1-2-B switch + alternator diodes

[markr]

Hi All,
I was reviewing some posts and became confused, so I had to ask the question:
I always understood that it was ok, with the engine running, to turn the 1-2-B switch between these positions, so long as it was not ever turned to OFF with the engine running. Turning to OFF risked frying the diodes in the alternator. To me, that is conventional wisdom. How else would you use your engine battery to start the engine then switch it over to charge one or both of your battery banks while motoring? I have now become confused because there seems to be some info out there about not changing the position at all of the switch once the engine is running. If this was the case, I would start the engine on ALL, leave it there until the engine went off, then switch to HOUSE. BUT: if I then run down the HOUSE, use ENGINE to start the engine, how would I then switch over the both to Charge HOUSE as I am motoring? Hmmmm

I realise that some owners have done an awful lot to their boats in terms of upgrades - echo chargers, whole changes to wiring and electical systems - which would be a better way of doing things (money,time notwithstanding). My '87 (#360) was pretty bare and original when I bought her and I am happy (budget and time allowing) to leave these basic systems in place. I don't intend on changing the 1-2-B system or the system of having simply house and engine bank (2 x 27's for house, 1 x 27 for engine, still working out where to out more house batteries when I can afford the money and time to install more).

So, what is the answer on turning the switch between 1-2-B when the engine is running? On the many other boats that I have sailed over the years, it has not been a problem do long as it was not turned to OFF. The electrical system on my boat is pretty much factory original, with the exception of the harness upgrades etc, but the 1-2-B system of charging the two banks is factory standard.

[stoney]

Mark,
There are those that will say that is a NO NO but I have switched from 1 to 2 to both for the past 10 years without frying my alt. You are correct that if you switch to off it will fry the diodes.  As long as your switch is a "make before break" you won't be interupting your alternator output.  Some switches may break contact from one contact before they make contact on the next post, obviously mine makes contact before it breaks the contact it is leaving.

clear as mud right.

all right guys, give me hell.

Steve

[markr]

Thanks Steve - you put your head above the parapet, now we are both in for it! LOL!

[Stu Jackson]

IT ALL DEPENDS ON HOW IT'S WIRED

Really.

Why boats were wired with the Alternator Output going through the 1-2-B switch, Reply #11 Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams: http://c34.org/bbs/index.php/topic,4949.0.html  Please note the important item in RED in this post.

Reply #18 and my wiring diagram #23 here  Stu's Wiring Diagram & The 1-2-B & Dual Circuit Switches:  http://c34.org/bbs/index.php/topic,4623.15.html

Some valuable input from Maine Sail from the co.com website, starts at the bottom of page one onto page two:  http://forums.catalina.sailboatowners.com/showthread.php?t=104505

These are the highlights.  You can do a lot more reading on this if you do an advanced search using the toolbar rather than just the search box and typing in "1-2-B" and my name.

[markr]

I asked the question to Catalina, about my 1987 which still has the original electric panel and battery selector switch. This was the response:

"The battery selector switch is a "make before break" switch, so you can switch from 1 to both to 2 without any problems.  Typically we use "break before make" switch for switching between shore power and generators as you can have phase issues with the AC systems.  I hope this helps."

I have not had any particular work done on my boat that would have changed this arrangement. The PO was the original owner and had left the boat pretty much as delivered to him.

I hope this helps?

[Stu Jackson]

Mark, given that the first thing I'd do is find out where your alternator output (AO) goes.  Discussed at length in one of the links I provided.  Then let's talk some more.  Make before break is fine, but sometimes the contacts on our "vintage" boats can get dirty.  As I said on another thread, is it worth the risk?  I know, I know, it's been workin' for the past 20 years...  But go look at the wiring harness story on Critical Upgrades - his connectors were melted inside, just waitin' to zap him...

Worst case is ya learn somethin' about how your boat is wired.

And here's another one:  our switch is 2-B-1-OFF so if I switch from 2 through B to 1, there is the possibility, however slight, that I could continue turning to OFF accidentally, simply because of the heaviness of the switch itself.  That's why I took the AO off the C post of the switch, and ran it directly to the house bank.  I can turn my bloody switch OFF with the engine running without ANY problems.  Really.

So, lemme know when you've finished reading the links and, up to you, we can continue this conversation - I'm "Linkman" when it comes to this stuff.

[Ron Hill]

Mark : I've previously talked to Perko and their switch is a "make before break". 
With the wiring harness upgrade (I surly hope you have!!!) you should have a #10 wire (as part of that upgrade) going from the alternator output to the starter solenoid stud. 
Even though that is a short run (approx 6" ?), I've always recommend that people use #6 or #4 wire. Being Ron, I also recommend they crimp & solder!!   A thought