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Thursday, June 14, 2012

Remote Battery Switch

After all of this planning and pulling of wire, it occurred that I neglected to choose a place for the main battery switch.  The purpose of the switch is to disconnect all DC loads from the batteries (except maybe bilge pumps). When poking screwdrivers around electrical components, near energized positive DC bits, there is a risk of fireworks. So having the switch to turn everything off will be very handy.
Typical manual battery switch
Now, were to put the switch? Typical installations have it near the breaker panel, as the main panel is accessible and the thick battery cables supplying the panel is nearby. But the Westsail's installation does not have a main panel. Instead it has some main DC distribution components in the engine room connected to the battery leads. So, how about the engine room? Well, the ABYC E-11 specification discourages this. The spec likes to see the switch in an easily accessible location, but NOT in the engine room. The reason is for safety. Should a fire break out in the engine room, and DC electrical power needs to be cut, you don't want to have to crawl into an area that is on fire, to access the switch.
Remote battery switch
The solution is a "remote controlled" battery switch installed in the engine room, inline on the positive lead between the main battery fuses and the DC distribution components. This particular switch, made by Blue Sea Systems, uses an "electrically operated magnetic latch solenoid", meaning, an internal magnet holds the switch's "throw" in either the on or off position. Applying a small current to one of two coils (on or off) via a small remote control panel switch moves the throw to the opposite position. The unit also has a manual override switch (the yellow thing on top in the picture) to manually turn on, off, or lock off. You can wire any number of the "remote control" switches anywhere in the boat.
remote control panel switch
So then, does this satisfy the ABYC E-11spec? I don't know. The battery switch, technically, is in the engine room (violates specification), but operation of the switch is remote outside the engine room, solving the access problem of the fire safety scenario cited (the reason for the specification in the first place). E-11 makes no mention of remotely operated battery switches, so I guess this qualifies as a 'grey area'?

E-11 aside, in this installation, the remote battery switch makes more sense than a manual one. Locating and installing a manual switch would have been more difficult.

4 comments:

Bill K said...

My thought on this is that if something goes wrong and there are sparks flying you might not have any electricity to operate the remote switch.

Just a different way to look at it.

Bill Kelleher

Robert Sutton said...

Bill. Yeah, I had though of that. The power for the switch can come from *any* battery. Not necessarily the ones that it switches. Starter battery? Comms battery? Thruster/windlass battery? As it requires little power, a few dry cells may even work. As the solenoid is not wired, and won't need to be for a while, I have some time to think on that one. Maybe install a battery switch for the battery switch? LOL

Anonymous said...

I put ALL the main switches / fuse in the engine room ( AC too ) and you already have the main fuses there ( I don't use fuse but modular breaker )
On the other side ALL fuse /switch in a distributed power system are remote controlled, and all this is in a 'grey area' where all electronic/digital controls are meant only for instruments and not for electric system.
Ignition protected equipments are required only for gasoline and propane/butane, not for diesel.
Some danger comes from 'vented' batteries with big charger / load: you need to take into account this and take some precautions. (not direcly over the batteries)
I don't know exacly how in US would be checked the electric system, but here in EU is the presumption that those who are able to do 'such complicated systems' knows the rules better than the inspectors.
Other problems are insurance, but this only AFTER the fire accidend !
And the switch for the battery switch as for the bilge pump and for alarm system and for ... all excluded from the battery switch are a must, not simply a joke (one for all ?) Check the instant power for the Blue Sea !

Claudio

Robert Sutton said...

Thanks for the tips Claudio. Yes, I have some circuit distribution BEFORE the main switch (fuse block) for bilge pumps and other devices. As for batteries, they are in a separate compartment from the engine room, but a bit confined, and I will need to do something about ventilation there.