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Combining Power Grounds?


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The manual has a very explicit warning not to combine the power grounds.

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However I'm planning to go from the cabin through a bulkhead connector into the engine bay and I'm trying to reduce the number of pins required.

  • Can they be combined on the other side of the connector in the engine bay with an appropriately sized wire which then goes to the engine block?
  • Am I safe to do the same with both connectors so 4 wires into 1 pin?
  • Or run each wire all the way, so 4 pins required on the bulk head connector.

 

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It should be ok through a single pin provided it can handle the current with a good safety margin above steady state to allow for in-rush and minimal voltage drop etc.  An Xtreme for instance, 10 aux outputs capable of 2A each, 8 inj drives capable of 5A each = 60A total ground current fully loaded  = unlikely to work through a single ground pin...

However if you only have 4 x injectors that pull 1A each and a few auxes pulling 0.5A then a single ground pin would be fine.

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22 hours ago, Adamw said:

It should be ok through a single pin provided it can handle the current with a good safety margin above steady state to allow for in-rush and minimal voltage drop etc.  An Xtreme for instance, 10 aux outputs capable of 2A each, 8 inj drives capable of 5A each = 60A total ground current fully loaded  = unlikely to work through a single ground pin...

However if you only have 4 x injectors that pull 1A each and a few auxes pulling 0.5A then a single ground pin would be fine.

Thanks.

How do the standard wires handle 60A? My understanding was they were 22 AWG so around 7A each = 28A total which is quite a bit less then the 60A max?

6 hours ago, Leo Malcolm said:

Was the intent of that "DO NOT JOIN" warning mostly so that someone doesn't combine too small of a gauge wire to all the power ground wires or was it more for noise immunity? Just intrigued.

I'm also curious about this as well.

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2 hours ago, Hyperblade said:

How do the standard wires handle 60A? My understanding was they were 22 AWG so around 7A each = 28A total which is quite a bit less then the 60A max?

The ground wires on the Link looms are 18awg, 120°C rated, so will handle about 15A each.  Obviously my 60A example was stating the worst case example so that you or anyone else that reads this post in future has good information to base their decisions on.  It would be very rare in real life to ever have a scenario where every output is running at 100% DC all at the same time but with power wiring it is important to consider what you have connected, the maximum DC/loads, the wire lengths, the insulation temperature rating and the amount of voltage drop that you consider is acceptable.  I have seen many fails in my time where the installer has assumed because the ECU works fine with a 5A fuse that they only need a ground capable of 5A.  

 

8 hours ago, Leo Malcolm said:

Was the intent of that "DO NOT JOIN" warning mostly so that someone doesn't combine too small of a gauge wire to all the power ground wires or was it more for noise immunity? Just intrigued.

All ground pins are connected internally to the same ground plane so I cant think of any electrical theory reason to do so, I suspect this is more just a statement that was made to encourage installers not to take shortcuts on arguably the most important wires.  

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