Planning a new electrical installation: couple of questions

[steve yates]

Once I have ripped everything out of my longbow, I’ll start rebuilding my electrics, having changed where the panels, batteries and cable runs will be.
My initial questions are
1) Are there any items which would not go through a main switch or breaker panel, but be connected directly to the battery bank? Or to their own seperate switch/nreaker, so far I have the bilge pump in my head and the engine witing which would go the engine start panel. ( i’m leaving all that in place)
on my little boat the planar heater is directly connected to the battery, but I dont think it has to be?
2) are there any cables which should not be bundled together in a cable run? and is there any rule of thumb on how many cables bundled together are too many?
3) Seems to me I can have a fused switch panel, or a breaker switch panel, or a switch panel connecting to seperate fuse blocks with labelled blade fuses, are there any particular advantages too one or the other?
I’m expecting there to be up to 24 switches ( if each load had their own switch which isnt of course necessary)
4) This might sound a daft question, butif iput in an nmea2000 network, is that just a communications network between devices or does it provide power to them also. In other words, are those devices still wired to a switch panel in the normal way if using the nmea backbone. I presume so but want to double check.
Thanks.

 

[Sandy]

Lets try and answer a few of your questions having rewired my own boat, and still not finished!

1) Are there any items which would not go through a main switch or breaker panel, but be connected directly to the battery bank? Or to their own seperate switch/nreaker, so far I have the bilge pump in my head and the engine witing which would go the engine start panel. ( i’m leaving all that in place) on my little boat the planar heater is directly connected to the battery, but I dont think it has to be?

Very much up to you what items you don't want to switch. My engine starter does not go through the switch panel, but does go through the master switch.

2) are there any cables which should not be bundled together in a cable run? and is there any rule of thumb on how many cables bundled together are too many?

Nope, but have you considered using multi cored cable as this allows for fewer runs, e.g. I have a three core cable serving the masthead lights. Common negative and a positive for the trilight and the anchor light. Make sure the total amps do not exceed what the cable is rated for.

3) Seems to me I can have a fused switch panel, or a breaker switch panel, or a switch panel connecting to seperate fuse blocks with labelled blade fuses, are there any particular advantages too one or the other?
I’m expecting there to be up to 24 switches ( if each load had their own switch which isnt of course necessary)

I went for a breaker switch panel as it meant that I did not need to carry a whole bunch of fuses. There are other fuses in the system including a mega fuse on the house bank and starter battery. ALL fuses are blade, why carry different amperage and types?

4) This might sound a daft question, butif iput in an nmea2000 network, is that just a communications network between devices or does it provide power to them also. In other words, are those devices still wired to a switch panel in the normal way if using the nmea backbone. I presume so but want to double check.

Most devices are powered by the NMEA2000 network, but not all, e.g. NOT my Garmin Chartplotter, but the depth sounder, wind sensor and associated instrumentation is. I've added a NMEA2000 barometer and air temperature sensor that display on the chart plotter as they are cheaper and more accurate than the posh brass kit!

Enjoy the frustrating job of rewiring, you will learn lot of new swear words, ache in all sorts of places and get covered in bruises. Best warn your partner otherwise some odd questions will be asked!

 

[Tranona]

Question 1. Bilge pump is common to wire direct, particularly if it is automatic. Also common to wire VHF direct, although I did not do that. Better not to wire direct to batteries, but to have either an "always on" terminal box, or more commonly have a common -ve bus bar and a +ve bus bar for the house bank and connect to those. This also makes it easier to connect things like a mains battery charger and reduces the number of connections direct to the battery. BTW I assume you are going to keep the house and engine start separate.

Question 3. 24 individual fused circuits is far too many - I have a 16 way panel for a similar sized boat. You can group some devices/circuits together and use mini distribution panels to break down to the individual devices. For example all my interior lights are on one switch and I have grouped "navigation" - GPS, chart plotter and AIS on one. Not much to choose between blade fuses and breakers - I chose the former because that is what was used on the panel that suited my layout. If you go for ready built panels then Blue Sea are good but expensive and don't have a huge range. I used Axon who have a huge range axoncontrol.co.uk. Good quality switches, well made and reasonably priced.

Question 2 already covered. Can't help on NMEA as have not gone that route.

Echo Sandy's last sentence. Enormously time consuming job and no matter how much you plan in advance you will learn and modify as you go along

 

[steve yates]

Yes I’m going to have a sep engine start battery, and maybe a windlass battery too, as I might have an empty ready built battery box location in a locker.

What is a distribution panel? As opposed to a switch panel? Good tip on the axiom stuff, I had already discounted blue sea panels by the prices.

 

[LadyInBed]

Whichever type of fuse / breaker panel you use, I would recommend having a couple of switches spare to allow for future expansion or for a used switch becoming faulty.

 

[thinwater]

Solar is typically direct.

Ofcourse, not everything needs a separate panel switch. They don't at home or in your car. Just a good accesible switch, and of course no more than 15 amps per circuit when everything is on (even if that is very unlikely).

 

[Tranona]

Yes I’m going to have a sep engine start battery, and maybe a windlass battery too, as I might have an empty ready built battery box location in a locker.

What is a distribution panel? As opposed to a switch panel? Good tip on the axiom stuff, I had already discounted blue sea panels by the prices.

Switch panel has the fused +ve switches for each named circuit. I used the term distribution panel to describe the little panels I made up, mostly using Wago connectors to break a circuit down to individual devices. Look at the photo I posted on your other thread to see example. Not the only way of doing it - I have used Blue Sea terminal blocks in the past.. With my interior lights I have 3 circuits already installed, which I kept as the cables were sound and running new cables through bulkheads and along deck beams would be a mammoth task, I again made up a board with 2 5 way Wagos (one for +ve, other for -ve) to link them together to one fused switch on the switch panel.

Two schools of thought on windlass batteries and much depends on the actual windlass power requirements and the relative location of the main batteries to the windlass motor. If you use the house bank you have to run heavy cables forward, size of which depends on the power of the windlass and the distance between them (length of cable run). The windlass maker will give a table to work out the size of cable required. Advantage is that you don't need the cost and weight of an extra battery plus a means of charging the battery. Downside is cost and difficulty of running heavy cables through the boat. I chose the bow battery route, partly because the battery was already there and partly because I wanted to add a bow thruster that could use the same battery. Charging is via a B2B 30A charger from the start battery which only needs 6mm cable rather then the 35mm or more that direct wiring from the house bank to the windlass needs. The cost of the B2B route plus battery is often much the same as the heavy cables.

 

[Kelpie]

I like to have the heater wired directly to the battery (with its own fuse and isolator).
They have a cool down cycle which is an important safety feature, so power should never be inadvertantly disconnected, which could potentially happen if wired in to the main domestic isolator.
It's just a best practice thing really, to make it slightly more idiot proof.

 

[Tranona]

That is how the Wallas heater was wired when I got the boat, but have removed the heater because it was badly installed with the heater itself in the cabin despite the instructions clearly stating it should not be! Also common to wire electric toilets independently. Rather than go back to the battery though makes sense to have a bus bar for the house bank +ve and a common -ve bus bar rather than clutter up the battery terminals.