If this is not done in the right way there is a risk of fire or serious damage or, probably less dramatically, a single fault could take down more systems than is should do, perhaps everything.
Protection can be with traditional fuses of various types or with circuit breakers (CBs) or more often a combination of both with CBs often for circuits for medium currents and fuses for low and very high currents, CB's can be less effective for the former and expensive for both.
Batteries, or battery banks, should have primary protection from shorts on major cables etc, they will normally be of the "ANL" type, be placed as close to the battery as possible and be in a dedicated fuse holder, it is tempting to put the fuse directly onto the battery but the fuses are vulnerable to vibration or stress and if it fails you are without power so is rather risky. Holders can be for a single fuse or several, the later may be useful for a master fuse plus the individual fuses on several branches (see below) but may not be appropriate for multiple batteries (e.g. the starter and service battery) as one will inevitably require an over long cable which would be unprotected.
In the picture below (click to enlarge) FB2 (left above the battery) is the fuse for the main service / domestic bank (for reasons explained elsewhere I have two service banks, the 2nd bank has the same type of fuse and holder located by the battery).
|Sancerre's main power distribution panel. Not as neat as I |
would like but not bad given growth, space etc.
- 1 x 25mm2 cable + 1 x 10mm2 cable = 35mm2 can used instead of a 35mm2 or
- 2 x 25mm2 cables = 50mm2 = 2 x 170 Amp rated capacity and is OK for charging between 85 & 180 Amps over 1.5 - 4 metres and gives more headroom at lower currents.
This is where you may need to get professional help, I have not researched the legal aspect of working with mains power on a boat (the safety issues should be obvious!) but on land some electrical work MUST be carried out by a "competent person" as I am qualified to HNC level in electrical and electronic engineering I consider myself a competent person so did not research this. I suspect that because the shore power system is all behind a plug and socket this does not apply but I have not confirmed that.
I also suspect that the initial fit of Sancerre's shore power was not done professionally because there was no consumer unit, CB's or fuses! The CB's at least are essential and the consumer unit is where you put them. CB's should be 2 pole and you should have both MCB and RCCB/RCD types, a consumer unit with a reverse polarity indicator is probably worth having but in UK a marina is very unlikely to suffer from this, things could be different elsewhere. Chandlers to not generally stock these but they are easily obtained from suppliers to caravaners who have the same issues, I got mine on eBay.
|Sancerre's shore power installation.|
I strongly recommend fitting a galvanic isolator / zinc saver, for more on this see my post How to turn a 3 hour job into a 3 day one - upgrading the Battery compartment wiring. (opens in new window).