Advice on Firewall Penetration Wiring Safety

I am about to drill holes in the firewall to run the EMS wiring, battery power lead, grounds, and other possible wires. I would like to know is there a safety issue of combining the power wires with all the EMS sensor wires in the same firewall penetration hole?

I have a large steel fitting that came with the Vans forward kit and I think all the wires will fit through it. If safety is an issue, I can drill a second 1/2 hole to run the power wire exclusively, but I prefer to limit the number of holes in the firewall.

Thanks for all the comments.

PhatRV said:

I am about to drill holes in the firewall to run the EMS wiring, battery power lead, grounds, and other possible wires. I would like to know is there a safety issue of combining the power wires with all the EMS sensor wires in the same firewall penetration hole?

I have a large steel fitting that came with the Vans forward kit and I think all the wires will fit through it. If safety is an issue, I can drill a second 1/2 hole to run the power wire exclusively, but I prefer to limit the number of holes in the firewall.

Thanks for all the comments.

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I can't imagine why there'd be an issue. If there's a short or something in an un-fused circuit that caused the power wire to fail (burn) then it taking out your EMS wring would be the least of your concern.

From a purely technical perspective, running high-current wires adjacent and parallel to small-signal sensor wires is generally a bad idea. Doing so opens up the possibility of coupling nasty electrical noise from the big fat high-current wires into the little small-signal wires.

I ended up with three penetrations. One for engine control cables. One for signal wires. One for power wires. I followed DanH's recommendation to use stainless steel feedthroughs with firesleeve and high-temp caulking compound. At the end of the day, if you execute the feedthrough installation well I don't believe the difference between having one or two feedthroughs is significant in terms of mitigating in-flight fire risk.

Canadian_JOY said:

From a purely technical perspective, running high-current wires adjacent and parallel to small-signal sensor wires is generally a bad idea. Doing so opens up the possibility of coupling nasty electrical noise from the big fat high-current wires into the little small-signal wires.

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Good point. I have not anticipated this issue so I will separate the power wires routing from the sensor wires. I bought the additional FW kits from Aircraft Spruce and they come with firesleave so I should be good in term of actual fire protection.

Thanks