Electrical General Questions

[corkscrew]

Here's a few general Questions......

I am trying to figure out some electrical questions for my mac (1997 26X) - As you see, I am not an electrician. I currently have a 27 Deep and a starting. My question is really the basics of wire gauge and fuse capacity. Is there a rule of thumb for what gauge wire to use with a device. How does this rule get modified if you have two devices attached to the same wire? For example. I will have a bilge attached to a wire...I am considering since that bilge really never runs attaching a run off of it to run my head electric sink....guess trying to understand ramifications if they both run at same time.

Second question comes in for the same thing...on my circuit board should I have a fues for every item? Or can I have both bilges for example attached to the same fuse block......how do you select a fuse to handle multiple devices?



Thanks

[MadMacX]

This site has some good info on what you are looking for. Don't know the people, but I purchase from them quite often.

http://stores.shop.ebay.com/Genuinedeal ... Guide.html_

Pat

Att'n. mods If this is a no no, please delete!!!!

[tangentair]

There is a mostly useful article in this month's Cruising World with a table that will answer your wire size questions and there was a much better article a few months back on general boat electrical service but I can not find it right now - and it may not have been Cruising World. I will look in my files at home after work unless someone else here remembers the one. There are also quite a few threads on wiring in the archives that would give food for thought regarding wiring, size and type, connectors, running the wire, etc.

[Hamin' X]

No problem on the link Pat, it looks like good info.

corkscrew,

Your wiring size and protection must be rated for the maximum load that may accumulate on an individual line. Also, consider using individual fuses at each appliance (light, radio, etc.), as well as a main circuit fuse, or breaker. If the device needs a 5 amp fuse and you are running more than one device, the protection for the main line must be equal to the sum plus about 10%. Without the individual fuses, you are only protecting the line and not each device.

As far as the bilge pump and sink combination goes, consider this: The bilge pump never runs unless it is needed. I think that you are inviting Mr. Murphy on board if you do this.

~Rich

[corkscrew]

Ok....so to be clear...in this scenario:

Say I had 2 bilge pumps on one line. I should:

- Have a rated fuse for each bilge
- Have a wire that can handle both bilges reqs combined
- Have a fuse on the line that can handle the max for both combined bilges

correct?

[Hamin' X]

You got it.

~Rich

[tangentair]

Ok....so to be clear...in this scenario:

Say I had 2 bilge pumps on one line. I should:

- Have a rated fuse for each bilge
- Have a wire that can handle both bilges reqs combined
- Have a fuse on the line that can handle the max for both combined bilges

correct?

As Rich said yes that will work,
.......so long as you understand that in this senario, you could have one pump burn up take out the main fuse and possibly some wiring, because you left a hatch open in a downpour or spring snow storm and a half deployed jib is funneling all the water it collects into the cabin, the other pump - which had it been on a seperate line would still have run as long as you had shore power or battery left - is also dead so while you might have gotten to the boat before it settled on the bottom or tore out your moring line cleats, by putting both pumps on the same fuse, you wired you boat to sink if either pump fails and takes out the fuse.

[corkscrew]

SO the best situation then would be:

Each bilge with it's own wire to handle that bilges amps
Each Bilge with it's own fuse to hand that bilges amps.

Now lets say I do this...but on the main breaker I want to have bilges wired to the same spot. Coul I have it as above, and then hit the circuit board and for the fuse have a fuse able to handle both units? That way they each have their own line and own fuse, but are wired to the same spot with a unified fuse?

I am still trying to find a chart or guide for choosing wires and fuses....can't seem to find anything.

Oh....and as a PS......speaking of electric. Are Macs equipted to deal with a lighting strike to the mast? What happens? Has anyone installed anything or have any thoughts?

[c130king]

I am getting ready to do a good bit of "fiddling" with my electrical system -- new fuse/switch panel, 2 x batteries, radio, stereo, autopilot, etc...

So I am studying this book:



I bought mine at Amazon -- Sailboat Electrics Simplified

There is lots of good info for the novice electrician...like me.

Good Luck with your set-up.

