Jumping a Sterling Battery Charger

Bob S

.
Sep 27, 2007
1,804
Beneteau 393 New Bedford, MA
Can anyone shed some light on what just normal 110v AC cable earth means? I just don't want to undersize the chassis ground.I have both 8 ans 12awg wire available in green. If 12awg is OK I'd prefer to use it.
It's nice to see Mr Sterling answering email questions. Thumbs up to Sterling!

Hi Bob,

The AC chassis earth can be just normal 110V AC cable earth.
The negatives and positive cables only need to be 10 gauge at max.
So, 4 gauge is fine for the positive.

Thank you for your inquiry,
Charles Sterling Junior

Sterling Power Products Ltd.
Unit 8, Wassage Way, Hampton Lovett Industrial Estate
Droitwich WR9 0NX United Kingdom
Tel: +44 (0)1905 771771
Fax: +44 (0)1905 779434
email: charles@sterling-power.com
Web: www.sterling-power.com



From: Bob Smith [mailto:bsmith@ssmach.com]
Sent: 12 April 2016 17:45
To: charles@sterling-power.com
Subject: Sterling Pro Charge Ultra
I am installing your 30a charger on my sailboat. The manual gives me wire size recommendations for the AC input and the DC output. (I am running 4awg on the DC side because my run is close to 30’ round trip). It does not recommend a wire size for the chassis ground. I have 8 and 12 awg green wire. Would either of these be OK?
Thank you,
Bob Smith
1995 Catalina 30 MK III Hull# 6324, Lovely Lady
Buzzards Bay, Massachusetts
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
i used # 10 tinned copper stranded for the ground but #12 would be ok ...it meets the 20 amp ac requirement as far as the dc cable i used #4 on my 40 amp dc charge cable to the batteries and fused it with an 80 amp fuse ...the cube type that goes on the post connecter
 
Feb 6, 1998
11,709
Canadian Sailcraft 36T Casco Bay, ME
Looks like you got Junior who failed to look up the requirements...

Chassis ground sizing is an ABYC standards requirement. I fully address this in my article on installing this charger.

Chassis ground can not be any smaller than one size below DC positive. So if you are using 4GA neg then you'd need 6GA chassis. Bottom line is the chassis ground needs to be able to carry full fault current from the DC side not just AC and the standards allow for, via an "exception" one wire gauge smaller than DC neg...

"ABYC A-31
31.6.5 DC GROUNDING CONNECTIONS

31.6.5.1
The DC grounding conductor shall,

31.6.5.1.1
be connected from the metallic case or chassis, to the engine negative terminal or its bus, and

31.6.5.1.2
shall be of an ampacity equal to that of the DC positive conductor.

EXCEPTION: The DC grounding conductor may be one size smaller than the minimum size conductor required for the DC current carrying conductors (see ABYC E-11, AC and DC Electrical Systems on Boats, “Allowable Amperage of Conductors For Systems Under 50 Volts”) providing the overcurrent protection device in the DC positive conductor is rated no greater than 135% of the ampacity of the DC grounding conductor and the conductor is no smaller than 16 AWG."
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
guess i will be changing the case ground to a larger size today thanks for pointing that out MS
 

Bob S

.
Sep 27, 2007
1,804
Beneteau 393 New Bedford, MA
Thanks Maine! I knew I read it somewhere but couldn't find it. I read and re-read your article but only scanned it looking for the size. What an asset you are to the sailing/boating community.