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Electronic package ground wire

Dec 28, 2010
462
Catalina 380 san pedro
Hi Maine Sail
I recently decided to upgrade my autopilot from a wheel pilot to a linear drive unit. As well I am installing chartplotter at the helm. My question is this: The installer requested a ground cable directly from my battery bank rather than from my newly installed ground terminal. Is this common practice?

Thanks in advance

Notes: The boat is a 96 Catalina 380 with two 4D gel cell batteries mounted under the deck in the galley area. I ran a new 2/0 ground cable back to the aft lazerette for this installation.
 
May 20, 2016
2,995
Catalina 36 MK1 94 Everett, WA
Sounds like over kill to me. When I put a Raymarine linear drive in my C36 the install manual only spec' d 10ga wire which I ran directly from my CB panel (hot and ground). Work great.
 
Dec 28, 2010
462
Catalina 380 san pedro
Thanks Leslie. I happened to have the 2/0 wire left over from my battery repositioning. My question is about the requirement to have the ground go directly to the battery. I bought 8 ga wire for the linear drive unit. I don't have the manuals yet since I haven't yet seen the units. I'm getting a head start on the wire runs so the install goes quickly.
 
Feb 6, 1998
11,453
Canadian Sailcraft 36T Casco Bay, ME
Electronics positive and negative and ground take off points should be as close to the battery bank as possible eg; positive battery bank bus and negative battery bank bus or it's load side of a shunt if so equipped. Ground should also be placed as close to the battery or the grounding bus as possible. The grounding wire carries no current so a shunt is not impacted.

Wiring as close to the bank as possible helps to minimize voltage transients in the system wiring. One of the biggest mistakes installers and DIY's make is to tap into the dc negative or dc positive anywhere, including the engine. The engine is really one of the worst locations for any electronics to pick up a DC positive or DC negative..
 
Dec 28, 2010
462
Catalina 380 san pedro
Thanks. I did go to great lengths to avoid tapping into the specific engine ground and I isolated the engine thru it's own dedicated ground and then I added a main shut off to the engine itself thru a battery on off switch. He was very specific that the ground should not go to any "bus" but directly to the battery. It just seems to be strange to me. I installed a ground bus bar less than 2 feet from the most distant battery ground terminal but again...he was very specific. I might post some photos if I get a chance.
 
Jun 28, 2005
438
Hunter H33 2004 Mumford Cove,CT & Block Island
You certainly wouldn't connect to battery terminal if you had a battery monitor installed. My guess is the installer wants to minimize the RFI the motor/controller might generate, or to minimize the effects on the autopilot from RFI generated by other equipment. There are other ways to control RFI at the motor/controller, if necessary. A separate ground ran back to the neg bus as you have done, will probably work fine. My background is as a retired EE who designed industrial/aerospace equipment which had to meet and be tested to EMI/RFI standards.
 
Dec 28, 2010
462
Catalina 380 san pedro
:dancing:I installed the new Bus Bar's in the aft lazzerette today. I'll be attaching the terminals back to the DC system over the weekend. I ordered a DC 8 circuit panel from Paneltronics and it should be in next week. It's starting to come together.
 

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