Grounding-Dedicated drain wire for ACU-100

[marchem]

The installation manual for the ACU-100 says to install a dedicated drain conductor (screen) to the vessel RF ground point (which in my case would be the negative battery terminal). I'm trying to figure out just what it is for, and why such a large conductor is called for (>#8 AWG for run >1 m). It seems to me that the actual connection at the ACU-100 won't take wire larger than #12!

[marchem]

Bumping this up with the hopes of getting a response. Basically I'm trying to figure out the purpose of the drain wire, and how critical it is on a sailboat installation.

Also wondering what size wire (or % voltage drop) is considered ok for the ACU-100. I'm thinking #10 for a <15' run.

[Chuck - Raymarine - Moderator]

marchem,

The drain (“screen” or “RF ground”) wire provides a ground return for noise and transient disturbances on the power supply that could interfere with the ACU-100 - the larger the drain wire, the lower the impedance and the more effective the connection will be.

The installation guide gives a preferred minimum drain wire size, for all ACU types, of 8awg for runs of >1m. This is based on the ACU-200/300/400 which have a crimp terminal connection for the drain wire that can handle this wire size. Unlike the ACU200/300/400 the ACU-100 uses a sealed connector (for above-decks use) that accepts 12awg (2.5mm2) max - this is the preferred drain wire size for the ACU-100.

[marchem]

Makes sense. I'll run a separate #12 for the shield.

[Chuck - Raymarine - Moderator]

You're welcome.

[daknecht]

I installed an EV-100 (ACU100) last year and was confused by the ground drain wire.
1. There is also a ground drain wire on the Seatalkng network, but that is a tiny wire. So how to join this to a #12 drain wire to the ACU-100 or do those need to be separate?
2. Why can't these be tied to the negative wire since that also goes back to the engine/battery ground?

[Chuck - Raymarine - Moderator]

daknecht,

Please click here to view a FAQ addressing this subject. The bare wire lead within a SeaTalkhs Power Cable is its drain lead. Should drain leads from more than one closely located products need to be joined, then you may want consider using a bus bar.