GDL 82 for my Sky Arrow?

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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MrMorden
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Re: GDL 82 for my Sky Arrow?

Post by MrMorden »

For the record, I was not saying you can't size CBs to twice the rated load of devices, and I'm agnostic on how you size CBs.

What I'm saying is you can't appropriately size a CB unless you know the amp rating of the wires behind it. If you have your GDL-82 connected with 10 gauge wiring, a 50A breaker might be safe. If you use 26 gauge wire, 3A might be too much. The breaker has to be sized to the wire, not to the device requirement...
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TimTaylor
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Re: GDL 82 for my Sky Arrow?

Post by TimTaylor »

Seems to me you would size the wires and breaker to meet the requirements of the device.
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MrMorden
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Re: GDL 82 for my Sky Arrow?

Post by MrMorden »

TimTaylor wrote:Seems to me you would size the wires and breaker to meet the requirements of the device.
That is the best way...figure the device requirements, then size the wire & breaker to suit. But in this case we're discussing of adding a new device to an existing breaker, it takes a little more thought to make sure it's a good setup.
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TimTaylor
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Re: GDL 82 for my Sky Arrow?

Post by TimTaylor »

MrMorden wrote:
TimTaylor wrote:Seems to me you would size the wires and breaker to meet the requirements of the device.
That is the best way...figure the device requirements, then size the wire & breaker to suit. But in this case we're discussing of adding a new device to an existing breaker, it takes a little more thought to make sure it's a good setup.
Agreed. I would run separate wiring and breaker, unless it's such low draw it doesn't matter.
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ShawnM
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Re: GDL 82 for my Sky Arrow?

Post by ShawnM »

MrMorden wrote:
TimTaylor wrote:Seems to me you would size the wires and breaker to meet the requirements of the device.
That is the best way...figure the device requirements, then size the wire & breaker to suit. But in this case we're discussing of adding a new device to an existing breaker, it takes a little more thought to make sure it's a good setup.
Yup and dont forget to factor in the length of the wire as this will need to be in the equation also so the wire doesn't melt. :shock: The device only draws 0.5A max so it is a minimal load but still there's math to be done.
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drseti
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Re: GDL 82 for my Sky Arrow?

Post by drseti »

MrMorden wrote: The breaker has to be sized to the wire, not to the device requirement...
Actually, all three (wire size, breaker current, and device load) are all inexorably linked. AC 43-13 has tables for determining the wire size required for a given load. Once you've chosen the right wire, you can then select the appropriate circuit breaker. There's a bit of convoluted (iterative) math involved - which is why they pay us engineers the big bux!
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Re: GDL 82 for my Sky Arrow?

Post by proemer »

My GTX 327 xponder is rated at an input of 15 Watts, typical, 22 watts max. (or well under 2 amps on a 14 V system). On the ground or in flight I've actually measured it (with alt encoder) at 1 to 1.5 amps.

So... it looks like adding the -82 to a 5 A breaker is possible, although as others have stated wire size, length, etc all are factors to be considered.

Pete
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