What Fuses on my new switch panel

[thesaintlyone]

So about to order an Axxon 12 switch Circuit Breaker Panel. I can specify which size fuses so which do I get
Requirements I think are gonna be so far:

1) LED Cabin Lights inc Vee & Head
2) 12v Power Sockets Throughout
(One will provide power to a 24" LED TV)
3) LED Navigation Lights Bow & Stern
4) LED Steaming Deck Light
5) LED Mast Head Light poss Tri-Color
6) Nasa Clipper Duet Depth/Speed
7) Rule Bilge Pump
8) VHF Radio
9)
10)
11)
12)

Regards

 

[lw395]

GPS/Plotter?
Car type radio?

I could suggest splitting the lighting so that one damaged cable does not leave you completely in the dark?
Possibly worth fusing the power sockets individually or in groups.

 

[VicS]

So about to order an Axxon 12 switch Circuit Breaker Panel. I can specify which size fuses so which do I get

Presumably you mean " which size circuit breakers do I get?"

This type of panel ?

or

For each circuit select the next available rating above the expected current. Remember that the max safe current for the wiring attached to each must be greater than the trip current Refer to the installation and operating instructions for the various items for recommended "fuse" values.

I'd expect 8 or 10 amp for the VHF
The value for the bilge pump will very much depend on the pump in question. It could be anything from 2.5 amps to 25 amps!
5 amp probably for the various LED light circuits and the Duet
The value for the sockets will depend upon what you will be wanting to power.

Other items you might add include an autopilot, a deck socket for a spot light as well as the items lw395 suggests. I agree with splitting the cabin lighting into two circuits.

 

[thesaintlyone]

This is the exact one

http://m.ebay.co.uk/itm/Marine-Swit...%3A975c220d1590a605a4cb162fffc13439%7Ciid%3A1

Ad says you can specify fuses at the time

 

[thesaintlyone]

What would be the reccomended pump for a 31ft westerly

 

[VicS]

Ad says you can specify fuses at the time

Circuit breakers, not fuses.

The difficulty will be knowing what to specify for any spare positions

 

[prv]

The difficulty will be knowing what to specify for any spare positions

Pick something common, regard it as a fancy blanking plug, and if it later turns out to be the right rating for something you fit, that's a bonus?

Pete

 

[Trundlebug]

I would group all the nav instruments on one fuse, apart from the vhf radio

Additional fuses required for:-

Water pump
Horn
Heater - if you have one
Water tank gauge

 

[VicS]

I would group all the nav instruments on one fuse, apart from the vhf radio

Additional fuses required for:-

Water pump
Horn
Heater - if you have one
Water tank gauge

Horn ?

The OP has a Westerly Longbow not a cruise liner

 

[thesaintlyone]

Yeah my bad not much sleep last night. So what rating circuit breakers do I need

 

[alahol2]

So about to order an Axxon 12 switch Circuit Breaker Panel. I can specify which size fuses so which do I get
Requirements I think are gonna be so far:

1) LED Cabin Lights inc Vee & Head 5A
2) 12v Power Sockets Throughout 20A
(One will provide power to a 24" LED TV)
3) LED Navigation Lights Bow & Stern 5A
4) LED Steaming Deck Light 5A
5) LED Mast Head Light poss Tri-Color 5A
6) Nasa Clipper Duet Depth/Speed 5A
7) Rule Bilge Pump 20A
8) VHF Radio 10A
9) 5A
10) 5A
11) 10A
12) 20A

Regards

 

[Tammany]

Not sure on amperage but you might get a few ideas from this as far as how many you need.

 

[thesaintlyone]

Cheers that helps alot

 

[David2452]

Presumably you mean " which size circuit breakers do I get?"

<pedant on> correctly would be resetable over current devices, but we knew what he meant.

 

[billcole]

Fuses and circuit breakers are there to protect against fires caused by wiring overheating in the event of a short circuit drawing excessive current through the wire. They should, therefore, be sized according to the current carrying capacity of you wiring, not by the current requirements of what is on the end of the wire.

 

[alahol2]

Fuses and circuit breakers are there to protect against fires caused by wiring overheating in the event of a short circuit drawing excessive current through the wire. They should, therefore, be sized according to the current carrying capacity of you wiring, not by the current requirements of what is on the end of the wire.

This is always trotted out in this type of thread and to my mind is only true under certain circumstances. If a piece of equipment is connected to the battery via over spec'd wires then according to this mantra you should over spec the fuse. That's rubbish.
A short within the equipment is just as likely to cause a fire as a short in the wiring. So why use a fuse/breaker that can carry 10/20/50 times the current that the equipment is expected to use?
Wires on a boat are often quite 'long' and I (we?) tend to over specify the wire size in order to minimise the voltage loss over that length. So, because we have over specified the wiring, should we be over specifying the fuses as well?

 

[VicS]

Fuses and circuit breakers are there to protect against fires caused by wiring overheating in the event of a short circuit drawing excessive current through the wire. They should, therefore, be sized according to the current carrying capacity of you wiring, not by the current requirements of what is on the end of the wire.

This is wrong as Aloah2 points out. and is often pointed out by David 2452 who is the forum's professional marine electrician

The fuse or cicuit breaker is there to protect the whole circuit, equipment and wiring alike. Its rating should not exceed the recommended or appropriate value for the equipment. The safe working current rating of the wiring must not be less than the fuse/ circuit breaker rating. Normally the need to minimise voltage drop in 12 volt circuits ensures that the wiring is more than adequately rated.

 

[billcole]

Yes, you're absolutely right,
"The safe working current rating of the wiring must not be less than the fuse/ circuit breaker rating"
was the point I was (not very clearly) trying to make
On my own boat I have (in one or two instances) separate in-line fuses of the correct (lower) rating at the back of pieces of equipment which share a line from the main wiring panel.

 

[[163233]]

Yes, you're absolutely right,
"The safe working current rating of the wiring must not be less than the fuse/ circuit breaker rating"
was the point I was (not very clearly) trying to make
On my own boat I have (in one or two instances) separate in-line fuses of the correct (lower) rating at the back of pieces of equipment which share a line from the main wiring panel.

Sorry, this is still confusing, am I right in thinking that the fuse (and wiring) should be sized marginally above the expected max current draw of the circuit?

So an LED light fitting expected to draw 1 amp max, wired up with 2inch thick 300 amp cables should still get a 1amp fuse on the circuit?

I presume if such a fitting mysteriously started to draw 5 amps I'd want it to trip?

 

[billcole]

The fuse or breaker should be set to trip at a little more than the expected current drawn under normal conditions.

The wiring should be rated for at least a bit more than the fuse/breaker tripping current, but can be rated for a lot bigger current, for example if you want to minimise the voltage that will be dropped over a long cable run, or think you might need more capacity in the future, or even if you just want to buy one reel of chunky cable and use it for all your wiring.

If you run several devices from one breaker on the main circuit with wiring that splits further on, then for best protection each device should have its own fuse or breaker (in the section of the supply wiring that it uses exclusively) rated at a little above its normal current while the main fuse for the whole circuit will need to be of a rating that can supply the total current for all the devices, (this is why mains plugs have a fuse in them as well as the house consumer unit having a fuse or breaker that feeds the whole ring main.)

What you're trying to achieve is that wherever a fault develops which draws an unusually high current then there is a fuse or breaker that blows or trips rather than something else getting hot enough to start a fire.