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Old 05-06-2018, 13:12   #1
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Location: Quebec (boat currently in Sardinia)
Boat: Bruce Roberts 45 (steel) - Armonid
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Isolating switch and combiner - obsolete?

We've purchased our boat... 15 years ago? Has a house bank (3x230Ah deep discharge FLA) and a starting battery. Both banks are totally independent. The starting battery is charged by a small alternator. The house bank is charged by solar and by two additional alternators.

The boat came with an isolating switch connected to the house bank. Something I never understood. In 15 years we never touched that switch. There is also a combiner, something I never used. I believe that the combiner worked with the regulators that were there when we bought the boat, something we've trashed and replaced with a Balmar Dual.

I am very tempted to ditch both. That would simplify the wiring. And if I remember properly, I read somewhere that it is preferable to run your house bank as is it were a single battery (do not use/recharge one differently from the others).

Before I do that, I'll consult with a marine electrician. But there are several knowledgeable people here, so let me ask if there's any benefit in keeping isolator/combiner.
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Old 05-06-2018, 13:27   #2
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Re: Isolating switch and combiner - obsolete?

There are a few very good safety reasons for keeping the isolation switch.

Most important, if you were to have an electrical short circuit and/or fire on the boat, you NEED to have a way to disconnect all power from all circuits RIGHT AWAY. A master isolation switch is the way to do this.

If you have a relay or switch fail and a piece of equipment continue to run when it NEEDS to stop (a windlass or electric sheet winch for example) having a master switch that shuts everything down is faster than trying to find the individual breaker in an emergency.

Finally, it is safer to disconnect all power draws from the battery before disconnecting wires from the battery terminals. It eliminates the arc that can ignite hydrogen gas venting from the battery.

Keep the switch
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Old 05-06-2018, 13:45   #3
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Re: Isolating switch and combiner - obsolete?

Interesting point.

Now, is there a difference between a master switch and switching a few breakers from the distribution panel?

(Not trying to argue. Just understand)
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Old 05-06-2018, 14:35   #4
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Re: Isolating switch and combiner - obsolete?

A master switch that isolates the entire bank is very useful, not just for safety.

You should test the combiner's terminals when charge sources are active, compared to when not.

Hiring a spark to help you thoroughly document your setup, start maintaining a detailed wiring diagram, would be a great idea.
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Old 05-06-2018, 15:11   #5
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Re: Isolating switch and combiner - obsolete?

Both your house bank and engine bank need switches. in a location you can get to in the event of a fire to shut off. Ie not in the engine room.

I don't know what your combiner is doing. With 3 Alts you should not need one between the engine and house bank.

Is it between house batteries that can be isolated? The 3 house batteries should be connected together and run as one
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Old 06-06-2018, 17:01   #6
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Re: Isolating switch and combiner - obsolete?

Master switch is essential--and the positive feeds from the house battery to the bus bars or fuse/ switch panel.

The best ones were mercury switches. Now they are just comparatively large metal contact plates on a rotary track. They need to carry heavy currents. They can not be replaced with circuit breakers--those are an additional safety factor--not a replacement option.

One needs to remember though--that when you switch off the battery isolator--EVERYTHING is switched off--including automatic bilge pumps and gas detectors.
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Old 06-06-2018, 21:12   #7
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Re: Isolating switch and combiner - obsolete?

Quote:
Originally Posted by Mike Banks View Post
One needs to remember though--that when you switch off the battery isolator--EVERYTHING is switched off--including automatic bilge pumps and gas detectors.

No those should stay on
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Old 06-06-2018, 21:42   #8
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Re: Isolating switch and combiner - obsolete?

Well--obviously that is the case--but you need to wire an additional switch for that.
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Old 06-06-2018, 21:46   #9
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Re: Isolating switch and combiner - obsolete?

Set up an essentials buss, wired to bypass the switch.
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