Rotary switch hot disconnect

[Nonchalant1]

The previous owner showed me how to turn off power at the boat and the dock before disconnecting or connecting the shore power cord by using the big rotary switch that selects power source. Every other position is "off". Now I just read in the Hatteras owners manual that you should first use the circuit breaker for the shore power inlet and then switch the big rotary selector switch to off. I've been doing it with just the rotary switch for 3 years - very convenient. The question is, can I be damaging the rotary switch contact points due to a "hot disconnect"? I always turn off anything big like A/Cs first. Do you others use the shore power inlet circuit breaker to turn off the power to the boat first?

Thanks,

Doug Shuman

[Genesis]

Absolutely. You should never use the rotary switch to disconnect if there is load on the circuit, as it will arc the contacts and eventually damage it.

Shoreside breakers are cheap ($10) - rotary switches are expensive ($$$$$$) - you choose which one to replace more frequently

[jim rosenthal]

Righto. As long as the shoreside breaker is ON the shore power cable is hot. The shore power cable inlet on the boat is also hot, and all the wires leading up to the rotary disconnect switch. The only way that the cable and all the wires leading to it are not hot is if the cable is unplugged or the breaker is off.

[Trojan]

Until the marina changes the dock service. I turn the AC breakers off on the main panel first. Then I disconnect the power cord at the shore. The shore breakers are 6 boats away. The only time the rotary switch is turned is when I run the geny. Using the rotary for a disconnect is a NO,NO. You can burn the contacts out real fast. The guys are right.

BILL

[REBrueckner]

Using the rotary switch without much load running is not a big deal, but as posted is not the best approach. Why switch power aboard when you can do it dockside.

I ALWAYS shut off the shorepower circuit breaker dockside first BEFORE connecting or disconnecting shorepower. It's the only failsafe way to start. Failure to do this can introduce an unbalanced voltage from a 220 supply to either of your 120 volt legs aboard as one cable connector or another makes momentary contact. Its also smart to check shore voltage and polarity at your electric panel BEFORE activating breakers, rotary switch or loads. Turn switches and breakers on BEFORE activating loads aboard.

You should never have a hot unplugged cable end swinging around the water or left dockside..

[Banshee36]

That all sounds like good advice. However a hot switch could be one of two things. One as stated above the contacts could be dirty or burnt. You could have some loose wires on the rotary switch wire connections or corrosion. Both would increase the amp draw and cause the switch to heat up.
JW

[MikeP]

I had never thought about this at all, thinking that the purpose of the rotary switch was exactly that - to change from one input to another.

Here's is my normal method for leaving the dock with shore power on and cable attached, rotary switch in the shore power position: Start Generator, let it warm up a bit; Move rotary switches to genny position; Shut off shore power breaker at the dock box; Disconnect cable from boat.

I have never paid any attention to what AC loads happen to be on at the time.

Is the recommendation that before transferring the load to the genny that the appropriate AC breakers be turned off and then, after the rotary is changed, the breakers be turned back on? The breakers are ganged so they can't be individually turned on to selectively add loading. So the point, as I understand it, is that it's better to wear out the breakers than wear out the roatary. I agree with that since the Rotary is very expensive. But I thought it was designed to handle switching these loads whereas breakers are not designed to be on/off switches.

I haven't read the Hatt info in the manual about this - guess I should!

[Nonchalant1]

Mike,

Me too! In switching to Genny, that's one hot disconnect and one hot connect each time. However, I rarely cruise with the genny on since we have an inverter for the fridge and a 32V water pump. I have always been careful not to switch the rotary on or off with a majpr load running, but 5 lights and the fridge isn't nothing.

Doug

[Traveler 45C]

Switching from shore power to genny power through the “off” position of the rotary switch should not be a problem. I shut down the master breakers on the boat before switching, no current draw, no arcs.

Then, when running on genny power, I shut down the dockside circuit breakers before unplugging the boat. I do this for the obvious safety reasons.

[Pascal]

in winter when we don't use the ac, i usually shutdown the breaker on the dock first, transfering the loads to the inverter automatically.

in summertime, i turn off each a/c individually and then disconnect with the rotaries and transfering to the genset. with the a/c off, there will be very little load left to arc in the rotaries... then i go to each A/C and restarts them usually which also ensures they dont' all start up at the same time!

the rotaries appear to have much beefier contacts than the circuit breakers, i thought breakers were primarly a safety device instead of an on/off switch.

i always keep the shore power cord on the boat... Im docked stern too so it runs along the port side to the stern. when we leave the dock, its end is stored on the aft deck, it's just a few feet. takes very little time.