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  #1  
Old 08-04-2018, 06:55 PM
AviatorJ AviatorJ is offline
 
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Location: Oklahoma City
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Default Breaker Sizing

I'm to the point now where I'm splitting my harness power wires for installation into the VPX. I had previously set up my VPX CB size using their Planner tool and have made adjustments to that over the years. The harness I received from Stein has the power leads labeled with a Amp number on them as well. However the Stein info isn't lining up with the VPX Planner info or the Garmin G3X installation manual.

Here's an example; GSU 25 (ADAHRS) in the VPX Planner is set as .2A actual draw with a CB size of 1.0A, On the Stein label it's labeled as 2A, and the Garmin doc it's listed as .2 as well. Maybe Stein meant, .2 but for the GEA 24 (EIS) Garmin docs have .43A max but Steins label says 5A.

My thought is obviously use Garmin documentation to ensure proper sizing, plus a 20% margin. I just wanted to make sure I'm not missing anything.

I'm also going to have to combine some items as well as put a few items on a fuse block. When I combine them, like say the Autopilot stuff, GMC 507 and three GSA 28, what is the best way to size that?
GMC 507 .2A
GSA .36 (Typical), 1.8A (Max), 2.8A (Max with 1 Amp trim motor at full load). Multiplied by 3 it's - 1.08A, 5.4A, 8.4A.

So do I take the highest load possible at 8.6A, add the 20% for at least a 10A CB? OR is it typical load, 5.6A with a CB of 7A rounded up?
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  #2  
Old 08-04-2018, 07:31 PM
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JonJay JonJay is offline
 
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Fuses and CB's are sized to protect the wire, not the device(s). You can downsize based on connected load, or if the device installation instructions state something smaller to be placed inline.
I would follow Steins labeling. He has done this a few times before

Ganging devices is ok, just make sure you size to protect the wire and add in protection or a separate circuit if the device calls for it.

Hope that makes sense.
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  #3  
Old 08-04-2018, 09:09 PM
AviatorJ AviatorJ is offline
 
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Going to have to rework some of my VPX stuff. I get that breakers are there to protect the wires but with the VPX you’re limited somewhat on breakers of various sizes. So if I can get away with using a 5 amp vs a 10 amp that helps me out.
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  #4  
Old 08-04-2018, 09:45 PM
TShort TShort is offline
 
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I did what you mentioned - I put some of the "less critical" devices with low draw and not much need to "monitor" with the VPX on a fuse block - like the GDL52R, the CO monitor, etc. Super easy to do, and with the current EFIS screens access to the fuse block etc is wide open and easy to get to.

[not to say the CO monitor isn't important ... but it has its own status light]
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  #5  
Old 08-04-2018, 11:11 PM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by AviatorJ View Post
Going to have to rework some of my VPX stuff. I get that breakers are there to protect the wires but with the VPX you’re limited somewhat on breakers of various sizes. So if I can get away with using a 5 amp vs a 10 amp that helps me out.
The breaker/fuse size may be to protect the wire, but if a specific wire is protected by a 10A breaker, that same wire will be equally protected by a 5A breaker, whether it is inside a VPX unit or a stand-alone panel item.

In my case I'm planning to go with the VPX numbers and the manufacturers current (amps not time) data.
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  #6  
Old 08-04-2018, 11:50 PM
AviatorJ AviatorJ is offline
 
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Quote:
Originally Posted by az_gila View Post
The breaker/fuse size may be to protect the wire, but if a specific wire is protected by a 10A breaker, that same wire will be equally protected by a 5A breaker, whether it is inside a VPX unit or a stand-alone panel item.

In my case I'm planning to go with the VPX numbers and the manufacturers current (amps not time) data.
I've been digging around a bit in more detail. Stein was right about the G5 and the 245 (Audio Panel). Garmin suggests 5 amps breaker on both these. So I'll go with that.

