A
Anonymous
Guest
Hear, hear!
What cable/wire for electrics
- Thread starter lockwood
- Start date
scuby
New member
Here are a few points arising.
I would prefer to use min size 1.5mm with a good insulation, preferably 2.5mm for a tricolor, tri-rated is ideal.
Why? Firstly all cables should be mechanically robust to prevent chafing and secondly if you do get a short the cable must be able to carry sufficient current to trip the breaker or blow the fuse. I have been doing some tests and breakers rated at 10a may trip at 20a but more likely higher. The earlier example suggests 1mm cable with a 35m run with a resistance of about 1 ohm. Using v/(IR) 12/1.0=12 amps will flow for a dead short which should trip a 3a breaker but will not trip a 10a breaker, it would probably just smoulder. Be warned, I have a breaker here, rated at 10a that doesn't trip below 25a.
American wiring regs specify a maximum of 3% drop for important circuits and 10% for non critical circuits. I recon being seen is quite important.
Corroded joint are a real problem, a faulty splice can happily smoulder away without ever blowing a fuse so minimise joints.
Crimped joints are fine but you must test them even with a ratchet tool they will sometimes pull out and I have had regular failures on high current application. I use non insulated crimps (with an insulation boot) which I then solder and seal with adhesive lined heatshrink in wet areas.
Tinned wire is great but very expensive, perhaps that is why many boat builders don't use it.
Back to the original question, you could consider a length of 2.5mm artic grade PVC insulated flex would be a reasonable choice for the mast as it is rugged, flexible and double insulated but not tinned.
I would prefer to use min size 1.5mm with a good insulation, preferably 2.5mm for a tricolor, tri-rated is ideal.
Why? Firstly all cables should be mechanically robust to prevent chafing and secondly if you do get a short the cable must be able to carry sufficient current to trip the breaker or blow the fuse. I have been doing some tests and breakers rated at 10a may trip at 20a but more likely higher. The earlier example suggests 1mm cable with a 35m run with a resistance of about 1 ohm. Using v/(IR) 12/1.0=12 amps will flow for a dead short which should trip a 3a breaker but will not trip a 10a breaker, it would probably just smoulder. Be warned, I have a breaker here, rated at 10a that doesn't trip below 25a.
American wiring regs specify a maximum of 3% drop for important circuits and 10% for non critical circuits. I recon being seen is quite important.
Corroded joint are a real problem, a faulty splice can happily smoulder away without ever blowing a fuse so minimise joints.
Crimped joints are fine but you must test them even with a ratchet tool they will sometimes pull out and I have had regular failures on high current application. I use non insulated crimps (with an insulation boot) which I then solder and seal with adhesive lined heatshrink in wet areas.
Tinned wire is great but very expensive, perhaps that is why many boat builders don't use it.
Back to the original question, you could consider a length of 2.5mm artic grade PVC insulated flex would be a reasonable choice for the mast as it is rugged, flexible and double insulated but not tinned.
SlowlyButSurely
Active member
When I wired up my boat I found that the biggest current was required by the fridge which needed 8amps at 12v. My local Lucas depot told me that 2.5mm wire would do the job, so I bought a large reel of twin core 2.5mm cable (as used for cars) and wired everything up with that (except for the battery and alternator cables).
2.5mm cable is a nice size to work with and when you've crimped on a connector you can be confident that it's a good strong joint. The other benefit of using the same size cable for everything is that all terminals are the same size.
18 years later it's all as good as new.
Good luck!
2.5mm cable is a nice size to work with and when you've crimped on a connector you can be confident that it's a good strong joint. The other benefit of using the same size cable for everything is that all terminals are the same size.
18 years later it's all as good as new.
Good luck!
towzer240
New member
try looking on the reading college web site, if you do a search u will find a link.
it should answer all your questions.
it should answer all your questions.
