Electrical panel - STANDBY MAINS circuit breaker

RWS · Post by **RWS** » Sun Apr 10, 2011 7:11 am

Take a look at the attached photograph of the 12 volt side of my 1983 Trojan International.

On the bottom left hand side are the circuit breaker STANDBY MAINS.

When I leave the boat I turn off the two 12 volt mains at the top of the panel, which essentially kills the boat with the exception of the bilge pumps (that's what I THOUGHT those standby mains were for)

The panel says "mains supply items below and or charger hi water alarm"

Does anyone know FOR SURE what those standby mains do?

THANKS !

RWS

koviak · Post by **koviak** » Sun Apr 10, 2011 7:42 am

RWS, the standby main is for bildge pumps, hi water alarm, horn and refrigerator. My 1989 is the same.

Big D · Post by **Big D** » Sun Apr 10, 2011 10:22 am

Makes sense that they would be for the pump circuit. Having said that, I've learned not to assume anything anymore when it comes to wiring and what a previous owner may have done/changed. I say pull back the panel and see where those circuits are getting thier power from. If the breakers are fed from a common bus off the "Standby Mains", you have your deffinate answer and will be able to tell if there have been any other modifications made. Disconnect shore power first.

Allen Sr · Post by **Allen Sr** » Sun Apr 10, 2011 7:58 pm

Your panel looks like the one in my 84 F36, and I can tell you for a fact on mine you turn the mains off and you still have power to the bilge pumps. If you pull the panel out where the power comes in to the mains up top there are jumpers down to the standby mains. The standby mains feed everything on that bottom row.

RWS · Post by **RWS** » Sun Apr 10, 2011 10:36 pm

main breakers turned off at top

bilge pumps run on manual fine

turned off STANDBY MAINS

bilge pumps still work on manual.

So what then do those Standby mains do?

Maybe I need to get out the schematic and take a look

RWS

Allen Sr · Post by **Allen Sr** » Mon Apr 11, 2011 5:54 am

It sounds like somebody rewired your panel?

S.A.M. · Post by **S.A.M.** » Mon Apr 11, 2011 9:26 am

My understanding was it shuts down all 12v circuits except for bilge pumps and alarms.

Last month when mine was on the hard, the starboard battery went dead. That's when I found out the refrigerator does not shut off. A real battery killer.

If you're on shore power, no big deal. But I thought the purpose was to kill all 12v draw except for safety equipment.

RWS · Post by **RWS** » Mon Apr 11, 2011 9:55 am

There are popout breakers for the bilge pumps.

The question then is What systems do those breakers protect/control?

RWS

rbcool · Post by **rbcool** » Sat Apr 16, 2011 7:07 pm

I think that breaker turns off the "Float switches" to the bilge pumps in case you have a fuel leak or other toxic stuff. Will test this tomorrow when the boat isn't rocking in these 50mph winds

Ron

RWS · Post by **RWS** » Sat Apr 16, 2011 8:01 pm

O.K.

Here's the schematic - just highlighting the 12 volt panel.

Am I missing something here?

RWS

rbcool · Post by **rbcool** » Sat Apr 16, 2011 8:18 pm

OK...I was right....., just went down and checked. With those 2 breakers off, float switches didn't work. I believe the reason for them is 2 fold..... what I mentioned earlier and to turn off the 12v fridge if you pull the boat out. Plus, when the boat is on the hard, you don't really need any of the things those breakers controll

Ron