St4000 - wiring and voltage drop

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum James,

As a best practice, it is recommended that autopilots be installed on a dedicated power circuit. When determining the appropriate gauge of wire for a given amount of current, it is important to understand that it is the round trip circuit (i.e. from the battery/power supply to the device being powered and then back to battery/ground) which must be considered. As such 14 AWG reduce the power supplied over the round trip distanced involved. Please see the table from Blue Sea Systems below addressing this subject:



In this case, I would have recommended that either 12 or 10 AWG (preferred) be used. It is also recommended that an clamp meter (instrument capable of sensing current (ex. Extech 400A Dual Input AC/DC Clamp Meter + NCV) to measure the current draw of the pilot under various operating conditions.