Jump to content

Mid-boat busbars, cable size


Clodi

Featured Posts

I'm in process of rewiring the boat & one of the excellent ideas on here is to install a mid-point fuesbox to facilitate any future installations etc. I want to do this using 30' of cable x2 but also using thick enough cable to cove installing a 12v fridge in the future. Basically I don't yet know what equipment will be run from here yet but does using 10m2 cable like THIS make sense?

Link to comment
Share on other sites

The general rule of thumb for wiring 12V compressor fridges is 1mm2 per metre run. 30’ is about 10m, meaning that 10mm2 would be the absolute minimum for a fridge at that location. Add in the extra connections of a busbar and isolator of some kind plus the possible extra loads and you can see that it’s really too small. I too would go for 25mm2

 

 

Link to comment
Share on other sites

Conventionally all cables go back to the distribution board near to the batteries. A central distribution board is a nice idea, and convenient, but there is potential for volt drops and "crosstalk" between appliances. You might find the lights flicker when the fridge or water pump turns on etc, and there is a risk of increased radio interference from some LEDs and computer power supplies (DC DC converters). I would go for 25mm as a minimum, and might even consider 35mm.

 

For the electrical geeks here...if you have a 12 to 19 computer supply then have a look at the input voltage with a 'scope....its not good ?

 

...............Dave

Link to comment
Share on other sites

1 hour ago, dmr said:

For the electrical geeks here...if you have a 12 to 19 computer supply then have a look at the input voltage with a 'scope....its not good

A little ferrite donut on the feed can help with that. 

Edited by WotEver
Spillung
Link to comment
Share on other sites

39 minutes ago, WotEver said:

A little ferrite donut on the feed can help with that. 

An adroit suggestion WotEver. I'm not sure how it will help though

50ec8f33a9acdd7dbc11401035d1f7ce.jpg

Edited by rusty69
Sorry,sorry, I couldn't resist...I luv donuts .mmmmmm
  • Haha 3
  • Horror 1
Link to comment
Share on other sites

5 hours ago, Clodi said:

I'm in process of rewiring the boat & one of the excellent ideas on here is to install a mid-point fuesbox to facilitate any future installations etc. I want to do this using 30' of cable x2 but also using thick enough cable to cove installing a 12v fridge in the future. Basically I don't yet know what equipment will be run from here yet but does using 10m2 cable like THIS make sense?

I’m planning on adding a more adequate cable from distribution panel to the front of the boat, more for voltage drop reasons than anything else, but am struggling to find a way to feed it/them given that everything is  currently behind stuff that was fitted after the original wiring.

 

How are you planning to feed your new thick wires?

Link to comment
Share on other sites

1 hour ago, rusty69 said:

I know. Boater Sam keeps telling me that, but he ain't here at the mo.

He doesn’t read anything you or me (or loads of others) write anyway so feel free to carry on. ;)

 

  • Haha 1
Link to comment
Share on other sites

6 hours ago, dmr said:

Conventionally all cables go back to the distribution board near to the batteries. A central distribution board is a nice idea, and convenient, but there is potential for volt drops and "crosstalk" between appliances. You might find the lights flicker when the fridge or water pump turns on etc, and there is a risk of increased radio interference from some LEDs and computer power supplies (DC DC converters). I would go for 25mm as a minimum, and might even consider 35mm.

 

For the electrical geeks here...if you have a 12 to 19 computer supply then have a look at the input voltage with a 'scope....its not good ?

 

...............Dave

Not got a scope any more. What is the problem with these units? Cheers.

Link to comment
Share on other sites

17 minutes ago, catweasel said:

Not got a scope any more. What is the problem with these units? Cheers.

Not really a problem but they do take the electricity in little gulps. Mine are on the end of quite a long dedicated cable run and they do corrupt the voltage quite badly, it drops very low on every gulp. We are talking very high frequencies here, its a potential problem rather than a serious issue.

 

Voltage drops on 12 volt wiring can be a bit troublesome. All my CD's are on the laptop and this connects to the "car stereo" which is some way away via a USB souncard. I had loads of background noise due to volt drops on the negative and had to fit an audio isolation transformer to fix this. Of course the central distribution idea might actually be better in this case.

 

...............Dave.

Link to comment
Share on other sites

12 minutes ago, dmr said:

Not really a problem but they do take the electricity in little gulps. Mine are on the end of quite a long dedicated cable run and they do corrupt the voltage quite badly, it drops very low on every gulp. We are talking very high frequencies here, its a potential problem rather than a serious issue.

 

Voltage drops on 12 volt wiring can be a bit troublesome. All my CD's are on the laptop and this connects to the "car stereo" which is some way away via a USB souncard. I had loads of background noise due to volt drops on the negative and had to fit an audio isolation transformer to fix this. Of course the central distribution idea might actually be better in this case.

 

...............Dave.

Thanks for explanation :)

Link to comment
Share on other sites

I used to wire new hire fleet boats and repair private boat electrics. I would suggest two or even 3x  25mm cables to your central distribution. If you under estimate now you can be faced with the difficult job of later additions. Far better to fit bigger now. This is what we used to do on all the hire fleet and I rewired several private boats with dull lighting problems and it made a vast difference with only the cost of a bit more cable.

Link to comment
Share on other sites

I have a central distribution point on my boat. It uses 10 mm cable, and runs my fridge and galley lights etc. BUT mine is half the length you are considering. I have checked volt drop and it is ok, but I wouldn't put much else on it. Yes the lights flicker when the fridge cuts in but only a brief dip.

All in all I agree that a bigger cable is needed. Also if you are likely to be annoyed by flickering lights then never put them on the same feed as a fridge  (or any pump) because the initial surge is always going to make lights flicker.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.