G
Guest
Guest
You have started the debate of the century
This topic is second only to Anchors .... and just marginally ahead of Battery systems.
You will hear about domestic cable with single copper wire being unsuitable - I've wired 3 boats with it and they still have all working fine after god knows how many years, you will hear all sorts about wiring kits from marine outlets etc. etc., you will hear about grounding and bonding ..............
The list will go on and on etc.
Me - B&Q was fine, MCB's in a consumer box, twin and earth cable .... to me if it could supply my fan heater at home of over 2KW .... then surely it could take the load on a boat !! And OH Dear ...... here I will be shot at dawn - it is NOT bonded to the shaft / engine / DC system etc. It is isolated. Only time it could ever have any chance of bridging the systems is if the charger ever developed a short across the 240 to 12 ...... but of course the MCB's would kick out ..... never had a problem ....
This topic is second only to Anchors .... and just marginally ahead of Battery systems.
You will hear about domestic cable with single copper wire being unsuitable - I've wired 3 boats with it and they still have all working fine after god knows how many years, you will hear all sorts about wiring kits from marine outlets etc. etc., you will hear about grounding and bonding ..............
The list will go on and on etc.
Me - B&Q was fine, MCB's in a consumer box, twin and earth cable .... to me if it could supply my fan heater at home of over 2KW .... then surely it could take the load on a boat !! And OH Dear ...... here I will be shot at dawn - it is NOT bonded to the shaft / engine / DC system etc. It is isolated. Only time it could ever have any chance of bridging the systems is if the charger ever developed a short across the 240 to 12 ...... but of course the MCB's would kick out ..... never had a problem ....
G
Guest
Guest
Little confused here ....
<<Say you have around 35m of cable there and back,>>
Why there and back ? Most cable runs for mast lights are a single cable - not a ring-main system ? EG - Mast of 30ft high = cable of 30ft to match mast + bit to exit to light, bit to exit bottom to socket ..... where is the other 30ft ????
<<Say you have around 35m of cable there and back,>>
Why there and back ? Most cable runs for mast lights are a single cable - not a ring-main system ? EG - Mast of 30ft high = cable of 30ft to match mast + bit to exit to light, bit to exit bottom to socket ..... where is the other 30ft ????
towzer240
New member
Re: Little confused here ....
the formula for working out cable size is as follows--
watts divided byvolts=amps.
volt drop = 0.0164 X amps X length in meters there and back divided by wire size in square mm to give a volt drop of less than 0.3 volt.
for example 10watt mast light = 0.84
0.0164X0.84X14(7metersX2)divivded by 0.75 = 0.257.
for more info try the reading -college.ac.uk/marine web site.
/forums/images/graemlins/confused.gif
the formula for working out cable size is as follows--
watts divided byvolts=amps.
volt drop = 0.0164 X amps X length in meters there and back divided by wire size in square mm to give a volt drop of less than 0.3 volt.
for example 10watt mast light = 0.84
0.0164X0.84X14(7metersX2)divivded by 0.75 = 0.257.
for more info try the reading -college.ac.uk/marine web site.
/forums/images/graemlins/confused.gif
Robin
Well-known member
Re: Little confused here ....
Nigel
Unless you have devised some magical way of connecting your electical items truly using a single wire then there are TWO leads one +ve and one -ve to each device. When you calculate voltage drop you need therefore to consider the total cable run from the battery to the device and back to the battery - hence the comments 'up and back'.
Robin
Nigel
Unless you have devised some magical way of connecting your electical items truly using a single wire then there are TWO leads one +ve and one -ve to each device. When you calculate voltage drop you need therefore to consider the total cable run from the battery to the device and back to the battery - hence the comments 'up and back'.
Robin
poriordan
New member
Lockwood, go practical for a change.
Readers replies are all sound but after all it is only a small boat and no wiring load. Multi core copper would be good if you can get it, only if not 1,5mmsq will have to fill its place. Connections you have to make sure are tight especially with 1.5mm single but that is your only worry. I've used it plenty of times and with alarm systems on a 12000hp supply boat out on the north sea.