I just have a lot of stuff, using up all my 10-15 amp breakers. I'm going to give it another hard go through and see what I can combine, or move to the 15A fuseblock I'm using.
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  #7  
Old 08-05-2018, 08:58 AM
AviatorJ AviatorJ is offline
 
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Need some help now working through my logic. When I run into issues of uncertainty I hyper focus until I resolve them. So I spent last night and this morning making a spreadsheet, doing some pivots and running amp tests in my garage.

Here's the crux of my issue, I have 10 items right now that are listed as needing 10 or greater circuit breaker. The problem being the VPX pro only has 9 10-15A pins available. So I need to shed one of the big ones listed below, somewhat in order of importance;
  • GTN 650 Comm 8A (Has to use a 10)
  • GTN 650 Nav 10A
  • Comm#2 8A (using a 10)
  • Pitot/AOA 15A
  • Boost Pump 10A
  • Strobes 15A (Might be able to use a 10A)
  • Landing Light Left 10A
  • Landing Light Right 10A
  • IBBS 10A
  • AccBlock 15A

I can't really touch the GTN, the GTR 20 (Comm#2), Pitot or Boost pump.

Getting into the lights the Strobes use a 10-15, I'll go with a 15 and walk it down if I can in the VPX. But AeroLED manual basically says give 5A to each light, 2 wings and 1 tail. Each Landing light is drawing 5.20 per my test in the garage. I really want the VPX to control Wig-Wag/Recog for the Vspeed feature so each light needs a 10A pin. Changing this would free up several pins but then recog becomes a manual process. It's doable just want to avoid it.

Here are the two items I think I can mess with, the IBBS and my accessory block. Now the IBBS utilizes a 10A pin for essentially charging since I'm not doing any pass-through power. That being the case would it make sense to add this to the 15A accessory block and use a 10A fuse blade?

The accessory block is a 12 place fuseblock that I'm hanging a bunch of random stuff off. For the most part low power items like oil damper, cowl flaps and things of that nature. The only items that could potentially max out the amps are the USB ports. I ran a test, seems an iphone uses about .7A and an Ipad uses about .9A, so if I had 4 Ipads plugged in I'm pushing about 3.6A. If I had 4 devices plugged into all the USBs at once with power, all while working the cowl flaps, ram air, oil damper and all the lights on... So 15A might be over kill here. Maybe I make this a 5A and control what's getting plugged into the USBs and when.

My other thought is hang the two USB chargers off the Pass-through power on the IBBS, this would allow me to easily make the AccBlock a 5A circuit.

So I guess what it comes down to is do I put the IBBS on the AccBlock or do I work through the reduction in Accblock size by pushing some stuff through the IBBS pass-through? (Leaning heavily towards putting the two dual USB Chargers off the IBBS Pass-through)
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Last edited by AviatorJ : 08-05-2018 at 09:14 AM.
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  #8  
Old 08-05-2018, 04:30 PM
Paul Thomas Paul Thomas is offline
 
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I haven't look at amps requirements for lights but those seem high; have you looked into using lights that are more efficient?
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  #9  
Old 08-05-2018, 04:58 PM
AviatorJ AviatorJ is offline
 
Join Date: Feb 2015
Location: Oklahoma City
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Quote:
Originally Posted by Paul Thomas View Post
I haven't look at amps requirements for lights but those seem high; have you looked into using lights that are more efficient?
In too deep on those lights. I've already done the wingtip mod for the VX's and have the lights sitting in my garage. I thought it seemed high as well but when I put some current through them and metered them out it was 5.2A each. So a 6 amp would have worked but the VPX goes 5-10A so I'll have to use a 10A and bring it down to 6ish.
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  #10  
Old 08-10-2018, 03:14 PM
OGee OGee is offline
 
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Location: Lakeway, TX
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Looking for comments regarding my IBBS - VPX wiring diagram. Will it work? Is there a better way? Thanks.

https://drive.google.com/file/d/19kc...ew?usp=sharing
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