Cheers,
Jim

[tangentair]

SO the best situation then would be:
Each bilge with it's own wire to handle that bilges amps
Each Bilge with it's own fuse to hand that bilges amps.
Now lets say I do this...but on the main breaker I want to have bilges wired to the same spot. .......are wired to the same spot with a unified fuse? ultimately all wires come back to the same fuse - the one in the cheap in line holder coming right off the battery - Think about your home breaker/fuse panel - the power comes into a main 80 or 100 or 200 amp breaker and then is distributed to individual circuits. That is what you want, group the items on the circuits based upon the impact of an individual failure - so running lights get their own individual circuit, anchor light, cabin lights can be on one or better two, electronics for cabin, electronics for cockpit, vhf radio, etc all get seperate circuits. Now I prefer circuit breakes because they can act as a switch, if you use a fuse you still need a switch to turn the circuit on or off. And you should upgrade to a main switch to disconnect the battery(s)

I am still trying to find a chart or guide for choosing wires and fuses....can't seem to find anything.go to Boarders or Barnes and Nobles and look in this months Cruising World, it has a very nice chart with wire size, by amperage by distance and also lists the typical amperage of common devices found on the boat

Oh....and as a PS......speaking of electric. Are Macs equipted to deal with a lighting strike to the mast? What happens? Has anyone installed anything or have any thoughts? a quick forum search has these two threads but the best protection is good insurance and attending church on Sunday instead of sailing

[Hamin' X]

.......so long as you understand that in this senario, you could have one pump burn up take out the main fuse and possibly some wiring, because you left a hatch open in a downpour or spring snow storm and a half deployed jib is funneling all the water it collects into the cabin, the other pump - which had it been on a seperate line would still have run as long as you had shore power or battery left - is also dead so while you might have gotten to the boat before it settled on the bottom or tore out your moring line cleats, by putting both pumps on the same fuse, you wired you boat to sink if either pump fails and takes out the fuse.

This is why I specified a rated fuse for each appliance. Example:

• Bilge Pump = 5 amp
  Bilge Pump = 5 amp
  Sink Pump = 2 amp

If all three of these are combined on the same properly sized wire, each would have it's own rated fuse in-line close to the individual appliance. 5+5+2=12 amps. The common hot wire should be protected at the switch panel by a 15 amp breaker, or fuse. If one unit should short, it will take out the lower rated individual fuse and leave power to the remaining items unaffected.

~Rich

[corkscrew]

Thanks for all the great info! One last thing, does anyone have multiple deep cycles? I am considering having two deep cycles instead of one. I understand that to keep it same 12 volt system and just double reserves, I need to run in parellel. Connecting + to + and - to -. Correct? Does anyone do this? I assume you use the same connectiong strategy for connecting the two deeps to the starting? I've also read about you have to take care in charging these? Any recommendations?

[Kelly Hanson East]

Most of the advice about starting batteries doesnt apply to Macs. The engines we put on the boats are so small and present such small cranking loads that putting traditional 'starting' and 'house' batteries on the boat is a waste of money, WADR to those who have those monster 115 HP, 140 HP on board.

[c130king]

My plan is 2 x Group 24 Deep Cycle batteries (won't buy them until I move back to the U.S.) and hook them up to a 1-2-Both-Off Switch and connect them with a Yandina Combiner for charging purposes.

Battery one connected to Switch position 1 and Battery two connected to Switch postion 2. On odd days I will run both the engine and the house on battery 1 and on even days I will use battery 2.

The Yandina Combiner will ensure that both get charged during engine runs no matter what postion the switch is in.

And of course I will turn the switch to off when leaving the boat.

Should only have to use both if something goes gloriously wrong.

Don't think a dedicated start battery is necessary.

There are several threads about this sort of thing.

Good Luck,
Jim

[Hardcrab]

Correct. + to+, - to -.

The only thing is both batteries should be the same age according to most mfgs.
It simply becomes one 12 cell battery located in two cases wired series and parallel.
Batteries are already composed of multiple 2 volt cells in one box.

No undue worries as to recharging a dual battery bank.
Dual bank is overkill for the starting battery duties.

A good minimum setup is a dedicated starting battery and a dual bank for house duties and a "Perko" type switch to keep it all charged and working.
Built in labeling. Position "1" is the single battery. Position "2" is the dual bank.

I just put a dual bank of Optimas in my M.
Deep cell group 24 for starting.
Two group 24 Optimas for house.
It all fits in the existing battery location.