Patrick.
Readers replies are all sound but after all it is only a small boat and no wiring load. Multi core copper would be good if you can get it, only if not 1,5mmsq will have to fill its place. Connections you have to make sure are tight especially with 1.5mm single but that is your only worry. I've used it plenty of times and with alarm systems on a 12000hp supply boat out on the north sea.
Patrick.
poriordan
New member
Re: You have started the debate of the century
Hi there Nigel,
Yeah, I've done same and still lasting. All anyone has to do is to make sure connections are good. Taking it from there, voltage drop as a few readers seem to go on about is little or almost nothing. Sorry about that lads only theory sometimes blockes progress !
Patrick.
Hi there Nigel,
Yeah, I've done same and still lasting. All anyone has to do is to make sure connections are good. Taking it from there, voltage drop as a few readers seem to go on about is little or almost nothing. Sorry about that lads only theory sometimes blockes progress !
Patrick.
A
Anonymous
Guest
Re: You have started the debate of the century
[ QUOTE ]
Sorry about that lads only theory sometimes blockes progress !
[/ QUOTE ]Hmmmm...I wouldn't have chosen the word "progress" to describe using solid copper connecting wire in mobile (i.e. non-household) applications! And the volt-drop thing is important for everything but the lightest loads and/or shortest runs.
[ QUOTE ]
Sorry about that lads only theory sometimes blockes progress !
[/ QUOTE ]Hmmmm...I wouldn't have chosen the word "progress" to describe using solid copper connecting wire in mobile (i.e. non-household) applications! And the volt-drop thing is important for everything but the lightest loads and/or shortest runs.
poriordan
New member
Re: You have started the debate of the century
Hi Lemain !
Good reply that !! Only question is if I was using 1.5 square ( as much as I do not like using it ) all connections have to be fail safe. This may not apply to some people's yachts where ship chandlers supply micky mouse masthead fittings and nav. lights etc. Vibration as we do agree on is a problem, but again, get your gear sorted out what ever cable you use. I've never done a job on pleasure boats before that I had to go back on - Has anybody else ?? By the way Lemain, do you know what the resistance is for 1 meter of 1.5mmsq. cable ??
Hi Lemain !
Good reply that !! Only question is if I was using 1.5 square ( as much as I do not like using it ) all connections have to be fail safe. This may not apply to some people's yachts where ship chandlers supply micky mouse masthead fittings and nav. lights etc. Vibration as we do agree on is a problem, but again, get your gear sorted out what ever cable you use. I've never done a job on pleasure boats before that I had to go back on - Has anybody else ?? By the way Lemain, do you know what the resistance is for 1 meter of 1.5mmsq. cable ??
A
Anonymous
Guest
Re: You have started the debate of the century
[ QUOTE ]
I've never done a job on pleasure boats before that I had to go back on - Has anybody else ??
[/ QUOTE ]I've inherited loads of bodged jobs. I don't recommend bodging, and if someone asks how to do a job in a public forum I try to tell them how to do it properly, not how to bodge it.[ QUOTE ]
By the way Lemain, do you know what the resistance is for 1 meter of 1.5mmsq. cable ??
[/ QUOTE ]Yes, it's around 1.75 Ohms per 100m, I think, from memory. Don't forget that you have to add the resistance in both wires and you'll be surprised how quickly the Ohms add up. Remember, Power = V**2/R so quite small changes in voltage cause a significant power loss to the load - e.g. dim bulbs. That's why you want low volt-drop. It's much more serious at 12V than at mains because the currents are 20 times as great for the same power levels. Or put it another way, for the same power light bulb on a boat as the one you have at home, the current needed to feed it is 20 times greater yet you want to supply it with regular domestic mains cable?
