Sizing the CB needs... Homebuilt wiring too

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

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

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.

"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.