaker on it.
>
>
> Ray.. as many others have told me.. you are right.. you size the breaker
> to the wire.. not the device..
>
> But you also size the wire being used.. to the current carried over the
> distance carried (as the nice lil FAA book shows)...
>
> So one sizes the wires to the device,, then the breakers to the wires..
>
> In my instance it makes a difference because I have a LOT of 5 amp
> breakers. For the wire runs involved, a 1, 5 or even 10 amp breaker will
> protect my wires adequately. But I also dont want to pop a breaker in
> normal operation.. "while protecting my wiring run"
>
> By they way.. thanks for the feedback on the 5A breaker.
>
> Dave

I believe Narco has the install manual on their website.

The install manual calls for a 1.5A circuit breaker. They list the power
requirements as 1.0A receive, 1.6A transmit, 0.26A pilot lights. I can
tell you that when I bought my airplane, the fuse (changed out for
circuit breakers since then) for the transponder was marked 1.5A. That
circuit feeds just the transponder and encoder. I had constant problems
with it blowing 1.5A fuses, not always but within a couple hours. I
took it to "the Radio Shop" in Worcester MA, who was a master service
center for Narco before Narco pulled service in house. They took one
look at the install, and said the problem is the 1.5A fuse is not
sufficient for that encoder's heater and that the 1.5A was what Narco
recommended for just the transponder. They checked the wiring to verify
no chafing and that it didn't go anywhere else, measured the current
with and without the encoder, and then remarked the fuse holder for 5A.

[Peter Dohm]

"Ray Andraka" > wrote in message
news:IH9Zg.7614$XX2.2429@dukeread04...
> Dave S wrote:
> > Ray Andraka wrote:
> >
> >>
> >> I believe the breakers are supposed to be sized to the wire, not to
> >> the radio. My transponder (was an AT150 with a trans-cal encoder, now
> >> an AT165) has a 5A circuit breaker on it.
> >
> >
> > Ray.. as many others have told me.. you are right.. you size the breaker
> > to the wire.. not the device..
> >
> > But you also size the wire being used.. to the current carried over the
> > distance carried (as the nice lil FAA book shows)...
> >
> > So one sizes the wires to the device,, then the breakers to the wires..
> >
> > In my instance it makes a difference because I have a LOT of 5 amp
> > breakers. For the wire runs involved, a 1, 5 or even 10 amp breaker will
> > protect my wires adequately. But I also dont want to pop a breaker in
> > normal operation.. "while protecting my wiring run"
> >
> > By they way.. thanks for the feedback on the 5A breaker.
> >
> > Dave
>
> I believe Narco has the install manual on their website.
>
> The install manual calls for a 1.5A circuit breaker. They list the power
> requirements as 1.0A receive, 1.6A transmit, 0.26A pilot lights. I can
> tell you that when I bought my airplane, the fuse (changed out for
> circuit breakers since then) for the transponder was marked 1.5A. That
> circuit feeds just the transponder and encoder. I had constant problems
> with it blowing 1.5A fuses, not always but within a couple hours. I
> took it to "the Radio Shop" in Worcester MA, who was a master service
> center for Narco before Narco pulled service in house. They took one
> look at the install, and said the problem is the 1.5A fuse is not
> sufficient for that encoder's heater and that the 1.5A was what Narco
> recommended for just the transponder. They checked the wiring to verify
> no chafing and that it didn't go anywhere else, measured the current
> with and without the encoder, and then remarked the fuse holder for 5A.

You are correct, and thanks for the link which I have now saved.

http://www.narco-avionics.com/

Choose "Manuals and Pinouts" and the AT-150A has a 17 page pdf manual.