[ QUOTE ]
I've never done a job on pleasure boats before that I had to go back on - Has anybody else ??
[/ QUOTE ]I've inherited loads of bodged jobs. I don't recommend bodging, and if someone asks how to do a job in a public forum I try to tell them how to do it properly, not how to bodge it.[ QUOTE ]
By the way Lemain, do you know what the resistance is for 1 meter of 1.5mmsq. cable ??
[/ QUOTE ]Yes, it's around 1.75 Ohms per 100m, I think, from memory. Don't forget that you have to add the resistance in both wires and you'll be surprised how quickly the Ohms add up. Remember, Power = V**2/R so quite small changes in voltage cause a significant power loss to the load - e.g. dim bulbs. That's why you want low volt-drop. It's much more serious at 12V than at mains because the currents are 20 times as great for the same power levels. Or put it another way, for the same power light bulb on a boat as the one you have at home, the current needed to feed it is 20 times greater yet you want to supply it with regular domestic mains cable?
poriordan
New member
Re: You have started the debate of the century
Hi there again Lemain,
Tks. for your comments. Looks like you have done a bit of thinking on this one. That's good !!
Sorry if you picked me up wrorg regarding household cable, but it's mainly NYM or equiv. marine type cable I normally use on marine applications. Know there is not too much of a difference regarding resistance etc, but fireproof and explosion proof is my only worry with this lot.
Regarding Ohms per meter, I think I'll have to get the books out again only your figure of 1.7 Ohms / 100 meter looks reasonable.
One question is though, what yacht / pleasure boat has a 100 meter run of cable ?
In any case Lemain, give your self a pat on the back for taking me up on that one, as been a Deep sea Chief Engineer for 25 years, ideas sometimes get more practical rather than paperwork.
Patrick
Hi there again Lemain,
Tks. for your comments. Looks like you have done a bit of thinking on this one. That's good !!
Sorry if you picked me up wrorg regarding household cable, but it's mainly NYM or equiv. marine type cable I normally use on marine applications. Know there is not too much of a difference regarding resistance etc, but fireproof and explosion proof is my only worry with this lot.
Regarding Ohms per meter, I think I'll have to get the books out again only your figure of 1.7 Ohms / 100 meter looks reasonable.
One question is though, what yacht / pleasure boat has a 100 meter run of cable ?
In any case Lemain, give your self a pat on the back for taking me up on that one, as been a Deep sea Chief Engineer for 25 years, ideas sometimes get more practical rather than paperwork.
Patrick
poriordan
New member
Re: You have started the debate of the century
Lemain,
Just going back on your post there again, and if anyone has gone back on jobs from other people - I certainly have a long list here.
Good to see someone else has the same problem !
Just have a trawler here in Cork at drydock at the moment after doing a gear box overhaul. Trusted the owner to tighten up the stern gland only he did not know his own strenght. Result - severe overheating causing bushing seizure and tube housing distortion. Talk about problems ....
Pat.
Lemain,
Just going back on your post there again, and if anyone has gone back on jobs from other people - I certainly have a long list here.
Good to see someone else has the same problem !
Just have a trawler here in Cork at drydock at the moment after doing a gear box overhaul. Trusted the owner to tighten up the stern gland only he did not know his own strenght. Result - severe overheating causing bushing seizure and tube housing distortion. Talk about problems ....
Pat.
B
bob_tyler
Guest
Re: Little confused here ....
Nigel,
I want to move my starter battery to a new position.
My engine is a Beta 13.5 with an 80 amp alternator. The battery will be about 3 metres from the starter motor.. Will 10m2 (sorry don't know how to type squared) cable for both pos & neg do?
Bob
Nigel,
I want to move my starter battery to a new position.
My engine is a Beta 13.5 with an 80 amp alternator. The battery will be about 3 metres from the starter motor.. Will 10m2 (sorry don't know how to type squared) cable for both pos & neg do?
Bob
